AAC24 Advanced Accelerator Concepts Workshop

21 Jul 2024, 08:00 → 26 Jul 2024, 19:30 US/Central

NIU Naperville Conference Center

John Power (Argonne National Lab), Jonathan Jarvis (Fermilab), Philippe Piot (Northern Illinois University & Fermilab)

The AAC24 workshop is a by-invitation biennial forum for intensive discussions on long-term research in advanced accelerator physics and technology. Since its inception in 1982, the AAC Workshop has become the principal US meeting for advanced particle accelerator research and development with strong international participation. We are anticipating over 250 scientists and research leaders in particle-beam, laser, and plasma physics to participate in this year’s meeting. This research supports the development of capabilities for the basic sciences, from photon science to high energy physics, as well as the development of compact accelerators for industrial, medical and security applications.

The AAC24 Workshop will host multiple working groups:

• WG1 : Laser-driven plasma wakefield acceleration
• WG2 : Laser-driven plasma acceleration of ions
• WG3 : Beam-driven plasma acceleration
• WG4 : Novel structure acceleration
• WG5 : Beam sources, monitoring and control
• WG6 : Radiation generation, medical and industrial applications
• WG7 : Linear Colliders

We look forward to seeing you in July of 2024!

AAC_SPONSOR_BROCHURE.pdf

Sunday, 21 July

1 Workshop registration

2 Sunday reception

Monday, 22 July

08:00 Breakfast

3 Welcome & logistics

Plenary: Plenary 1

Convener: John Power (Argonne National Lab)

4 The 10 TeV Wakefield Accelerator Collider Design Study

From its inception, the Advanced Accelerator field has considered future colliders as the ultimate goal of high-gradient accelerator technology [1]. In the decades that followed, there has been rapid experimental progress [2,3,4] and a conceptual evolution of what future colliders based on Wakefield Accelerator (WFA) technology might look like. The recent P5 Report [5] calls for “vigorous R&D toward a cost-effective 10 TeV pCM collider based on proton, muon, or possible wakefield technologies.” Specifically, the P5 Report requests “the delivery of an end-to-end design concept, including cost scales, with self-consistent parameters throughout.” In this presentation, we will outline the requirements and challenges for a 10 TeV WFA collider. We will describe a community-driven design study based on working groups and performance metrics to produce a unified 10 TeV collider design concept, including a timeline with deliverables. Finally, we will discuss funding scenarios for this multi-year, multi-FTE effort.

[1] R. Ruth et al. “A Plasma Wake Field Accelerator” Particle Accelerators 17, 171-189 (1985)
[2] E. Esarey et al. “Physics of laser-driven plasma-based electron accelerators” Rev. Mod. Phys. 81, 1229 (2009)
[3] C. Jing “Dielectric Wakefield Accelerators” Rev. Accel. Sci. Tech, 9, 127-149 (2016)
[4] M. Hogan “Electron and Positron Beam–Driven Plasma Acceleration” Rev. Accel. Sci. Tech, 9, 63-83 (2016)
[5] P5 Report https://www.usparticlephysics.org/2023-p5-report/

Speaker: Spencer Gessner (SLAC)

5 Advanced Accelerator Concepts and the 2023 P5 Report

Advanced accelerator concepts have potential to enable future colliders. Recent progress includes multi-GeV acceleration, positron acceleration, strong structure loading and focusing, staging of two modules, beam shaping for efficiency, high gradient structures and greatly improved beam quality which recently enabled wakefield-based FELs.

The recent 2023 Particle Physics Project Prioritization (P5) report describes priorities to guide work over the coming decade. Generic R&D is important to extend the reach of accelerators. This is important to future colliders and stewardship of nearer-term applications with broad benefit. R&D attracts high-level talent important to develop machine design and projects.

To follow the HL-LHC and a Higgs Factory, R&D should be pursued towards the 10 TeV parton center of momentum (pCM) scale by colliding muons or protons, or possibly an electron-positron (or gg) collider based on wakefield technology. To make an informed decision — one we hope to make within the next 20 years—one or more concept must reach technical maturity, allowing reliable estimation of cost and risk.

Wakefield collider concepts are in the early stages of development, with conceptual parameter sets developing. An end-to-end design concept, including cost scales, with self-consistent parameters throughout is an important next step requiring focus and engagement with the collider and high energy physics communities. Experiments and test facilities should be used to demonstrate acceleration and beam requirements of a stage for a future collider based on wakefield technology, operation with two linked multi-GeV stages, and methods to reduce cost and risk, guided by collider R&D.

