Ph.d. degree
Budapest University of Technology and Economics, Hungary, 2019

Eszter Dian

Supervisor: Péter Zagyvai, Richard Hall-Wilton, Szabolcs Czifrus

Optimisation of Signal-to-Background Ratio for Thermal Neutron Detectors

Keywords:

• Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc)
• Neutron detectors (cold, thermal, fast neutrons)
• Gaseous detectors

Abstract:

The recent restructuring of the 3He market and the high performance required at the European Spallation Source (ESS) opened a new frontier for neutron detector development. A potent new solution for the large area detectors of the chopper spectrometers at the ESS is the Multi-Grid thermal neutron detector, an Ar/CO2 gas filled proportional chamber with solid 10B4C neutron converter. As the high Signal-to-Background Ratio (SBR) is a key requirement, for these instruments Monte Carlo simulations were performed to determine the neutron induced intrinsic gamma and scattered neutron background of the detector and their impact on the SBR. Neutron activation and gamma production were simulated with MCNP for a general Ar/CO2 gas filled detector, and Geant4 detector model was developed, validated and applied for neutron scattering simulations for the Multi-Grid detector. The model was applied for shielding design development to reduce the scattered neutron background and so increase the SBR.