Measurement of wide energy range neutrons with a CLYC(Ce) scintillator

Abstract

The CLYC(Ce) (Cs2LiYCl6:Ce3+) scintillator can identify different particles with various specific energy losses and is capable of measuring the fast neutron energy via the 35Cl(n,p)35S reaction. Thus, it is rational to expect using this detector for monitoring the on-site neutron dose rate for astronauts or equipments working at a spacecraft, which may undergo the irradiation of cosmic rays of energetic protons or alpha particles that could induce the production of spallation neutrons. However, as the spallation neutrons, as well as the moderated neutrons, have an energy distribution from the thermal region to several hundred MeV, the direct measurement of the neutron spectrum, which helps calculate the exact value of dose rate in the spacecraft, requires that the energy response matrices should be known in advance. In this study, we calibrated a Φ38 mm × 38 mm CLYC(Ce) scintillator detector with the Back-n beamline at the China Spallation Neutron Source (CSNS), acquiring its energy response matrices (ERM) ranging from 0.1 MeV to 100 MeV. To verify the CLYC(Ce) scintillator detector's capability for measuring neutrons with such a wide region, using the ERM, the energy spectrum of the Back-n beamline was reconstructed and the result conformed to the CSNS-measured result well; a good conformation between the reconstructed spectrum and the standard Watt fission neutron spectrum of 252Cf was also observed. This calibrated detector then was used to measure the cosmic-ray induced neutron spectra at five different sites in China of various altitudes. The measured neutron fluxes at five different sites conformed to results predicted by the EXcel based Program Atmospheric Cosmic-ray Spectrum (EXPACS). The results presented in this study indicate that the CLYC(Ce) scintillator detector is promising to be used in spacecraft as a neutron monitor with a wide energy range.