Speaker: Dr Cameron Geddes (LBNL)

6 Status and Outlook of Advanced Accelerator Concepts Research in Europe

European research groups and institutions, often working in close collaboration with others from around the world, work on all aspects of advanced accelerator research.
In this talk I will give an overview of research efforts in Europe, highlight recent key results, and indicate anticipated future directions.

Speaker: Simon Hooker (University of Oxford)

10:30 Coffee Break

Plenary: Plenary 2

7 Low divergence and high charge multi-GeV acceleration of electrons with a < 300 TW laser

The first demonstrations of fully optical multi-GeV laser wakefield acceleration (LWFA) have been enabled by the advent of low density (~$10^{17}$ $cm^{-3}$), meter-scale plasma waveguides generated in supersonic gas jets [1-7]. In this talk, I will present results from our recent LWFA experiments using plasma waveguides up to 30 cm in length, which have produced sub-milliradian divergence electron bunches with nC-level charge in the 1-10 GeV range [6,7]. I will also discuss our extensive simulation efforts, which are motivated by physics understanding and optimization of accelerator performance. These efforts include models of meter-scale hydrodynamic waveguide formation and their experimental benchmarking [8], and new, important regimes of LWFA drive pulse propagation [5] that strongly affect the laser wakefield acceleration dynamics. Finally, I will discuss the use of consistent, high charge multi-GeV electron bunches to generate muons in high-Z materials.

Funding Acknowledgements: This work was supported by the U.S. DoE (DE-SC0015516, LaserNetUS DE-SC0019076/FWP#SCW1668, and DE-SC0011375), NSF (PHY2010511), DARPA’s Muons for Science and Security Program (MuS2). Simulations used DoD HPC support provided through ONR (N00014-20-1-2233). E.R. is supported by NSF GRFP (DGE 1840340). Portions of work prepared by LLNL under Contract DE-AC52-07NA27344.

[1] Feder et al., Phys. Rev. Res. 2, 043173(2020).
[2] Shrock et al., Phys. Plasmas 29, 073101(2022).
[3] Miao et al., Phys. Rev. X. 12, 031038(2022).
[4] Miao et al., Physics Today 76 (8), 54-55(2023).
[5] Shrock et al., Under review, arXiv:2309.09930(2023).
[6] Shrock et al., In preparation(2024).
[7] Rockafellow et al., In preparation(2024).
[8] Miao et al., Under review, arXiv:2404.13632(2024)

Speaker: Ela Rockafellow (University of Maryland)

8 Multi-GeV monoenergetic electron beams from an optical shock front accelerator

Laser-accelerated electron beams have been the subject of intense research in the last few decades. The general direction in the field is the development towards ultralow beam emittance, necessitating controlled injection methods to ensure electron trapping in the laser-driven plasma wave. Due to its simplicity, one of the more popular injection mechanisms relies on a downward step in gas density created by a shock wave oriented perpendicularly to the wakefield propagation direction. Upon crossing this step, the plasma wave breaks and locally injects a bunch of electrons, leading to quasi-monoenergetic electron bunches due to the uniform acceleration distance for all particles. A main drawback of this scheme is the fact that this braking wave injects the electrons into a phase of the wake that is close to the zero-field crossing, leading to a significantly reduced electron energy compared to the self-injection scheme yielding broadband pulses. The consequence has been an energy limit of approx. 1 GeV for such shock-injected bunches. With a novel optical method to generate the shock, we can gain additional degrees of freedom such as a flexible density ratio before and after the shock, allowing to shift the injection point more into the high-field phase of the plasma wave. Using this approach, we have recently demonstrated 2-2.5 GeV, monoenergetic electron beams from our ATLAS laser facility. Such beams are intended to drive our experiments into Breit-Wheeler pair creation in the non-perturbative regime.

