Some studies on thermal neutron detectors: simulations and experiments

Abstract

Neutron detectors are used in various applications—from national security to understanding solids through neutron scattering. Thermal neutron detection is particularly important because of larger cross section of interaction than fast neutrons. There are materials capable of thermal neutron detection like Gadolinium (157Gd), Cadmium(113Cd), Helium (3He), Boron (10B) and Lithium (6Li), but they are limited in number. The available gas detectors are large in size. Helium-3 is getting economically difficult to procure. So, the quest to find new materials having neutron detection properties is on. Recently, a new material called Boron Carbide has been invented, having excellent thermal neutron detection properties. The potential of using it as a solid-state semiconductor detector is being explored. In the present work, efficiency of Boron Carbide as a thermal neutron detector is studied using Geant4 simulations and results are discussed. Simulations on various other thermal neutron detectors are also done, and results are compared with those obtained using Boron Carbide detectors. Simulations on moderation of fast neutrons with different materials are done and optimum thickness of moderators is estimated. The response of LaCl3:Ce for thermal neutrons is simulated and results are compared with the experimental results reported in literature. Experiments are performed to detect thermal neutrons, after moderating the fast neutrons from 252Cf source, using BC501A detector and results are discussed. Moderation of fast neutrons using Ultra-high-molecular-weight polyethylene (UHMWPE) is verified experimentally using an indirect approach with the help of BC501A detector.