4:00 PM - 6:00 PM
[15p-P14-64] Experimental Estimation of Neutron Yield from 7Li(p,n) Reaction for Source Term Estimation System for Accelerator-based BNCT
Keywords:BNCT, ABNS, source term
Our research group has been developing an accelerator-based neutron source(ABNS) for BNCT. The ABNS project of Osaka University employs an electrostatic accelerator which produces low energy neutrons via p-Li (7Li(p,n)7Be) reaction. This neutron yield and angular distribution are known to be affected by the 7Li enrichment, chemical form, and thickness of target. Therefore, it is important for an optimum ABNS design to compare and examine characteristics of various kinds of targets. However, very few systems estimating their neutron yields and angular distributions were proposed. The present study aims at development of an easy-to-use calculation code system to evaluate the source term performance of accelerator based neutron sources. In the present study, experimental results necessary for validation of the system are descirbed in parallel with development of the system.
At first, we made three kinds of targets composed of thick natLi metal plate, 7Li-enriched one and LiF plate. The targets were bombarded with 2.5, 2.7, 2.9 MeV protons using the Dynamitron accelerator at Fast Neutron Laboratory in Tohoku University. To determine the neutron yield accurately, we measured two objects. One is the number of incident protons and the other is the number of generated neutrons. The number of protons incident on the Li target was measured directly from the target current with a current integrator. As for the number of neutrons generated, since it is exactly the same number of 7Be, we measured 478keV gamma-rays emitted via 7Be decay to7Li in the half life of 53 day with a handy CdTe detector before and after the irradiation and succeffsully determined the exact number of neutrons.
From the measurement results, we found that the neutron yield of natLi was twice larger than that of LiF, and the ratio of the values (natLi/LiF) showed different depending on the incident proton energy. Furthermore other results (Lee et al. and Yanch et al.) supported the presently measured values.
Completing development of the present system, we are validating it and will expand the system to be able to estimate performance of various neutron source terms for various targets and energies.
At first, we made three kinds of targets composed of thick natLi metal plate, 7Li-enriched one and LiF plate. The targets were bombarded with 2.5, 2.7, 2.9 MeV protons using the Dynamitron accelerator at Fast Neutron Laboratory in Tohoku University. To determine the neutron yield accurately, we measured two objects. One is the number of incident protons and the other is the number of generated neutrons. The number of protons incident on the Li target was measured directly from the target current with a current integrator. As for the number of neutrons generated, since it is exactly the same number of 7Be, we measured 478keV gamma-rays emitted via 7Be decay to7Li in the half life of 53 day with a handy CdTe detector before and after the irradiation and succeffsully determined the exact number of neutrons.
From the measurement results, we found that the neutron yield of natLi was twice larger than that of LiF, and the ratio of the values (natLi/LiF) showed different depending on the incident proton energy. Furthermore other results (Lee et al. and Yanch et al.) supported the presently measured values.
Completing development of the present system, we are validating it and will expand the system to be able to estimate performance of various neutron source terms for various targets and energies.