Speaker: Stefan Karsch (Ludwig-Maximilians-Universität München, Munich, Germany)

9 High-energy electron beams in optically-formed plasma channels

Future applications of laser-plasma accelerators will require one or more stages providing multi-GeV energy gain. Preformed plasma channels can increase the maximum energy gain of a laser-plasma accelerator. Recently, hydrodynamic optical-field-ionized (HOFI) plasma channels [1-3] have gained attention because i) they produce tightly confined channels at densities required for multi-GeV acceleration, and ii) contain no external structure making them ideal for >kHz operation. In the first half of the talk, we discuss high-quality beam production in HOFI plasma channels. We explore the use of a density down-ramp generated between neutral gas immediately prior to the channel and the channel itself to trap electrons. We demonstrate generation of 1.2 GeV bunches with percent-level energy spread, using sub-100 TW laser pulses [4]. In the second half of the talk, we discuss experiments to guide PW-scale pulses in 30-cm-long HOFI plasma channels. Understanding how the laser pulse evolves in the spatial and temporal domain during propagation is critical for high energy gain, and maintaining high bunch quality during acceleration. We present experimental results investigating drive laser propagation in HOFI plasma channels at the BELLA PW laser. We demonstrate conditions under which the channel can be tailored to match the drive laser focus at plasma densities suitable for multi-GeV accelerators, and present example electron beams from those experiments.

[1] R. Shalloo et al., Phys. Rev. E (2018)
[2] A. Picksley et al., Phys. Rev. E (2020)
[3] L. Feder et al., Phys. Rev. Research (2020)
[4] A. Picksley et al., Phys. Rev. Lett. (2023)

Speaker: Alex Picksley (Lawrence Berkeley National Lab)

12:30 Lunch

WG1

WG2

WG3

WG4

15:30 Coffee Break

WG1

WG3

WG5

WG6

Poster: Poster 1

Tuesday, 23 July

08:00 Breakfast

Plenary: Plenary 3

10 A Pathway toward a SWFA-based Compact Coherent Light Source

Structure wakefield accelerators (SWFAs) offer a path to high accelerating gradient using either collinear wakefield acceleration or two-beam acceleration (TBA). In the past five years, significant progress has been made in operating accelerating structures powered externally by short radiofrequency pulses generated from thew wakefield of decelerating bunches. Such a TBA approach has demonstrated the operation of X-band accelerating structures with surface electric fields approaching GV/m, including a radio-frequency photoinjector with photocathode field close to 0.4 GV/m. Correspondingly, efforts are currently underway to integrate these advancements into a water-window free-electron laser (FEL) demonstration experiment.

This presentation charts a path toward an SWFA-based FEL. It will particularly address the beam dynamics challenges associated with generating bright electron bunches for FEL applications and high-charge bunches for wakefield generation. We will also describe ongoing experimental activities aimed at achieving reliable short-pulse operation of high-gradient accelerating structures and the generation of bright electron bunches. Additionally, we will discuss potential designs for accelerating structures operating in the short-pulse regime and explore options for an integrated accelerator supporting the operation of a compact FEL operating in the water-window regime.

Speaker: Prof. Philippe Piot (Argonne National Laboratory)

11 Attosecond x-ray free-electron lasers utilizing an optical undulator in a self-selection regime

Accelerator-based x-ray free-electron lasers (XFELs) are the latest addition to the revolutionary tools of discovery for the 21st century. The two major components of an XFEL are an accelerator-produced electron beam and a magnetic undulator, which tend to be kilometer-scale long and expensive. A proof-of-principle demonstration of free-electron lasing at 27 nm using beams from compact laser wakefield accelerators was shown recently by using a magnetic undulator. However, scaling these concepts to x-ray wavelengths is far from straightforward as the requirements on the beam quality and jitters become much more stringent. Here, we present an ultracompact scheme to produce tens of attosecond x-ray pulses with several GW peak power utilizing a novel aspect of the FEL instability using a highly chirped, prebunched, and ultrabright tens of MeV electron beam from a plasma-based accelerator interacting with an optical undulator. The FEL resonant relation between the prebunched period and the energy selects resonant electrons automatically from the highly chirped beam which leads to a stable generation of attosecond x-ray pulses. Furthermore, two-color attosecond pulses with subfemtosecond separation can be produced by adjusting the energy distribution of the electron beam so that multiple FEL resonances occur at different locations within the beam. Such a tunable coherent attosecond x-ray sources may open up a new area of attosecond science enabled by x-ray attosecond pump/probe techniques.

