First sub-MeV nuclear reaction measurements in a heavy-ion storage ring

Abstract Heavy-ion storage rings present a novel approach to studying nuclear reactions for astrophysics that have so far resisted traditional methods. In this paper, we report the first nuclear reactions studied in a ring at sub-MeV centre-of-mass energies. This is a major advance in nuclear reaction measurements at rings that lays the foundations for future investigations to address key problems in nuclear astrophysics affecting a wide range of stellar environments. We investigated the ^15 15 N (p, p) ^15 15 N and ^15 15 N (p, α) ^12 12 C reactions in inverse kinematics from E = 1. 125 MeV/u down to E = 426 keV/u, using the CARME array in the low-energy CRYRING@ESR heavy-ion storage ring, located at the GSI Helmholtz Center for Heavy Ion Research. Our (p, p) scattering results are in excellent agreement with theoretical R matrix predictions. We also report on a (p, α) measurement at E = 426 keV/u, corresponding to E cm cm = 403 keV, by far the lowest energy at which a nuclear reaction has ever been measured in a heavy-ion storage ring.