Double Differential Neutron Yields From Thick Targets Induced by Relativistic Carbon and Uranium Beams

Abstract

In order to design appropriate shielding for the next generation high-intensity acceleratorfacilities like e.g. FAIR, knowledge of neutron emissions induced by relativistic heavy ion beams stopping in accelerator components or concrete shielding is indispensable. Measured neutron spectra can directly be used as source terms for Monte-Carlo transport calculations. Thus measurements were carried out in Cave B of the SIS accelerator at GSI in order to determine double differential yields of fast neutrons produced by heavy ion beams in thick stopping targets. Three different beam-target combinations were investigated: (a) 12C beam (400 MeV/u) stopping in a 20 cm thick graphite target, (b) 12C beam (1 GeV/u) stopping in a 20 cm thick iron target, and (c) 238U beam (1 GeV/u) stopping in a 20 cm thick iron target. Fast neutrons emerging from the targets were detected by a BaF2 scintillator positioned at various angles with respect to the primary beam axis. The neutron energy was obtained from time-offlight measurements. A comparison of the measured double differential yields with the Monte-Carlo code FLUKA and measurements with the so called Large Area Neutron Detector (LAND) at GSI are presented.