Speaker: Prof. Xinlu Xu (Peking University)

12 Demonstration of a reliable, high gain laser plasma accelerator driven free electron laser

Compact free electron laser (FEL) technology enabled by plasma-based accelerators is rapidly maturing with several milestone demonstrations in the last several years. Still, critical work is needed to bridge the gap from proof of concept experiments to reliable operation of laser plasma accelerator (LPA) driven FELs. At the BELLA Center, we have Hundred Terawatt Undulator beamline equipped with an electron beam transport section that culminates in a 4m long, strong focusing undulator. Recent efforts have produced reliable operation of a high gain FEL.

This work was supported by the U.S. Department of Energy (DOE) Office of Science, the Office of Basic Energy Sciences, and the Office of High Energy Physics, under Contract No. DE-AC02-05CH11231, and through a CRADA with Tau Systems

Speaker: Sam Barber (LBNL)

10:30 Coffee Break

Plenary: Plenary 4

13 Exploiting novel liquid sheet targets for the generation of bright MeV proton beams

Laser-plasma acceleration has enormous potential to provide compact sources of ultra-short ion beams. However, several factors hamper their wider adoption, such as the low shot-to-shot stability, large beam divergence and the difficulty of high-repetition rate operation. In this talk I will outline an approach for overcoming these challenges by a novel liquid sheet target, developed at the SLAC National Accelerator Laboratory. I will report on recent experiments at the GEMINI TA2 laser facility (10 TW, 5 Hz) which demonstrated stable acceleration of few MeV proton beams with high flux and low-divergence proton beams in comparison to typical laser-accelerated ion beams. Supporting PIC simulations have shown that the presence of background vapour around the target plays an important role in the observed collimation of the proton beam. The measured proton beams are already suitable for applications requiring high proton flux and the platform can be extended to kHz repetition rates or higher laser energies extending the utility of the source to a wide range of applications in radiobiology, materials science and fundamental physics.

Speaker: Charlotte Palmer (Queen's University Belfast)

14 Above 150 MeV proton acceleration with 10 PW laser system at ELI NP

Currently, the Extreme Light Infrastructure – Nuclear Physics (ELI-NP) facility is running the most powerful laser in the world. The commissioning of the 10 PW laser system began at the end of 2022 and continued until recently. The first ever 10 PW shot focused on target was fired on April 2023 and since then a constant effort has been made to improve the laser performance and the experimental areas.
The high-power laser system (HPLS) is a Ti:Sa-based laser with wavelength centered at 810 nm. It has 2 arms that can deliver up to 240 J in about 23 fs at a repetition rate of a shot per minute. The maximum peak intensity achieved on target is of several $10^{22}$ Wcm$^{-2}$. Such intensity was employed to investigate the acceleration of ions via the TNSA-RPA mechanism. Several diagnostics were employed to characterize the interaction and investigate the laser performance extensively. Interesting results have been obtained, as a record high proton energy of about 150 MeV.
The laser system generally exhibits very good performances, although existing issues have been exposed, as for instance, pre-pulses in the picoseconds and nanoseconds range that prevent an optimal interaction.
Further investigation and optimization of laser-matter interaction with the 10 PW laser will be performed this year, meanwhile, some improvement in the HPLS will be also made.

Speaker: Dr DOMENICO DORIA (Extreme Light Infrastructure – Nuclear Physics (ELI-NP))

15 Exploration of ultra-high dose rate radiobiology with laser-driven protons at BELLA

Laser-driven (LD) proton sources are of interest for various applications due to their ability to produce short proton bunches with high charge. These sources can be used in biological studies investigating improvements to radiation cancer therapy. Recently, the differential sparing effect on normal tissues versus tumors using the delivery of high radiation doses >10 Gy at extremely high dose rates (DR), has received increasing attention. However, the molecular and cellular mechanisms underlying the sparing effect are not yet fully understood. To explore these mechanisms, we have implemented a beamline at the BELLA PW that delivers LD proton bunches at ultra-high instantaneous DR (UHIDR) up to 10$^8$ Gy/s. This allowed us to investigate in vivo the acute skin damage and late radiation-induced fibrosis in mouse ears after UHIDR with 10 MeV LD protons and prescribed doses of several 10s of Gy. We observed sparing of healthy mouse ear tissue after irradiations with LD proton bunches at UHIDR compared to irradiations with 300 kV x-rays at clinical dose rates and similar total dose. Recent improvements to the LD proton source, delivery beamline, and diagnostic suite have also enabled the first peptide sample irradiations to explore the FLASH effect on the molecular level. This talk will provide a summary of radiobiology research activities at the BELLA PW.

