Position sensitive GEM-based thermal neutron detector prototype with 10B4C converter

Abstract

In the last decade, several efforts have been made by the scientific community to find alternatives to 3He, the most effective gas used for thermal neutron detection, which is virtually extinct [1]. Common alternatives make use of isotopes such 157Gd, 10B, and 6Li, due to their high neutron capture cross-section [2]. We present in this work our detector prototype: a 10 cm x 10 cm double GEM stack with an aluminum cathode, coated with a 2:2 μm thick 10B4C layer deposited by the European Spallation Source (ESS). The detector operates under ArCO2 (90/10) open flow at atmospheric pressure. The neutrons are detected through the gas ionization charges created by the outcomes of the 10B(n;α)7Li capture reaction. These charges are collected in a 256x256 strip readout plane produced by CERN, connected to resistive chains we designed for this project and produced in the local industry. We tested the prototype in the IPEN IEA-R1 nuclear reactor with a 1:4Å monochromatic neutron beam. We will report experimental measurements showing that the prototype presented high stability, position sensitivity with spatial resolution better than 3mm (obtained by 2 methods), detection efficiency of 2:66(30)%, and good agreement with simulated results regarding the energy spectrum of the neutron capture products. We will finally discuss further methods to be adopted for enhancing detection efficiency.