Improvement of gamma-ray subtraction procedure for a current-mode neutron detector with a pair of ⁶li- and ⁷li-glass scintillators

A current-mode neutron detector with a pair of ⁶Li- and ⁷Li-glass scintillators has been developed to measure high-flux neutrons in a boron neutron capture therapy field. Neutrons are basically measured by subtracting gamma-ray component using current outputs from the ⁷Li-glass scintillator. In the present study, the difference in the gamma-ray sensitivity between the ⁶Li- and ⁷Li-glass scintillators and the neutron sensitivity for the ⁷Li-glass scintillator due to the ⁶Li contamination were also considered to improve the gamma-ray subtraction precision. The gamma-ray subtraction procedure was experimentally investigated in thermal neutron fields with ²⁵²Cf and ²⁴¹Am-Be neutron sources, which have different gamma-ray intensities per unit neutron fluence. A linear relation between neutron fluence and current output was obtained for the neutron detector in the two types of thermal neutron fields with different gamma-ray intensities. It was found that the gamma-ray subtraction procedure is useful for current-mode neutron detectors. (authors)