銅標的に対する345 MeV/uウラン入射により生成する中性子エネルギースペクトルの測定

Radioactive Isotope Beam Factory (RIBF) at RIKEN accelerates $^{238}$U ions up to 345 MeV/u. The operational maximum beam current of $^{238}$U is about 70 particle nA now. The maximum permitted intensity of $^{238}$U beam at RIBF is 300 particle nA. Optimization of the radiation shielding design is desired for upgrade of beam current to more than 1 particle μA in the future. Neutron production thick target yields (TTY) by 345 MeV/u $^{238}$U beam is essential as a source term in shielding design. However, there is no data of this reaction. In this study, neutron TTY by $^{238}$U beam on a copper target is measured.

The experiment was carried out at Zero Degree Spectrometer beam line of RIBF. The 345 MeV/u $^{238}$U beam was induced on a Cu target of 10 mm thick, which was longer than the range of incident ions. Neutrons produced in the target were measured with NE213 liquid organic scintillators, which was set at 0$^{\circ}$, 45$^{\circ}$ and 90$^{\circ}$ from the beam axis. Time-of-Flight technique was applied to determine the kinetic energies of neutrons. The comparison between measured TTY and simulation results by PHITS will be discussed.