Advances in Radioactive Isotope Science

28 May 2017, 09:00 → 2 Jun 2017, 16:00 US/Mountain

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Sunday, 28 May

14:00 On-Site Registration Open

18:00 Welcome Reception

Monday, 29 May

1 Logistics and Welcome

2 QED and the Hyperfine-structure Puzzle in Hydrogen-like and Lithium-like Bismuth

The possibility of testing quantum electrodynamics (QED) in very strong fields by laser spectroscopy on heavy highly charged ions has been opened by the first observation of the hyperfine splitting in hydrogen-like bismuth in 1994 [Klaft et al. Phys. Rev. Lett 73, 2428 (1994)]. The electrons in these systems experience the strongest magnetic fields available in the laboratory, but the significance as a test for QED of this and following experiments on other species was limited by the unknown magnetic moment distribution inside the nucleus. However, it was suggested that a so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like ions of the same isotope can be used to cancel nuclear structure effects and provide an accurate test of QED [Shabaev et al., Phys. Rev. Lett. 86, 3959 (2001)]. The transition in Li-like Bismuth was observed for the first time in 2011 at the Experimental Storage Ring ESR located at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt [M. Lochmann et al., Phys. Rev. A 90, 030501 (2014)]. Yet the accuracy of the result was limited by the calibration of the electron cooler voltage, determining the ion velocity. Here, we report on improved laser spectroscopic measurements on bismuth ions of both charge states ( 209Bi82+ and 209Bi80+) at the ESR. The accuracy was improved by about an order of magnitude compared to the first observation in 2011. We will present the measured transition energies of both hydrogen- and lithium-like bismuth and the experimentally determined value for the specific difference in 209Bi which is in contradiction with theoretical predictions. Possible reasons will be discussed and ways to further investigate this puzzle by laser spectroscopy on radioactive species will be discussed.

Speaker: Prof. Wilfried Nörtershäuser (TU Darmstadt)

3 Ion Traps for Precision Experiments at TRIUMF

Ion traps are of growing popularity at rare-isotope-beam facilities due to their textbook-like conditions and tailorability. This versatility is exemplified at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN) facility, where ion traps are used for beam preparation and high-precision measurements. Penning trap mass spectrometry has provided insight into the evolution of the N = 20 shell in the island of inversion, nucleosynthesis via the r-process, and the unitarity of the quark-mixing matrix. In-trap decay spectroscopy research has focused on branching ratios to investigate the double-beta-decay problem and now includes studies of the role of electronic structure in nuclear decay. Moreover, investigations with preparatory traps are being used to extend the reach of TITAN, by reducing beam contamination, improving beam availability beyond ISOL-produced beams, and increasing ion bunch size. A selection of recent highlights and advances will be presented.

Speaker: Dr Anna Kwiatkowski (TRIUMF)

4 The Search for Fundamental Symmetry Violation in Radium Nuclei

Electric dipole moments (EDMs) are signatures of time-reversal, parity, and charge-parity (CP) violation, which makes them a sensitive probe of expected new physics beyond the Standard Model, such as supersymmetry. No experiment has yet observed a non-zero EDM to challenge the Standard Model. Due to its large nuclear octupole deformation and high atomic mass, the radioactive Ra-225 isotope is a favorable EDM case; it is particularly sensitive to CP-violating interactions in the nuclear medium. We have developed a cold-atom approach of measuring the atomic EDM of Ra-225 atoms held stationary in an optical dipole trap. We previously demonstrated this technique with an initial experimental upper limit of |d(225Ra)| < 5e-22 e-cm (95% C.L.), and have since improved this limit 36-fold to 1.4e-23 e-cm. This is not only the first time laser-cooled atoms have been used to measure an EDM, but also the first time the EDM of any octupole deformed species has been measured. Upcoming improvements are expected to dramatically improve our sensitivity, and significantly improve on the search for new physics in several sectors. This work is supported by U.S. DOE, Office of Science, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

Speaker: Dr Matthew Dietrich (Argonne National Lab)

5 Magnetic Moment Measurement of Isomeric State of Cu-75 Using Spin-aligned RI Beam at RIBF

Unstable nuclei with extremely unbalanced proton-to-neutron ratio often exhibit evolved shell structure and collectivity such as vibrated/deformed shapes, which compete with each other to determine the resultant structure. The nuclear magnetic moment is one of the important observables with which we can catch a glimpse into the competition. A technique to orient the nuclear spin is necessary for the magnetic moment measurement. Recently a scheme of the two-step reaction was developed to produce high spin alignment (rank-two orientation) in RI beams [1]. This scheme realizes high spin alignment as well as high production yield of RI beams by combining a technique of momentum dispersion matching at the beam transportation. It has opened up opportunities to produce spin alignment for unstable nuclei, for which the spin alignment would have tended to significantly attenuate if the conventional scheme was employed because of the mass difference between a projectile and the final fragment. The two-step scheme was employed in the magnetic moment measurement of the isomeric state of the neutron-rich nucleus Cu-75. The experiment was carried out at RIBF. The Cu-75 beam with spin alignment reaching 30% was produced from a primary beam of U-238 via an intermediate product of Zn-76. For the measurement of the magnetic moment, a method of time-differential perturbed angular distribution (TDPAD) was employed. Owing to the high spin alignment realized with the two-step scheme, the oscillation in the TDPAD spectrum was observed with significance larger than 5 sigma. The magnetic moment of the 66.2-keV isomer, which is one of the two low-lying isomers in Cu-75, was determined for the first time. In this talk, the magnetic moment measurement employing the two-step scheme will be introduced and the result of the experiment of Cu-75 will be presented. Discussions on the competition between shape and shell at the neutron-rich Cu isotopes, through the precise analysis of the magnetic moment with a help of the state-of-the-art Monte Carlo shell model calculation, will also be given. References: [1] Y. Ichikawa et al., Nature Phys. 8, 918 (2012).

Speaker: Dr Yuichi Ichikawa (RIKEN Nishina Center)

10:45 Coffee Break

6 Explosive Nucleosynthesis of Heavy Elements: An Astrophysical and Nuclear Physics Challenge

Half of the elements heavier than iron are produced by the r process under extreme conditions. To identify its site remains one of the major challenges in nuclear astrophysics. Advances in the description of neutrino-matter interactions and its implementation in core-collapse supernova modelling have lead to the conclusion that supernova explosions only contribute to the production of elements with Z < 50. Compact binary mergers are currently considered the best candidate for the main r-process site. These events are expected to produce gravitational waves, likely to be observed by the LIGO collaboration, and eject large amounts of neutron-rich material where the r process operates. In this talk, I will discuss the important role of nuclear physics to determine the r-process yields from compact binary mergers. In addition to neutron captures and beta decay, fission rates and yields of superheavy neutron-rich nuclei are fundamental to understand the r-process dynamics and nucleosynthesis. Mergers constitute also ideal candidates to directly observe the r-process via an electromagnetic transient due to the radioactive decay of r-process material. This type of event, known as kilonova, may have already been observed associated with the gamma-ray burst GRB 130603B.

Speaker: Gabriel Martinez-Pinedo (GSI Darmstadt and TU Darmstadt)

7 Advances in Explosive Nuclear Astropysics

Breathtaking results from the Planck satellite mission and Hubble space telescope have highlighted the key role modern Astronomy is playing for our understanding of Big Bang Cosmology. However, not so widely publicized is the similar wealth of observational data now available on explosive stellar phenomena, such as X-ray bursts, novae and Supernovae. These astronomical events are responsible for the synthesis of almost all the chemical elements we find on Earth and observe in our Galaxy, as well as energy generation throughout the cosmos. Regrettably, understanding the latest collection of observational data is severely hindered by the current, large uncertainties in the underlying nuclear physics processes that drive such stellar scenarios. In order to resolve this issue, it is becoming increasingly clear that there is a need to explore the unknown properties and reactions of nuclei away from the line of stability. Consequently, state-of-the-art radioactive beam facilities have become terrestrial laboratories for the reproduction of astrophysical reactions that occur in explosive stellar events. In this talk, both direct and indirect methods for studying key astrophysical reactions using radioactive beams will be discussed.

Speaker: Dr Gavin Lotay (University of Surrey)

8 Direct Measurements of α-capture Cross Sections Relevant for Nuclear Astrophysics

Since helium is the second most abundant element in the universe, there are numerous reaction rates involving α-particles that play a key role in nuclear astrophysics. For instance, some (α,p) reactions have been found to be fundamental for the understanding of X-ray bursts and the production of 44Ti in core-collapse supernovae. Furthermore, some (α,n) reactions are considered to be important neutron sources in different astrophysical scenarios. Direct measurements of these reactions at relevant astrophysical energies are experimentally challenging because of their small cross sections and the intensity limitation of radioactive beams. In this talk I will describe a novel technique to study (α,p) and (α,n) reactions using a Multi-Sampling Ionization Chamber (MUSIC), a simple and highly efficient active target system with a segmented anode that allows the investigation of a large energy range of the excitation function. Recent results on the direct measurement of (α,n) and (α,p) reactions in the MUSIC detector will be presented. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.

Speaker: Melina Avila (Argonne National Laboratory)

9 Neutron Capture Reactions for the Astrophysical r process

The astrophysical r process is responsible for the synthesis of about half of the isotopes of the heavy elements. Although the general characteristics of the process have been known for a while, the astrophysical site where it takes place has not been unambiguously determined. Efforts to better understand this important process span across many fields, including astronomical observations of metal-poor stars, modeling of the possible scenarios, sensitivity studies, nuclear theory calculations and nuclear experiments. One of the nuclear inputs that have a large impact on the final abundance calculations is neutron-capture reaction rates. These reactions are practically unconstrained far from stability due to the difficulty in studying them with direct techniques. As a result, astrophysical calculations have to rely on theoretical models, which differ from each other by factors of 10-1000. Therefore, indirect experimental approaches are required, and this talk will present the development of a new technique to experimentally constrain these important (n,γ) reaction rates far from stability. The relevant experiments were done at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University using the γ-calorimeter SuN. New results in the mass region of A=70 and the impact on r-process calculations will be presented.

Speaker: Artemis Spyrou (NSCL/MSU)

12:40 Lunch Break

10 Unveiling New Features in the Exotic Landscape of Light Nuclei with Direct Reactions

Radioactive (RI) beams are allowing us to uncover the unknown properties of nuclei at the extremes of nuclear binding. This is leading to revelation of new phenomena associated with exotic structures like nuclear halo and skin that stretch beyond the bounds of our conventional knowledge. The evolution of neutron skin/surface in neutron-rich nuclei can cause mutation of the nuclear shell structure and give rise to exotic excitation modes such as soft dipole resonance states. The new features in exotic nuclei challenge our understanding of the nuclear force. Reaction spectroscopy with both ISOL and in-flight RI beams offer complementary avenues that have different sensitivities to different characteristics of the exotic nuclei. The presentation will discuss how direct reactions with the low-energy re-accelerated beams at TRIUMF and the IRIS reaction spectroscopy facility with solid H2/D2 targets have opened access for obtaining some precise spectroscopic information of exotic nuclei. Recent explorations of unbound states in light nuclei around the drip-lines will be presented. It will be shown that the low-energy scattering opens a new avenue to constrain the nuclear force with its ability of connecting to the ab initio theory. The relativistic energy in-flight beams allow us to probe into the nucleon distribution and nuclear radii that characterize the exotic nuclear halo and skin. Recent measurements at the GSI fragment separator FRS will be reported to elucidate the development of neutron skin and evolution of nuclear halo correlations in neutron-rich nuclei.

Speaker: Prof. Rituparna Kanungo (Saint Mary's University)

11 Four-body Continuum Effects in d+11Be Elastic Scattering

The main goal of the Continuum Discretized Coupled Channel (CDCC) method is to solve the Schrödinger equation for reactions where the projectile presents a cluster structure, and a low dissociation energy. The CDCC method has been introduced forty years ago [1] to describe deuteron induced reactions. Owing to the low binding energy of the deuteron, it was shown that including continuum channels significantly improves the description of d+nucleus elastic cross sections [1, 2]. The simplest variant of CDCC describes scattering of a two-body nucleus with a structureless target, but extensions to three-body projectiles have been performed recently (see, for example, ref. [3]). The projectile continuum is approximated by a finite number of square-integrable states, up to a given truncation energy. We present here a new development of the CDCC method, which aims at describing reactions where the projectile and the target have a low separation energy. This leads to four-body (or more) calculations. Since continuum states are included in both colliding nuclei, the number of channels can be extremely large. We solve the coupled-channel system by using the R-matrix method on a Lagrange mesh [4]. A first application is presented for d+11Be elastic scattering and breakup, which have been measured recently at Ecm=45.5 MeV [5]. The 2H and 11Be nuclei are defined by 2H=p+n and 11Be=10Be+n structures. We choose the Minnesota potential [6] as nucleon-nucleon interaction, and the Koning-Delaroche global potential [7] as nucleon-10Be optical potentials. We show that including continuum states of 2H and of 11Be is necessary to reproduce well the experimental data. References: [1] G. H. Rawitscher, Phys. Rev. C9 (1974) 2210. [2] M. Yahiro et al., Prog. Theor. Phys. Suppl. 89 (1986) 32. [3] T. Matsumoto et al., Phys. Rev. C70 (2004) 061601. [4] P. Descouvemont and D. Baye, Rep. Prog. Phys. 73, (2010) 036301. [5] J. Chen et al. , Phys. Rev. C94 (2016) 064620. [6] D.R. Thompson, M. LeMere, and Y.C. Tang, Nucl. Phys. A286 (1977) 53. [7] A.J. Koning and J.P. Delaroche, Nucl. Phys. A713 (2003) 231.

Speaker: Dr Pierre Descouvemont (Universite Libre de Bruxelles)

12 Transfer Reactions with Isomeric Beams

Nuclear reactions induced by isomeric beams have long been considered an extremely attractive tool for nuclear structure, nuclear reactions and nuclear astrophysics studies. One of the most interesting cases is in 26Al, where a 0+ isomer is located 228 keV above the 5+ ground state. Proton captures on both, the ground state and the isomeric state, could have a direct impact on the abundance of 26Al in the Galaxy. In this talk, I will discuss our efforts to develop and characterize an isomeric 26Alm beam with sufficient intensity, purity, high isomer-to-ground state ratio and energy resolution to study transfer reactions induced by the 0+ isomer in 26Al. Results on the measurement of the 26Alm(d,p)27Al reaction and its astrophysical implications will also be presented.

Speaker: Prof. Sergio Almaraz-Calderon (Florida State University)

13 Isospin Symmetry Studies Using Direct Reactions on Fragmentation Beams

The neutron-proton exchange (isospin) symmetry results in striking symmetries in nuclear behavior between isobaric analogue states (IAS). The very small differences in excitation energy between the IAS can be interpreted in terms of Coulomb, and other isospin-non-conserving, effects. The analysis of these energy differences has been shown to be a sensitive probe of nuclear structure effects and provides stringent tests of model calculations (e.g.[1-5]). New experimental techniques have been applied in the last few years to access excited states in isobaric multiplets of larger isospin through spectroscopic studies of proton-rich nuclei heading towards the proton drip-line. Knockout reactions have recently been shown to provide a successful and versatile technique for accessing states on interest in proton-rich nuclei for isospin-related studies. The direct nature of the 1-nucleon and 2-nucleon knockout mechanism yields selective population specific analogue states within a multiplet, allowing studies of isospin-symmetry breaking - see e.g. [6]. In this talk, the latest results using knockout reactions on radioactive beams at NSCL will be presented, including an analysis of mirrored knockout reactions and population of high-spin states through knockout from a high-spin isomer [7]. Theoretical analysis of both the reaction cross sections and isospin-symmetry breaking effects across the multiplets in the f7/2 shell will be presented. In the shape-coexistence region around A~70, the strongly competing nuclear shapes have been predicted to yield the potential for the breakdown of isospin symmetry across a multiplet (e.g. [8]). To test these ideas, the study of the full A=70 isobaric triplet has been the subject of a number of experimental studies, to examine the extent to which isospin symmetry is retained. The recent identification of excited states in 70Kr [9] now completes this triplet. These data and their interpretation will be presented. References: [1] Bentley and Lenzi, Prog. Part. Nucl. Phys. 59, 497 (2007) [2] Zuker et. al., Phys. Rev. Lett. 89, 142502 (2002) [3] Ekman et al., Mod. Phys. Lett. A20, 2977 (2005) [4] Kaneko et al. Phys. Rev. C89, 031302(R) [5] Bentley et al. Phys. Rev. C92, 024310 (2015) [6] Davies et. al., Phys. Rev. Lett. 111 072501 (2013) [7] Milne et al., Phys. Rev. C 93, 024318 (2016) and Phys. Rev. Lett. 117, 082502 (2016) [8] Petrovici et al. Phys. Rev. C91, 014302 (2015) [9] Debenham et al. Phys. Rev. C94, 054311

Speaker: Prof. Michael Bentley (University of York)

14 np Pairing Viewed From Transfer Reactions

Neutron-proton pairing is the only pairing that can occur in the T=0 and the T=1 isospin channels. T=1 particle-like pairing (n-n or p-p) has been extensively studied unlike T=0 neutron-proton pairing. The over-binding of N=Z nuclei could be one of its manifestation. Neutron-proton pairing can be studied by spectroscopy as in ref.[1].We have studied it through transfer reactions in order to get more insight into the relative intensities of the two aforementioned channels. Indeed, the cross-section of np pair transfer is expected to be enhanced if the number of pairs contributing to the populated channel is important. Neutron-proton pairing is predicted to be more important in N=Z nuclei with high J orbitals so that the best nuclei would belong to the g9/2 shell [2]. However, considering the beam intensities in this region, we have focussed on fp shell nuclei (56Ni and 52Fe). The measurement was performed at GANIL with radioactive beams produced by fragmentation of a 75A MeV 58Ni beam on a 185 mg.cm-2 Be target purified by the LISE spectrometer. An efficient set-up based on the coupling of the MUST2 and TIARA Silicon arrays for charged particle detection with the EXOGAM gamma-ray detector was used. Measuring both 52Fe (N=Z=26) which is a partially occupied 0f7/2 shell nucleus and 56Ni (N=Z=28) which has a fully occupied 0f7/2 shell allowed us to study np pairing along the f7/2 shell and to draw conclusions with respect to the previous studies in the sd-shell. Results on the nature of the n-p pairing will be discussed based on the relative intensities of the 0+ and 1+ states populated in the 56Ni(p,3He)54Co and 52Fe(p,3He)50Mn reactions and on the angular distributions compared with DWBA calculations. References: [1] B. Cederwall et al, Nature 469 (2011) 469. [2] P. van Isäcker et al, Phys. Rev. Lett. 94 (2005) 162502.

Speaker: Dr Marlène Assié (IPN)

16:05 Coffee Break

15 Direct Detection of the Elusive 229mTh Isomer: Milestone Towards a Nuclear Clock

The isomeric first excited state of 229Th possesses the lowest excitation energy of all known nuclei. Its energy has been predicted to be 7.6 eV [1] and could in principle allow to populate this isomeric state with state-of-the-art lasers. This has led to multitude of proposed applications, the best known therein is a nuclear optical clock, that could outperform today’s existing atomic optical clocks. However, progress has so far been hindered by the vague and indirect knowledge of the transition energy and lifetime of the isomeric state. The isomer decays via several decay channels to its ground state, whose strength depends on the electron environment of the nucleus: internal conversion (IC) decay occurs as soon as the binding energy of an electron in the surrounding of the nucleus is below the energy of the isomer. Other decay channels are regular ɣ decay or bound internal conversion, where a bound electronic state is excited. The measurements that led to the first direct detection of the isomer, as well as recent measurements of the internal conversion decay lifetime of neutral 229mTh, are presented in the talk: In our experimental setup, 229mTh is populated via a 2% decay branch of the 233U α decay. Therefore a 233U α recoil source is placed in a buffer gas stopping cell, filled with ultra-pure helium that thermalizes the 229(m)Th recoil ions. The ions are extracted in a gas jet into a segmented radio frequency quadrupole (RFQ) that allows for beam cooling and bunch creation. Behind the RFQ, other daughter nuclei from the 233U decay chain are removed with a quadrupole mass separator and a charge state of the ion can be selected. The 229(m)Th ions are then collected directly on an MCP detector that is used for neutralization of the ions and for the subsequent detection of the internal conversion electron emitted during the ground-state decay of the isomer [2]. With the creation of ion bunches with a width of 10 µs, it was possible to determine the half-life of the internal conversion decay to be 7(1) µs [3]. This work was supported by DFG (Th956/3-1), by the European Union’s Horizon 2020 research and innovation programme under grant agreement 664732 “nuClock” and by the LMU department of Medical Physics via the Maier-Leibnitz Laboratory. References: [1] B.R. Beck et al., PRL 98, 142501 (2007). [2] L. v.d. Wense et al., Nature 533, 47 (2016). [3] B. Seiferle et al., Phys. Rev. Lett. 118, 042501 (2017).

Speaker: Mr Benedict Seiferle (Ludwig-Maximilians-Universität München)

16 Two-proton Radioactivity - A Nuclear Structure Tool Beyond the Drip Line

Two-proton radioactivity is the latest nuclear decay mode discovered. It consists of the emission of a pair of protons from a nuclear ground state. According to the definition by V. Goldanskii who was the first to discuss this new type of radioactivity extensively, one-proton radioactivity is not allowed to be an open decay channel for two-proton radioactivity (2p) candidates. In pioneering experiments at GANIL and GSI, this new radioactivity was discovered in 2002 and meanwhile 19Mg, 45Fe, 48Ni and 54Zn are established 2p emitters. These results allowed a detailed comparison with the theoretical models available and showed that, at the level of precision of the experimental data and of the predictive power of the models, nice agreement was obtained. The latest step in the investigation of 2p radioactivity was the use of time-projection chambers to study the decay dynamics via measurements of the individual proton energies and the relative proton-proton emission angle. A first experiment at GANIL and a high-statistics experiment performed at MSU on 45Fe allowed to gain first insights into the decay characteristics by comparison with a three-body model. Meanwhile 54Zn has also been studied with a TPC at GANIL and 2p radioactivity was confirmed for 48Ni at MSU. In a recent experiment at the BigRIPS separator of RIKEN, a new 2p emitter, 67Kr, was discovered and its basic decay characteristics have been established, whereas two other 2p radioactivity candidates, 59Ge and 63Se, have been shown to decay by beta decay. The decay characteristics of 67Kr are in disagreement with established models and might be a hint for a different decay mode. The talk will quickly review the experimental status and present in more detail the new results. Future studies of new 2p emitters will also be discussed.

Speaker: Dr Bertram Blank (CEN Bordeaux-Gradignan)

17 First Spectroscopy in 40Mg

40Mg, with 12 protons and 28 neutrons, lies at the edge of the neutron drip-line and at the intersection of two established regions of nuclear deformation. It is the heaviest Mg isotope experimental accessible today. With the observed collapse of the N=28 neutron shell closure below 48Ca, 40Mg is expected to have a large static prolate deformation, and extends the “peninsula” of deformation reaching from N=20 to 28 in the Mg isotopes. In addition, valence neutrons are expected to occupy the low-l 1p3/2 state, and it is possible that the picture of 40Mg could be one of a well-deformed core surrounded by a neutron halo. With the convergence of effects relating to collective nuclear motion, single-particle effects, and potentially weak-binding, the structure of 40Mg provides a rare and important benchmark for nuclear theories extending to the dripline. I will present first spectroscopic results for 40Mg, populated following one proton knockout from a secondary radioactive ion beam of 41Al at RIBF, and using the DALI2 gamma-ray detector.

Speaker: Dr Heather Crawford (Lawrence Berkeley National Laboratory)

18 Exotic Neutron-rich Medium-mass Nuclei with Realistic Nuclear Force

The nuclear shell model provides a successful and unified description of both stable and unstable nuclei. Especially for the unstable nuclei, experimental information is less abundant than for stable ones, theoretical challenges play an ever increasing role. In this work, we will first report on the physics in so-called “island of inversion” with the model space of the sd+pf shell, and then move to the description of the shell structure of N=28,32,34 and 40 with the model space of pf+sdg shell. In both cases, it is crucial that the newly developed extended Kuo-Krenciglowa (EKK) theory of effective nucleon-nucleon interaction enables us to derive an interaction suitable for several major shells (sd + pf or pf + sdg in this case), unlike conventional Kuo-Krenciglowa (KK) theory. In the first half of this talk, we will present such an application to the island of inversion, including the cases where conventional approaches with fitted interactions encounter difficulties. By using such an effective interaction obtained from the Entem-Machleidt QCD-based χN3LO interaction and the Fujita-Miyazawa three-body force, the energies, E2 properties, and spectroscopic factors of low-lying states of neutron-rich Ne, Mg, and Si isotopes are nicely described, as the first shell-model description of the “island of inversion” without fit of the interaction. The long-standing question as to how particle-hole excitations occur across the sd-pf magic gap is clarified with distinct differences from the conventional approaches. The shell evolution is shown to appear similarly to earlier studies. In the second half, we need to incorporate the effective interaction for pf + sdg shell at least, to describe N=28,32,34 and 40 magic numbers in a unified manner. Starting from a fundamental nuclear force has a great advantage in this case, because too few experimental data are available to fit two-body matrix elements in such a large model space. We will present results of a large-scale calculation on Ca, Ti, Cr, Fe and Ni isotopes with a wide range of neutron number.

Speaker: Dr Naofumi Tsunoda (Center for Nuclear Study, the University of Tokyo)

Tuesday, 30 May

19 Recent Highlights From the Shores of the Island of Stability

The hunt for heavy element reached so far proton number 118. In 2016, the IUPAC/IUPAP Joined Working Party validated the discovery of the elements with the proton number 113,115, 117, and 118. Thus, these elements were named and received their place in the periodic table. Besides the search for new elements, the studies of the basic properties of the heaviest elements are of interest for nuclear physics, atomic physic and chemistry. New and improved experimental techniques provided excess to these properties. I will give an overview on the latest research highlights and a personal view on the future of the research field of the heaviest elements.

