Development of detector for neutron monitor of wide energy range. Joint research

Radiation monitoring of neutrons in high-power proton accelerator facilities is very important for radiation safety management for workers and members of the public. In the present study, a neutron detector that can evaluate dose of neutrons in the energy range from thermal energy to 100MeV was developed using an organic liquid scintillator, a boron-loaded scintillator and a sup 6 Li glass scintillator. First, a method was developed to evaluate neutron doses above several MeV by a spectrum weight function (G-function) which is applied to the organic liquid scintillator, and the validity of the methods was confirmed by dose evaluation in some neutron fields. Second, the G-function was applied to the boron-loaded scintillator which detects thermal neutrons by sup 1 sup 0 B(n, alpha) sup 7 Li reaction, in order to expand the covering neutron energy range. The response function and the G-function of the scintillator were evaluated by experiment and calculation, and the characteristics of dose measurement were analyzed. It was found from the results that the boron-loaded scintillator can evaluate neutron dose by applying the G-function. However, it is difficult to discriminate neutron event below 1MeV by the scintillator of alpha particle produced from sup 1 sup 0 B(n, alpha) sup 7 Li reactions in a field accompanying background of gamma rays. Third, a hybrid detector of sup 6 Li glass and organic liquid scintillators was developed to overcome the difficulty of the boron-loaded scintillator. The optimized configuration of two detectors was designed by Monte Carlo calculation codes, and then the detector was fabricated. The efficiency and response function of detectors were evaluated based on the calculated results and the measured results in some neutron fields. It was concluded from these results that the developed hybrid detector in this study can be used as a detector for neutron monitoring of wide energy range from thermal to 100MeV.