Optimization of the Neutron Detector Design Based on the 6LiF/ZnS(Ag) Scintillation Screens for the GAMMA-400 Space Observatory

Abstract

The Neutron Detector (ND) is a new detector sub-system for the future GAMMA-400 space observatory. It aims to complement the instrument's GAMMA-400 electromagnetic calorimeter (CsI(Tl), total depth is 25.0 X0) in identifying cosmic-ray electrons from ∼ 100 MeV up to 3 TeV. Such electrons are of significant scientific interest, but their identification is complicated by the overwhelmingly more abundant hadronic cosmic rays, hence making significant hadronic rejection power of paramount importance. Particle showers initiated by nuclei in the GAMMA-400 calorimeter have a profile different from an electron-induced electromagnetic cascade, and the hadron rejection power deriving from this difference can be significantly enhanced by making use of the thermal neutron activity at late (>100ns) times relative to the start of the shower. Indeed hadron-induced showers tend to be accompanied by significantly more neutron activity than electromagnetic showers. In the described ND for capturing thermalized neutrons applied isotope 6Li, which is part of the scintillation screen 6LiF/ZnS(Ag). ND placed are under the electromagnetic calorimeter. The results GEANT4 simulation of the ND shows that ND has high neutron detection efficiency.