Shape Control of Small Li Glass Composite Scintillator for Optical-fiber-based Detectors

Boron neutron capture therapy (BNCT) is one of the radiation therapies using neutrons. In BNCT, neutron monitoring is essential to ensure safety and evaluate the effect of treatments. As a neutron monitor for BNCT, we are developing an optical-fiber-based neutron detector using a small Li glass scintillator. This type of detector shows a clear neutron peak in the pulse height spectrum and has a high counting-rate capability owing to its short decay time. However, the sensitivity of the detector is uncontrollable owing to its random scintillator shape. In this study, we propose a Li glass transparent composite scintillator, in which Li glass grains and UV-curable resin are mixed, to realize a small and shape-controlled scintillator. We first fabricated the Li glass transparent composite scintillator and then experimentally confirmed that its response showed a clear neutron peak. We also fabricated an optical-fiber-based neutron detector using the Li glass transparent composite scintillator. The scintillator was formed into a hemispherical shape at the tip of an optical fiber. We confirmed the response of the optical-fiber-based detector, which showed a clear neutron peak. The experimentally evaluated sensitivity of the fabricated optical-fiber-based detector roughly agreed with the sensitivity estimated from its shape and size. Therefore, we conclude that the sensitivity of the optical-fiber-based neutron detector can be roughly controlled by using the Li glass transparent composite scintillator.