Speaker: Dr Julia Even (KVI-CART, University of Groningen)

20 Laser Spectroscopy of the Heaviest Elements

The study of the hyperfine structure and the isotope shifts of spectral lines enables properties of atomic nuclei to be obtained in a comprehensive and nuclear model-independent way. These properties include the spin, magnetic dipole and electric quadrupole moments, and changes in the mean-square charge radii. Hence, the establishment of such optical studies in the region of deformed nuclei around nobelium-254 would inevitably attract a high level of interest of both, nuclear physics and atomic physics communities. For atomic physics, for instance, already the observation of atomic transitions in these very heavy elements would provide a stringent test of atomic theories and models addressing relativistic and quantum electrodynamic effects. These studies, however, stagnated for many years at the element fermium for which weighable samples can still be obtained. Elements beyond fermium are challenging in this respect as they are solely produced in nuclear fusion reactions, best at rates of a few atoms per second when utilizing powerful particle accelerators. Only recently successful laser spectroscopy of nobelium in single atom-at-a-time quantities was reported [M. Laatiaoui et al., Nature, 538 (2016) 495]. Several atomic transitions in nobelium-254 were observed and characterized for the first time, providing valuable data and a powerful benchmark for atomic modelling. To this end, the so-called RAdiation Detected Resonance Ionization Spectroscopy (RADRIS) technique was employed. The fusion products of interest were separated from the primary beam and thermalized in a buffer-gas stopping cell. Those remaining in a positive charged state were accumulated on a catcher filament. Then, the accumulated atoms were evaporated from the filament, ionized in a two-step photoionization process by pulsed lasers and finally guided by suitable electric fields to a silicon detector where they were unambiguously identified via their unique radioactive decay fingerprint. The investigations were extended to the isotopes nobelium-253 and nobelium-252, which were produced at even lower rates than nobelium-254. Moreover, first steps towards laser spectroscopy of lawrencium-255 were initiated. In my talk, I will highlight the recent findings and give prospects for high-precision measurements using the in-jet laser ionization spectroscopy [R. Ferrer et al., accepted to Nat. Commun.] capable of resolving nuclear isomerism in atomic spectra of these heaviest radionuclides.

Speaker: Dr Mustapha Laatiaoui (KU Leuven)

21 Superheavy Element Studies at LBNL

Despite knowing about SHE for more than a decade, several important questions about these nuclei remain unanswered, including what are the atomic numbers, Z, and masses of these nuclei. Recently, our group has been working towards answering this intriguing question through one of three methods: (i) linking the SHE to known nuclides (ii) Z identification through observation of characteristic x-rays (iii) mass determination through mass analysis. This talk will review the progress that has been made for each of the three methods at LBNL and discuss possible avenues for the future. * This work was supported by the U.S. Department of Energy, Office of Science, Nuclear Physics, Low Energy Physics Program, through the Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231

Speaker: Jacklyn Gates (Lawrence Berkeley National Lab)

22 Influence of Fission on the Prospects for Discovering the Next New Element

The four elements that were officially named most recently were all discovered in so-called “warm fusion” reactions, where compound nuclei with excitation energies of ~40 MeV are produced. The key to these experiments has been the use of neutron-rich 48Ca projectiles, which produce nearly spherical compound nuclei when reacting with actinide targets. The relatively neutron-rich compound nuclei have relatively low neutron binding energies and relatively high probabilities of survival against fission. However, more recent experiments to produce new elements using heavier projectiles have not been successful. The cross sections for all of these reactions are extremely small, so recent work at Texas A&M University has studied the reactions of similar projectiles with lanthanide rather than actinide targets. Systematic variation of the projectile and target have allowed for variation of the capture cross section as well as the difference in neutron binging energy and fission barrier height. Excitation functions for the xn and pxn exit channels of a large number of projectile/target combinations have been measured using the MARS spectrometer. A simple theoretical model has been developed that allows for the estimation of the fission and particle emission probabilities from the compound nuclei. It adequately describes the cross sections of 48Ca-induced reactions using only the fission and neutron emission widths, but describing the cross sections of reactions induced by 44Ca and 45Sc projectiles requires the inclusion of the proton and alpha emission widths. Collective effects have been found to be significant, and are needed for accurate description of the cross sections. These results suggest that the discovery of new elements will largely be controlled by the ability of the compound nucleus to survive against fission. This talk will summarize the previous work, the most recent results using 40Ar and 44Ca projectiles, and the theoretical model. Additional remarks will be made on the prospect of using radioactive beams for heavy element synthesis.

Speaker: Prof. Charles Folden (Texas A&amp;M University)

10:40 Coffee Break

23 Nuclear Structure Studies far from Stability with Gamma-ray Spectroscopy

Far from the valley of beta stability, the nuclear shell structure undergoes important and substantial modifications. In medium-light nuclei, interesting changes have been observed such as the appearance of new magic numbers, and the development of new regions of deformation around nucleon numbers that are magic near stability. The observed changes help to shed light on specific terms of the effective nucleon-nucleon interaction and to improve our knowledge of the nuclear structure evolution towards the drip lines. In the last years, particular effort has been put from both the experimental and theoretical sides on the study of neutron-rich nuclei where these effects manifest more dramatically and their evolution can be followed along the isotopic and isotonic chains. Very interesting results have been obtained in proton-rich nuclei and in particular along the N=Z line. The most precise tool to study the excited nuclear states and their decay properties is high-resolution gamma-ray spectroscopy. Detailed nuclear structure information is becoming available with stable and radioactive beams by means of large gamma-ray spectrometers coupled to key complementary instrumentation that increases the selective power. A review of the recent experimental findings will be presented together with their theoretical interpretation.

Speaker: Prof. Silvia M. Lenzi (University of Padova and INFN, Padova, Italy)

24 Extending the Reach of ab Initio Nuclear Theory

A major goal of modern nuclear structure theory is to produce calculations with meaningful uncertainty estimates. Achieving this goal requires ab initio many-body methods which can employ realistic nuclear interactions and solve the Schrodinger equation with reliable precision. The past decade has witnessed a tremendous growth in the range of applicability of ab initio many-body methods, first in light nuclei, then to medium-mass closed shells, one or two particles or holes on top of closed-shells, and ground states of even-even nuclei. I will discuss recent developments in the valence-space in-medium similarity renormalization group method, which enable ab initio treatment of ground and excited states of essentially all nuclei up to mass number A~100.

Speaker: Dr Ragnar Stroberg (TRIUMF)

25 Proton and neutron-rich systems at and beyond the drip lines - from GSI to FAIR

In my presentation, I’d like to address experiments using unbound nuclei very far from the valley of stable nuclei, and exploring their extreme properties. The availability of intense secondary beams in conjunction with efficient detection setups allows for a production and study of the most extreme nuclear systems in terms of asymmetry of proton and neutron number in the continuum. Nuclei close to the drip-lines, exhibiting exotic properties themselves, are used as seeds for a subsequent production process in knockout reactions at relativistic energies. These nuclear systems challenge nuclear structure theory being open quantum systems far from the valley of beta stability as well as reaction theory while trying to describe their production mechanisms. The analysis of all particles in a kinematically overdetermined setup lead to the observation of energy and angular correlations as well as particular correlations within the different observables. The link to intrinsic properties of the unbound systems has to be explored by comparing properties of seed nuclei and to the experimental findings in the continuum. In my talk I will exemplify the above-mentioned methods, and present selected data on light systems from exotic Helium to Neon isotopes and show particular developments on the way to the upcoming FAIR facility.

Speaker: Dr Haik SIMON (GSI Helmholtzzentrum für Schwerionenforschung GmbH (GSI), Darmstadt, Germany)

26 Gamow-Teller Giant Resonances in 132Sn

The Gamow-Teller (GT) transition is one of the most basic excitation modes in nuclei, exhibiting a strong and highly repulsive collectivity as the so-called GT giant resonance (GTGR). The study of the GTGR is an essential step to elucidate the nuclear interactions and structures underlying the collectivity as well as to construct the nuclear models that can reliably describe phennomena whose behaviours are governed by nuclear spin-isospin responses such as weak-interaciton processes in astrophysical sites and double beta decay nuclei. Despite of these importances of the GTGR, the existing data are only limited to stable nuclei and there have been no data in nuclei far from the stablitity line. In this talk, the first experimetnal determination of the GT transition stregths from 132Sn to 132Sb, performed using the (p,n) reaction at RIKEN RIBF, will be presented with answers on the questions such as "the spin-isospin collectivity can be different, if one goes far from the stability line?", "most sophisticated nuclear models could reproduce the data". The speaker will also give an overview of the GT studies on nuclei that will be emergning at RIKEN RIBF in the near future.

Speaker: Dr Masaki Sasano (RIKEN Nishina Center)

12:40 Lunch Break

Breakout 1: Tuesday Before PM Coffee

27 Shape Coexistence in Gold, Mercury and Bismuth Isotopes Studied by In-source Laser Spectroscopy at RILIS-ISOLDE

The competition between spherical and deformed configurations at low energy gives rise to shape coexistence in the neutron-deficient isotopes around Z~82 and N~104 [1]. Along the isotope chain of a number of elements this leads to an abrupt change in the mean-square charge radius of the nuclear ground state when entering the neutron-deficient region. The most notorious case is the shape staggering in the Hg isotopes [2]. An extended experimental campaign to study the mean-square charge radii of the ground and isomeric states of these nuclides, and thereby investigating such regions of nuclear shape changes, is being conducted at ISOLDE by the RILIS-Windmill-ISOLTRAP collaboration. The measurements rely on the high sensitivity achieved by combining in-source laser resonance ionization spectroscopy, ISOLDE mass separation, the Windmill spectroscopy setup [3] and the Multi-Reflection Time-of-Flight (MR-ToF) mass separation technique [4]. In this contribution, we will present the systematics of charge radii and electromagnetic moments recently obtained at ISOLDE for the long isotopic chains of gold (IS534), mercury (IS598) and bismuth isotopes (IS608). For the lightest Au isotopes, a persistence of the strong deformation up to 180Au was demonstrated for the first time, followed by what we call a ‘jump back to sphericity’, whereby 176mg,177,179Au possess much lower deformation compared with strongly deformed 180-186Au. For the Hg chain, a termination of shape staggering and transition to more spherical shapes in the lightest 177-180Hg isotopes were deduced. A large odd-even shape staggering at 187-189Bi, similar to the well-known staggering in the Hg isotopes, was observed at the same neutron number. These three chains clearly demonstrate striking similarities in the shape staggering and shape changes when approaching the neutron mid-shell at N=104, while the lightest gold and mercury chains show the strong tendency towards the smooth nearly-spherical behavior. The data will be compared to mean-field based calculations and discussed within a generic shell-model approach for shape coexistence. References: [1] K. Heyde and J. Wood, Rev. Mod. Phys. 83, 1467 (2011). [2] J. Bonn, G. Huber, H.-J. Kluge, L. Kugler, and E. Otten, Phys. Lett. B 38, 308 (1972). [3] A.N. Andreyev et al,, Phys. Rev. Lett. 105, 252502,(2010). [4] R. N. Wolf et al., Nucl. Instr. and Meth. A 686, 82-90 (2012).

Speaker: Prof. Andrei Andreyev (Physics Department, University of York)

28 Charge radii of neutron-deficient 52,53Fe produced by projectile fragmentation

A kink at a nucleon shell closure in mean-square charge radii r2 along an isotopic chain is a distinct feature of charge radii [1], though the underlying mechanism still remains elusive. Such a feature is clearly visible in the Ca chain at the N = 28 neutron shell closure, which has been a major challenge for nuclear theory to understand [2]. In the present study, the r2 of 52,53Fe below N = 28 were determined [3] to investigate how the pattern of r2 around N = 28 changes when moving from semi-magic Ca to Fe isotopes, where the neutron-proton polarization effects are enhanced. The 52,53Fe beams were produced by fragmentation of a 160-MeV/nucleon 58Ni beam in a Be target at NSCL at MSU. The 52Fe or 53Fe beams were selected using the A1900 fragment separator [4], thermalized in a gas stopper [5], and extracted at an energy of 30 keV. The Fe+ beam was then transported to the BECOLA facility [6] and bunched-beam collinear laser spectroscopy was performed to measure atomic hyperfine structures (hfs). Ion beams of the transition-metal Fe are known to be notoriously difficult to produce at ISOL facilities due to long release times from thick targets. The novel scheme of in-flight separation followed by gas stopping was used in the present study for the first time for laser spectroscopy. This is a major step forward and complements such capabilities well established at ISOL facilities, where significant data on r2 have been obtained for selective elements [1]. The r2 of 52,53Fe were determined from the isotope shifts of the hfs. The multi-configuration Dirac-Fock method was used to calculate atomic factors. The obtained r2 of Fe exhibits a sharp kink at N = 28, which appears to have a similar structure to the Ca chain. The nuclear density functional theory was used to interpret the results. The underlying mechanisms of the kinks in r2 of Fe and Ca, as well as the experimental details, will be discussed. This work was supported in part by the NSF, the U.S. DOE, the German RF, the German MST, the Russian SF and the Russian FBR. [1] P. Campbell et al., Prog. Part. Nucl. Phys. 86, 127 (2016). [2] R. F. G. Ruiz et al., Nat. Phys. 12, 594 (2016). [3] K. Minamisono et al., Phys. Rev. Lett. 117, 252501 (2016). [4] D. J. Morrissey et al., Nucl. Instrum. Methods Phys. Res. B 204, 90 (2003). [5] K. Cooper et al., Nucl. Instrum. Meth. Phys. Res. A 763, 543 (2014). [6] K. Minamisono et al., Nucl. Instrum. Meth. Phys. Res. A 709, 85 (2013).

Speaker: Dr Kei Minamisono (NSCL/MSU)

29 Results of the First Physics Experiment with 132Xe and 208Pb Targets at the SCRIT Facility

Electron elastic scattering is a simple but very powerful tool to investigate the detailed internal structures of nuclei since it can measure the precise charge density distribution through the well-known electromagnetic interaction. Although the charge density distributions have been already measured for many stable nuclei by former electron scattering experiments, the method has yet to been applied to short-lived RIs since it has been technically difficult to realize a high luminosity (> 1027 cm-2s-1) for electron-RI scattering to complete the measurement within a reasonable experiment period of time. SCRIT (Self-Confining RI Ion Target) method is a novel and unique technique to realize such a high luminosity of the electron-RI scattering by trapping RI targets 3-dimensionally inside an electron storage ring (SR2) with a barrier potential applied by a SCRIT device and the electron beam potential itself. Following the success of the feasibility test of the SCRIT method, the construction of the SCRIT facility at RIKEN RIBF building has begun in 2008. The SCRIT facility consists of the SR2 with the SCRIT device, an ISOL system called ERIS (Electron-driven RI separator for SCRIT) which utilizes the photo-fission process of uranium to produce RIs, a race-track microtron which provides 150MeV electron beams to the SR2 and the ERIS, and SCRIT detectors to measure the angular cross-section of scattered electrons. At the SCRIT detectors, the angular distribution of scattered electrons is measured by WiSES (Window-frame Spectrometer for Electron Scattering), and the absolute luminosity of electron-RI scattering is obtained from the bremsstrahlung photons measured by LMon (Luminosity Monitor). After a decade of developments, the SCRIT facility has finally come to the stage of physics experiment. In 2015-2016 the first physics experiment has been performed using stable 132Xe and 208Pb targets with the electron beam energy of 150-300MeV. The SCRIT device has achieved a luminosity above 1027 cm-2s-1, and angular cross-sections of elastically scattered electrons have successfully been measured by the SCRIT detectors. In this contribution, we will present the results of the first physics experiment with 132Xe and 208Pb targets as well as the performances of the SCRIT device and detectors, then discuss some technical difficulties and on-going developments aiming at the world first electron scattering experiment with short-lived RI targets.

Speaker: Akitomo Enokizono (Rikkyo University)

30 About Possible Ambiguities From Alpha Spectroscopy and Direct Mass Measurements of Neutron-deficient Actinium and Radium Isotopes

Due to the two-body nature of the alpha decay, nuclear alpha spectroscopy has become one of the most relied upon techniques for accurate linking of nuclear masses. Based on a single nucleus of well-known mass serving as anchor point, masses of all mother and daughter nuclei that possess an alpha-decay channel can be determined precisely by the energy of the emitted alpha particles and, if present, subsequent gamma rays. However, the evaluation of masses from spectroscopic data can be influenced by presently unknown (especially low-lying) states in the alpha-daughters and also from complicated spectra that include a large number of isotopes at the same time. In such cases as, e.g., 150Ho in the 1990’s [1], direct mass measurements with high precision are desired for clarification. At the gas-filled recoil ion separator GARIS-II behind the RILAC accelerator at the RIKEN, the nuclides 210-214Ac have been produced by 169Tm(48Ca,xn)217-xAc and 210-214Ra by 169Tm(48Ca,pxn)217-xRa reactions. Direct mass measurements of these isotopes have so far been carried out only for 211,214Ra [2,3] by Penning-trap mass spectrometry at ISOLDE/CERN. The other isotopes have been investigated by alpha spectroscopy from the 1960’s on (see e.g. [4]) and more recently by alpha-gamma coincidence measurements performed at GSI (see e.g. [5,6]). Direct mass measurements of the eight simultaneously produced isotopes have been performed using a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) coupled to GARIS-II [7]. In this contribution the experimental results, which include six new direct mass measurements, will be presented. Among the new measurements, the existing data in a somewhat wider region of neutron-deficient heavy isotopes and possible future impact of direct mass measurements will be discussed in the context of the significant energy scales of collective effects in heavy nuclei. References: [1] D. Beck et al., Eur. Phys. J. A 8, 307 (2000) [2] C. Weber et al., Nucl. Phys. A 803, 1 (2008) [3] M. Kowalska et al., Eur. Phys. J. A 42, 351 (2009) [4] K. Valli et al., Phys. Rev. 167-4, 1094 (1968) [5] F.P. Heßberger et al., Eur. Phys. J. A 8, 521 (2000) [6] F.P. Heßberger, S. Hofmann, D. Ackermann, Eur. Phys. J. A 16, 365 (2000) [7] P. Schury et al., Nucl. Instrum. Meth. B 376, 425 (2015)

Speaker: Dr Marco Rosenbusch (RIKEN Nishina Center for Accelerator-Based Science)

31 Determining Quasifission Time-scales in Superheavy Element Formation Reactions

D.J. Hinde 1, M. Dasgupta 1, D.Y. Jeong 1, E. Prasad 1, C. Simenel1, H. David 2, Ch.E. Düllmann 2,3,4, J. Khuyagbaatar 2,3, A. Yakushev 2,3 1 Department of Nuclear Physics, ANU, Canberra, Australia; 2 GSI, Darmstadt, Germany; 3 Helmholtz-Institut Mainz, Germany; 4 University of Mainz, Germany. Quasifission competes strongly with fusion in reactions forming superheavy elements. The heaviest element that in practice can be created using a 48Ca beam is Z=118 (Oganesson), which has recently been formally approved and named. To form still heavier elements by fusion, use of heavier projectiles is necessary. In general it is understood that heavier projectiles such as 50Ti, 54Cr, 64Ni give lower yields of heavy elements than does 48Ca. In cold fusion, this seems to be associated with the magicity as well as the neutron-richness of 48Ca. Evidence is seen in both evaporation residue cross sections and fission characteristics. In the case of actinide (hot fusion) collisions, it is not clear whether it is the neutron-richness and low Z of 48Ca that has led to the successful synthesis of superheavy elements from 112 to 118, or whether its doubly-magic property is also critical. It is important to understand this question to reliably predict cross sections for reactions to create new superheavy elements in future. To address this issue, measurements of quasifission mass-angle distributions have been carried out very recently at the Australian National University. Projectiles of 48Ca, 50Ti, 54Cr, 58Fe and 64Ni bombarded (radioactive) targets of 249Cf, 248Cm, 244Pu, 238U and 232Th respectively. Fusion in each reaction forms Z=118 compound nuclei with similar masses A from 296 to 298. Beam energies from below-barrier to above-barrier have been measured. With an enhanced MWPC detector setup allowing c.m. angular coverage from 20 to 160 degrees, these new mass and angle data reveal the difference in the typical reaction timescale, and the associated mass evolution dynamics in these reactions. This new information is complementary to previous fission mass-energy distribution measurements, and throws light on the difference between cold fusion and hot fusion reaction dynamics.

Speaker: Prof. David Hinde (Australian National University)

32 First Direct Mass Measurements on Mendelevium with an MRTOF Mass Spectrograph

Precision mass measurements of unstable nuclei, providing direct measure of the nuclear binding energy, are invaluable for nuclear structure study and have potential for particle identification of atomic nuclide by the precision mass value. For trans-fermium nuclei, of importance for understanding the shell evolution in heavy nuclear system to inspect mass models toward so-called island of stability and the unique identification during new elements search, the mass measurements require fast measurement time even for such a heavy mass nuclei and high efficiency to tolerate extremely low production yields. Direct mass measurements of trans-fermium nuclei were, so far, performed for only 6 nuclei of nobelium and lawrencium with the Penning trap mass spectrometer SHIPTRAP [1,2]. Recently we implemented a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) located after a cryogenic helium gas cell coupled with the gas-filled recoil ion separator GARIS-II [3] and performed direct mass measurements of mendelevium isotopes for the first time. Using $^{48}$Ca beam on $^{\rm nat}$Tl target, we produced $^{249-251}$Md by fusion-evaporation reaction and successfully measured those masses including new masses of $^{249-250}$Md with sub-ppm precision. They were extracted as doubly charged atomic ions from the gas cell as well as other actinides such as nobelium and fermium. Combined with known alpha decay $Q$-value of $^{249-250}$Md, we could newly determine masses of isotopes on the decay chain from bohrium to berkelium. References: [1] M. Block {\it et al.}, Nature 463 (2010) 785 [2] E.M. Ramirez {\it et al.}, Science 337 (2012) 1207 [3] P. Schury {\it et al.}, Phys. Rev. C (accepted)

Speaker: Dr Yuta Ito (RIKEN Nishina Center)

33 Experiments Synthesizing Super-heavy Fl and Og Isotopes with Target Materials From ORNL Irradiated at JINR, Dubna

More than 50 super-heavy nuclei, which have been identified in fusion-evaporation reactions between 48Ca beams and actinide targets [1,2], form what is known as the ‘Hot Fusion Island’ - a part of the Island of Stability. Most of these nuclei have been discovered in experiments at the Dubna Gas Filled Recoil Separator (DGFRS), using actinide target materials produced at Oak Ridge National Laboratory[3]. These studies have been recently augmented by using a new highly segmented Si detector and digital detection system[4,5] commissioned by the ORNL-UTK team and implemented at the DGFRS. The system has robust analysis capabilities, especially for very short lived activities, and detection efficiency at high beam rate. The utility of this new system will be detailed by discussing the observation of heavy and super-heavy recoils and the subsequent alpha and/or spontaneous fission radiations. The measurement of several Th activities from the 48Ca + natYb calibration reaction will be shown including activities on the order of 1 μs. Spontaneous fission and alpha decay of heavy implants observed during irradiations of Pu and Cf targets will be shown. This includes the discovery of a new Flerovium isotope[5], recent observations of 294Og, as well as details of the experiment running through February 2017 which may attempt to synthesize a chain of alpha activities which would connect the ‘Hot Fusion Island’ to the ‘Nuclear Mainland’. References: [1] Yu. Ts. Oganessian, J. Phys. G: Nucl. Part. Phys. 34 (2007) R165. [2] Yu. Ts. Oganessian and V. K. Utyonkov, Rep. Prog. Phys. 78 (2015) 036301. [3] J.B. Roberto et. al. Nucl. Phys. A, 944 (2015) 99. [4] R. Grzywacz et al., Nucl. Instrum. Meth. Phys. Res. B 261(2007)1103. [5] V.K. Utyonkov, N.T. Brewer et al., Phys. Rev. C 92 (2015) 034609. *Supported by the U.S. DOE Office of Nuclear Physics under contracts DE-AC05-00R22725 (ORNL), DE-FG02-96ER40983 (UTK), DE-FG-05-88ER40407 (Vanderbilt) and DE-AC52-07NA27344 (LLNL), and Russian Foundation for Basic Research Grants, grants Nos. 13-02-12052 and 16-52-55002.

Speaker: Nathan Brewer (JINPA/ORNL/UTK)

34 The New Isotopes 240Es and 236Bk

The neutron-deficient 240Es nucleus was synthesized for the first time using the fusion-evaporation reaction 209Bi(34S,3n)240Es at the Accelerator Laboratory of University of Jyväskylä (JYFL), Finland. The gas-filled recoil separator RITU [1] was used to separate the fusion-evaporation products from the primary and scattered beam. The radioactive decays originating from 240Es and its daughters, including the hitherto unknown 236Bk, were measured with the focal plane spectrometer GREAT [2]. Identification of 240Es was made on the basis of recoil-alpha-alpha correlated chains ending with the known granddaughter 236Cm. A significantly high electron-capture delayed fission (ECDF) probability was measured for 240Es [3]. The new isotope 236Bk that was populated in the alpha decay of 240Es was identified by its ECDF branch [3]. These new data show a continuation of the exponential increase of ECDF probabilities in more neutron-deficient isotopes. The results on the decay properties of 240Es and 236Bk together with the data analysis will be presented. References: [1] M. Leino et al., Nucl. Inst. Meth. Phys. Res. B 99, 653 (1995) [2] R. D. Page et al, Nucl. Inst. Meth. Phys. Res. B 204, 634 (2003) [3] J. Konki et al., Phys. Lett. B 764, 265 (2017)

Speaker: Mr Joonas Konki (University of Jyväskylä)

Breakout 2: Tuesday Before PM Coffee

35 Understanding the Nature of the Low-energy Enhancement in the Photon Strength Function of 56Fe

The recent discovery of the low-energy enhancement in the photon strength function (PSF) of medium mass nuclei in the Fe and Mo region [1] has attracted great experimental and theoretical attention, as it may represent a new decay-mode [2]. The presence of an enhanced decay probability of low-energy gammas rays below the neutron threshold has the potential to greatly affect a broad range of applications including the astrophysical r-process and nuclear reactors [3-4]. Recent shell model calculations on 94Mo, 95Mo and 90Zr show that the enhancement could be due to a large B(M1) strength for low energy gamma-rays caused by orbital angular momentum recoupling of high-j orbits [5], while other mechanisms suggest an enhanced E1 strength [6]. A recent experiment designed to confirm the multipolarity and determine the electric or magnetic character of transitions in the region of the PSF enhancement in 56Fe was performed at ATLAS/ANL using GRETINA and the Phoswich Wall [7]. A 16 MeV proton beam was used to inelastically excite an 56Fe target to the quasicontinuum where it promptly decayed by gamma-ray emission. The PSF can be extracted using two-step cascades from the quasicontinuum to specific low-lying levels by a model independent method first employed in 95Mo [8]. This method is being extended to take advantage of GRETINA as a polarimeter to obtain angular and polarization information in the region of the low-energy enhancement of the PSF. Preliminary results will be discussed. References: [1] T. K. Eriksen, et al. Phys. Rev. C 90, 044311 (2014) [2] B.A. Brown and A.C. Larsen, Phys. Rev. Lett. 113, 252502 (2014) [3] M.B. Chadwick, et al. Nucl. Data Sheets 112 2887 (2011) [4] A.C. Larsen and S. Goriely, Phys. Rev. C 82, 014318 (2010) [5] R. Schwengner, S. Frauendorf, and A.C. Larsen, Phys. Rev. Lett. 111, 232504 (2013) [6] E. Litvinova and N. Belov, Phys. Rev. C 88, 031302(R) [7] D. G. Sarantites, et al. Nuclear Instruments and Methods A, 790, 42-55 (2015) [8] M. Wiedeking, et al. Phys. Rev. Lett. 108, 162503 (2012) This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contracts No. DE-AC02-05CH11231, DE-SC0014442, and No. DE-AC02-06CH11357. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.

