Design of a Compact Neutron Spectrometer Using the CLYC Scintillator

Abstract

Astronauts and spacecraft are exposed to space radiation from a variety of sources, including cosmic rays, cosmic-ray-induced neutrons and gamma rays. To determine the neutron dose to astronauts and spacecraft, an onboard neutron spectrometer with small size and low consumption design is required. The time-of-flight spectrometer and the moderation spectrometer are rejected for its long flight path and for its heavy-mass moderators, respectively. The organic scintillators have an ill-conditioned response matrix to reconstruct neutron spectrum as the responses to neutrons in different energies are highly similar. This paper presents a new design of compact neutron spectrometer using the newly developed CLYC (Cs2LiYCl6: Ce) scintillator which is sensitive to both thermal neutrons and fast neutrons. An anti-coincidence scintillator is used to reject the incident charged particle events, and the Pulse Shape Discrimination (PSD) ability of CLYC scintillator was utilized to reject gamma events. This compact neutron spectrometer uses the response matrix of monoenergetic neutrons ranging from thermal to 100 MeV and the response to incident neutrons to determine the neutron spectrum with the Iteratively Reweighted Least Squares (IRLS) algorithm. The work is verified by the simulation results of Geant4.10.02 code, it shows that the constructed neutron spectrum agrees well with the incident spectrum.