Work was supported by the U.S. DOE Office of Science, Offices of FES and HEP, and LaserNetUS under Contract No. DE-AC02-05CH11231 and a Laboratory Directed Research and Development Grant, PI A. M. Snijders.

Speaker: Lieselotte Obst-Huebl (Lawrence Berkeley National Laboratory)

12:30 Lunch

WG1

WG3

WG5

WG6

15:30 Coffee Break

WG2

WG5

WG6

WG7

Wednesday, 24 July

08:00 Breakfast

Plenary: Plenary 5

16 MeV-scale Dielectric Laser Acceleration

Dielectric Laser Accelerators (DLAs) have been shown to produce GeV/m acceleration gradients and therefore the potential to shrink commercial accelerators to the cm scale. However, increasing energy gain requires multi-mm interaction lengths, which has previously been limited by dephasing. Progress in optical techniques has made controlling the phase in optical pulses common and available in scientific laboratories. Here we show that applying a liquid-crystal-mask in combination with a pulse front tilt enables the implementation of coherent control on a simple dual grating laser accelerator. Such nearly limitless live-tuning capability for the accelerator enable software-based correction of structure and optical system imperfections, implementation of transverse focusing schemes, control of the output electron beam energy and number of particles accelerated, ultimately maximizing the interaction length for up to 0.5 MeV energy gain.

Speaker: Sophie Crisp (UCLA)

17 Coherently-combined fiber lasers for driving plasma accelerators at kHz repetition rates

Laser-plasma accelerators (LPAs) have great potential to be compact and economic, and can enable many applications in science, industry, and medicine, from wakefield colliders (e.g. 10TeV) and precision LPA facilities (e.g. kBELLA) to photon and particle sources. These applications need new kHz rep-rate laser driver technologies producing Joules of pulse energy, up to 100’s kW average power, and tens-of-percent wall-plug efficiency.

We developed a novel, energy/power scalable laser driver approach based on multidimensional coherent combining of ultrashort pulses from fiber lasers. Fiber lasers are the most efficient high power laser technology to date. Spatial beam combining enables average power and pulse energy scaling, and temporal pulse combining (stacking many amplified pulses into a single pulse) reduces fiber amplifier arrays needed for high energy to a practical size.

We have demonstrated close-to-full energy extraction (~10mJ) from 85µm-core Yb-doped fiber amplifiers and temporal combining of 81 amplified pulses. 4-channel spatial-temporal combining has achieved ~30mJ pulses at kHz rep-rates. We have shown diffractive combining of 2-D ultrashort-pulse beam arrays, and robust control of combining 81 beams. We also demonstrated record-short pulses (42fs) from fiber combination systems using spectral combining. Ongoing efforts are developing integrated fiber amplifier modules, and building scaled-up fiber systems (100-200mJ, 30-100fs, 1kW). Past and ongoing development has established a path to meet the needs of precision LPAs like kBELLA, their applications, and future colliders.

This work is a collaboration between LBNL, University of Michigan, LLNL, Optical Engines, nLight, and is supported by DOE Office of Science, DARPA, Moore Foundation.

Speaker: Dr Tong Zhou (Lawrence Berkeley National Lab)

18 Overcoming the Limitations of Laser-Wakefield Acceleration with Structured Light Fields

For the last few decades, the development of Laser-Plasma Accelerators (LPAs) has attracted high interest due to the capacity of plasma to produce and sustain extremely high electric fields. The accelerating gradients in plasma accelerators can exceed 100 GV/m, which is three orders of magnitude larger than those obtained in metallic-cavity accelerators. This promisingly offers very compact alternatives to conventional linear machines . However, a high field is not the only ingredient required for achieving high multi-GeV energy gains. The accelerated beam must also follow this field over long distances. Currently, the identified main challenges for LPAs include the diffraction and depletion of the driver laser, as well as the dephasing of the accelerated beam with the driven plasma waves. Diffraction and pump depletion cause the laser intensity to decrease during acceleration, eventually suppressing the wakefield. Dephasing results from the mismatch between the phase velocity of the accelerating field and that of the electron beam, leading the electron beam toward a decelerating phase of the wake.
In this context, we discuss two approaches for overcoming these limitations and increasing the beam energy. First, we present the experimental demonstration of quasi-monoenergetic electron beam acceleration at the GeV level in a plasma waveguide created by a quasi-Bessel beam shaped by an axiparabola mirror. Another concept involves advanced optical shaping of the laser driver, allowing diffraction-free propagation over a long distance while controlling the group velocity of the laser. This approach significantly extends the effective dephasing length.