Speaker: Dr Jones Michael (LBNL)

36 Ba-ion Extraction From High Pressure Xe Gas for Double-beta Decay Studies with nEXO

An RF-only ion funnel has been developed to efficiently extract single Ba ions from a high-pressure (10 bar) xenon gas into vacuum. Gas is injected into the funnel where ions are radially confined by an RF field while the neutral gas escapes. Residual gas flow alone (without any DC drag potential) transports the ions longitudinally through the funnel. In the downstream chamber the ions are captured by a sextupole ion guide and delivered to an ion detector. The xenon gas is captured by a cryopump and then recovered back into storage cylinders for future use. With the current setup ions were extracted from xenon gas of up to 10 bar and argon gas of up to 7.8 bar. These are the highest gas pressures ions have been extracted from so far. The ions were produced by a Gd-148 driven Ba-ion source or a Cf-252 fission source placed in the high pressure gas. The ion transmission has been studied in detail for various operating parameters. A mass spectrometer has been used for mass-to-charge identification of the extracted ions. This identification is being improved to further investigate the properties of the funnel and to measure the Ba-ion extraction efficiency of this setup. This approach of ion extraction is intended for application in a future large-scale Xe-136 neutrinoless double-beta decay (0nbb) experiment. The technique aims to extract the bb-decay product, Ba-136, from the xenon gas and detect it unambiguously and efficiently. This individual identification of the decay product allows for an ideally background-free measurement of 0nbb by vetoing naturally occurring backgrounds. This identification enables a higher level of sensitivity to the 0nbb decay half-life and thus is a more sensitive probe of the nature of the neutrino.

Speaker: Thomas Brunner (McGill and TRIUMF)

37 Charged-particle Spectroscopy with the Optical TPC

Nuclei far from stability with a large imbalance between the number of protons and neutrons exhibit characteristic decay modes which are still far from being fully explored, both experimentally and theoretically [1]. One of them is emission of beta-delayed charged particles, which occurs for nuclei close to the proton drip-line. In addition to single (beta p) and double (beta 2p) delayed protons known since long, other channels, like the recently observed delayed emission of three protons ( beta3p) become important. Delayed emission of charged particles has been also observed for very neutron-rich nuclei. Good understanding of such decays is necessary when the correct knowledge of beta strength distribution is demanded. Experimental investigations of exotic and rare decay channels require special instrumentation offering efficiency and sensitivity. An example of such an approach is the Optical Time Projection Chamber (OTPC) developed at the University of Warsaw. Designed with the specific goal to study two-proton radioactivity (2p), it proved to be an excellent tool for investigation of other decay channels accompanied by emission of charged particles. Among interesting results obtained with help of the OTPC, in addition to 2p spectroscopy [2,3], are the first observation of the beta 3p decay mode in three nuclei [4,5,6], a study of 6He decay into the alpha + d continuum [7], and a measurement of beta-delayed tritons from 8He [8]. In the talk I will give a short overview of the charged-particle spectroscopy of exotic and rare decay channels investigated with help of the OTPC detector. In more detail I will discuss the decays of 6He and 8He, as well as the most recent results obtained for decays of 26P and 27S. At the end I will sketch some ideas for future studies, including an ambitious search for beta-delayed protons emitted by 11Be. References: [1] M. Pfützner, M. Karny, L. Grigorenko, and K. Riisager, Rev. Mod. Phys. 84, 567 (2012). [2] K. Miernik et al., Phys. Rev. Lett. 99, 192501 (2007). [3] M. Pomorski et al., Phys. Rev. C 90, 014311 (2014). [4] K. Miernik et al., Phys. Rev. C 76, 041304(R) (2007). [5] M. Pomorski et al., Phys. Rev. C 83, 014306 (2011). [6] A.A. Lis et al., Phys. Rev. C 91, 064309 (2015). [7] M. Pfützner et al., Phys. Rev. C 92, 014316 (2015). [8] S. Mianowski et al., to be published.

Speaker: Prof. Marek Pfutzner (University of Warsaw)

38 Excursion Far Beyond the Proton Dripline Along Ar and Cl Isotopes

Nuclei beyond the proton drip line have been intensively investigated in recent years, and their structure exhibited exotic features that cannot be found in particle-stable nuclei. For instance, two-proton (2p) radioactivity of elements was discovered on 45Fe. In spite of the experimental advances, most 2p-decay precursors remain unexploited though their low-excitation spectrum is expected to be discrete. This naturally causes the question: How far beyond the driplines the nuclear structure phenomena fade and are completely replaced by continuum dynamics? In this talk, the first spectroscopic studies of the chains of 2p emitters 31,30,29Ar and their 1p-unbound subsystems 30,29,28Cl will be reported. The corresponding experiment is based on measurements of in-flight decays of the 2p emitters and tracking trajectories of their decay products by microstrip silicon detectors [1]. The lowest states in 30Ar and 29Cl point to a violation of isobaric symmetry in the structure of these unbound nuclei (i.e., the Thomas-Ehrmann shift). The 2p decay has been identified in a transition region between simultaneous 2p and sequential proton emissions from the 30Ar ground state, which is characterized by interplay of three-body and two-body decay mechanisms. Such a phenomenon, never observed before, is argued to be common in 2p-unbound nuclei and could be of interest for other disciplines dealing with few-body systems [2]. The spotted dramatic change of odd-even mass staggering in 2p-unbound nuclei calls for further systematic investigation. Systematic studies of the ground and excited states of unbound Ar and Cl isotopes have revealed that the Thomas-Ehrmann shifts are even larger for the 29Ar and 28Cl isotopes in comparison with 30Ar and 29Cl, respectively. Predictions for even more remote isotopes 28Ar and 27Cl are provided by using the elaborated models. For these isotopes, the Thomas-Ehrmann effect is expected to be less important, as their isobaric mirror partners are located near the neutron drip line. References: [1] I. Mukha et. al., Phys. Rev. Lett. 115 (2015) 202501. [2] T.A. Golubkova, X.-D. Xu, L.V. Grigorenko, I.G. Mukha, C. Scheidenberger and M.V. Zhukov, Phys. Lett. B 762, 263 (2016).

Speaker: Dr Ivan Mukha (Helmholzzentrum GSI)

39 Study of ⁶⁸Co Low-energy Structure via β Decay

The N = 40 subshell closure, which arises from the energy separation of the νpf shell and the νg9/2 single-particle state, has long been investigated for its impact on nearby neutron-rich nuclei. The fragility of this N = 40 subshell closure is highlighted by the sudden onset of collectivity as protons are removed from the νf7/2 single-particle state. Cross-shell excitations have been used to describe the observation of shape coexistence between spherical and prolate-deformed configurations. Within the neutron-rich odd-A Co isotopes, shape coexistence is supported through the identification of a (1/2⁻) shape isomer found at low energies alongside higher-spin states associated with the normal-order configurations. For ⁶⁸Co, a recent paper on a β-decay study at the National Superconducting Cyclotron Laboratory (NSCL) [1] concluded that the lowest-energy state can be attributed to a deformed configuration, further extending the presence of shape coexistence to this nucleus. This work reports on ⁶⁸Co as determined from the analysis of new data from NSCL utilizing the selectivity of low-spin β decay from ⁶⁸Fe to populate ⁶⁸Co. An expanded description of the low-lying structure of ⁶⁸Co will be presented. This work was supported in part by the National Science Foundation (NSF) under Contract No. PHY-1102511 (NSCL) and Grant No. PHY-1350234 (CAREER), by the Department of Energy National Nuclear Security Administration (NNSA) under Grant No. DE-NA0002132 and Award No. DE-NA0003221 and through the Nuclear Science and Security Consortium under Award No’s DE-NA0000979 and DE-NA0003180, by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC-06CH11357 (ANL) and Grant No’s. DE-FG02-94ER40834 (UM) and DE-FG02-96ER40983 (UT), and by the U.S. Army Research Laboratory under Cooperative Agreement W911NF-12-2-0019. References: [1] S.N. Liddick et al., Phys. Rev. C 85, 014328 (2012).

Speaker: Dr B.P. Crider (NSCL / MSU)

40 Shape Coexistence in the 78Ni Region: Intruder Second 0+ State in 80Ge

The coexistence of normal and intruder nuclear states close in energy is a characteristic feature of nuclear structure [1]. The lowering in energy of states originating from excitations across the shell closures is a delicate balance between the energy cost to break the shell gap, and the gain in pairing and quadrupole energy. A region of great interest for these studies is the N = 50 isotonic chain, down to 78Ni. On the one hand, the size and reduction of the N = 50 gap in exotic nuclei are a much debated issue, impossible to reproduce with two-body forces from first principles. On the other hand, the presence of the g9/2 d5/2, s1/2 neutron shells across the gap determines a large quadrupole interaction. Therefore, the search for excited 0+ states from two-particle two-hole (2p - 2h) excitations in the region can help to set benchmarks for nuclear models in the region. The N = 48 80Ge nucleus was studied by means of beta-delayed electron-conversion spectroscopy at ALTO [2]. The radioactive 80Ga beam was produced through the ISOL photofission technique and collected on a movable tape for the measurement of and e- emission following decay. An electric monopole E0 transition which points to an intruder second 0+ state was observed for the first time. This new 639 keV state is lower than the first 2+ level in 80Ge (659 keV), and provides evidence of shape coexistence close to 78Ni. This result will be compared with theoretical estimates, helping to explain the role of monopole and quadrupole forces in the weakening of the N = 50 gap at Z = 32. The evolution of intruder 0+ states towards 78Ni will be discussed. It will also be pointed out how these and other findings [3] may hint to a "s1/2 physics" in this region, and how this relates to recent measurements of unexpected high-energy gamma radiation following beta decay beyond N=50 [3]. References: [1] K. Heyde and J. L. Wood, Rev. Mod. Phys. 83, 1467 (2011) [2] A. Gottardo et al., Phys. Rev. Lett. 116, 182501 (2016) [3] X. F. Yang et al., Phys. Rev. Lett. 116, 182502 (2016) [4] A. Gottardo et al., submitted for publication (2017)

Speaker: Dr Andrea Gottardo (Institut de Physique Nucléaire d'Orsay - IPN / LPSC Grenoble)

41 Search for the Neutron Dripline for Fluorine and Neon Isotopes

Particle-bound isotopes along the neutron dripline have been searched for fluorine (Z = 9) and neon (Z = 10) isotopes at the RIKEN RI Beam Factory (RIBF) by using projectile fragmentation of an intense 48Ca beam at 345 MeV/nucleon and the large-acceptance fragment separator BigRIPS. Observation of null counts for 32F, 33F and 35Ne, 36Ne isotopes and comparison with their expected production yields have showed that existence of particle-stable states of these isotopes is excluded with high confidence levels. It is thus found that the most neutron-rich isotopes 31F and 34Ne previously observed are the heaviest of these isotopes. The confirmed neutron driplines have thus been extended for the first time since nearly 20 years ago, in which the 24O isotope was confirmed to be on the dripline of oxygen (Z = 8) isotopes. The present determination of neutron driplines will provide keys to understand the nuclear stability at extremely neutron-rich conditions.

Speaker: Prof. Toshiyuki Kubo (FRIB/NSCL, Michigan State University)

42 The AME2016 Atomic Mass Evaluation

The Atomic Mass Evaluation (AME) has been serving the research community with the most reliable source for comprehensive information related to the atomic masses since 1950s. It provides the best values for the atomic masses and their associated uncertainties by evaluating all available experimental data from nuclear reactions, radioactive decays and direct mass measurements using a weighted, least-squares method approach. The last atomic mass evaluation, AME2012, was published in December 2012 [1,2] and the main aspects of AME2012 have been presented at the last ARIS conference [3]. Since the publication of AME2012, the experimental knowledge of atomic masses has been continuously expanding along two main directions, including: measurements aimed at high-precision mass values and at the most exotic nuclei far from the stability. The AME2016 will be published in March, 2017. At this conference, the AME2016 will be presented and compared with the previous AME2012 evaluation. The impact of new mass measurements will be reviewed and discussed. References: [1] G. Audi, M. Wang, A.H. Wapstra, F.G. Kondev, M. MacCormick, X. Xu, B. Pfeiffer, Chinese Physics C, Vol. 32, (2012) 1287-1602. [2] M. Wang, G. Audi, A.H. Wapstra, F.G. Kondev, M. MacCormick, X. Xu, B. Pfeiffer, Chinese Physics C, Vol. 32, (2012) 1603-2014. [3] M. Wang, G. Audi, F.G. Kondev, M. MacCormick, X. Xu, JPS Conference Proceedings, V6 (2015)010001.

Speaker: Dr Meng Wang (Institute of Modern Physics, Chinese Academy of Sciences)

15:45 Coffee Break

Breakout 1: Tuesday After PM Coffee

43 Monopole and Dipole Transitions in Light Nuclei

Cluster structures have been found in light unstable nuclei as well as stable nuclei. For instance, neutron-rich Be isotopes show remarkable cluster structures of a 2 alpha core with surrounding excess neutrons. For C isotopes, three-body cluster structures in excited states have been suggested and attracting a great interest. How can we experimentally probe such the cluster structures ? For the ground states, it is useful tool to measure charge radii along an isotope chain because they reflect the cluster development though the proton distribution. For excited states, monopole and dipole excitations, which are measured by inelastic scatterings, can be useful approaches. Low-energy isoscalar(IS) and isovector(IV) strengths separated from the giant resonances appear originating in new collective modes such as cluster modes and valence neutron modes, respectively. Our aim is to clarify the natures of low-energy ISM, ISD, IVD strengths and understand the mechanism of the separation of low-energy strengths from the GR strengths. For this aim, we apply a newly-developed method, the shifted base AMD, and combine it with the cluster GCM. The framework can describe the GR modes given by the coherent 1p-1h excitations as well as the large amplitude cluster modes. Applications to 9Be and 10Be and that to 12C are reported. In 9Be and 10Be, the IVGDR in E > 20 MeV shows a two peak structure because of the dipole excitation in the 2-alpha core with the prolate deformation, whereas the low-energy E1 resonances appear in E < 20 MeV exhausting 20% of the TRK sum rule. The 1- resonance at E~15 MeV in 10Be has a 6He+alpha cluster structure and shows the remarkable E1 strength because of coherent contribution of two valence neutrons. The calculated E1 strengths reasonably describe the experimental photonuclear cross sections. We also investigate the ISM and ISV strengths in 12C and discuss the remarkable low-energy strengths for cluster states separating from the GR strengths. We show that the monopole and dipole excitations are good probes to pin down the cluster structures in the excited states.

Speaker: Prof. Yoshiko Kanada-En'yo (Department of Physics, Kyoto University)

44 A Hybrid Configuration Mixing Model for the Low-lying States of Unstable Nuclei

We have recently introduced a new approach, which is meant to be a step towards complete low-lying spectroscopy of odd-mass nuclei. In the first applications, we have limited ourselves to a magic core plus an extra neutron or proton. The model does not contain any free adjustable parameter, but is based on a Hartree Fock (HF) description of particle states and Random Phase Approximation (RPA) calculations for core excitations: the coupling between these states is treated self-consistently and the resulting Hamiltonian is solved exactly. The model is an extension of previous Particle-Vibration Coupling (PVC) calculations. However, at variance with these, it also includes the coupling with non-collective core excitations and can also describe states of shell-model type like 2 particle-1 hole. The underlying spirit is of course related to filling the gap between shell model-like approaches for low-lying spectroscopy, and the traditional HF+RPA approach to high-lying states like giant resonances. At present, we apply this model by using Skyrme functionals. We shall discuss the results for neutron-rich nuclei in the Ca region and around 132Sn. In these cases the agreement with existing experimental data is generally good. We shall also demonstrate the usefulness of such a model for low-lying spectroscopy of more neutron-rich, weakly bound systems.

Speaker: Gianluca Colò (University of Milano and INFN)

45 Quantifying Uncertainties for Optical Model Parameters and Cross Sections

While uncertainty quantification has been applied to many fields within nuclear theory, it is still relatively unstudied in reaction theory. There are many sources of these uncertainties, including but not limited to the effective potentials used, model approximations and simplifications, and structure functions. Many of these have been investigated [1], however, they have not been systematically studied. For instance, the uncertainties from optical model parameterizations are often calculated by computing the difference between the cross sections that result from two parameterizations used within the same reaction framework. Although this gives a relative error between the two, it does not give a systematic way to quantify the uncertainty from a given parameterization. To begin to quantify the uncertainties coming from these optical model parameterizations, chi-square fitting to elastic scattering data is used to constrain the depth, radius, and diffuseness of each term in the optical model potential. From these fits, 95% confidence bands can be constructed around cross-section calculations from the best-fit parameterizations. Correlations between the parameters can also be explored. Correlations within the model itself can be taken into account using a correlated chi-square fitting function, which produces lower chi-square values, larger confidence bands, and a more physical description of the data. We will discuss results from this process as applied to 12C-d elastic scattering and transfer, as well as 45Fe-n elastic and inelastic scattering. [2] This fitting procedure, however, only explores the parameter space around a given minimum and does not provide a way to include knowledge about the physical constraints on the parameters. As an alternative, a Bayesian analysis can be performed, using a Markov Chain Monte Carlo to explore the parameter space – constrained by the elastic scattering data and physical limits on the optical model parameters. Results from this first exploration will be shown, along with comparisons to the chi-square fitting procedure. Finally, possible future developments will be discussed. References: [1] A.E. Lovell and F.M. Nunes, J. Phys. G: Nucl. Part. Phys. 42 034014 (2015) [2] A.E. Lovell, F.M. Nunes, J. Sarich, and S.M. Wild, arXiv:1611.05126v1 [nucl-th] 4 Nov 2016

Speaker: Amy Lovell (MSU/NSCL)

46 Time-dependent Description Nuclear Collisions and Infinite Nucleonic Systems

Time-dependent nuclear density functional theory (TDDFT) is a tool of choice for describing heavy ion collisions. Here we present a study of nuclear focusing on the aspect of nucleonic clustering in the intermediate states. To visualize emergent clusters, we use the nucleonic localization function, which is based on the probability of finding two nuclei with same spin and isospin at a given point. This measure was shown to be an excellent indicator for clustering in time-independent DFT calculations. We show that the TDDFT solutions exhibit strong clustering especially in the collision of light nuclei. The nucleonic localization is also an excellent measure of clustering in time-dependent simulations and gives important insights into the reaction mechanism. TDDFT can also be used to describe infinite systems such as nuclear pasta, which is present in the inner crust of neutron stars. Here we study the time-dependent modes of nuclear rods. To reduce finite-volume effects, we utilize the twist-averaged boundary conditions (TABC). We show that only with the help of TABC we can extract important information pertaining to the inner crust of neutron stars.

Speaker: Dr Bastian Schuetrumpf (NSCL / Michigan State University)

47 Challenges in Describing Near-Barrier Fusion: Pinning Down the Interplay of Breakup, Transfer and Fusion

Understanding the interactions of weakly bound nuclei, and their reaction outcomes, is a key challenge in nuclear reactions research. Apart from the well-known channel coupling effects, reaction dynamics involving weakly-bound nuclei has added complexity due the presence of low-lying particle unbound states, not just in the interacting nuclei but also in neighboring nuclei that are populated following nucleon transfer. Currently there is no theoretical model to describe all the modes of breakup (particularly transfer-triggered breakup) and their effect on fusion. Thus, experimental observations play a crucial role in formulating theoretical models of near-barrier reaction dynamics. The findings of suppression of above barrier complete fusion, first observed using weakly bound stable beams, and later for light radioactive beams, led to idea that the suppression is caused by breakup of the projectile before reaching the fusion barrier. This idea was tested recently using a large angular acceptance detector array to measure coincident charged fragments following breakup of weakly bound stable beams on a wide range of targets. A recently developed classical model was combined with new experimental observables to separate breakup that occurs in the incoming trajectory from that in the outgoing trajectory. This separation proved crucial as it shows that breakup prior to reaching the barrier is insufficient to explain the observed suppression of complete fusion. Thus some other mechanism must also be contributing to suppression of complete fusion. These new measurements will be presented and possible mechanisms that can cause reduction in fusion will be discussed. The latter will draw on similarities observed in experiments with well-bound nuclei where transfer to highly excited states is being investigated as a possible doorway to energy dissipation that can reduce complete fusion cross sections. These emerging ideas built on recent experiments serve as pointers to the development of new models.

Speaker: Prof. M. Dasgupta (Australian National University)

48 Mass Measurements of Neutron-rich Rare-earth Isotopes

The rapid neutron capture process (r process) is thought to be responsible for the production of roughly half of the heavy elements found in nature, however the site of the r process is unknown and remains one of the most active areas of research in nuclear astrophysics. Testing r-process predictions requires experimental nuclear data inputs including masses, beta-decay properties, and neutron-capture rates. A recent study [1] has posited a link between the formation of the rare-earth peak near N = 100 and an array of potential r-process sites, but there is currently little available nuclear data in this region. As current RIB facilities improve and next-generation facilities come online, the opportunity to test such r-process calculations and inspire others is quickly growing. One such facility is CARIBU, located at Argonne National Laboratory, where intense beams of neutron-rich isotopes are produced from the spontaneous fission of 252Cf. The recent commissioning of a MR-TOF at CARIBU provides highly mass-resolved (R>50,000) beams to the low-energy experimental area where the Canadian Penning Trap mass spectrometer (CPT) is housed. A major upgrade to the detector system at the CPT has been made in order to implement the contemporary Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) mass measurement technique [2], which has allowed us to probe further from stability than was previously possible. PI-ICR is intrinsically more efficient than other Penning trap mass measurement schemes and offers increased sensitivity to more weakly produced isotopes without loss in precision. Buoyed by the MR-TOF, this new technique has been used to determine the masses of a number of previously unmeasured rare-earth nuclides around A~160 in the past year. The benefits of PI-ICR and the astrophysical implications of the newly measured masses will be discussed. References: [1] M. Mumpower et al., ApJ, 833, 282, 2016 [2] S. Eliseev et al., Phys. Rev. Lett. 110, 082501, 2013 [3] T.Y. Hirsh et al., Nucl. Instr. Meth. Phys. Res. B, 376, 229, 2016 This work was supported by the following: NSERC SAPPJ-2015-034, NSF grants PHY-1419765 and PHY-14330152, and the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.

Speaker: Rodney Orford (McGill University)

49 Precision Mass Measurements of Neutron-rich In Isotopes Relevant to r-process Calculations

Mass measurements of nuclei far from stability provide an important input to nuclear structure studies and simulations of the rapid-neutron capture process (r-process), the proposed mechanism by which many of the elements heavier than iron are created. Since the exact astrophysical site of this process is still under debate, the route by which the chain of neutron captures, photodissociations and beta decays proceeds through the nuclear chart is uncertain, and sensitive to the model inputs. Precise neutron separation energies, derived from mass measurements, are particularly important for the calculation of elemental abundances predicted by various r-process scenarios. The TITAN experiment at TRIUMF has recently measured the masses of the ground and isomeric states of the neutron-rich indium isotopes A=125-130 using the time-of-flight ion cyclotron resonance technique in a precision Penning trap. Isotopes near neutron shell closures, such as $^{125-130}$In, are particularly important for r-process calculations. At these points, the rate of neutron capture slows, resulting in experimentally observed abundance peaks. The indium isotopes presented here lead up to the N=82 shell closure at $^{131}$In, and their mass uncertainties are critical for predictions of the A=130 abundance peak. They also present a significant improvement in precision over previous measurements, from which only $^{129}$In/$^{129m}$In were well known. This increase in precision will feedback into r-process calculations and mass models, leading to improved future predictions. The significance of these new high-precision mass measurements for elemental abundance predictions will be discussed, as well as the implications for nuclear structure, based on comparisons to theory.

Speaker: Dr Carla Babcock (TRIUMF)

50 Informing Neutron Capture on Tin Isotopes in r-process Freeze Out

About half of the elements heavier than iron are formed in rapid neutron capture, r-process nucleosynthesis. Mumpower, Surman, McLaughlin, and Aprahamian [1] have identified unknown nuclear observables that can significantly impact final abundances and could also help to constrain the site of the r process. One of these observables are neutron capture rates at late times, freeze-out, in an r-process event, in particular on the N<82 isotopes of tin. To determine spectroscopic strengths and inform neutron capture rates, the (d,p) reactions were measured in inverse kinematics with radioactive 126,128,130,132Sn and stable 124Sn beams at the Holifield Radioactive Ion Beam Facility. Reaction protons were measured with SuperORRUBA highly segmented silicon strip detectors. The experimental differential cross sections were analyzed in the Finite-Range ADiabatic Wave Approximation framework [2] with Koning-Delaroche global optical model parameters to deduce neutron spectroscopic factors that were then used to calculate the direct-semi-direct (DSD) neutron capture cross sections with the CUPIDO code [3]. The present DSD cross sections are lower than those calculated by Chiba et al. [4] before the excitation energies and spectroscopic factors of 1/2- and 3/2- states in neutron-rich Sn isotopes had been measured, and significantly lower than the (n,γ) cross sections from statistical processes expected for N<82 tin isotopes. To understand the statistical contribution to the (n,γ) rate requires a valid surrogate and techniques that can exploit radioactive ion beams. The (d,pγ) reaction has recently been validated as such a surrogate [5] and the Gammasphere-ORRUBA setup [6] is well-suited for such measurements in inverse kinematics. The present talk would present the DSD results for neutron-rich Sn isotopes and the prospects for deducing the statistical component of neutron capture near the r-process path. This work by the ORRUBA collaboration is in supported in part by the U.S. Department of Energy and National Science Foundation. [1] M.R. Mumpower, R. Surman, G.C. McLaughlin, A. Aprahamian, Prog. Part. Nucl. Phys. 86, 86 (2016). [2] N.B. Nguyen, F.M. Nunes and R.C. Johnson, Phys. Rev. C 82, 014611 (2010). [3] G. Arbanas, F.S. Dietrich, A.K. Kerman, Perspectives on Nuclear Data for the Next Decade, p. 105 (2005). [4] S. Chiba et al., Phys. Rev. C 77, 015809 (2008) [5] A. Ratkiewicz et al., to be published [6] S.D. Pain et al., to be published.

