2015 Active Targets and TPC for Nuclear Physics Experiments Workshop

Nuclear reactions studied at small momentum transfers

19 May 2015, 16:25

25m

Lecture Hall (National Superconducting Cyclotron Laboratory)

Oral Presentation Physics and Experiments Session 8

Speaker

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

Description

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 should be measured at extremely low energies (down to few hundred keV). Solid targets are, therefore, not suitable for these reactions. There are two 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 study ISGMR. With the active target, the main goal was to study ISGMR with an active target of helium. Preliminary results of both methods will be presented during the workshop and the methods will be compared to each other.