Speaker: Cedric Thaury (CNRS)

10:30 Coffee Break

Plenary

19 Bunching of relativistic electron beams for superradiant Compton scattering

Inverse Compton scattering by relativistic electrons off intense laser pulses provides an attractive option for compact radiation sources in the (soft) X-ray spectral range. Tunability of the radiation wavelength is greatly increased by varying the crossing angle in the interaction. On the other hand, the radiated power from these sources is typically rather low, limiting the range of applications. By imposing a spatial modulation on the electron beam the Compton yield can be enhanced by many orders of magnitude via superradiant emission even when considering limiting contributions by realistic spot sizes, energy spread and beam emittance. However, attaining the required density modulation at the relevant electron beam energy is still a major challenge. We will discuss our experimental efforts on two alternative methods of achieving the required density modulation for superradiant Compton scattering at the UCLA Pegasus laboratory: ponderomotive bunching by two lasers at different frequencies and attosecond velocity bunching using an s-band buncher linac in conjunction with a x-band linearizer. Our plans to observe the coherent enhancement of Compton scattering in the near future are considered

Speaker: Brian Schaap (UCLA)

20 3D structure of microbunched electron beams from plasma wakefield accelerators

Plasma-wakefield accelerators use tabletop equipment to produce relativistic femtosecond electron bunches. Optical and x-ray diagnostics have established that their charge concentrates within a micron-sized volume, but its sub-micron internal distribution, which critically influences gain in free-electron lasers or particle yield in colliders, has proven elusive to characterize. Here, by simultaneously imaging different wavelengths of coherent optical transition radiation (COTR) that a laser-wakefield-accelerated e-bunch generated when exiting a metal foil, we reveal the structure of the coherently-radiating component of bunch charge. Key features of the images are shown to correlate uniquely with how plasma electrons injected into the wake by either a plasma-density discontinuity, by ionizing high-Z gas-target dopants, or by uncontrolled laser-plasma dynamics. With additional input from electron spectra, spatially-averaged COTR spectra, and particle-in-cell simulations, we reconstruct coherent 3D charge structures. The results demonstrate essential metrology for next-generation compact X-ray free-electron lasers driven by plasma-based accelerators.

Speaker: Maxwell LaBerge (HZDR)

21 Generation of arbitrary bunch shapes using a multileaf collimator and emittance exchange

Precision shaping of the phase space of beams is essential for advanced acceleration methods, such as enhancement of the transformer ratio in beam driven wakefield concepts. We have experimentally demonstrated a method to generate arbitrary bunch profiles, with high precision, in a rapid, "on-demand" manner. The approach is based on a multileaf collimator (MLC) with independently actuated tungsten strips which selectively scatter unwanted particles to create high-fidelity transverse beam distributions. In conjunction with an emittance exchange beamline (EEX) at the Argonne Wakefield Accelerator, the MLC-generated transverse profiles are transformed into longitudinal bunch profiles that are highly variable, including ramped profiles with adjustable features. Enabled by novel features such as magnetically coupled actuation without lubricants, this MLC operates in ultrahigh vacuum environments. Engineering improvements of the MLC, based on a stack of shaped rotors, will also be introduced, in addition to an algorithm for mask setting. The many degrees of freedom of the MLC enable the optimization of experimental figures of merit using feed-forward control and advanced machine learning techniques.

Speaker: Nathan Majernik (SLAC)

12:30 Lunch

13:30 Outing to Downtown Chicago. Architectural Boat Tour on Chicago River.

Thursday, 25 July

08:00 Breakfast

Plenary

22 AWAKE: proton driven plasma wakefield acceleration for particle physics applications

AWAKE is a proton-driven plasma wakefield acceleration experiment at CERN. Proton drivers provided by the CERN accelerators carry a large amount of energy per bunch (~20kJ) and per particle (~400 GeV), sufficient to excite GV/m fields over tens to hundreds of meters in a single plasma. Drivers are initially much longer than the plasma wavelength and must be self-modulated to resonantly excite high amplitude wakefields.
In this contribution, we present an overview of recent AWAKE experimental results on: the observation of motion of ions and the filamentation instability using a 10m-long discharge plasma source; the demonstration of wakefield reproducibility when self-modulation is seeded; the suppression of self-modulation with a linear plasma density gradient as well as results of the effect of a plasma density step in the self-modulation plasma. Further, we describe AWAKE’s plan towards application of this acceleration scheme to particle physics.