Speaker: Prof. Jolie Cizewski (Rutgers University)

51 Measurement of 21Na(α,p)24Mg Cross Section for the Study of 44Ti Production in Supernovae

While core collapse supernovae have long captured the attention of physicists and astronomers, surprisingly little is currently known about the nature of the explosion mechanism. This is due to the complexity of the explosion, the large computational requirements for even 2D simulations, and the lack of precise nuclear physics inputs to these models. One of the few methods by which this explosion mechanism might be studied is through a comparison of the amount of 44Ti observed by space based γ-ray telescopes and the amount predicted to have been generated during the explosion. For these comparisons between observations and models to be made, however, more precise nuclear physics inputs are required. The reaction 21Na(α,p)24Mg has been identified as one of the key reactions affecting the 44Ti mass fraction by factors of 10 or more. There are currently no published data on this reaction. A direct experimental measurement of the 21Na(α,p)24Mg cross section has been carried out at TRIUMF, Canada. This experiment utilised the TUDA facility at ISAC-I. The 21Na radioactive beam, at high intensity, impinged on a 2cm wide gas target, containing 100 torr of 4He. A downstream silicon array, consisting of a dE-E telescope, detected the reaction protons. An upstream silicon array measured beam back-scattered from a Au foil located at the entrance of the gas target, for normalisation. Data were collected at four laboratory energies covering Ecm=3.2-2.5 MeV, which is approximately the top half of the 2GK Gamow Window. Preliminary analysis results will be presented, along with details of the experimental challenges encountered and the steps taken to overcome them.

Speaker: Dr Alison Laird (University of York)

Breakout 2: Tuesday After PM Coffee

52 Shape Evolution in Neutron-rich Kr Isotopes Beyond N=60: First Spectroscopy of 98,100Kr

Across the nuclear chart, some of the most drastic known shape transitions appear in the A~100 region at N=60 for neutron-rich Zr and Sr isotopes [1,2]. Such a sudden rearrangement of a whole nucleus only adding a couple of nucleons is a peculiar feature of the nuclear system highlighting the subtle interplay between collective and microscopic degrees of freedom. Transitional regions where this phenomenon happens are thus preferential areas to be mapped experimentally. Neutron-rich Kr isotopes are especially interesting in this respect since this sudden increase of collectivity at N=60, like in the Zr and Sr chains, was not observed for 96Kr [3]. Instead, a smooth reduction of E(2+1) and rise of B(E2,0+->2+) excitation strength suggest a gradual development of collectivity. Mass measurements of 96Kr, and 98,100Rb isotopes together with charge radii studies also emphasized that this abrupt shape transition at N=60 extends down to Z=37 and not to Z=36 in 96Kr but could not rule out that such a transition is not shifted to higher neutron numbers [4, 5]. To explore and delineate the boundaries of this nuclear shape transition region [4], we performed the first in-flight γ-ray spectroscopy of very neutron-rich 98,100Kr nuclei during the 2015 SEASTAR campaign using (p,2p) direct reactions from 99,101Rb isotopes at 266 and 257 MeV/u respectively. Thanks to the state-of-the-art combination of the RIBF facility, a 100-mm thick liquid hydrogen target and the MINOS+DALI2 setup, we identified their 2+ states but also additional low-lying states in 98Kr providing the first experimental evidence of the lowering in energy of an excited configuration coexisting with the ground-state one. These new experimental results will be discussed and compared to beyond mean-field calculations [6,7], which link them to the coexistence of oblate and prolate configurations at low energy. Interesting differences on how these configurations are predicted to order and mix around 98,100Kr will be described since they call for future experimental and theoretical benchmarks in the region. References: [1] S. A. E. Johansson, NP 64, 147 (1965). [2] K. Heyde and J. L. Wood, RMP 83, 1467 (2011). [3] M. Albers et al., PRL 108, 062701 (2012). [4] S. Naimi et al., PRL 105, 032502 (2010). [5] V. Manea et al., PRC 88, 054322 (2013). [6] T. R. Rodriguez, PRC 90, 034306 (2014). [7] J.-P. Delaroche, PRC 81, 014303 (2010).

Speaker: Dr Freddy Flavigny (IPN Orsay)

53 Collectivity in the Vicinity of 78Ni: Coulomb Excitation of Neutron-rich Zn at HIE-ISOLDE

Nuclei in the vicinity of 78Ni have recently been in focus of many experimental and theoretical investigations. In particular, the neutron-rich Zn isotopes, only two protons above the Ni isotopic chain, are ideally suited to study the evolution of the Z = 28 proton shell gap, and the stability of the N = 50 neutron shell gap. In the last decade, several experiments were performed to study the collectivity in the even-even Zn isotopes between N = 40 and N = 50 [1-4], but their results are not consistent; consequently, the evolution of nuclear structure in the neutron-rich Zn nuclei is not fully understood. The ISOLDE facility finished in 2016 the first phase of a major upgrade in terms of the energy of post-accelerated exotic beams bringing it up from 3 MeV/u to 5.5 MeV/u. The increased beam energy strongly enhances the probability of multi-step Coulomb excitation, giving experimental access to new excited states and bringing in-depth information on their structure. The very first HIE-ISOLDE beam experiment in October 2015 and its continuation in 2016 have been dedicated to the study of the evolution of the nuclear structure along the zinc isotopic chain. The preliminary results discriminate between the two experimental values of B(E2; 4+ → 2+) in 74Zn, and yield for the first time a B(E2; 4+ → 2+) value in 78Zn. [1] J. Van de Walle, et al. Phys. Rev. Lett. 99 14501 (2007). [2] J. Van de Walle, et al. Phys. Rev. C, 79:014309 (2009). [3] M. Niikura et al., Phys. Rev. C 85 054321 (2012). [4] C. Louchart, et al. Phys. Rev. C, 87:054302 (2013).

Speaker: Prof. Piet Van Duppen (KU Leuven - IKS)

54 Shape Coexistence in Neutron-rich Odd-mass S Isotopes

Collective motions in atomic nuclei such as rotation and vibration have been characterized by the ground-state shape as a single basis. This picture can be altered in exotic nuclei with unusual proton-to-neutron ratios if the nuclear shape changes drastically at low excitation energies. The phenomena of shape coexistence occur when two or more states with distinct shapes exist in a nucleus within a narrow energy range. Recently there has been an increasing interest for shape coexistence phenomena in neutron-rich S isotopes. Previous studies suggested that the N=28 shell gap is weakened in the neutron-rich region inducing strong competition among different configurations as well as fairly large collectivity in 40,42,44S isotopes. Therefore it is important to address the question as to how shape coexistence manifests itself and persists in neutron-rich odd-mass S isotopes in the vicinity of N = 28. Model-independent lifetime measurements of the 43,45S excited states were performed by applying the Recoil Distance Method with the TRIPLEX Plunger in conjunction with GRETINA to fast rare isotope beams at the NSCL. We will discuss the search for isomeric or long-lived states in 45S and attempt to fully characterize the band structure of the low-lying states in 43S, which provide key information to establish a comprehensive picture of the shape coexistence in this region.

Speaker: Dr Tea Mijatovic (NSCL)

55 Collectivity Along N=50: The Neutron-magic 92Mo and 94Ru

The 100Sn nucleus, being the heaviest bound doubly-magic nucleus with equal number of protons and neutrons, has attracted considerable interest from the experimental as well as theoretical point of view. In particular, the structure of this nucleus and its neighbours are excellent benchmark cases to test state-of-the-art shell-model calculations in the region. Such models, predict an inversion of the B(E2;4+->2+) trend towards the complete occupation of the g9/2 orbital -thus towards 100Sn-, owing to an increasing pairing-strength along the N=50 isotones [1], differently to what has been observed for the neutron-rich Z=28 isotopes, where neutrons occupy the same orbitals. To test experimentally this phenomenon, the AGATA gamma array, installed recently at the GANIL laboratory, has been used, in combination with the IKP Cologne plunger [2], with the aim to measure the reduced transition probabilities for the 4+->2+ and 2+->0+ yrast transitions in 94Ru and 92Mo nuclei. The multi-nucleon transfer (MNT) reaction mechanism has been unconventionally [3] used to populate the proton rich nuclei of interest. Contrary to fusion evaporation, MNT reactions allow, to populate directly medium to low angular momentum states, even in presence of isomers, thus, allowing the direct determination of the lifetimes. In this experiment, a 92Mo beam with an energy of 716.9 MeV impinged in the stretched 92Mo target of the Plunger, while a 24Mg foil was used to degrade the energy of the reaction products. The reaction products of interest were identified with the magnetic spectrometer VAMOS++ [4], while the gamma-ray in coincidence were measured using AGATA [5]. Preliminary results on the obtained lifetimes and reduced transition probabilities for the 4 +->2 + and 2 +->0 + yrast transitions in 94 Ru and 92Mo will be shown. In this contribution these results will be interpreted on the basis of shell model predictions, allowing also for the comparison of the nuclear structure trends between the valence mirror symmetry partners 56-78Ni Z=28 isotopes and 78Ni-100Sn N=50 isotonic chain. References: [1] A.F. Lisetsky et al. PRC 70, 044314 2004 [2] A. Dewald et al., Prog. Part. Nucl. Phys. 67, 786 (2012) [3] R. Broda et al. PLB 251 (90) 245 [4] M. Rejmund, et al., Nucl. Instr. and Methods in Phys. Res. A 646 (1) (2011) 184 [5] S. Akkoyun, et al., Nucl. Instr. and Methods in Phys. Res. A 668 (2012) 26

Speaker: Rosa María Pérez Vidal (Instituto de Física Corpuscular, CSIC-Universitat de València)

56 Gamma-spectroscopy of Neutron-rich $^{79}$Cu Through Proton Knockout

Nuclear shell structure is evolving when going into more and more exotic regions. As a consequence, the conventional magic numbers can be different far from stability. Over the last years, the RIB factory at RIKEN has become available, providing primary beam of uranium with intensities that are now sufficient for gamma spectroscopy of neutron-rich copper isotopes next to $^{78}$Ni ($Z=28$, $N=50$). We shall present the results of the in-beam spectroscopy of $^{79}$Cu (N=50), produced through the $^{80}$Zn(p,2p)$^{79}$Cu knockout reaction at RIKEN. A $^{238}$U beam, with an energy of 345 MeV/nucleon, was sent on a $^{9}$Be target, creating a cocktail of radioactive isotopes. These isotopes went through the BigRIPS spectrometer, for identification and selection, and reached MINOS [1], a liquid-hydrogen target surrounded by a TPC used for proton tracking, where the knock-out reactions took place. The isotopes produced went through the ZeroDegree spectrometer for identification. The DALI2 scintillator array was surrounding MINOS for $\gamma$-ray detection. $\gamma$-$\gamma$ coincidences permitted to build the first level scheme of $^{79}$Cu, with levels up to 4.6 MeV, and the results were compared to Monte-Carlo shell-model calculations [2]. We show that the $^{79}$Cu nucleus can be described in terms of a valence proton outside a $^{78}$Ni core, implying the magic character of the latter. References: [1] A. Obertelli et al., Eur. Phys. J. A 50, 8 (2014). [2] Y. Tsunoda, T. Otsuka, N. Shimizu, M. Honma, and Y. Utsuno, Phys. Rev. C 89, 031301(R) (2014).

Speaker: Louis Olivier (IPN Orsay)

57 Transition Strengths in 22,23Mg as Tests of ab Initio Theory

Recent theoretical developments in ab initio nuclear theory techniques make calculations of the properties of sd-shell nuclei possible without a reliance on phenomenology. In particular, in-medium similarity renormalization group (IM-SRG) and coupled-cluster theory have demonstrated promising results in describing the collective properties of nuclei, for example in self-conjugate 20Ne and 24Mg [1, 2, 3]. In principle, such techniques might allow for the elimination of phenomenological effective charges, accounting for physics lost in model truncations by correctly evolving the necessary operators. Two Coulomb-excitation measurements were performed with the TIGRESS setup at the TRIUMF ISAC-II facility with the goal of providing precise E2 transition strengths in 22,23Mg to allow for more detailed scrutiny of results from modern, ab initio methodologies. Furthermore, in a previous measurement an apparent deviation in the ratio of isoscalar and isovector contributions to the E2 transition strength was observed in 21Na [4]. The results of the present measurement will be used to determine whether this deviation extends to neighbouring nuclides. The results of the two measurements will be presented and compared with modern nuclear theory, both ab initio and phenomenological, including a first measurement of the sign of the diagonal matrix element of the first-excited 2+ state in 22Mg through the reorientation effect. Results will be presented in the context of other Tz = −1,−1/2 isotopes, providing for a systematic evaluation of transition strengths within the sd-shell. References: [1] S. R. Stroberg et al., Phys. Rev. C 93 051301R (2016). [2] S. R. Stroberg et al., Phys. Rev. Lett. 118, 032502 (2017). [3] G. R. Jansen et al., Phys. Rev. C 94 011301R (2016). [4] M. A. Schumaker et al., Phys. Rev. C 78 044321 (2008).

Speaker: Dr Jack Henderson (TRIUMF)

58 Shape Isomerism in 66Ni

The phenomenon of shape isomerism is related to the existence, in the nuclear potential energy surface (PES), of a secondary minimum associated with large deformation and separated from the primary minimum (ground state) by a high barrier. Shape isomers at spin zero have clearly been observed, so far, only in actinide nuclei. The existence of shape isomers in lighter systems has been a matter of debate for a long time: a rather restricted number of candidates was suggested by various mean-field theoretical approaches [1,2,3] and 66Ni turned out to be the lightest nucleus for which all models indicate the existence of a pronounced secondary PES minimum. In 66Ni, among the six lowest excitated states three have spin-parity assignment 0+. Monte Carlo Shell Model Calculations [4] which correctly predict the existence of all these three excited 0+ states, show that the 0+_4 excitation should exhibit well-deformed prolate shape and be separated by a substantial barrier from the spherical main minimum. Indeed, the calculated B(E2) probabilty from 0+_4 into the spherical 2+ is found to be significantly hindered pointing to the 0+_4 state as a candidate for shape isomer. To check this prediction, we performed a measurement of the lifetimes of 0+ excitations in 66Ni at the Bucharest Tandem Laboratory. By employing the two-neutron transfer reaction 64Ni(18O,16O)66Ni, at sub-barrier energy of 39 MeV, all three lowest-excited 0+ states in 66Ni were populated and their gamma-decay was observed by employing gamma-coincidence technique with the ROSPHERE HPGe array. The population pattern of the 0+ states clearly indicated that 0+_4 corresponds to the prolate deformed 0+ excitation predicted by theory. The 0+ states lifetimes were measured with a plunger device and, in particular, for the 0+_4 to 2+_1 decay the B(E2) values of 0.2 W.u. was found. The measured hindrance of E2 decay from the prolate 0+_4 to the spherical 2+_1 state is in line with the results of MCSM calculations, although the experimental magnitude is smaller. This result makes 66Ni a unique nuclear system, apart from 236U and 238U, in which a retarded gamma-transition from a 0+ deformed state to a spherical configuration is observed, pointing to a shape isomer-like behaviour. References: [1] P. Bonche et al., Nuc. Phys. A 500, 308 (1989). [2] M. Girod et al., Phys. Rev. Lett. 62, 2452 (1989). [3] P. Moeller et al., Phys. Rev. Lett. 103, 212501 (2009). [4] Y. Tsunoda et al., Phys. Rev. C 89, 031301(R) (2014).

Speaker: Prof. Silvia Leoni (Università di Milano and INFN sez. Milano)

59 E0 Transitions and Shape Coexistence in 54,56,58Fe

Doubly magic nuclei and their nearest neighbours serve as an ideal testing ground for the nuclear shell model, and consequently enable us to define effective nuclear interactions. Collective states in nuclei near 56Ni can be attributed to multiparticle-multihole excitations from the 1f7/2 to the 2p3/2, 1f5/2 and 2p1/2 orbits across the N, Z=28 shell gap. Properties of excited 0+ states as well as E0 and E2 transition strengths are sensitive probes of the underlying nuclear structure. A systematic study of the stable N=28-32, even-even iron isotopes was performed and E0 transitions between the lowest excited 0+ states and the ground states were measured. Data were obtained in an experimental campaign at the ANU Heavy Ion Accelerator Facility. Excited states of 54,56,58Fe were populated using (p,p’) reaction at beam energies of 6.9 MeV (54Fe), 6.7 MeV (56Fe) and 7.0 MeV (58Fe). Internal conversion electron and electron-positron pair spectra were measured using the superconducting electron spectrometer “Super-e”, and singles γ-rays were measured with a HPGe detector. In addition, the investigation is supplemented with information on angular distributions, angular correlations, and γ−γ coincidences, measured with the CAESAR detector array under the same experimental conditions. In order to deduce E0 matrix elements, the experimental data was evaluated using the available lifetime information from Doppler-shift attenuation measurements following inelastic neutron scattering, carried out at the University of Kentucky. Results and interpretation of the systematic study, as well as a more detailed description of the experiment and procedure will be presented in this talk.

Speaker: Dr Tibor Kibedi (Department of Nuclear Physics, RSPEE, The Australian National University)

60 The Nature of 0+ Sates in Deformed Nuclei

The existence and characterization of multi-phonon vibrational modes in deformed nuclei remains an open question in nuclear structure. The question revolves around the possible degrees of freedom in deformed nuclei [1-4]. Rotational motion is an expected feature of deformed nuclei, the open challenge is whether the granularity of nuclei allows single or multiple quanta of vibrational oscillations or excitations superimposed on the equilibrium deformed shape of the nucleus. The lowest lying such shape effecting oscillations or vibrations would be quadrupole in nature, resulting in two types of vibrations: beta (K=0+) with no projection on the symmetry axis and gamma with a projection of K=2+. Vibrational spectra can, in principle, be constructed from one or more quanta of these states resulting in two-phonon betabeta$ (K=0+), betagamma (K=2+), and gammagamma (K=0+ and 4+) types of vibrational excitations. Single phonon gamma vibrational bands and low-lying K=0+ bands have been known for some time and they are abundant in various regions of deformation, including the rare-earth region of nuclei, albeit without systematic knowledge of level lifetimes. The gamma vibration seems to be well characterized as the first excited K= 2+ band and exhibits a systematic behavior across the region of deformed nuclei with typical B(E2; 2+ --> 0+g.s. values of a few Weisskopf units (W.u.). The energies of the first excited K=0+ bands and their B(E2) values show a different picture. The energies and associated B(E2) values of the first excited K = 0+ bands vary greatly throughout the deformed region. There are several examples of two-phonon quadrupole vibrational excitations in a number of nuclei exhibiting various degrees of the full collective transition strength with wide ranges in energy anharmonicities. Yet, the question regarding the viability of the K= 0+ excitations as the beta-vibration in deformed nuclei remains open to discussion and debate. I would like to present some of our recent lifetime measurements across isotopic chains of the Gd, Dy, and Er isotopes to contribute to the discussion.

Speaker: Prof. Ani Aprahamian (University of Notre Dame)

Wednesday, 31 May

61 Electromagnetic Response in Nuclei: From Few- to Many-body Systems

The electromagnetic response of nuclei is a fundamental quantity to calculate, since due to its perturbative nature a clean comparison with experimental data can be performed. First priciples computations are key to bridge nuclear physics with the underlying QCD regime [1]. Nowadays this valuable information is not only accessible for the lightest nuclei, but novel theoretical approaches are being developed to tackle nuclei with a larger number of nucleons. Combining the Lorentz integral transform with the coupled-cluster method recently allowed us to perform ab initio calculations of response functions and related sum rules for light and medium-mass nuclei [2,3]. I will present recent highlights on neutron skins and polarizabilities and discussed them in the context of recent and future experiments [4,5]. References: [1] S. Bacca and S. Pastore, J. Phys. G: Nucl. Part. Phys. 41 123002 (2014). [2] S.Bacca et al., Phys. Rev. Lett. 111m 122502 (2013). [3] M.Miorelli et al., Phys. Rev. C 94, 034317 (2016). [4] G. Hagen et al., Nature Physics 12, 186-190 (2016). [5] J. Birkhan et al., arXiv:1611.07072.

Speaker: Prof. Sonia Bacca (TRIUMF)

62 Nuclear Forces for ab Initio Nuclear Theory

Predictive power requires the ability to quantify theoretical uncertainties. While it is true that theoretical error estimates are difficult to obtain, the pursuit thereof plays a pivotal role in science. Reliable theoretical errors can help to determine to what extent a disagreement between experiment and theory hints at new physics, and they can provide input to identify the most relevant new experiments. In this talk I will show that nuclear theory is at a stage where such questions can be addressed. Chiral effective field theory can be used to systematically bridge the gap from low-energy quantum chromodynamics to nucleons and pions as effective nuclear-physics degrees of freedom. Following this avenue we have made the quantification of theoretical uncertainties possible through the incorporation of state-of-the-art statistical and computational tools. In particular, we employ two different approaches to determine the coupling constants of chiral nuclear interactions: (1) The simultaneous optimization of nucleon-nucleon, pion-nucleon and few-nucleon data, and (2) In-medium optimization for which binding energies and radii of selected isotopes of carbon and oxygen are also used as input data. I will present results from both of these different approaches that together provide important steps towards our understanding of nuclear forces.

Speaker: Christian Forssén (Chalmers University of Technology)

63 Where is the Neutron Drip-line for Oxygen?

The presence of neutron and proton shell closures in the nucleus $^{28}$O, together with strong continuum coupling effects, make neutron-rich oxygen isotopes a unique laboratory for testing nuclear models. In this work, we investigate neutron-rich oxygen isotopes using the Gamow Shell Model and the Density Matrix Renormalization Group method with an effective finite-range two-body interaction optimized to the bound states and resonances of $^{23-26}$O assuming a core of $^{22}$O. Our results suggest the existence of narrow excited states in $^{25}$O and $^{27}$O decaying by neutron and gamma emission, and a near-threshold ground-state for $^{28}$O.

Speaker: Dr Kevin Fossez (NSCL/MSU)

64 Ab Initio Studies of Nucleonic Matter

Nucleonic matter has important implications on many branches of nuclear science: from the bulk properties of exotic nuclei to the equation of state of neutron star matter. After we have extended the self-consistent Green’s function (SCGF) theory to account for three-nucleon forces, it is now possible to make reliable predictions of nucleonic matter at both zero and finite temperatures and with full chiral interactions, a task that was not possible until a few years a ago. The talk will present the SCGF approach as a very convenient way to investigate microscopic and thermodynamical properties of nucleonic matter. Among recent results, the prediction of the liquid-gas phase transition critical temperature in symmetric matter appears to be in reasonable agreement with experimental outcomes. Also studies of both saturation properties and finite temperature behaviors in infinite matter are pointing towards the necessity to refine the fitting procedure of low-energy constants. Moreover, I will show how first-principle tests of thermal approximations used in equations of state to study stellar environments questions the validity of such simulations.

Speaker: Dr Arianna Carbone (TU Darmstadt)

10:40 Coffee Break

65 The Difference a Few Neutrons Makes in the Fusion of Light Nuclei: Structure and Dynamics

Fusion of neutron-rich light nuclei at near barrier energies involves the interplay of both structure and dynamics. Examination of fusion for an isotopic chain of nuclei provides a means to access the low density tail of the neutron density distribution and the polarizability of nuclear matter. Development of a new technique that allows measurement of the fusion cross-section at near barrier energies will be presented. The direct measurement of fusion residues with this technique is used to extract the fusion cross-section. The measured fusion excitation functions for 18,19O + 12C and 39,47K + 28Si will be shown and the observed fusion enhancement will be compared with theoretical model predictions.

Speaker: Prof. Romualdo Desouza (Indiana university)

66 How Does Breakup of Light Weakly-bound Projectiles Affect Fusion?

Fusion reactions provide the means to discover new elements, produce new exotic isotopes, investigate nuclear structure, and study many-body quantum dynamics. The fusion of light, weakly-bound projectiles (e.g., 6,7Li, 9Be) with heavy targets at above-barrier energies is found to be suppressed by 25-35% compared to both model expectations, and to fusion of strongly-bound projectiles [1]. This presents a major challenge to our understanding of fusion, particularly for measurements with nuclei far from stability. Due to their low breakup thresholds, direct breakup of these nuclei into their intrinsic clusters (6Li→αd, 7Li→αt, 9Be→ααn) may prevent fusion – after breakup, capture of the complete charge of the projectile is be hindered. Although these direct breakup modes are present, many unbound states are also accessible via nucleon transfer [2]. For example, 7Li can disintegrate through proton pickup, forming unbound 8Be. This mode becomes dominant as the target mass decreases, with direct breakup negligible for A<60 [3]. To infer the influence of breakup on fusion we need to understand both the mechanisms causing breakup and their timescales. Narrow resonances such as the 8Be 0+ (τ≈10−16 s) survive much longer than the collision time (10−21 s), and will arrive at the fusion barrier intact. Thus they are not expected to contribute to fusion suppression. Only if breakup occurs on the timescale of the collision (e.g. via the short-lived 8Be 2+ state) can fusion be suppressed. Here we discuss recent measurements of sub-barrier breakup and their interpretation in terms of a classical dynamical model [4]. In the absence of a quantum model for transfer triggered breakup, classical trajectory models were developed, guided by experimental insights, to understand breakup and incomplete fusion in near-barrier collisions. Comparison with experimental measurements have shown how the correlations of the breakup fragments are altered by their proximity to the target nucleus at breakup [5] providing a probe of breakup timescales. These results suggest that the detailed structure of the intermediate states populated is crucial in determining the influence of breakup on fusion. References: [1] L. F. Canto et al., Phys. Rep. 596, 1 (2015) (and refs. therin) [2] D. H. Luong et al., PLB 695, 105 (2011) [3] S. Kalkal et al., PRC 93, 044605 (2016) [4] A. Diaz-Torres et al., PRL 98, 152701 (2007) [5] E. C. Simpson et al., PRC 93, 024605 (2016)

Speaker: Dr Edward Simpson (Australian National University)

67 Progress in Fission Investigated in Complete Kinematic Measurements

The observation of asymmetric fission in 1948 was one of the main discoveries promoting the nuclear shell model. However, more than 75 years after its discovery fission still represents a challenge for nuclear physicists. In particular, the stabilization of the heavy fission fragment around A~140 initially explained in terms of the double shell closure around Z=50 and N=82 or N~88 was questioned by K.H. Schmidt and collaborators ten years ago. More recently, asymmetric fission partitions around 180Hg were observed by A. Andreyev and collaborators and interpreted by P. Moller without any shell effects. Concerning the dynamics of fission the situation is not better. Pre- and post-scission particle emission and fission probabilities indicate that simple statistical approaches are not valid and models describing the dynamics of the process are required. Because of the complexity of time-dependent microscopic approaches, models based on transport equations (e.g. Fokker-Planck or Langevin) including dissipative and stochastic terms where the main ingredients are the potential landscape and the friction and inertia tensors are used. The friction or viscosity parameter is particularly interesting since it quantifies the magnitude of the coupling between collective and intrinsic degrees of freedom in fission. The complete isotopic and kinematic identification of both fission fragments recently achieved using coulex induced fission in inverse kinematics should represent a real breakthrough in the investigation of fission providing answers to many of the open questions. In the near future this experimental progress could even improve taking advantage of quasi-free nucleon scattering inducing fission, e.g. (p,2pf).

