Speaker
Description
With obtaining radioactive isotope (RI) beam with a wide range of mass number, the utilization of high-intensity uranium-238 beam is adopted or planned, such as Facility for Rare Isotope Beams.
As one of the such facilities, Radioactive Isotope Beam Factory (RIBF) at RIKEN provides uranium-238 beam, the energy of which is 345 MeV/u. The current intensity of the uranium-238 beam is 70 pnA. Aiming at high-efficient RI beam production, a future improvement of the uranium-238 beam intensity is in progress. Because a number of neutrons is generated due to the reaction between the uranium-238 beam and a copper beam dump, the optimization of a radiation shielding is indispensable. The shielding around the beam dump at RIBF was originally designed by the Moyer model with estimating the source term from the neutron production thick target yields (TTYs) data of neon beam. Due to the derivation, an uncertainty of the source term was remained. Thus, the more accurate source term is absolutely important at RIBF. An improvement of the performance for computers enabled us to estimate the source term by nuclear reaction models, such as Quantum Molecular Dynamics (QMD). However, the availability of the models should be examined prior to applying the source term calculation. Therefore, a measurement of the TTY is strongly desired at RIBF.
The purpose of this study is to measure the neutron production TTY from uranium-238 beam of 345 MeV/u on a copper target for 0˚, 45˚, and 90˚ with a time-of-flight technique and to obtain the benchmark of the QMD models implemented in Particle and Heavy Ion Transport code System and Geometry ANd Tracking 4.
The comparison among our measured data and the calculations shows that QMD results underestimate our measured data at all measured angles. Especially, the underestimation by approximately 70% is observed at 90˚.