Speaker: Marlene Turner (CERN)

23 Latest Results on PWFA Experiments from FACET-II

FACET-II is a national user facility that offers a unique capability for developing advanced acceleration and coherent radiation generation techniques using high-energy electron beams. In this talk, we will present the latest results from plasma wakefield acceleration (PWFA) experiments at FACET-II, focusing on the following topics. First, we provide evidence of energy depletion of the 10 GeV drive beam and efficient energy transfer from the beam to the wake, in both beam-ionized and laser-preionized plasmas, which is a crucial stepping stone towards achieving high energy transfer efficiency from the drive to the witness bunch in the ultimate two-bunch PWFA configuration. We will also show examples of machine-learning-enabled beam tuning to increase drive beam density, thereby enhancing energy transfer efficiency. Next, we present results on generating high-energy, low-emittance beams via downramp and ionization trapping in PWFA. Using density downramp injection, we achieve the generation of electron bunches exceeding 20 GeV with small energy spread and emittance. Additionally, we show the generation of multi-GeV, multi-color electron beams via ionization injection, resulting from periodic injection induced by betatron oscillations of the drive bunch. Finally, we will discuss the first experimental attempts at beam matching to a lithium density upramp and share preliminary results from the two-bunch PWFA experiment.

Acknowledgement: The FACET-II Facility at SLAC National Accelerator Laboratory and the work at UCLA has been funded by the U.S. DoE Office of HEP.

Speaker: Chaojie Zhang (UCLA)

24 Observation of space-charge field screening in plasma, and other recent experimental results from SPARC_LAB.

The space-charge field of a relativistic bunch is screened in plasma due to the presence of mobile charge carriers. We experimentally investigate such screening by measuring the effect of dielectric wakefields driven by an electron bunch in an uncoated dielectric capillary where the plasma is confined [1]. We show that the plasma screens the space-charge field and therefore suppresses the dielectric wakefields when the distance between the bunch and the dielectric surface is much larger than the plasma skin depth. We also present recent experimental results from SPARC_LAB on guiding of electron bunches in a curved plasma-discharge capillary [2], and on focusing and acceleration in an all-plasma compact device [3]. We discuss the impact of these results on the design of EuPRAXIA@SPARC_LAB, a user-oriented free-electron laser based on plasma wakefield acceleration.

[1] L. Verra et al., submitted (2024)
[2] R. Pompili et al., accepted in Phys. Rev. Lett. (2024)
[3] R. Pompili et al., Phys. Rev. E 109, 055202 (2024)

Speaker: Livio Verra (INFN/Frascati National Laboratory)

10:30 Coffee Break

Plenary

25 BeamNetUS: Accelerating Beam-Based Research

Beam test facilities have been an integral part of accelerator science research, education, and applications development. However, awareness of their capabilities is limited, and potential new researchers typically face a multitude of barriers in accessing their capabilities, such as a lack of centralized information on facility capabilities or how to engage with them. BeamNetUS is a network of facilities that aims to directly address these problems through improving awareness and access to these unique facilities. For its pilot campaign, the network includes facilities at Argonne National Laboratory, Brookhaven National Laboratory, Fermi National Accelerator Laboratory, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, and Thomas Jefferson National Accelerator Facility. These facilities provide complementary capabilities enabling research in plasma physics, beam physics, material science, radiofrequency sources and structures, nuclear physics and electron beam irradiation. In this talk, I will discuss the structure of BeamNetUS as well as the network’s efforts to create a streamlined process for engagement, with the aim of providing access to these facilities for groups without established connections. A program of awards evaluated through a competitive review process with a remit towards creating new, productive engagements will allow access to the facilities without cost for non-proprietary use in 2025.