Speaker: Prof. Jose Benlliure (Universidade de Santiago de Compostela)

68 Microscopic Theory of Nuclear Fission

Since its discovery in the late nineteen thirties, nuclear fission has remained one of the most complex and elusive problems in physics and gaps in our understanding of this phenomena can impact progress in other areas. For example, in basic science accurate knowledge of spontaneous fission half-lives is key to predicting the stability of superheavy elements, and fission fragment charge and mass distributions are also important ingredients in simulations of the formation of elements in nuclear capture processes (fission recycling). In applications of nuclear science for energy production, fuel cycle optimization is also strongly dependent on the characteristics of the fission process in actinides. In all these examples, measurements are either difficult, for technological, financial or safety reasons, or simply impossible. Therefore, most information comes from theoretical predictions. These predictions are often based on powerful semi-phenomenological models that have been developed several decades ago and have been finely tuned on existing data, which limits their predictive power. In an ideal world, a predictive theory of fission should instead be based solely on quantum many-body methods and our best knowledge of nuclear forces. Today, there is a consensus that the nuclear energy density functional theory (DFT) is currently the best framework to achieve a microscopic description of fission. Unfortunately, the proper implementation of nuclear DFT comes at a tremendous computational cost, which explains why progress had been relatively slow in the past. The recent development of leadership computing facilities in the USA, Europe and Asia has, however, introduced a paradigm shift: Calculations that were simply unfeasible only 5 or 10 years ago can now be completed in just a few hours. Such a massive increase in computing power has opened entirely new perspectives and triggered a spectacular renaissance of fission studies. After a historical introduction to fission theory and models, I will give an overview of the DFT approach to nuclear fission and highlight a few selected results.

Speaker: Dr Nicolas Schunck (Lawrence Livermore National Laboratory)

69 Don’t be Such a Scientist: The Intersection of Science, Communication and Policy

For most of our professional lives, we perform fundamental research with a goal towards solving problems that advance scientific knowledge. Such a career requires significant investment in education, skill in analytical thinking and problem solving, and usually some sort of sustained federal funding of instrumentation and personnel. Although the costs associated with basic research are small compared to other federal expenditures, in the current funding era we are increasingly asked to justify the taxpayer investment in scientific research. Simultaneously, we wish to continue to attract the best students into our field. Both the persuasion of people to support a pro-science policy and the attraction of new people into a STEM career require better communication skills than most of us have ever developed. In Randy Olsen’s book: “Don’t be Such a Scientist”, he argues that we have done such a poor job communicating science that we are lucky it continues in the US at all! The evolution of one particular scientific career from basic nuclear science into one with an applied environmental science direction using nuclear science techniques will be presented. This includes using ion beam analysis to study lake sediments, and to trace flame retardants from consumer products into our environment. Recent studies focus on an emerging class of chemicals of concern (Per- and Polyfluorinated Alkyl Substances) that are ubiquitous in in our textiles, food packaging, personal care products and industrial uses. But the most significant of these findings required improved communication skills in order to achieve any significant effect on science policy. Therefore, it could be argued that more of us should develop the type of communication skills necessary to alter the science policy landscape in the US.

Thursday, 1 June

70 Nuclear Structure Studies by Measurements of Nuclear Spins, Moments and Charge Radii Via Collinear Laser Spectroscopy at ISOLDE

High-resolution laser spectroscopy at ISOLDE gives access to properties of nuclear ground states and long-lived (> 5ms) isomeric states of radioactive nuclei far from stability, such as nuclear spins, nuclear magnetic and quadruple moments and charge radii [1]. These fundamental properties of exotic nuclei provide important information for the investigation of the nuclear structure in different regions of nuclear chart. Currently, two complementary collinear laser spectroscopy set-ups are available at ISOLDE: one for optically detected Collinear Laser Spectroscopy (COLLAPS) [2] and one for Collinear Resonant Ionization Spectroscopy (CRIS) [3]. By combining these two techniques, the nuclear structure in several key regions of the nuclear chart is been studied, from the very neutron-deficient to the very neutron-rich side of the nuclear landscape. Recent results from studies in the Ca and Ni regions will be presented and an outlook to future opportunities will be presented. References: [1] P. Campbell et al., Progress in Particle and Nuclear Physics 86, 127 (2016). [2] http://collaps.web.cern.ch/ [3] http://isolde-cris.web.cern.ch/isolde-cris/

Speaker: Prof. Gerda Neyens (KU Leuven)

71 Manifestation of Three-nucleon Spin-orbit Interaction in Nuclear Charge Radii

The nuclear charge radii have supplied high-precision and model-independent data on nuclear structure. In particular, thanks to the collaboration of atomic physics, difference of the charge radii among isotopes, i.e. isotope shifts (field shifts, to be more precise), have been measured with striking precision. The isotope shifts have been known to be a good indicator for variation of nuclear structure along an isotopic chain. They may also provide information of the nucleonic interaction. The isotope shifts in the Pb nuclei was suggested to be relevant to the isospin content of the nucleonic LS interaction two decades ago. However, fictitious degeneracy or level inversion had to be introduced to reproduce the observed kink in the isotope shifts of the Pb nuclei. Via a self-consistent mean-field (SCMF) study, I point out that the three-nucleon (3N) interaction, which has been indicated by the chiral effective field theory (EFT) and pointed out to narrow the gap between the theoretical description and experiments of the ls splitting, may also solve the problem of the isotope shifts. The kink in Pb is described fairly well with a reasonable single-particle-level difference between the relevant orbitals. It is found that the close charge radii between 40Ca and 48Ca, which is another long-standing problem, are well reproduced as well. As the SCMF calculations clarify physics mechanism how the 3N LS interaction influences the nuclear charge radii, these data can be regarded as a manifestation for the 3N LS interaction. It is suggested that kinks as observed in Pb can be universal at the neutron magicity in the isotopes with magic proton numbers. As an example, a kink is predicted in the isotope shifts of Sn at N=82, which will be a touchstone of this picture linking the nuclear radii and the 3N LS interaction.

Speaker: Prof. Hitoshi Nakada (Chiba University)

72 The Use of Storage Rings in the Study of Reactions at Low Momentum Transfers

Several nuclear reactions are best investigated when the momentum transfer to the nucleus is small. Among these are the IsoScalar Giant Monopole Resonance (ISGMR) which helps determine one of the parameters of the equation of state, namely the incompressibility of nuclear matter, and proton elastic scattering from nuclei which is sensitive to parameters of nuclear density such as the matter root-mean-square radius. These have been extensively studied in the past using stable beams. However, with the advent of radioactive ion facilities around the world, it is desirable to study these reactions with unstable nuclei. The reactions, however, have to take place in inverse kinematics in which the radioactive ions impinge on a light target (hydrogen or helium). Simple kinematics calculations show that the outgoing recoil particles possess extremely low energies (down to few hundred keVs). External targets are, therefore, not suitable for these reactions. There are two alternative methods to deal with this challenge: either do the experiments in storage rings with gas jet targets or any other thin targets, or perform the measurements with an active target which also acts as a detector. In both cases, the energy threshold will be much lower than a fixed target of a reasonable thickness. We have performed measurements with the radioactive 56Ni using both methods. In the ring measurements, proton elastic scattering was the main goal for this nucleus while feasibility studies were done with 58Ni and a helium target to investigate ISGMR. In this presentation, the experimental method used in the storage ring will be discussed along with some results, and a comparison will be made with the results of the active target measurements.

Speaker: Prof. Nasser Kalantar-Nayestanaki (KVI-CART/Univ. of Groningen)

73 Beta-delayed Neutron Spectroscopy with VANDLE, Evidence for Gamow-Teller Decay of 78Ni Core

The beta-delayed neutron emission of neutron-rich isotopes near 78Ni and 132Sn regions were studied using the neutron time-of-flight technique with Versatile Array of Neutron Detectors at Low Energies (VANDLE). We have measured neutron energy spectra, which showed emission from states at excitation energies high above neutron separation energy. This effect was previously not observed in the beta-decay of mid-mass nuclei. For the example cases of 83,84Ge, large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation and was interpreted as evidence for allowed beta-decay to core-excited states of 78Ni. To describe the observed features of this decay, we have developed shell model calculations in the proton fpg9/2, and neutrons extended fpg9/2+d5/2 valence space using realistic interactions. Enhanced and concentrated beta-decay strength for neutron-unbound states may be common for very neutron-rich nuclei and would lead to intense beta-delayed high-energy neutrons or multi-neutron emission probabilities that in turn will affect astrophysical nucleosynthesis models.

Speaker: Prof. Robert Grzywacz (University of Tennessee)

10:40 Coffee Break

74 Shape Coexistence in Neutron-rich Strontium Isotopes at N=60

Neutron-rich A~100 nuclei are among the best examples of interplay of microscopic and macroscopic effects in nuclear matter. A dramatic onset of quadrupole deformation is observed in the neutron-rich Zr and Sr isotopes at N=60, making this region an active area of experimental and theoretical studies. This rapid shape transition is accompanied by the appearance of low-lying 0+2 states. Low-energy Coulomb excitation experiments were to study properties of coexisting structures in 96,98Sr (N=58,60) using post-accelerated exotic Sr beams from REX-ISOLDE. The experiments were carried out in the particle-gamma coincidence mode using the MINIBALL HPGe array coupled to an annular Double Sided Silicon Detector. Reduced transition probabilities and spectroscopic quadrupole moments were extracted from the measured differential Coulomb excitation cross sections. The results support the scenario of shape transition at N=60 giving rise to coexistence of two very different configurations in 96,98Sr. In 96Sr, the spectroscopic quadrupole moment of the first 2+ state was found to be small and negative, corresponding to a weak prolate deformation. In 98Sr, the large and negative spectroscopic quadrupole moments in the ground state band prove its well-deformed prolate character, while the value close to zero obtained for the 2+2 state confirms that a spherical configuration coexists with the deformed configuration of the ground state. The comparison of the B(E2) values and the spectroscopic quadrupole moments between the 2+1 state in 96Sr and the 2+2 state in 98Sr underlines their similarity and further supports the shape inversion when crossing the N=60 line. Furthermore, a very small mixing between the coexisting structures was determined from measured intra-band transition probabilities in 98Sr. This effect has been attributed to the rapidity of the shape change at N=60: a larger mixing would give rise to a more gradual transition from spherical to deformed ground state in Sr isotopes, like what is observed in other areas of shape coexistence, for example neutron-deficient Kr and Hg isotopes. The experimental results, together with a detailed comparison with new beyond-mean-field calculations, will be presented. The present work will be also highlighted in a larger framework of the shape change in the mass region.

Speaker: Dr Emmanuel Clement (CNRS-GANIL)

75 Recent Developments in Shape Coexistence Studies

The information on collective properties of nuclei far from stability has dramatically improved in recent years due to the availability of radioactive ion beams used, e.g., for Coulomb excitation studies both below the Coulomb barrier and at relativistic energies. These studies are complemented by spectroscopic studies and lifetime measurements applied to other reaction mechanisms suitable for producing exotic nuclei. Over the last few years we have carried out a research program using these complementary techniques, and applied them to several mass regions, where shape coexistence and a sudden evolution of nuclear shapes are expected. In this presentation recent results for two such mass regions will be presented, the A~70 nuclei at and beyond the N=Z line and neutron-rich nuclei in the A~100 region. In the first case the closeness and influence of the proton drip line on the shape properties is being explored, while in the second case the evolution of nuclear shapes beyond the onset of strong deformation at N=60 (in particular in Sr and Zr isotopes) as well as the importance of the triaxial degree of freedom in the Mo and Ru isotopes at N~64-70 are of strong current interest. In this presentation recent results will be presented that were obtained using several different facilities: On one hand, using stable beams from GANIL and the combination of the VAMOS and EXOGAM spectrometers, heavy-ion induced fission was used to obtain new lifetime results in several Zr, Mo, Ru and Pd isotopes. On the other hand radioactive neutron-rich beams from the CERN-ISOLDE and ANL-Caribu facilities were used to perform Coulomb excitation experiments yielding new electro-magnetic matrix elements in the same nuclei. Finally, the even more exotic proton-rich nuclei around A~70 were studied using relativistic Coulomb excitation of fragmentation beams from the RIBF facility at RIKEN.

Speaker: Dr Wolfram KORTEN (CEA Saclay)

76 First Experiment in the 100Sn Region Using HIE-ISOLDE

In this presentation results from the first experiment with the new post-accelerator HIE-ISOLDE at CERN will be given. HIE-ISOLDE expands the possibilities offered by its predecessor, REX-ISOLDE, by increasing the final energy of the radioactive beam (RIB) to 5 MeV/u and 10 MeV/u in two steps, using a set of new superconducting cavities. The first step, to 5 MeV/u, facilitates e.g. the use of heavier targets in the the Coulomb excitation program that was started with REX-ISOLDE. In practice this means that the earlier measurements, that were largely restricted to excitation of the lowest lying states in the RIB, now can include states at higher energies, and simultaneously substantially increase the statistics for the states addressed in the REX-ISOLDE campaign. The first production run with HIE-ISOLDE was part of the program in the 100Sn region. In this case the use of the new post-accelerator means that the measurements of the transition probabilities from the ground state to the first excited 2+ state in the light even Sn isotopes, that earlier were statistics limited, now are observed with some two orders of magnitude higher statistics. In addition, multi-step excitation is observed providing further information on the yrast sequence in these isotopes. The new results will be discussed and put into the context of earlier measurements and theoretical interpretations.

Speaker: Prof. Joakim Cederkall (Lund University)

77 Properties of Mg and S Isotopes in a Beyond Mean Field Theory.

Traditionally effective interactions like Skyrme, Gogny or relativistic interactions have been used in basic mean field approaches to describe with great success bulk properties of ground states of nuclei, such as masses, quadrupole moments, radii, etc. However, recent developments in beyond mean field calculations, with particle number and angular momentum projection in conjunction with the Generator Coordinate Method (with the deformations $(\beta,\gamma)$, pairing gaps $(\Delta_Z,\Delta_N)$ and angular frequency as generator coordinates) have shown that the Gogny force [1,2] is also able to provide high quality nuclear spectroscopy. This approach has recently been extended to odd-even nuclei [3] allowing thereby to perform isotopic (isotonic) studies of nuclear properties. The strong point of this approach is the ability to simultaneously provide a good description of bulk properties, like binding energies and multipole moments, as well as an accurate and detailed account of excitation energies and transition probabilities. As a validation of the theory in this talk we present a study of the Magnesium isotopic chain. We obtain an outstanding description of the ground-state properties, in particular binding energies, odd-even mass differences, mass radii and electromagnetic moments among others. At the same time a comprehensive study of the spectroscopic properties of $^{25}$Mg is discussed. These studies, together with the spectrum and the transition probabilities of the nuclei $^{42}$Si and $^{44}$S, show that these calculations provide an accuracy comparable with state-of-the-art shell model calculations with tuned interactions. The advantages of the present approach as compared to the shell-model one are the added value of the intrinsic system interpretation and that the interaction, the Gogny force, is well known for its predictive power and good performance for bulk properties all over the chart of nuclides. References: 1.- M. Borrajo, T. R. Rodriguez and J. L. Egido, Phys. Lett. B 746 (2015) 341-346 2.- J. L. Egido, M. Borrajo and T. R. Rodriguez, Phys. Rev. Lett. 116 (2016) 052502. 3.- M. Borrajo and J. L. Egido, Phys. Lett. B 764 (2017) 328–334

Speaker: Prof. J. Luis Egido (Universidad Autonoma de Madrid)

12:45 Lunch Break

Breakout 1: Thursday Before PM Coffee

78 High-resolution Laser Ionisation Spectroscopy of Heavy Elements in Supersonic Gas Jet Expansion

Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. In such measurements, however, it is difficult to combine a high efficiency with a high spectral resolution. Recently, we have demonstrated the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability [1]. A significant improvement in the spectral resolution by more than one order of magnitude was achieved in these experiments without loss in efficiency. Spatial constraints and limitations of the pumping system in the present setup prevented a high quality jet formation and, as a consequence, an optimal spatial and temporal laser-atom overlap. Offline characterization studies at the newly commissioned In-Gas Laser Ionization and Spectroscopy (IGLIS) laboratory at KU Leuven [2] are being carried to overcome these limitations in future experiments when dedicated IGLIS setups are in operation at new generation radioactive beam facilities [3]. These studies also include the characterization of the flow dynamics and the formation of supersonic jets produced by de Laval nozzles with different Mach numbers using the Planar Laser Induced Fluorescence technique on copper isotopes, the test of a new gas-cell design with better transport and extraction characteristics and the characterization of a high-power, high-repetition rate laser system. Extrapolation of the online results on the actinium isotopes show that the performance of the technique under optimum conditions can reach a final spectral resolution of 100 MHz (FWHM) and an overall efficiency of 10% when applied in the actinide region. In this presentation we will briefly summarize the on-line results and mainly will focus on the characterization studies and future prospects of the in-gas-jet resonance ionization technique applied on very-heavy elements. References: [1] R. Ferrer et al., Nat. Commun.8, 14520 doi: 10.1038/ncomms14520 (2017). [2] Yu. Kudryavtsev et al. Nucl. Instr. Meth. B 376, 345–352 (2016). [3] R. Ferrer et al., Nucl. Instr. Meth. B 317, 570–581 (2013).

Speaker: Dr Rafael Ferrer (KU Leuven IKS)

79 Recent Technical Developments and New Scientific Endeavors at IGISOL

Since the successful commissioning of the IGISOL-4 facility, Jyväskylä, throughout 2012-2014 [1], we have moved towards full operation. The gradual evolution of the ion guide method for a universal production of both volatile and non-volatile elements has been driven by the pursuit of physics research on both sides of the valley of beta stability. The on-going development of new ion (and atom) manipulation techniques as well as new production methods at IGISOL-4 has been driven by the needs of the evolving scientific program. This contribution will provide an overview of the current status of developments as well as highlighting new themes of research. In collaboration with Uppsala University we have been simulating the fission process to understand the stopping and extraction efficiency of the ion guide used for proton-induced fission [2]. Importantly, this also supports and guides our experimental progress towards neutron-induced fission. The latter has seen the characterization of neutron energies and intensities at different angles using neutron activation and time-of-flight methods [3]. In December 2016 we successfully extracted stopped fission fragments products using neutron-induced fission for the first time. In order to provide a variety of stable beams of elements required for laser spectroscopy as well as mass spectrometry, an off-line ion source which combines discharge-, surface ionization and (in the future) laser ablation, has been commissioned. A core theme of the facility is the program of optical spectroscopy and laser developments. I will summarize the current status of our expansion of the solid state laser infrastructure for use in collinear laser spectroscopy. Exciting new programs include laser ionization of long-lived actinide isotopes coupled with high-resolution spectroscopy [4,5], as well as a new research theme in cold atom physics. This latter theme, led by University College London, has seen the installation of a new atom trap with the goal of achieving coherent gamma-ray emission via a Bose-Einstein Condensate of 135mCs isomers. References: [1] I.D. Moore et al., Nucl. Instrum and Meth. In Phys. Res. B 317 (2013) 208. [2] A. Aladili et al., Eur. Phys. J. A 51 (2015) 59. [3] D. Gorelov et al., Nucl. Instrum and Meth. In Phys. Res. B 376 (2016) 46. [4] I. Pohjalainen I.D. Moore et al., Nucl. Instrum and Meth. In Phys. Res. B 376 (2016) 233. [5] A. Voss, I.D. Moore et al., submitted to PRA (2016).

Speaker: Prof. Iain Moore (University of Jyväskylä)

80 Recent Upgrades of the Penning-trap Mass Spectrometer SHIPTRAP for High-precision Mass Measurements

Penning­-trap mass spectrometry allows direct and reliable measurements of atomic masses with very high precision. This technique is especially suitable to investigate the nuclear structure evolution of radioactive nuclides through measurements of binding energies. The heaviest elements investigated to date in pioneering experiments with the SHIPTRAP setup at GSI, Darmstadt, have been nobelium and lawrencium [1,2]. The existence of such heavy nuclei is intimately connected to nuclear shell effects that stabilize them against spontaneous fission. The direct measurement of the masses of {252−255}^No and {255,256}^Lr has allowed mapping the strength of the deformed subshell closure at N=152. In order to extend such studies to heavier and more exotic nuclides, the efficiency, precision and sensitivity of the SHIPTRAP setup is being further increased [3]. In particular, a cryogenic buffer gas-stopping cell [4] has been recently commissioned and the whole SHIPTRAP setup has been relocated on a 3-degree beam line at the SHIP (Separator for Heavy Ion reaction Products) recoil separator, in preparation for future online campaigns aiming at direct mass measurements of elements beyond Lr. To this end, the novel Phase-Imaging Ion-Cyclotron-Resonance technique (PI-ICR) [5], recently developed at SHIPTRAP, will be applied for the first time to the region of the heaviest elements. This new method allows mass measurements with only a few ion counts, i.e. at the lowest production yields. In addition, it reaches an accuracy level of 10^{-9}, even for short-lived nuclides (T_(1⁄2)≤1s). Such high precision is required in the context of neutrino physics, another field of SHIPTRAP activities, for instance in Q_(β/EC) measurements [6]. Q-values with uncertainties of few eV are demanded in experiments that aim at the determination of the neutrino mass (hierarchy) or the search for neutrinoless double-β decays. This contribution will present an overview of the recent results of the measurements related to the neutrino physics as well as the present status of the SHIPTRAP setup. References: [1] M. Block et al., Nature 463 (2010) 785. [2] E. Minaya Ramirez et al., Science 337 (2012) 1207. [3] M. Block, Nuclear Physics A 944 (2015) 471. [4] C. Droese et al., Nucl. Instr. Meth. Sec. B 338 (2014) 126. [5] S. Eliseev et al., Appl. Phys. B 114 (2014) 107. [6] S. Eliseev, et al., Phys. Rev. Lett. 115 (2015) 062501.

Speaker: Dr Francesca Giacoppo (Helmholtz-Institut Mainz and GSI Helmholtzzentrum für Schwerionenforschung GmbH)

81 New ISOLDE Setup for Laser Polarization and for Studies Using Spin-polarized Nuclei

Spin-polarized beams of radioactive nuclei can be of interest for studies in different fields, such as nuclear structure, fundamental interactions, or material science and life sciences. This is the motivation behind a recent initiative to build a permanent ISOLDE beamline, called VITO, devoted to various studies with polarized and non-polarized beams, as described in Ref. [1]. Within this initiative, we have recently developped the experimental setup which allows to polarize with lasers the ions and atoms of interest, detect their polarization via beta-decay asymmetry and in addition, use these beams for various studies, including beta-detected NMR and fundamental interaction investigations. The experimental setup for spin-polarization with lasers and for beta-asymmetry studies was designed at the beginning of 2016. It was installed at ISOLDE in the summer of 2016 and successfully commissioned with spin-polarized radioactive beam of 26,28Na in autumn 2016 [2]. The next stages of the project include a system to perform studies in liquid hosts as well as a setup for beta-gamma and decay spectroscopy on spin-polarized nuclei. This contribution will briefly review the principles of laser spin polarization and beta-NMR spectroscopy, it will present in detail the newly installed experimental setup and the results of the commissioning beamtime, and will close by the presentation of the planned experiments [1, 3]. References: [1] R. Garcia Ruiz et al., Perspectives for the VITO beam line at ISOLDE, CERN, EPJ Web of Conferences 93, 07004 ( 2015) [2] M. Kowalska et al., New laser polarization line at the ISOLDE facility, submitted to J. Phys. G (2016) [3] A. Jansco et al., TDPAC and β-NMR Applications in Chemistry and Biochemistry, submitted to J. Phys. G (2016)

Speaker: Dr Magdalena Kowalska (CERN)

82 Advancing Penning Trap Mass Spectrometry of Rare Isotopes at the LEBIT Facility

The Low-Energy Beam and Ion Trap (LEBIT) facility [1] at the National Superconducting Cyclotron Laboratory (NSCL) remains the only facility that employs Penning trap mass spectrometry for high-precision mass measurements of rare isotopes produced via projectile fragmentation. This powerful combination of a fast, chemically insensitive rare isotope production method with a high-precision Penning trap mass spectrometer has yielded mass measurements of short-lived rare isotopes with precisions below 10 ppb across the chart of nuclides. The most recent LEBIT measurement campaigns have focused on fundamental interactions such as T=1/2 mirror decay Q-values (C-11 [2] and Na-21 [3]), and superallowed -decay Q-values (O-14 [4]), and the nuclear mass surface near N=40 (Co-68,69). LEBIT has also recently been used to measure the Q-values of several neutrinoless -decay candidates and highly forbidden decays, using ions produced offline with local ion sources. In order to expand the experimental reach of Penning trap mass spectrometry to nuclides delivered at very low rates, the new Single Ion Penning Trap (SIPT) has been built. SIPT uses narrowband FT-ICR detection under cryogenic conditions to perform mass measurements of high-impact candidates, delivered at rates as low as one ion per day, with only a single detected ion. Used in concert with the existing LEBIT 9.4-T time-of-flight mass spectrometer, the 7-T SIPT system will ensure that the LEBIT mass measurement program at NSCL will make optimal use of the wide range of rare isotope beams provided by the future FRIB facility. * This material is based upon work supported by the by the National Science Foundation under Contract No. PHY-1102511 and PHY-1126282. References: [1] R. J. Ringle, S. Schwarz, and G. Bollen, Int. J. Mass Spectrom. 349-350, 87 (2013). [2] K. Gulyuz, et. al, Phys. Rev. Lett. 116, 012501 (2016). [3] M. Eibach, et. al, Phys. Rev. C 92, 045502 (2015). [4] A. A. Valverde, et. al, Phys. Rev. Lett. 114, 232502 (2015).

