Lithium Targets as Neutron Sources for Nuclear Astrophysics at the Soreq Applied Research Accelerator Facility


  Moshe Friedman [1]  ,  Gitai Feinberg [1,2]  ,  Michael Paul [1]  ,  Alexander Arenshtam [2]  ,  Dan Berkovits [2]  ,  Danny Kijel [2]  ,  Ido Silverman [2]  
[1] Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel
[2] Soreq Nuclear Research Center, Yavne 81800, Israel

Nucleosynthesis of heavy elements in stellar environments is governed in major part by neutron capture processes. Simulating the stellar interior in the laboratory and measuring the cross section of neutron-induced reactions requires neutron sources with a specific energy spectrum. Asymptotic Giant Branch (AGB)-star shells of temperature of ~300 MK (kT~ 25 keV) are believed to be a major site for production of nuclides by the slow (s-)process. This environment may be simulated in the laboratory by the 7Li(p,n)7Be reaction with protons of average energy ~30 keV above threshold (Ethr= 1.880 MeV). A Liquid-Lithium Target (LiLiT) designed to withstand intense proton beams (up to 2-4 mA), a major issue for conventional lithium targets, is being built at Soreq NRC for the Soreq Applied Research Accelerator Facility (SARAF) and is expected to produce neutron intensities up to ~4-8×1010  s-1, more than one order of magnitude higher than presently available. This neutron intensity will allow us to extend the study of neutron-induced reactions to targets of unstable nuclides important to nucleosynthesis. In a first stage, the setup will be characterized using a Solid LiF Target (SoLiT) at lower beam intensities. An experiment designed to test the solid target and to measure the neutron spectrum and intensity is planned, using the beam of a Van de Graff accelerator. A code for simulation of the neutron generation was written and results will be presented together with simulations of the neutron transport using the GEANT4 code.