Neutron Emission Profile of d-Be Reaction with Low-energy Deuteron Beam for Accelerator Neutron Source

Abstract

The neutron emission profile of the 9Be(d,n)10B nuclear reaction using a low-energy deuteron beam (300 keV) was examined to develop an accelerator neutron source for boron neutron capture therapy (BNCT). The gamma rays corresponding to the transition from excited levels of 10B were measured using a high-purity Ge detector. By analyzing the gamma-ray yields, the transition probability to each excited state of 10B was determined and the neutron yields for the individual energies were evaluated. The emission of the 3.8 MeV neutron was approximately 42% of the total emission, and other neutron emissions from 1.1 to 4.5 MeV were clearly specified. A neutron moderator assembly using heavy water (D2O) or Be metal was designed in order to obtain thermal neutrons from the d-Be reaction with high efficiency. The simulations of neutron transport in the assembly were performed using the Monte Carlo code MCNP4C. Thermal, epithermal, and fast neutron fluxes were calculated as a function of the moderator thickness. The experimentally evaluated neutron emission property was reflected in the simulation. The results indicate that the use of the D2O moderator is suitable for thermal neutron production and shielding of fast neutrons rather than that of Be.