Speaker: Dr Ryan Ringle (NSCL)

83 BRIKEN Beta-delayed Neutron Detector Array at RIKEN*

Beta-delayed neutron emission (βn) points to the structure of involved nuclei and helps to understand the competition of allowed and first forbidden β-transition during the decay process. The resulting β1n and βxn branching ratios affect the nucleosynthesis pattern in the r-process [1]. BRIKEN array has been assembled by a multinational collaboration at the BigRIPS separator at RIKEN laboratory (Wako, Japan) to study the decay properties of the most neutron-nuclei produced through the fragmentation of high intensity 238U beam. BRIKEN includes the world-largest array of 3He counters, highly segmented silicon detectors AIDA [2] and Ge clovers. 3He tubes and Ge signals are analyzed using Struck digital modules. The efficiency of present hybrid BRIKEN configuration at BigRIPS, with 140 3He tubes and 2 clovers, is over 60% over a wide βn energy range up to few MeV [3]. Four accepted experiments aim in a large number of βn-emitters to be studied for the first time. The proposed studies cover the regions of nuclei from 76Co to 167Eu. In particular, it is intended to measure new beta-delayed neutron (βn) emission properties for nuclei near doubly-magic 78Ni. The first direct measurement of 20 P1n values for nuclei between 76Co and 92Se including that one of the doubly-magic 78Ni as well as the discovery of 14 β2n emitters between 80Cu and 91As and the determination of their P2n values is expected. BRIKEN was partially commissioned in 2016 during parasitic studies with 238U and 48Ca fragments. The main experiments are likely to be performed in early May 2017. Supported by the U.S. DOE Office of Science. Project partially supported and inspired by the IAEA Coordinated Research Project for a "Reference Database for beta-Delayed Neutron Emission. References: [1] R. M. Mumpower et al., Prog. Part. Nucl. Phys. 86, 86, 2016. [2] C. Griffin et al., in Proc. of NIC XIII Conf., 7-11 July 2014, Debrecen, Hungary, http://www.nic2014.org, Proceeding of Science (PoS NIC 097 (2014). [3] A. Tarifeno-Saldivia et al., https://arxiv.org/abs/1606.05544, IOP Journal of Instrumentation, 2016. * presentation on behalf of BRIKEN Collaboration

Speaker: Dr Nathan Brewer (ORNL/UTK)

84 Recent Results From the Active Target Time Projection Chamber

The Active Target Time Projection Chamber (AT-TPC) built at NSCL was recently commissioned using re-accelerated beams from the completed ReA3 linac. This detector is well suited to the energy domain covered by this accelerator, around the Coulomb barrier, using inverse kinematics reactions with radioactive nuclei. Its main asset is the enhanced luminosity gained from the active target concept that allows to use a thick target while retaining the good resolutions necessary for this type of scattering experiments. Another important aspect is the ability to measure excitation functions of reactions from a single beam energy. Data taken on the reactions 4He+4He at 2-3 MeV/u and 46Ar+p at 4.6 MeV/u will be presented, as well as the methods and processes used in the analysis. The latter reaction was the first experiment performed with a re-accelerated radioactive beam at the NSCL. Its aim is to study the structure of 47Ar via the measured properties of resonant analog states in 47K populated via the 46Ar+p elastic scattering reaction at Coulomb energies. Although widely used in direct kinematics with stable targets, this method hasn’t been so far applied to radioactive beams in inverse kinematics for medium to heavy mass nuclei. Methods for track analysis and noise rejection will be shown. Future developments of the detector and its electronics to improve the quality of this type of data will also be presented.

Speaker: Mr Daniel Bazin (NSCL/MSU)

85 The ISOLDE Facility and the HIE-ISOLDE Project, Recent Results

ISOLDE is the CERN facility dedicated to the production of radioactive ion beams for many different experiments in the fields of nuclear and atomic physics, materials science and life sciences. The ISOL method involves in this case the bombardment of a thick target with an intense proton beam, producing high yields of exotic nuclei with half-lives down to the millisecond range. By a clever combination of target and ion source units pure beams of over 1000 different nuclei of 74 elements have been produced and delivered to experiments where properties of the nuclei such as masses, radii, decay modes, structure and shapes are determined. This year ISOLDE celebrates its 50 anniversary of production of radioactive beams offering the largest variety of post-accelerated radioactive beams in the world today. The HIE ISOLDE upgrade (HIE stands for High Intensity and Energy), intends to improve the experimental capabilities at ISOLDE over a wide front. The main feature is to boost the energy of the beams, going in steps from previous 3 MeV/u via 5.5 MeV/u to finally 10 MeV/u, and to accommodate a roughly fourfold increase in intensity. In 2016 Physics with 5.5 MeV/u for A/q = 4.5 was available and six experiments were done with beams from 9Li to 142Xe and energies up to 6.8 MeV/u in the case of 9Li were achieved. In this contribution highlights from ISOLDE and from the HIE-ISOLDE project will be presented.

Speaker: Prof. Maria J G. Borge (ISOLDE-CERN)

Breakout 2: Thursday Before PM Coffee

86 Quantum Self-organization and Nuclear Shapes

The nuclear deformation is driven by the quadrupole-quadrupole (QQ) component in the effective nucleon-nucleon (NN) interaction. Intuitively speaking, the actual nuclear shape is determined by the following mechanism, relevant driving force deformation = --------------------. resistance In the case of quadrupole deformation, the relevant driving force is the QQ force mentioned above, and a well-known example of the resistance is pairing interaction. There is another resistance power, that is, single-particle energies. If the single-particle orbits are separated too far, there is no sizable mixing among them, and hence no Jahn-Teller effect, namely, no deformation. Thus, single-particle energies, which can be viewed as the Nilsson levels at zero deformation, play crucial roles. Such single-particle energies have been considered to be close to constant within a nucleus. However, recent Monte Carlo Shell Model calculations on exotic Ni and Zr isotopes [1,2] showed that strongly-deformed bands are created and stabilized not only by strong effects of the QQ interaction but also by the change of single-particle energies of relevant orbits. For instance, in 98Zr, the relevant neutron single-particle orbits are spread over 5 MeV in its spherical ground state, whereas they become more degenerate within 2 MeV range in the first excited deformed 0+ state (Fig. 3 of [2]), due to massive proton excitations into g9/2 etc. We can regard this kind of phenomena as examples of the quantum self-organization, where atomic nucleus gains a certain shape (or collective mode in general) also by optimizing single-particle energies for this particular shape. This can be done if the NN interaction, particularly its monopole part, has rather strong orbital dependeces (e.g. tensor force) and the occupation numbers of relevant orbits can be reshuffled. This quantum self-organization can occur more frequently towards heavier nuclei with more orbits, exhibiting more beautiful rotational bands, for instance. The same mechanism can be applied to general many-body quantum systems with (i) mode-driving force and resistance controlling force, (ii) two Fermi liquids like protons and neutrons. In addition to shape coexistence and quantum shape phase transition, further developments will be discussed. References: [1] Tsunoda, Otsuka et al, PRC 89, 031301 (2014) [2] Togashi, Tsunoda, Otsuka et al. PRL 117, 172502 (2016)

Speaker: Prof. Takaharu Otsuka (University of Tokyo)

87 Precision Mass Measurements of Nutron-rich Chromium Isotopes into the <i>N</i>=40 "Island of Inversion": From a New "ISOL" Beam to ab-initio Shell Model Calculations.

As first hinted at in the mid-seventies by pioneering on-line mass measurements of neutron-rich Na isotopes, the spherical shell, or sub-shell, gaps described within the shell model of the atomic nucleus are prone to rapid evolution with proton and neutron number. Far from being isolated, the region of shell erosion around N=20 is actually part of a larger “archipelago of islands of inversion”. One such island, around N=40, is thought to exhibit maximum quadrupole deformation for ⁶⁴Cr. However, the mass surface in the chromium chain, approaching N=40, remains too imprecisely known. Over the last thirty-years, on-line Penning-trap mass spectrometry associated with the “ISOL” production technique has proven to be a particularly successful tandem for the precise determination of the mass of exotic species. Although chromium was not considered to be a traditional thick-target “ISOL” element, successful laser-ionization developments^[1] combined with highly sensitive mass spectrometry techniques enabled the mass measurements of ^52-63Cr, during two recent experimental campaigns at the ISOLDE facility, using the Penning-trap mass spectrometer ISOLTRAP^[2]. The mass values obtained are of greatly refined precision thus shining new light on the development of ground-state collectivity towards N=40 in the chromium chain. Very recently, an ab-initio method, rooted in the IM-SRG framework, has been developed enabling the derivation of shell-model Hamiltonians from first principles thus extending the reach of ab-initio calculations to mid-shell nuclei^[3]. A comparison of these state-of-the-art shell model calculations with our results will be presented. References: [1] Goodacre et al., Spect. Chimica Acta B, In Press (2017). [2] Mukherjee et al., Eur. Phys. J. A 35, 1-29 (2008). [3] Stroberg et al., Phys. Rev. Lett. 118, 032502 (2017).

Speaker: Mr Maxime Mougeot (CNRS, Universite Paris Sud, Orsay)

88 High-sensitivity and High-resolution Laser Spectroscopy of 76,77,78Cu at CRIS

The Collinear Resonance Ionization Spectroscopy experiment (CRIS) at ISOLDE combines the high sensitivity of resonance ionization spectroscopy with the high resolution offered by collinear laser spectroscopy. The first experiments at CRIS demonstrated the ability to reach exotic isotopes, normally out of reach for collinear laser spectroscopy methods based on photon detection, with an intermediate resolution [1].  Further developments have focused on improving the resolving power, to the point where it now matches the resolution of other collinear laser spectroscopy methods [2]. With this performance, the CRIS experiment is ideally suited to study the evolution of nuclear structure in regions far from stability. Several ISOLDE experiments have been working towards the region around the doubly magic 78Ni. Previous laser spectroscopy work [3-7] clearly demonstrated the inversion of the πf5/2 and the πp3/2 orbitals between 73Cu and 75Cu as the νg9/2 orbital is filled. This inversion is currently understood in terms of the tensor interaction between the neutrons and protons [8] which could potentially result in a quenching of the Z=28 shell gap towards N=50 [9]. This contribution will focus on the application of the high-resolution CRIS technique to the study of neutron-rich copper isotopes in the vicinity of N=50. The g-factors, quadrupole moments and charge radii of these neutron rich copper isotopes will provide additional information to gauge the robustness of the magicity of the Z=28 shell in 78Ni. During the last campaign in April 2016, measurements have been performed on 15 Cu isotopes, including for the first time high resolution measurements of the very exotic isotopes 76,77,78Cu, where 78Cu was produced at a rate of only 20 ions/s. These measurements provide information on the spin, magnetic moment, quadrupole moment and charge radius. The obtained data will be compared to large scale shell model calculations. References: [1] K.T. Flanagan et al., PRL 111, 212501 (2013) [2] R.P. de Groote et al., PRL 115, 132501 (2015) [3] K.T. Flanagan, PRL 103, 103, 142501 (2009) [4] P. Vingerhoets, PRC 82, 064311 (2010) [5] P. Vingerhoets, PLB 703, 1 (2013) [6] K. T. Flanagan, PRC 82, 041302(R) (2010) [7] U. Köster et al, PRC 84, 034320 (2011) [8] T. Otsuka et al, PRL 95, 232502 (2005) [9] K. Sieja et al., PRC 81, 061303(R) (2010) [10] J. Hakala et al., PRL 101, 052502 (2008) [11] Z. Y. Xu et al., PRL 113, 032505 (2014)

Speaker: Mr Ruben de Groote (KU Leuven)

89 Weakly Bound and Unbound Light Nuclei From ab Initio Theory

In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. One of the newly developed approaches is the No-Core Shell Model with Continuum (NCSMC) [1,2], capable of describing both bound and scattering states in light nuclei starting from chiral two- (NN) and three-nucleon (3N) interactions. We will present latest NCSMC calculations of weakly bound states and resonances of the exotic halo nucleus 11Be and discuss its strong E1 transitions and photo-dissociation [3]. We will also discuss its mirror 11N, an unbound 10C+p system, and highlight the role of chiral NN and 3N interactions in the description of the 10C(p,p) scattering measured recently at TRIUMF. Further, we will present ongoing applications of the NCSMC to 11C(p,p) scattering and the 11C(p,γ)12N radiative capture of relevance to astrophysics. Finally, we will show our preliminary results for the unbound and controversial 9He nucleus. References: [1] S. Baroni, P. Navratil, and S. Quaglioni, Phys. Rev. Lett. 110, 022505 (2013); Phys. Rev. C 87, 034326 (2013). [2] P. Navratil, S. Quaglioni, G. Hupin, C. Romero-Redondo, A. Calci, Physica Scripta 91, 053002 (2016). [3] A. Calci, P. Navratil, R. Roth, J. Dohet-Eraly, S. Quaglioni, G. Hupin, Phys. Rev. Lett. 117, 242501 (2016).

Speaker: Dr Angelo Calci (TRIUMF)

90 Recent Developments of the Gamow Shell Model for Nuclear Structure and Reaction

Dripline nuclei exhibit different properties compared to those lying close to the valley of stability. The ground states of those systems can form halo structures or can even be unbound to particle emission. In fact, dripline nuclei are open quantum systems, for which the proximity of the continuum of unbound scattering states must be taken into account theoretically. To this end, the Gamow Shell Model (GSM) has been successfully introduced to study loosely bound and resonant nuclear many-body states [1]. The GSM is rooted in the one-body Berggren basis, comprising bound, resonant and scattering states. The continuum degrees of freedom are thus included at basis level, and the configuration mixing between many-body basis states contributes to inter-nucleon correlations. For very large GSM matrices, where Lanczos and Davidson methods can no longer be used, the Density Matrix Renormalization Group (DMRG) has been introduced [2]. In order to use GSM to describe nuclear reactions, the Resonating Group Method (RGM) has been applied [3]. In the RGM method, a basis of channels is constructed from target and projectile states, which generate compound many-body basis states. Target states and projectile states are calculated in GSM, as they consist of bound or resonant eigenstates of the GSM Hamiltonian. Scattering wave functions and reaction cross sections can then be calculated. In this presentation, various GSM applications to structure and reactions of light nuclei will be presented. They include: 18Ne(p,p) [3] and 14O(p,p) [4] reactions, where the proton-rich 19Na and 15F nuclei are unbound, as well as 6Li(p,gamma)7Be, 6Li(n,gamma)7Li [5], 7Be(p,gamma)8B, and 7Li(n,gamma)8Li radiative capture reactions [6] of astrophysical interest. References: [1] N. Michel et al., Phys. Rev. Lett. 89 (2002) 042502 [2] J. Rotureau et al., Phys. Rev. Lett. 97 (2006) [3] Y. Jaganathen et al., Phys. Rev. C 89, (2014) 034624 [4] F. de Grancey et al., Phys. Lett. B 758, (2016) 26-31 [5] G.X. Dong et al., J. Phys. G: Nucl. Part. Phys. 44 (2016) 045201 [6] K. Fossez et al., Phys. Rev. C 91, (2015) 034609

Speaker: Dr Nicolas Michel (NSCL/MSU)

91 Resonance and Continuum in Atomic Nuclei

Resonance is a general phenomenon happening in classic or quantum systems. It plays a special role in weakly-bound or unbound quantum systems. An unbound quantum system, such as atomic cluster or unbound nucleus, can emerge in the form of intrinsic resonance. Starting from realistic nuclear forces, we have developed a core Gamow shell model which can describe resonance and continuum properties of loosely-bound or unbound nuclear systems. To describe properly resonance and continuum, the Berggren representation has been employed, which treats bound, resonant and continuum states on equal footing in a complex-momentum plane. To derive the model-space effective interaction from realistic forces, the full Q-box folded-diagram renormalization has been developed for the nondegenerate complex-momentum space. The CD-Bonn potential is softened by using the Vlow-k method. Choosing O-16 as the inert core, we have calculated sd-shell neutron-rich oxygen isotopes, giving good descriptions of both bound and resonant states. The isotopes O-25 and O-26 are calculated to be resonant even in their ground states. Excited-state resonance spectra have been calculated and analyzed systematically for neutron-rich oxygen isotopes, compared with available experimental observations.

Speaker: Prof. Furong Xu (Peking University)

92 Recent Progress in Building Novel Nonlocal Energy Density Functionals

Numerous applications of nuclear DFT have shown a tremendous success of the approach, which by using a dozen-odd coupling constants allows for correct description of a multitude of nuclear phenomena. However, recent analyses indicate that the currently used models have probably reached their limits of precision and extrapolability. The question of whether these can be systematically improved appears to be one of the central issues of the present-day investigations in nuclear-structure theory. In this talk, I will present status of theoretical developments that aim to build novel nonlocal energy density functionals (EDFs). In particular, we recently proposed [1] to use a two-body regularized finite-range pseudopotential to generate nuclear EDFs in both particle-hole and particle-particle channels, which makes them suitable for beyond-mean-field calculations. We derived a sequence of pseudopotentials regularized up to next-to-leading order (NLO) and next-to-next-to-leading order (N2LO), which fairly well describe infinite-nuclear-matter properties and finite open-shell paired and/or deformed nuclei. Solutions of the corresponding self-consistent equations were implemented in spherical and triaxial symmetries, codes FINRES4 [2] and HFODD [3], respectively. In Landau theory of Fermi liquids, the particle-hole interaction near the Fermi energy in different spin-isospin channels is probed in terms of an expansion over the Legendre polynomials. In Ref. [4] we showed general expressions for Landau parameters corresponding to a two-body central local regularized pseudopotential and we showed results obtained for the two recent parametrizations NLO and N2LO, adjusted in Ref. [1]. In Ref. [5] we showed results of the Hartree-Fock-Bogolyubov calculations performed using these two parametrizations. We discussed properties of binding energies and pairing gaps determined in semimagic spherical nuclei. The results were compared with benchmark calculations performed for the functional generator SLyMR0 [6] and functional UNEDF0 [7]. References: [1] K. Bennaceur et al., arXiv:1611.09311 [2] K. Bennaceur et al., to be submitted to Comp. Phys. Comm. [3] J. Dobaczewski et al., to be submitted to Comp. Phys. Comm. [4] A. Idini et al., arXiv:1612.00378 [5] K. Bennaceur et al., Proc. of 6th Int. Conf. on "Fission and Properties of Neutron-Rich Nuclei", arXiv:1701.08062 [6] J. Sadoudi et al., Phys. Scr. T154, 014013 (2013) [7] M. Kortelainen et al., Phys. Rev. C 82, 024313 (2010)

Speaker: Prof. Jacek Dobaczewski (University of York)

93 Fusion with Exotic Nuclei Using Microscopic Methods

Fusion reactions are affected by nuclear structure and many dynamical processes.Some effects of internal nuclear structure on reactions such as heavy-ion fusion can be seen by studying features of experimental fusion barrier distributions.Until more recently, theoretical modelling of these reactions were largely of phenomenological nature. Whilst this approach is useful to start with and works very well for light stable systems, moving towards heavier and more exotic systems demands more powerful theory to be able to both describe processes observed experimentally and predict fusion cross sections for exotic nuclei. Upcoming exotic beam facilities provide motivation to understand reaction with neutron rich nuclei theoretically. Microscopic approaches based on energy density functionals (EDF) provide insightful tools to study heavy-ion reactions including fusion. The same EDF can be used to describe both structure and reaction properties on the same footing [1]. Based on this method, one can investigate reaction dynamics, such as near barrier fusion, with both stable and exotic nuclei [2,3]. We use both static and time-dependent versions of the EDF method to study the fusion reactions along isotopic chains. For instance, there are clear differences between potential barriers calculated with static and time-dependent Hartree-Fock methods. A key result is that the dynamics plays a major role in the reaction, washing out static effects such as neutron skins which are expected to lower the bare potential barrier [2]. Instead, coupling to transfer channels, which have been studied microscopically in [3], is shown to play an important role. References: [1] C. Simenel, M. Dasgupta, D. J. Hinde and E. Williams, Phys. Rev. C 88, 064604 (2013). [2] K. Vo-Phuoc, C. Simenel and E. C. Simpson, Phys. Rev. C 94, 024612 (2016). [3] K. Godbey, A. S. Umar and C. Simenel, Phys. Rev. C 95, 011601(R) (2017).

Speaker: Dr Cedric Simenel (Australian National University)

15:45 Coffee Break

Breakout 1: Thursday After PM Coffee

94 β -delayed Neutron Emission Studies for Heavy Isotopes

β-decay is the most common way for neutron-rich nuclei to reach the stability valley. However, when the neutron separation energy is lower than the Qβ-value, β-delayed neutron emission [1] takes over a dominant role in these β-decays, decreasing the mass of the nucleus by one unit (β1n) or more in the case of multiple neutron emission (β2n, β3n, ...). The study of the neutron branching ratios, Pn, is crucial for a better understanding of the astrophysical rapid neutron capture (r-) process where neutron emission can become dominant during freeze-out when the material decays back to stability. So far only a third of the around 600 accessible isotopes that are neutron emitters have been measured, the heaviest ones with masses up to A~150 [2], plus a single measurement for 210Tl [3]. Concerning multiple neutron emission, only 24 of the ~300 accessible isotopes have been measured up to mass A=100. In this contribution the results of two recent measurements with the neutron detector BELEN [4] will be presented. A first experiment performed at the GSI Darmstadt (Germany) with the Fragment Separator allowed for the first time the determination of the P1n values of several isotopes of Hg and Tl for masses beyond A>200 and N>126 [5]. A second experiment that took place at the IGISOL facility in Jyvaskyla (Finland) allowed to measure the heaviest β2n emitter identified so far, 136Sb. The resulting P2n value is much smaller than previously assumed. In addition, the P1n values of many important fission products in this mass region were remeasured with higher precision [6]. An outlook will be given about the BRIKEN campaign at RIKEN (Japan) which was commissioned in November 2016 and will start data taking in May 2017. BRIKEN aims to perform in the next years measurements for more than a hundred β1n-, dozens of β2n- and several β3n-emitters, lots of them for the first time and in the most exotic regions reached so far. References: [1] R.B. Roberts, R.C. Meyer and P. Wang, Phys.Rev. Vol.55, 510 (1939). [2] B. Pfeiffer and K-L. Kratz, Progress in Nucl. Energy, Vol.41, 39-69 (2002). [3] G. Stetter, Sci. Abstr., 16, 1409 (1962). [4] M.Gomez-Hornillos et al., Hyperfine Interactions 223, 185 (2014). [5] R.Caballero-Folch, C.Domingo-Pardo et al., Phys.Rev.Lett., Vol.117, 012501 (2016). [6] J.Agramunt et al., Nuclear Data Conference, Bruges (Belgium) (2016).

Speaker: Dr Roger Caballero-Folch (TRIUMF)

95 Gamma and Fast-timing Spectroscopy Around 132Sn From the Beta-decay of In Isotopes

During the last two decades there has been a substantial effort directed to gather information about the region around the neutron-rich 132Sn[1]. Nuclei in the regions of shell closures with a large N/Z ratio such as 132Sn are of great interest to test nuclear models and provide information about single particle states. More stringent tests of the models can be provided by the reduced transition probabilities connecting nuclear states. In this work we have used fast-timing and gamma spectroscopy to study five Sn nuclei, including the doubly magic 132Sn, the two neutron hole 130Sn and two-neutron particle 134Sn, and the one-neutron hole 131Sn and one-neutron particle 133Sn. The Sn isotopes were studied at the ISOLDE facility, where their excited states were populated in the beta-decay of In isomers, produced in a UCx target unit equipped with a neutron converter. The In isomers were ionized using the ISOLDE Resonance Ionization Laser Ion Source (RILIS), which for the first time allowed isomer-selective ionization. The measurements took place at the new ISOLDE Decay Station (IDS), equipped with four highly efficient clover-type Ge detectors, along with a compact fast-timing setup consisting on two LaBr3(Ce) detectors and a fast beta detector. The setup incorporated a tape transport system to remove longer-lived activities. Indium isotopes with masses ranging from 130 to 134 were produced. The RILIS isomer selectivity made it possible to produce odd-mass In isotopes with a clean separation between the 9/2+ and 1⁄2- beta-decaying isomers. For the even isotopes, such as 130In, it was also possible to separate the 5+, 10- and 1- isomers. We report on the lifetime of the 331-keV 1/2+ level in 131In, which provides information on the M1 transition to the ground state and on its degree of forbiddeness, similar to what has been recently been measured in [2]. In addition we explore the presence of the h11/2 single particle level at 65.1 keV[3] using coincidences. For 133Sn we discuss the identification of the 1363-keV level as the 2p1/2 single-particle state, and on the search for the missing 13/2+ state [4]. We also report on the search for the particle-hole multiplet states that have not been identified yet in the even Sn isotopes, in particular in 132Sn. References: [1]A. Korgul et al, Phys Rev Lett 113,132502(2014) [2]R. Lica et al, Phys Rev C93,044303(2016) [4]B. Fogelberg et al Phys Rev Lett C 70,034312(2004) [3]J. M. Allmond et al Phys Rev Lett 112,172701(2014)

Speaker: Mr Jaime Benito García (Universidad Complutense de Madrid)

96 Gamow-Teller Decay of 74Co and Decay Properties of 78Co→78Ni

First experimental studies of the doubly magic nucleus 78Ni became possible [1,2] and are needed to provide critical data to test robustness of the nuclear shell structure and model the astrophysical r-process [3]. One way to study the structure of neutron-rich nickel isotopes (Z = 28) is to investigate decays of the respective cobalt precursors (Z = 27). This method has been successfully implemented in fragmentation-type experiments reaching the very exotic 77Co. While it is presently not possible to produce 78Co with sufficient rate to use it for studies of excited states in 78Ni, the decay measurements of 78Co will be possible with the new facilities under construction around the world and beam intensity upgrades. Nevertheless, information on the β decay of the most neutron rich cobalt isotopes enables us to predict decay properties of 78Co to 78Ni. We will present new data on the decay of 74Co, which we use to extend the systematics on the decay of even-A cobalt isotopes to predict decay properties of 78Co. Low-energy level structure of 74Ni was investigated through the β-decay of 74Co at the National Superconducting Cyclotron Laboratory (NSCL). The ions of 74Co were produced by projectile fragmentation of 82Se ions at an energy of 140 MeV/nucleon on a 9Be target. The particle identification was performed on an event-by-event basis by measuring energy loss (ΔE) in a silicon detector placed in the beam line and time-of-flight (TOF) between focal planes. The separated fragments were implanted in a germanium double-sided strip detector [4]. The experimental data show existence of two β-branching states in 74Co based on observation of two γ-ray cascades populating low- and high-spin states in 74Ni. The origin of the decay is attributed to the strong Gamow-Teller transformation from νf5/2 to πf7/2. The systematics of the B(GT) strength distribution in neutron-rich cobalt isotopes and N=51 isotones indicate the robustness of the closed core in 78Ni. Predictions for decay properties of 78Co are made from the systematics and shell model calculations. References: [1] C. Engelmann et al., Z. Phys. A 352, 551 (1995). [2] M. Bernas et al., Phys. Lett. B 415, 111 (1997). [3] E. M. Burbidge et al., Rev. Mod. Phys. 29, 547 (1957). [4] N. Larson et al., Nucl. Instr. Meth. A 727, 56-64 (2013).

