Indirect studies on astrophysical reactions at the low-energy RI beam separator CRIB

Abstract

Studies on nuclear astrophysics, nuclear structure, and other interests have been performed using the radioactive-isotope (RI) beams at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study (CNS), the University of Tokyo. A type of measurement to study astophysical reactions at CRIB is by the elastic resonant scattering with the thick-target method in inverse kinematics. An example is the alpha resonant scattering with Be-7 beam, related to the astrophysical Be-7(alpha,gamma) reactions, which is relevant in the hot p-p chain and vp-process in supernovae. Other alpha resonant scattering measurements with S-30, Be-10, O-15, and Ne-18 beams have been performed at CRIB, using the thick-target method. There have also been measurements based on other experimental methods. The first Trojan horse method (THM) measurement using an RI beam has been performed at CRIB, to study the F-18(p, alpha)O-15 reaction at astrophysical energies via the three body reaction(2)H(F-18, alpha O-15)n. The F-18(p, alpha)O-15 reaction rate is crucial to understand the 511-keV gamma-ray production in nova explosion phenomena, and we successfully evaluated the reaction cross section at novae temperature and below experimentally for the first time.