Characterisation of the Spatial Resolution and the Gamma-ray Discrimination of Helium-3 Proportional Counters

TL;DR

This paper characterizes the spatial and energy resolution of Helium-3 proportional counters, evaluates their gamma-ray discrimination capabilities, and explores pulse shape discrimination as a method to improve gamma-ray rejection.

Contribution

It provides the first measurements of gamma-ray sensitivity in Helium-3 detectors and investigates pulse shape discrimination for enhanced gamma-ray rejection.

Findings

Measured energy resolution and spatial resolution of Helium-3 detectors.

Quantified gamma-ray sensitivity and its contributing factors.

Demonstrated feasibility of pulse shape discrimination for gamma-ray rejection.

Abstract

We discuss over the energy resolution we measured for several Helium-3 proportional tubes. The energy resolution of a Helium-3 detector is strictly related to the discrimination between gamma-rays and neutrons that can be achieved. We also discuss the different contributions to the energy resolution; these provide information about how the helium-3 counters operate. We measured the spatial resolution of position sensitive Helium-3 detectors in order to quantify and understand the limit that can be achieved with this technology. The gamma-ray sensitivity is the efficiency for miscounting a gamma-ray pulse as a neutron pulse. This quantity is crucial to determine the performance of the detectors.None of the gamma-ray sensitivity measurements described in the literature involves Helium-3 detectors. We measured the gamma-ray sensitivity for several Helium-3 detectors, providing a useful term of comparison for the alternative technologies. We investigated the different contributions that give rise to the gamma-ray sensitivity in a detector. In order to better understand these contributions we performed several Monte Carlo simulations. In order to improve the gamma-ray sensitivity, we tested the feasibility of gamma-ray pulse rejection via Pulse Shape Discrimination (PSD). While proving its feasibility, we quantify the magnitude of the gamma-ray rejection in Helium-3 tubes. The implementation of the PSD technique on Helium-3 detectors was also investigated in order to set a possible starting point for the PSD implementation on Boron-10 detectors.