Speaker: Dr Shintaro Go (University of Tennessee)

97 Beta-Decay and Mass-Measurement Studies of Deformed, Neutron-Rich Nuclei in the A~160 Region*

Properties of deformed, neutron-rich nuclei in the A~160 region are important for achieving a better understanding of the nuclear structure in this region where little is known owing to difficulties in the production of these nuclei at the present RIB facilities. These properties are essential ingredients in the interpretation of the rare-earth peak at A~160 in the r-process abundance distribution, since various theoretical models depend sensitively on the nuclear structure input. Predicated on these ideas, we have initiated a new experimental program at Argonne National Laboratory. The first experiment recently took place where a combination of the CARIBU radioactive beam facility with the new SATURN decay station and the X-array clover array was performed. We focused initially on several odd-odd nuclei, where decays of both the ground state and an excited isomer were investigated. Because of the spin difference, a variety of structures in the daughter nuclei were selectively populated and characterized based on their decay properties. Results from these studies will be presented, including the first identification of beta-decaying isomers in both 160Eu and 162Eu, together with predictions using multi-quasiparticle blocking calculations that include the effect of the residual nucleon-nucleon interactions. Mass measurements using the Canadian Penning Trap aimed at measuring the excitation energy of the beta-decaying isomers were also carried out and new results will be also reported. *This research is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC02-06CH11357 (ANL) and by the National Science Foundation under Grant No. PHY-1502092 (USNA). This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.

Speaker: Dr Filip Kondev (Argonne National Laboratory)

98 Intruder States in Neutron Rich Phosphorus Isotopes Near N=28

Understanding the evolution of shell structure as a function of N/Z is one main focus of current nuclear structure studies. The force behind the migration of orbitals is the monopole part of the tensor interaction. Refinement of this monopole term to increase the predictive powers of shell model calculations underscores the need for more experimental information, specially for excited states in exotic nuclei. Odd Z and odd-odd nuclei provide one of the most stringent tests of shell model predictions as many more degrees of freedom are available. The structure of odd Z phosphorus isotopes (N = 22 – 25) were investigated at the National Superconducting Cyclotron Laboratory via the beta decay of Si isotopes. Following allowed beta decay, intruder states were populated in the P isotopes which could be identified based on the measured logft values. First gamma transitions in 38,40P were observed de-exciting the strongly populated 1+ states. These 1+ states at relatively low energy (~2MeV) with parity opposite to the 2- ground state are core excited 1p-1h states (1). The occurrence of intruder states at low energies highlights the importance of pairing and quadrupole correlation energies in lowering the intruder states despite the N = 20 shell gap. Configuration interaction shell model calculations with the state-of-art SDPF-MU effective interaction were performed to understand the structure of these 1p1h states in the even-A Phosphorus isotopes. States in 40P with N = 25 were found to have very complex configurations involving all the fp orbitals leading to deformed states as seen in neutron rich nuclei with N ~ 28. The calculated GT matrix elements for the beta decay highlight the dominance of the decay of core neutrons over the valence neutrons in neutron rich nuclei when neutrons and protons occupy shells of opposite parity. Unlike the even A isotopes, for the odd A isotopes the negative parity intruder states lie at higher excitation energies and the beta decay strength was found to be fragmented. Systematic discussion of the results for 37-40P will be presented highlighting the effects of adding neutrons on the shell structure. References: 1) V. Tripathi et al., accepted in PRC, 1/24/2017 This work was supported by NSF grants PHY-1401574 (FSU) and PHY-1068217 (NSCL), US DoE under contracts DEAC02-05CH11231 (LBNL) and DE-SC00098 (FSU) and JSPS KAKENHI (Japan), Grants No. 25870168 and 15K05094.

Speaker: Dr Vandana Tripathi (Department of Physics, Florida State University, Tallahassee Fl 32306, USA)

99 Shape Coexistence in Neutron-rich 31Mg Investigated by Beta-gamma Spectroscopy of Spin-polarized 31Na

One of the long-standing subjects of nuclear physics is the shape transition of the ground state far from the beta-stability line. In particular, neutron-rich nuclei with neutron number close to the neutron magic number N = 20, so-called the “island of inversion”, have attracted much attention. In this mass region of the nuclear chart, it was suggested that the ground states are rather deformed, although these nuclei have a nearly-magic number of neutrons. In the recent theoretical studies [1, 2], not only the ground-state deformation but also shape coexistence were suggested in a low excitation energy region of nuclei in the island of inversion. In the present work, we study on neutron-rich nucleus 31Mg (N=19). The level structure of odd-mass 31Mg is one of the most sensitive probe of shape coexistence, because the nuclear structure is strongly affected by the configuration of the last neutron. However, up to now, none of the spins and parities, which are the key quantities to understand the nuclear structure, were not firmly assigned except for the ground state. In such a situation, it is rather difficult to discuss the structure of 31Mg. In the present work, the detailed level structure of 31Mg is investigated by our extremely promising method [3] to assign spin-parity of excited states based on the beta-gamma spectroscopy of the spin-polarized 31Na. The experiment was performed at ISAC in TRIUMF, where a highly polarized 31Na beam is available. Our method is successfully applied to the excited states of 31Mg, and the spins and parities of 5 levels in 31Mg are unambiguously determined by detection of the beta-ray asymmetry. The firm spin-parity assignments for the exited states enable us to compare with the theoretical calculations of the AMD+GCM framework [1] on level-by-level basis. It is found that the levels in 31Mg are categorized into three types of largely deformed rotational bands, states with spherical natures, and a state which cannot be explained by theoretical models at present. The recent shell model [2] also predicts the levels with the three different configurations below 1 MeV, and they are in good agreement with the experimental results. These facts provide clear evidence for the shape coexistence in a low excitation energy region of 31Mg. References: [1] M. Kimura, Phys. Rev. C 75, 041302(R) (2007). [2] E. Caurier et al., Phys. Rev. C 90, 014302 (2014). [3] K. Kura et al., Phys. Rev. C 85, 034310 (2012).

Speaker: Dr Hiroki Nishibata (RIKEN Nishina Center)

100 Detailed Spectroscopy of Neutron-rich Sn Isotopes with GRIFFIN

The region of neutron-rich tin isotopes near A = 130 is of great interest to nuclear structure. In particular, 132Sn with 50 protons and 82 neutrons represents a doubly magic nucleus and provides an essential benchmark for the shell model far from stability. Understanding the structure of this nucleus provides a foundation to comprehend the single-particle nature of excited states in neighboring isotopes. With no excited states below 4 MeV, 132Sn can be considered to be the most magic among heavy nuclei. Among known excited states, several particle-hole multiplets have been identified, as well as a collective 3- level characteristic of doubly magic nuclei [1,2]. In addition to nuclear structure considerations, the region around 132Sn is also useful in astrophysics, as studying the properties of these nuclei is key to understanding the r-process path and its role in creating the A = 130 abundance peak. The nucleus 132Sn has recently been studied as part of a campaign to investigate the structure of neutron-rich tin isotopes at the TRIUMF-ISAC facility. Excited states in 132Sn were produced from the beta-decay of 132In. A low-energy beam of 132In was delivered to the GRIFFIN experimental station [3], where the 16 high-purity germanium clovers were used to detect gamma-rays. In addition, SCEPTAR [4], an array of 20 plastic scintillators, was used to detect beta-particles to create beta-gamma-gamma coincident spectra. This experiment represents the most sensitive study of 132Sn to date, allowing for the identification of new weakly fed levels as well as confirmation of spin and parity assignments of several excited states via angular correlation measurements. In this talk, I will present new results on the levels in this nucleus as well as prospects for other Sn isotopes. References: [1] B. Fogelberg et al., Phys. Rev. Lett. 73, 2413 (1994). [2] P. Battacharyya et al., Phys. Rev. Lett. 87, 062502 (2001). [3] C.E. Svensson and A.B. Garnsworthy, Hyperfine Interact. 225, 127 (2014). [4] G.C. Ball et al., J. Phys. G 31, S1491 (2005).

Speaker: Dr Kenneth Whitmore (Simon Fraser University)

101 Decay Spectroscopy of Neutron-Rich Cd Around the \mbox{\textit{N} = 82} Shell Closure

The neutron-rich Cadmium isotopes around $A=130$ are of special interest to both nuclear structure and astrophysics. Situated near the well-known magic numbers at $Z=50$ and $N=82$, these nuclei are prime candidates to study the evolving shell structure observed in exotic nuclei. Additionally, the extra binding energy observed around the nearby doubly-magic $^{132}$Sn has direct correlations in astrophysical models, leading to the second r-process abundance peak at $A\approx130$ and the corresponding waiting-point nuclei around $N=82$. The $\beta$-decay of the $N=82$ isotope $^{130}$Cd into $^{130}$In was first studied a decade ago [1], but the information for states of the lighter indium isotope ($^{128}$In) is still limited. These motivating factors has led us to perform detailed $\gamma$-ray spectroscopy following the $\beta$-decay of $^{128-132}$Cd using the GRIFFIN [2] facility at TRIUMF, which is capable of performing spectroscopy down to rates of \mbox{0.1 pps}. The ongoing analysis of the $^{128,131,132}$Cd will be presented. Already in $^{128}$Cd, 23 new transitions and 15 new states have been observed in addition to the 4 previously observed excited states [3]. Its half-life has also been remeasured via the time distribution of the strongest $\gamma$-rays in the decay scheme with a higher precision [4]. For $^{131}$Cd, results will be compared with the recent EURICA data. These data highlight the unique capabilities of GRIFFIN for decay spectroscopy on the most exotic, short-lived isotopes, and the necessity to re-investigate also "well-known" decay schemes for missing transitions. References: [1] I. Dillmann {\it et al}, Phys. Rev. Let. {\bf 91}, 162503 (2003) \h\ [2] C.E. Svensson and A.B. Garnsworthy, Hyperfine Int. {\bf 225}, 127 (2014) \\ [3] B. Fogelberg, Proc. Intern. Conf. Nuclear Data for Science and Technology, Mito, Japan, p.837 (1988) \\ [4] R. Dunlop {\it et al}, Phys. Rev. C {\bf 93}, 062801(R) (2016).

Speaker: Nikita Bernier (TRIUMF/UBC)

102 Spying on Intruders in the 68Ni Region with Fast Timing

The nucleus 68Ni is the portal to the understanding of the modification of shell structure in the Z=28 and N=40 region and the appearance of collective phenomena. In spite of showing some of the characteristics of a doubly magic nucleus, the two-neutron separation energy does not show evidence for an enhanced N=40 harmonic oscillator shell gap, and collectivity emerges for 66Fe and 64Cr with just one and two proton pairs less than 68Ni. The changes in shell structure around 68Ni are driven by excitations across the Z=28 and N=40 shell gaps, where the neutron g9/2 and d5/2 configurations and the proton p3/2 orbital play a key role. This scenario provides the breeding ground for shape-coexistence. Indeed, several 0+ states have been observed in 68Ni below 3 MeV [1,2]. They can be explained in the framework of Monte Carlo shell model calculations [3], which yield prolate bands built on strongly deformed 0+ states appear for several eve Ni Isotopes, and by multiple particle-hole excitations in the shell model framework [4]. A similar picture is observed for 66Ni, where three excited 0+ states have been identified [5]. The coexistence of configurations has been observed in the Z=27 Co isotopes, for which low-lying proton intruders have been reported in 65,67Co [6]. In this paper we investigate of intruder configurations via the fast timing ATD bgg(t) measurement of excited level lifetimes in nuclei around 68Ni. The nuclides under study were populated in the beta-decay chains of Mn isotopes, strongly produced at ISOLDE on a UCx target, and selectively ionized by RILIS. We report on level lifetimes in 68Ni, in particular on investigation of the transition connecting the third 0+ with the first 2+, and compare it to the recent result by Crider et al. [4]. We provide information on the lifetime of the third 0+ 2671-keV level in 66Ni, and on the transition connecting it to the first excited 2+ level. We interpret these supposedly similar configurations in 66Ni and 68Ni in the shell model framework. We also investigate the role of proton intruders by examining the state at 1095 keV in 65Co, whose lifetime has also been measured. References: [1] F. Flavigny et al., Phys. Rev. C 91, 034310 (2015) [2] B.P. Crider et al., Phys. Lett. B 763, 108 (2016) [3] Y. Tsunoda et al., Phys. Rev. C 89, 031301 (2014) [4] S.M. Lenzi et al., Phys. Rev. C 82, 054301 (2010) [5] W.F. Mueller et al., Phys. Rev. C 61, 054308 (2015) [6] D. Pauwels et al., Phys. Rev. C 79 044309 (2009)

Speaker: Luis M Fraile (Universidad Complutense de Madrid)

Breakout 2: Thursday After PM Coffee

103 Charge Exchange Reactions of Unstable Nuclei and the Beta-Decay Strength

The Gamow-Teller transition (G-T) strengths are important for understanding nucleosynthesis in stars. The transition strength not only from a ground state but also from an excited state become important in some cases. Charge exchange reactions provide information of G-T strength even for transitions to excited states. However such studies had been done only at around stable nuclei. Here we show the first measurement of charge exchange (p,n) reaction on C isotopes from A=12 to 19 and demonstrate the feasibility of such experiments. In the present experiment, production cross sections of nitrogen isotopes from high-energy (~950 MeV per nucleon) carbon isotopes on hydrogen have been measured. The fragment separator FRS at GSI was used to deliver C-isotope beams. Since the production of nitrogen is mostly due to charge-exchange (Cex) reactions below the proton separation energies, the present data reveal Gamow–Teller and/or Fermi transition strength at low excitation energies for neutron-rich carbon isotopes. The windows of a Cex reaction below the proton emission threshold and window of the beta-decay are very close with each other for neutron rich nuclei because of the small neutron separation energy. Comparisons of transition strength obtained by two methods were made for C isotopes and consistent results were obtained for nuclei of which beta-strength are known. In light nuclei most of the transition is allowed and thus no complications due to forbidden transition is seen. The Cex cross section increases for more neutron-rich C isotopes indicating the increase of sum of the beta strength within the window. Since the two windows are almost same for nuclei along the r-process path, studies of charge exchange reactions of r-process nuclei would provide information on the total strength of beta decay complementary with the half-life measurement in which decay strength are weighted by the decay energy of each decay channel. A simultaneous measurement of the neutrons and fragments is expected to give us more detailed information. Perspective and future experiments will be discussed in addition.

Speaker: Prof. I. Tanihata (School of Physics and Nuclear Energy Engineering and IRCNPC, Beihang University, Beijing 100191, China and RCNP, Osaka University, Ibaraki, Osaka 567-0047, Japan)

104 Structure of Unbound Nuclei 10-N and 9-He

Evolution of nuclear structure of Nitrogen isotopes (Z=7) and N=7 isotones with increasing imbalance between protons and neutrons has been a focus of intense scrutiny since the discovery of parity inversion in 11-Be. Yet, the level structure of the most exotic nuclear systems with 7 neutrons or protons (such as 9-He, 10-Li, 10-N) remain uncertain and presents a major challenge both theoretically and experimentally. Recent experimental results that shed light on the structure of 9-He and 10-N will be discussed. The low-lying levels in 10-N (mirror of 10-Li) have been populated in 9-C+p resonance scattering [1]. The location of the 2s1/2 shell in this most neutron deficient isotope of Nitrogen is now firmly established. Properties of the ground and first excited states of 10-N will be discussed. The level structure of 9-He was studied through the T=5/2 isobaric analog states in 9-Li, populated via 8-He+p resonance scattering [2]. No narrow T=5/2 structures were observed in the proton spectrum, providing strong evidence that there are no narrow, near neutron threshold states in 9-He, suggested previously in several other experiments (see [3] and references therein). The new experimental results provide a good basis for better understanding of shell evolution in Z/N=7 nuclear systems and for making reliable extrapolations on the structure of 10-Li and 9-N (never observed) isotopes. References: [1] J. Hooker, G.V. Rogachev, V.Z. Goldberg, et al., Phys. Lett. B (submitted). [2] E. Uberseder, G.V. Rogachev, V.Z. Goldberg, et al., Phys. Lett. B 754 323 (2016). [3] T. Al Kalanee, et al., Phys.Rev. C 88, 034301 (2013).

Speaker: Dr Grigory Rogachev (Texas A&M University)

105 Probing Neutron-Proton Correlation and 3N-force in 12C

Direct observation of neutron-proton (np) correlations and 3N-froce in nuclei is the long-sought goal in nuclear physics. Two-nucleon knockout reactions offer a powerful tool as the reaction cross section is a direct probe of nucleon correlations. The experimental data of 12C on a carbon target reveal that the inclusive cross sections of residues from np removal channel (10B) is approximately 6-8 times greater than those for nn pair (to 10C) and pp pair (to 10Be) [1,2], already in excess of the 16/6 ≈ 2.7 ratio from simple pair counting in 12C. Such enhancement however could not be described by the calculations using eikonal reaction dynamics and microscopic structure from the effective-interaction shell model and the no-core shell model with chiral NN+3N interactions [3]. To further investigate the nature of nucleon correlations and the origin of discrepancy between the observations and theories, we have performed the first final-state exclusive np-removal cross section measurements using DALI2 gamma-detection array and SAMURAI spectrometer at RIKEN. By the gamma-residue coincidence measurement, the partial cross sections to 10B and 10Be T=0 and T=1 final sates following np and pp removal from 12C at 200 MeV/u were extracted. The experimental results indicate the insufficient treatment of T=0 np-correlations and 3N-force in the current microscopic structure models. In this talk, the experimental setup and the physics results will be discussed. References: [1] D. L. Olson et al., Phys. Rev. C. 28, 1602 (1983) [2] J. M. Kidd et al., Phys. Rev. C. 37, 6 (1988) [3] E. Simpson P. Navrátil, R. Roth, and J. A. Tostevin, Phys. Rev. C 86, 054609 (2012).

Speaker: Dr Jenny Lee (The University of Hong Kong)

106 Neutrons Correlations in the Continuum of Two (core + 4n) Systems

Nuclear correlations involved in neutron-rich nuclei, up to the drip line, play essential roles in the understanding and modeling of neutron captures in the r-process nucleosynthesis as well as in the understanding of phenomena linked to the neutron star superfluidity. They are also interesting in view of generalizing the Ikeda conjecture, commonly applied to alpha clusters, to dineutron clusters above the corresponding emission threshold. We have discovered a novel method that allows to reveal neutron correlations in the nucleus and to search for dineutron contribution. This was achieved by studying the decay of high energy states above S2n populated after the sudden knockout of a deeply bound nucleon. This sudden approximation, together with a quasi-free knockout process can reliably be assumed, owing to the high energy of the projectile used (440MeV/u) during the experiment. This experiment, performed at GSI, required the complex and innovative R3B-LAND setup to determine the full kinematics of the reaction. My presentation will be focused on the n-n correlations observed in the decay of unbound states in the 18C and 20O (viewed as 14C+4n and 16O+4n, respectively) populated via the sudden knockout of a proton in 19N and a neutron in 21O, respectively. We have studied the evolution of the n-n correlations as a function of the increasing energy Ed of the neutrons and compared the decay patterns of the two systems; i.e. the former, in which neutron pairs are in principle kept intact, and the second in which the 16O core is broken, leaving two unpaired neutrons. We used a simulation that takes into account the different decay mechanisms (direct, sequential and dineutron decay) and the final state interactions to interpret the experimental data. Using information on n-n and core-n momenta, we show that we can clearly distinguish direct from sequential decays. Remarkably, direct decays are strongly dominant in 18C up to Ed=8MeV, beyond which sequential decay amounts to only 20%. A very strong enhancement is found at small relative neutron momentum angles, that is discussed in term of a dineutron component. This is in contrast to the case of 20O, in which sequential decays dominate already at low Ed, and in which much weaker n-n correlations are observed. Due to the success of this method, we are planning in a near future to extend such a study to other systems closer to the drip line and to generalize the study of neutron correlations to the 4n decay channel.

Speaker: Mr Aldric REVEL (GANIL)

107 Evidence for Z=6 Subshell Cclosure in Neutron-rich Carbon Isotopes

The nuclear magic numbers, as we know in stable nuclei, consist of two different series of numbers. The first series – 2, 8, 20 – is attributed to the harmonic oscillator potential, while the second one – 28, 50, 82, and 126 – is due to the spin-orbit interactions. The spin-orbit interactions are known to be significant and responsible for the large (spin-orbit) splitting of the single-particle states in heavy nuclei. These interactions, however, are expected to diminish in light nuclei due to the low orbital angular momenta. This general expectation is supported by the fact that there is an apparent lack of fingerprints for a `magic number’ (subshell closure) at 6 or 14 [1], which might have arisen from the widening 1p1/2-1p3/2 and 1d3/2-1d5/2 gaps, respectively, in the stable nuclei. A possible subshell closure at N=6 has been suggested both theoretically [2] and experimentally [3] in the very neutron-rich 8He isotope. For Z=6 and 14, possible subshell closures have been suggested [4] in the semi-magic 14C and 34Si. In this talk, we will present experimental evidence for a prevalent subshell closure at proton number Z=6 in the neutron-rich carbon isotopes. We investigated (i) the point proton density distribution radii, combining our recent data for Be, B and C isotopes measured at RCNP, Osaka University and GSI, Darmstadt, with the available data from Ref. [5]; (ii) the atomic masses [6]; and (iii) the electromagnetic transition strengths [7] for a wide range of isotopes. Our systematic analysis revealed marked regularities which support a prominent proton `magic number’ Z=6 in 13−20C. References: [1] M. G. Mayer, Nobel Lectures in Physics, 20 – 37 (1963). [2] T. Otsuka et al., Phys. Rev. Lett. 87, 082502 (2001). [3] F. Skaza et al., Phys. Rev. C 73, 044301 (2006). [4] I. Angeli and K. P. Marinova, J. Phys. G: Nucl. Part. Phys. 42, 055108 (2015). [5] I. Angeli and K. P. Marinova, At. Data Nucl. Data Tables 99, 69 – 95 (2013). [6] M. Wang et al., Chinese Phys. C 36, 1603 – 2014 (2012). [7] B. Pritychenko et al., At. Data Nucl. Data Tables 107, 1 – 139 (2016).

Speaker: Dr Hooi Jin ONG (RCNP, Osaka University)

108 Direct Measurements of (α,p) Reactions with ANASEN

The LSU-FSU Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) has been developed, in part, for the direct measurement of (α,p) reactions with radioactive beams. It is currently installed at the John D. Fox Superconducting Accelerator Laboratory at FSU. The ANASEN detector consists of position-sensitive proportional counter aligned with the beam axis surrounded by a barrel-shaped array of double-sided silicon strip detectors. Utilizing an active gas target, ANASEN is able to measure the excitation function of reactions through a range of energies relevant to astrophysics. Recently, two measurements on neutron-deficient N=8 nuclei were made with ANASEN. Both measured reactions are important to the understanding of Type-I X-ray bursts. Sensitivity studies of reaction network calculations indicate that the rate of the 18Ne(α,p)21Na reaction plays an important role in breakout into the rp-process from the hot CNO cycles in Type-I X-ray bursts [1,2]. The rate of the 17F(α,p)20Ne reaction has significant influence on both the output light curve and the composition of ashes in multi-zone X-ray burst model calculations [3]. The results of these measurements will be presented. This work was supported by the National Science Foundation through awards PHY-0820941 and PHY-1401574 and by the Department of Energy, Office of Science, under grants No. DE-FG02-96ER40978. References: [1] P. Mohr and A. Matic, Phys. Rev. C 87, 035801 (2013). [2] A. Parikh et al. ApJS 178 110 (2008). [3] Cyburt et al. ApJ 830 55 (2016).

Speaker: Dr Jon Lighthall (Louisiana State University)

109 Investigation of 198Hg and 199Hg Through Direct Reactions for the Interpretation of EDM Limits

The observation of a large permanent electric dipole moment (EDM) would represent a clear signal of CP violation from new physics outside the Standard Model. The 199Hg isotope currently provides the most stringent limit on an atomic EDM, which is converted to a limit on the nuclear EDM via a calculation of the Schiff moment. To do this knowledge of the nuclear structure of 199Hg is required. Ideal information to further develop and constrain the 199Hg Schiff moment nuclear structure theoretical models are the E3 and E1 strength distributions to the ground state, and E2 transitions amongst excited states. The high level density of 199Hg makes those determinations extremely challenging, however similar information can be obtained from exploring surrounding even-even Hg isotopes. One of the most direct ways of measuring the E3 and E2 matrix elements is through inelastic hadron scattering, and single-nucleon transfer reactions on targets of even-even isotopes of Hg can yield important information on the single-particle nature of 199Hg. As part of a campaign to study the Hg isotopes, a number of experiments have been performed using the Q3D spectrograph at the Maier-Leibnitz Laboratory, with 22 MeV deuteron beams impinging on enriched Hg32S targets. The first experiment accesses the E2 and E3 matrix elements in 198Hg via inelastic deuteron scattering. We measured 9 angles ranging from 10 to 115 degrees up to an excitation energy of 5 MeV. The second set of measurements discussed will be single-nucleon transfer reactions, 198Hg(d,p)199Hg with spin-parity assignments and spectroscopic factors extracted through distorted-wave Born approximation calculations with global optical model parameter sets.