Speaker: Navid Vafaei-Najafabadi (Stony Brook University)

26 LaserNetUS: opportunities for the AAC community

LaserNetUS was launched in 2018, with a mission to advance and promote intense ultrafast laser science and applications. Since its inception, the network has transformed the landscape of high-power and high-intensity laser research, and it has grown into a community of over 1300 users. Additionally, it promotes worldwide collaborations and provides scientists, students, and underrepresented communities with broad access to unique facilities and enabling technologies. LaserNetUS has gone through 6 cycles of open calls for proposals, and over 130 unique experiments have been successfully executed across the network. Following on the success of LaserNetUS, other networks, such as beamNet, are launched to stimulate scientific discovery.
This talk will present LaserNetUS and scientific achievements across its 13 facilities over the first five years of operation, with particular emphasis on topics relevant for the AAC community. The breadth of laser parameters in pulse energy (from sub-Joule to a few kilojoules), pulse duration (from about 10 femtoseconds to 10s of nanoseconds) and repetition rate (up to 10 Hz) have enabled unique discoveries and applications in plasma-based particle acceleration, high energy density science, fusion energy, magnetic field generation, and plasma diagnostics. The talk will further present perspectives on the future of the network and how it can continue to stimulate high impact science in plasma physics, as well as in other scientific disciplines, medicine or industry.

Speaker: Felicie Albert

27 Long-term community engagement with US industry for the next high energy physics collider

The United States government high energy physics community develops state-of-the-art particle accelerator technologies, which later must be purchased from abroad to support domestic projects, because US-based firms are not consistently prioritized for government programs of record. In contrast, the high energy physics communities in Europe and Asia work to nurture their domestic industrial bases. Products developed by L3Harris Applied Technologies, Inc. (ATI) include large-scale pulsed power systems, commercial electron linacs for sterilization, high-power electromagnetic radiation systems, and flash X-ray radiography test equipment. ATI is an example of a domestic organization with complementary resources and capabilities for supporting the development and construction of the pre-injector linac for the Electron-Ion Collider (EIC) project. This presentation will provide a commercial perspective on how the US government high-energy physics community could engage US industry such that it would make business sense to continue operating in this space over a period of decades. Our shared goal is that domestic products and services will be available to support the next big US collider in the long term, as well as other accelerator facilities.

Speaker: Dr Yoko Kawai Parker (L3Harris)

12:30 Lunch

WG1

WG2

WG3

WG4

15:30 Coffee Break

WG5

WG6

WG7

18:00 AAC banquet at Mason Sabeka in Naperville

Friday, 26 July

08:00 Breakfast

Plenary

28 Summary of the ALEGRO 2024 Workshop at IST

ALEGRO, the Advanced LinEar collider study GROup, is an international study group created in 2017 to promote Advanced and Novel Accelerators (ANAs) for High-Energy Physics applications. It is driven by the ICFA-ANA panel. ALEGRO organizes workshops (CERN 2017, Oxford 2018, CERN 2019, DESY 2023, IST 2024) to energize the ANA community around applications to particle and high-energy physics. The implementation by the laboratory Directors Group (LDG) of a roadmap for ANAs  is taking place in the context of the European Strategy for Particle Physics (ESPP). It is centered around existing international programs: AWAKE, EuPRAXIA and HALHF. In the US, the P5 has recently recommended the design of a 10TeV CM lepton collider or of a 100TeV pCM hadron collider.
The goals of the ALEGRO 2024 Workshop at IST were to take stock of progress with ANAs, and to initiate a world-wide effort on the design of a 10TeV CM, ANA-based lepton collider.
The first goal was addressed by inviting speakers to present recent scientific results. The second one was addressed through sessions in which major participants in the ESPP and P5 processes summarized the implementation of the recommendations and roadmaps that emerged from these processes. Also, invited speakers described major ANA-related programs and facilities addressing challenges related to collider development.
A document summarizing the outcome of the workshop and the presentations will be generated.
I will report on the 2024 workshop at IST. I will also outline the status of the international collaboration to develop an ANA-based collider concept.

Speaker: Prof. Patric Muggli (Max Planck Institute for Physics)

29 Summary of the P5 vision for Accelerators

I will give an overview of the 2023 P5 recommendations for accelerators as well as rollout plans, processes, recent HEP organizational changes and possibly share some personal perspectives and thoughts.

Speaker: Derun Li (LBNL)

30 Discussion on integrated design of a linear collider

This discussion focuses on the planning for R&D toward a linear collider based on advanced acceleration concepts.

Speakers: Carl Schroeder (Lawrence Berkeley National Laboratory), Chunguang Jing (Euclid Techlabs), Emilio Nanni (SLAC National Accelerator Laboratory)

10:30 Coffee Break

Plenary: Students Presentations

31 Closing Remarks

12:45 Lunch