Speaker: Alejandra Diaz Varela (University of Guelph)

110 Quasi-free Proton Knockout Reactions on the Oxygen Isotopic Chain

According to the Independent Particle Model (IPM) single-particle (SP) states are fully occupied up to the Fermi energy with spectroscopic factors (SF) of one. However, it is well known from electron-induced proton knockout that the SP strength is reduced to about 60-70% for stable nuclei, which has been attributed to the presence of short- and long-range correlations[1]. This finding has been confirmed by nuclear knockout reactions using stable and exotic beams, however, with a strong dependency on the proton-neutron asymmetry [2]. The observed strong reduction of SP cross sections for the deeply bound valence nucleons in asymmetric nuclei is theoretically not understood. To understand this dependency quantitatively a complementary approach, quasi-free (QF) knockout reactions, is introduced. QF knockout reactions in inverse kinematics at relativistic energies provide a direct way to investigate the SP structure of stable and exotic nuclei [3]. We have performed a systematic study of spectroscopic strength of oxygen isotopes using QF (p,2p) knockout reactions in complete kinematics at the R3B/LAND setup at GSI with secondary beams containing 13−24O. The oxygen isotopic chain covers a large variation of separation energies, which allow a systematic study of SF with respect to neutron-proton asymmetry. We will present results on the (p,2p) cross sections for the entire oxygen isotopic chain obtained from a single experiment. By comparison with the Eikonal reaction theory [4] the SF and reduction factors as a function of separation energy have been extracted and will be compared to existing data in literature. The results include total and partial cross sections extracted by means of gamma-coincidence measurements as well as momentum distributions. The latter are sensitive to the angular momentum of the knocked-out nucleon in the projectile. Finally, a brief report will be given on a pioneer experiment performed at RIKEN where the QF (p,2p)-fission reaction was employed for the first time on 238U as a benchmark test for future applications to determine fission barriers of neutron-rich exotic nuclei near 208Pb and 214Bi. This work is supported by the GSI-TU Darmstadt cooperation agreement and the BMBF Verbundforschung under contract 05P15RDFN1. References: [1] L.Lapikas NPA 553,297c (1993). [2] J.A.Tostevin, A.Gade PRC 90,057602 (2014). [3] V.Panin et al. PLB 753,204-210 (2016). [4] T.Aumann, C.Bertulani, J.Ryckebusch PRC 88,064610 (2013).

Speaker: Dr Leyla Atar (TU Darmstadt, GSI and University of Guelph)

111 Study on the Isoscalar Excitation of the Pygmy Dipole Resonance in 68Ni

N.S. Martorana, L. Acosta, M.V. Andrés, G. Cardella, F. Catara, E. De Filippo, S. De Luca, D. Dell'Aquila, B. Gnoffo, E.G. Lanza, G. Lanzalone, I. Lombardo, C. Maiolino, S. Norella, A. Pagano, E.V. Pagano, M. Papa, S. Pirrone, G. Politi, F. Porto, L. Quattrocchi, F. Rizzo, P. Russotto, A. Trifirò, M. Trimarchi, M. Vigilante, A. Vitturi Recently, much relevance has been given to the collective states in neutron-rich nuclei. The remarkable interest in these states is driven by the presence of an electric dipole response around the nucleon binding energy [1,2]. This mode, the so called Pygmy Dipole Resonance (PDR), although is carrying few per cent of the isovector Energy Weighted Sum Rule (EWSR) has a strong relation with the symmetry energy and it has been used as a further tool to constrain it. It is predicted to be present in almost all nuclei with neutron excess: in particular for nuclei far from the stability line. This mode can be populated by both isoscalar and isovector probes due to the properties of its transition densities [3]. Several experiments, with both the probes, have been performed on stable nuclei [1,2,4,5]. Whereas, the study of the PDR with unstable nuclei has been done in pioneering experiments carried out at the GSI, using relativistic Coulomb excitations on 132Sn [6] and 68Ni [7] isotopes. We use, for the first time, an isoscalar probe to excite the PDR on an unstable isotope. The experiment with a 68Ni beam at 33 MeV/nucleon on a 12C target was performed at LNS-INFN of Catania. The unstable beam was produced by In Flight Fragmentation method in a dedicated In Fligth Radioactive Ion Beams (FRIBs) transport line. The detector systems CHIMERA [8] and Farcos [9] were used to detect both gamma and charged products. References: [1] D. Savran, T. Aumann and A. Zilges, Prog. Part. Nucl. Phys. 70, 210 (2013). [2] A. Bracco, F.C. L. Crespi, and E. G. Lanza, Eur. Phys. J. A 51 (2015). [3] E. G. Lanza, A. Vitturi, M. V. Andrés, F. Catara and D. Gambacurta, Phys. Rev. C 84, 064602 (2011). [4] D. Savran et al, Phys. Rev. Lett. 100, 232501 (2008). [5] J. Endres et al, Phys. Rev. C 80, 034302 (2009). [6] P. Adrich et al, Phys. Rev. Lett. 95, 132501 (2005). [7] O. Wieland et al, Phys. Rev. Lett. 102, 092502 (2009). [8] A.Pagano et al Nucl. Phys. A 734 (2004) 504. [9] E.V. Pagano et al, EPJ Web of Conferences 117, 10008 (2016).

Speaker: Nunzia Simona Martorana (LNS-INFN, Catania, Italy)

19:30 Conference Dinner

Friday, 2 June

112 Applications of β-radiation Detected NMR in Wet Chemistry, Biochemistry and Medicine

Many physiological processes in nature are governed by the interaction of biomolecules with metal ions. Some biologically highly relevant metal ions, such as Mg2+, Cu+ and Zn2+, are silent in most spectroscopic techniques leaving wide gaps in understanding their biological functions. Therefore, there is the need for finding new experimental approaches to directly study these metal ions. Recently, β-radiation detected nuclear magnetic resonance (β-NMR) spectroscopy was successfully applied to liquid samples at the ISOLDE and ISAC facilities at CERN and at TRIUMF, Canada’s national laboratory for particle and nuclear physics, respectively. This marks an achievement, which opens new opportunities in the fields of wet chemistry. In contrast to earlier measurements, the resonance spectra of 31Mg+ implanted into different ionic liquid samples, recorded at ISAC, showed highly-resolved resonances originating from Mg ions occupying different coordination geometries, illustrating that β-NMR can in fact discriminate between different structures – the first and very important step towards the applications of this technique in biochemistry and medicine. Recorded resonance line widths are comparable or even narrower than the ones in conventional NMR spectroscopy on similar systems, underlining the complementarity and advantages of β-NMR. After these successful tests, a new spectrometer for bio-β-NMR experiments is currently under construction at TRIUMF’s β-NMR facility, which will allow for experiments not only on different samples, such as gels, and liquids, but also at different vacuum environments (10-7 mbar - 50 mbar). Results from the recent β-NMR experiments with 31Mg+ ions performed at TRIUMF, the former tests at the ISOLDE, as well as future plans will be presented and discussed.

Speaker: Dr Monika Stachura (TRIUMF)

113 Keeping up the Standards: Applying New Nuclear Decay and Structure Data for Radionuclide Metrology

The radioactivity group based at the UK's National Physical Laboratory (NPL) is responsible for traceability of radiological standards and sources. This work requires the use of a range of novel and high-precision radiation detection systems which can be utilised to provide definitive standards of the stoichiometry, decay rate and physical nature of emissions from different samples of radioactive materials. The link in the unbroken calibration chain for measurements of activity concentrations of radiopharmaceuticals and other radioactive sources / reference materials is based at the NPL, which is responsible for the ultimate traceability to the Becquerel (Bq) within the UK. This talk will outline some of the experimental techniques which are used to provide primary and secondary standards for radioactivity calibrations based on gamma-ray and/or charged particle spectrometry and highlight the importance of robust, evaluated nuclear data in such underpinning applications. An example of the recent standardisation of the naturally occurring isotope 223Ra [1,2] will be presented. This is of particular current focus as this radionuclide is both a member of the actinium (4n+1) decay chain headed by 235U and also the main therapeutic component in the radiopharmaceutical XOFIGO© [3]. The presentation will also outline some of the other methods for the production and radiochemical separation of 236Np as a long-lived tracer for 237Np via ICP - Mass spectrometry measurements in nuclear waste management [4]. Finaly, progress on the use of a digitally-based system for primary standardisations of 60Co and 134Cs, using coincident gamma-ray spectroscopy using LaBr3(Ce) detector modules (the NANA spectrometer) will be presented [5]. References: [1] Collins, S.M; et al., 2015. Direct measurement of the half-life of 223Ra. Applied Radiation and Isotopes, 99, pp.46-53; Collins, S,M. et al., 2015. Precise measurements of the absolute γ-ray emission probabilities of 223Ra and decay progeny in equilibrium. Applied Radiation and Isotopes, 102, pp.15-28. [3] https://www.xofigo-us.com/patient/index.php [4] Larijani, C. et al., 2015. Progress towards the production of the 236gNp standard sources and competing fission fragment production. Radiation Physics and Chemistry, 116, pp.69-73. [5] Lorusso, G. et al., 2016. Development of the NPL gamma-ray spectrometer NANA for traceable nuclear decay and structure studies. Applied Radiation and Isotopes, 109, pp.507-511.

Speaker: Prof. Patrick Regan (University of Surrey and UK National Physical Laboratory)

114 Understanding of Decay Heat and the Reactor Anti-neutrino Spectrum Using Total Absorption Spectroscopy

Total Absorption Spectroscopy is a unique technique characterized by high efficiency detection of gamma-ray radiation. This property, used in the study of beta decay of unstable nuclei, allows for the total detection of the deexcitation path of daughter nuclei. This makes it an ideal technique to establish the true beta-decay feeding pattern, especially for the decays of nuclei suffering from the Pandemonium Effect [1]. Recent studies show that the measurements of fission products by total absorption spectroscopy are extremely important to understanding the decay heat and anti-neutrino spectrum emitted from nuclear reactors [2]. Decay heat is determined on the basis of the average energy of gamma and beta radiation emitted in the beta decay of fission products. Incomplete knowledge of the decay schemes, in particular, omission of beta transitions to high-excited states, causes an underestimation of the electromagnetic part of the decay heat and a revaluation of the beta component. This was observed by comparison with direct measurements[3]. The solution is to measure the beta decay of fission products using high-efficiency systems such as total absorption spectrometers. The number of reactor anti-neutrino interactions measured by inverse-beta decay detectors is about 6% smaller than the expected number of events, which is named the reactor anti-neutrino anomaly [4]. The anti-neutrino energy spectrum, obtained from the fission product beta-decay schemes, is used to calculate the total anti-neutrino flux emitted by reactor cores and the number of anti-neutrino interactions with the detector matter. The measurements of the beta decay of fission products using the total absorption technique allow verification of the expected number of interacting reactor anti-neutrinos with matter. In this contribution we present several results of total absorption spectroscopy measurements of the beta decay of nuclides abundantly produced in the reactor core. The measurements were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) with the Modular Total Absorption Spectrometer (MTAS), the largest total absorption spectrometer in the world. The results and their impact on the decay heat and anti-neutrino spectra reconstruction will be presented and discussed. References: 1. J. Hardy et al., Phys. Lett. B71, 307, 1977 2. BC. Rasco et al., PRL 117, 092501, 2016 3. T. Yoshida et al., OECD report, NEA, 2007 4. G. Mention et al., PRD 83, 073006, 2011

Speaker: Dr Aleksandra Fijalkowska (Rutgers University)

115 Tree-Ring-Dating of Millennial Climate Change Across Southern Africa with AMS

High-resolution palaeoclimate records that might contribute to testing climate models are rare and often they are inadequately resolved in terms of their chronology or the precision of the proxy. Combining disparate evidence has yielded a rainfall record for the last 200 years that is suggestive but has large errors associated with it. This record reconstructs a drying trend that is contrast with the model reconstructions and forecasts for the region of Southern Africa. In addition the high-resolution rainfall record derived from tree rings in Zimbabwe does not reflect the same interannual variability for records from the Limpopo River Valley. This research project has obtained 1000-year isotopic tree ring records that are duplicated in each of the major climate regimes in southern Africa. This was readily achieved as the existing inventory of trees that are immediately available for analysis offers high level of coverage. Tree ring analysis is a promising technique to accomplish this in terms of rainfall, but it emerges that most of the long-lived tree species in southern Africa form irregular rings that prevent the use of traditional ring analysis. It is possible to calibrate the tree isotope records at the level of precision that is required Among the tree species that demonstrably proxy palaeoclimates through isotopes, there are key species that are both long-lived and their distribution covers the main target sampling areas. The A.erioloba trees cover the more arid part of the subcontinent and they have been shown to grow to more than 1000 years in age. The southern limit of the baobab distribution represents the East/West transect that is desired, and a recent study on the age of baobabs has demonstrated that they can achieve ages in the order of 2000 years. The Podocarpus trees are from wetter areas including coastal and mountain forests and they have also been demonstrated to grow in excess of 1000 years. The conclusion that may be drawn from this is that it is feasible that a stable light isotope palaeoclimate for the broader southern African landscape may be derived from isotopic analysis of tree rings. The ring structures have been identified and their chronology is under establishment through application of radiocarbon dating at iThemba LABS with the Accelerator Mass Spectrometry (AMS) facility. The ring counting and radiocarbon chronologies will be reconciled to provide the absolute dates for the individual isotope measurements.

Speaker: Dr Simon Mullins (iThemba LABS)

10:40 Coffee Break

116 Charting New Ground with ISOLTRAP: A Survey of Recent Nuclear Binding-energy Studies

In the last years the main experimental approach to the complex nuclear many-body problem has been to track the variation of nuclear properties with the number of protons and neutrons. This justifies the ever-growing number of radioactive ion beam experiments and the great importance of binding energies, which are among the first observables reaching into unexplored regions of the nuclear chart. Their trends are sensitive to a wide range of nuclear-structure phenomena of single-particle or collective type and hence they constitute, for virtually every model, an essential input quantity. In pioneering the techniques of on-line Penning-trap mass spectrometry, the ISOLTRAP experiment [1] at ISOLDE/CERN has dedicated many years of research to the study of exotic systems at various frontiers of the nuclear chart. In this work some of the most recent results will be presented. The masses of neutron-rich cadmium isotopes around 130Cd are an incursion into the effect of the N = 82 magic number below the tin isotopic chain and its impact on r-process nucleosynthesis [2], while the masses of neutron-rich copper isotopes up to 79Cu give important insight into the evolution of the Z = 28 and N = 50 “shell closures” and the double magicity of 78Ni. Midway between magic numbers, the masses of strontium, rubidium and krypton isotopes beyond N = 60 delineate the “nuclear-shape transition” in the region of nuclides of mass A = 100. Most of these new measurements have demonstrated the importance of ISOLTRAP’s multi-reflection time-of-flight mass spectrometer (MR-TOF MS) [3], either as beam purifier or as mass-measurement apparatus. Since its implementation in the ISOLTRAP setup the MR-TOF MS has become a versatile beam-analysis tool. The variety of applications of the MR-TOF MS, as well as recent advances in the implementation of the phase-imaging ion-cyclotron-resonance technique [4] at ISOLTRAP, will be presented. References: [1] Mukherjee et al., Eur. Phys. J. A 35, 1-29 (2008). [2] D. Atanasov et al., Phys. Rev. Lett. 115, 232501 (2015). [3] R. Wolf, F. Wienholtz et al., Int. J. Mass. Spectrom. 349-350, 123-133 (2013). [4] S. Eliseev et al., Phys. Rev. Lett. 110, 082501 (2013).

Speaker: Vladimir Manea (CERN, Geneva, Switzerland)

117 The Rare-RI Ring Ready to Explore Terra Incognita

The Rare-RI Ring at the RIBF/RIKEN facility has been recently commissioned and is now ready to start its mission of measuring masses of extremely rare isotopes. The unique location of the Rare-RI Ring at the RIBF/RIKEN facility presents an extraordinary chance to measure nuclear masses in the Terra Incognita. These nuclear masses are of particular importance in understanding the synthesis of chemical elements via the r-process but also crucial in understanding nuclear structure far from stability. The Rare-RI Ring is based on the Isochronous Mass Spectrometry technique that allows reaching a mass measurement precision of 10^-6 in less than 1 ms. Therefore, making mass measurements of extremely short-lived nuclei with low production yields possible. The full operation of the Rare-RI Ring has been achieved in three commissioning stages. In this contribution, the three commissioning experiments will be summarized and the current performance will be presented. Finally, the perspective of our physics program will be shown.

Speaker: Dr Sarah Naimi (Riken Nishina Center)

118 Recent Mass Measurements for Nuclear Astrophysics at JYFLTRAP

JYFLTRAP is a cylindrical double Penning trap mass spectrometer [1] located at the Ion Guide Isotope Separator On-Line (IGISOL) [2] facility in Jyväskylä. In total, over 330 atomic masses for nuclear structure, fundamental physics and nuclear astrophysics have been measured with JYFLTRAP. In this contribution, I will focus on recent mass measurements for nuclear astrophysics obtained after the recommissioning of JYFLTRAP at the IGISOL-4 facility in 2014. In the neutron-deficient side, 31Cl [3] and 52Co [4] are among the most exotic nuclei ever studied at JYFLTRAP. Their masses are important for testing the isobaric multiplet mass equation as well as for the rapid proton capture (rp) process occurring e.g. in type I X-ray bursts. The new, more precise proton separation energy for 31Cl helps to constrain astrophysical conditions where 30S can act as a waiting point in the rp process. We have also improved the precisions of proton-capture Q-values relevant for calculating the proton-capture rates for two key reactions, 25Al(p,g)26Si and 30P(p,g)31S [5]. Accurate knowledge of the reaction rates is needed for more reliable calculations of the amount of cosmic 1809-keV gamma rays and abundances of intermediate-mass elements in novae, respectively. In the neutron-rich side, we have recently extended our studies to the heavier fission-fragment region relevant for understanding the formation of the rare-earth peak in the astrophysical r-process. References: [1] T. Eronen et al., Eur. Phys. J. A 48 (2012) 46 [2] I.D. Moore et al., Nucl. Instrum. Meth. Phys. Res. B 317 (2013) 208 [3] A. Kankainen et al., Phys. Rev. C 93 (2016) 041304(R) [4] D.A. Nesterenko et al., arXiv:1701.04069 [nucl-ex] [5] L. Canete et al., Eur. Phys. J. A 52 (2016) 124

Speaker: Dr Anu Kankainen (University of Jyvaskyla)

119 Nuclear Structure Studies Based on Energy Density Functionals

The self-consistent nuclear mean-field framework based on universal energy density functionals provides an accurate description of ground-state properties and collective excitations over the entire nuclear chart, from relatively light to super-heavy nuclei, and from the valley of beta-stability to the particle drip-lines. Based on this framework, structure models have been developed that go beyond the mean-field approximation and take into account collective correlations related to restoration of broken symmetries and fluctuation of collective variables. These include the generator-coordinate method with projections on particle number, angular momentum and parity, the collective Hamiltonian for quadrupole and octupole degrees of freedom, the microscopic interacting boson-fermion model. Among the most interesting recent applications of this framework are studies of shape evolution and shape-phase transitions: the occurrence of rigid triaxial deformations, quadrupole and octupole shape transitions in rare-earth nuclei and light actinides, and signatures of shape transitions in odd-mass nuclei.

Speaker: Prof. Tamara Nikšić (Department of Physics, Faculty of Science, University of Zagreb)

12:45 Lunch Break

120 Poster Winner Announcement

121 Instrumentation for the SPES Facility

The SPES Radioactive Ion Beam facility at INFN-LNL is presently in the construction phase. The facility is based on the ISOL method with an UCx Direct Target able to sustain a power of 10 kW. The primary proton beam is provided by a high current Cyclotron accelerator with energy of 35-70 MeV and a beam current of up to 0.75 mA. Neutron-rich radioactive ions are produced by proton induced Uranium fission at an expected fission rate of the order of 1E13 fissions per second. After ionization and selection the exotic isotopes are re-accelerated by the ALPI superconducting Linac at energies of 10 AMeV. The key feature of SPES is to provide high intensity and high-quality beams of neutron rich nuclei to perform forefront research in nuclear structure, reaction dynamics and interdisciplinary fields like medical, biological and material sciences. New instrumentation is required for operation with unstable beams and needs to be implemented coherently with the relevant milestones of the facility. Non-reaccelerated beams will be used for beta decay studies aided by the state of the art setup planned to this purpose. Reaccelerated beams, making use of direct reactions, will exploit magnetic spectrometers coupled to gamma array. The Galileo gamma spectrometer is being implemented to this purpose. An early phase of Galileo is presently operating with stable beams, selected preliminary results will be presented. For the operation with the first reaccelerated beams the AGATA tracking array will be installed at Legnaro in conjunction with a variety of ancillary detectors. A superconducting solenoid is planned to be used in conjunction with an active target and a high resolution missing mass spectrometer is under study in order to allow simultaneous measurement of excitation and de-excitation energy. Some examples of physics opportunities will be discussed.

Speaker: Dr Francesco Recchia (University of Padova)

122 High-intensity Superconducting ECR Ion Source SECRAL

RIB accelerator requests high power primary ion beam which actually very much depends on performance of the front-end ion source. SECRAL (Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou) is a superconducting-magnet-based ECRIS (Electron Cyclotron Resonance Ion Source) for the production of intense highly-charged heavy ion beams. It is one of the best performing ECRISs worldwide and the first superconducting ECRIS built with an innovative magnet to generate a high strength Minimum-B field for operation with heating microwaves up to 24-28 GHz. SECRAL has so far produced a good number of CW (Continuous Wave) intensity records of highly-charged ion beams, in which the beam intensities of 40Ar12+ and 129Xe26+ have exceeded 1 emA for the first time by an ion source. The great performance of SECRAL is accumulation of a number of technical advancements, such as the innovative magnet system for better plasma confinement and more effective double-frequency (24+18 GHz) heating with an optimized 24 GHz wave coupling to operate at higher wave power with improved plasma stability.SECRAL source has run into operation to deliver highly charged ion beams for HIRFL accelerator for more than 9 years and total beam time more than 30000 hours, which has demonstrated its excellent stability and reliability. This talk will present the innovative magnet structure and the latest development of SECRAL ECR ion source.

Speaker: Prof. Hongwei Zhao (Institute of Modern Physics, Chinese Academy of Sciences)

123 Production of N = 126 Nuclei and Beyond Using Multinucleon Transfer Reactions for KISS Project

Multinucleon transfer (MNT) reaction between two heavy ions at energies around the Coulomb barrier is considered as a promising candidate to produce and investigate exotic nuclei. It is expected to provide a mean to efficiently produce especially neutron-rich nuclei around the neutron magic number of 126, which is difficult to access by other production methods. The nuclear region of the neutron magic number N = 126 has been attracting an astrophysical interest because it is the waiting point nuclei on the r-process path, which are considered as progenitors of the peak at the mass number of 195 in the solar r-abundance distribution. We have constructed the KEK Isotope Separation System (KISS) at RIKEN RIBF facility to produce, separate and measure the nuclear properties of those neutron-rich nuclei around the neutron magic number N = 126, which will be produced by the MNT reaction. KISS consists of an argon gas cell based laser ion source and an isotope separation on-line (ISOL), to produce pure low-energy beams of neutron-rich isotopes around N = 126 and to study their beta-decay properties. We adopted the reaction system of 136Xe + 198Pt, which is considered to be one of the best candidates to efficiently produce the nuclei of interest. In order to investigate the feasibility of the nuclear production of the system, we have studied the collisions between 136Xe and 198Pt at the laboratory energy of 8 MeV/nucleon by using the EXOGAM gamma-ray array coupled to the large acceptance magnetic spectrometer VAMOS++ at GANIL. In this presentation, we will show the experimental results of nuclear production by the 136Xe + 198Pt reaction system, where the promising potential of the production of new isotopes around and beyond the neutron shell N = 126 by MNT reactions were demonstrated. We will discuss about the production of those nuclei using MNT reactions at KISS.

Speaker: Dr Yutaka Watanabe (Wako Nuclear Science Center, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK))

124 Charge Breeding Techniques for European Facilities

In the frame of two european collaborative projects, EMILIE and ENSAR 2, the charge breeding techniques are being improved. While SPIRAL 1 at GANIL and SPES will use an ECR charge breeder, ISOLDE is upgrading its charge breeder. The two techniques present different advantages and drawbacks which were thoroughly studied during the past decade. The ECR charge breeder has recently benefited from different upgrades. As an example, the SPIRAL 1 charge breeder has reached a new level of performances with its upgraded vacuum, injection / extraction optics and RF coupling. Better understanding of the capture process could be obtained. Despite these progresses, the observed behavior of the charge breeding time as a function of the support gas and plasma parameters raises new questions. This behavior is presently being studied by simulation before new on-line data is obtained with the SPIRAL 1 charge breeder. Efficient acceleration of medium mass (A>40) to heavy ions to high energy requires the use of a highly performing EBIS charge breeder. ISOLDE is presently working on the improvement of the EBIS electron optics, making use of a new high-compression gun at low energies and high current and large trapping capacities. While EBIS charge breeders provide the highest charge states, the pulsed structure of the Highly Charged Ion (HCI) beam makes their use cumbersome for many experiments. The EMILIE debuncher has been constructed at LPC Caen for an easy manipulation of the longitudinal phase space of the HCI beam to match the needs of the experiments. The availability of fast and high repetition rate ion production in combination with debunching technology allows to build a versatile and flexible injection system for various linac- and cyclotron-based post acceleration schemes.

Speaker: Dr Pierre Delahaye (GANIL)

125 Towards A Single Atom Microscope for Nuclear Astrophysics

We are developing the technique of optically detecting individual atoms embedded in thin films of cryogenically frozen solids. Noble gas solids such as frozen neon are an attractive medium because they are optically transparent and provide efficient, pure, stable, & chemically inert confinement for a wide variety of atomic and molecular species. The excitation and emission spectra of atoms embedded in solids can be separated by up to hundreds of nanometers making optical single atom detection feasible. We propose to couple a single atom microscope (SAM) detector to a recoil separator with the goal of measuring rare nuclear reactions relevant for nuclear astrophysics. The recoil separator would minimize the heat load on SAM while allowing for isotope discrimination. This technique has the potential to capture and detect every product atom with near unity efficiency. Because of the additional selectivity provided by resonantly exciting the atomic transitions of the captured product atom, SAM would have a negligible false positive rate which would help loosen the often demanding beam rejection requirements imposed on recoil separators. Our primary focus and long term goal is to measure the Ne-22(He-4,n)Mg-25 reaction, an important source of neutrons for the s-process, in the astrophysically relevant center-of-mass energy regime. We will describe the SAM concept in more detail, some of the critical technical challenges, and our progress towards demonstrating optical single atom detection of atoms embedded inside of solid neon.

Speaker: Prof. Jaideep Singh (NSCL/MSU)

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