Event Identification in $^3$He Proportional Counters Using Risetime Discrimination

TL;DR

This paper introduces a simple risetime and pulse height discrimination method for neutron detection in $^3$He counters, achieving high alpha and noise rejection to improve signal-to-background ratios in low-background environments.

Contribution

The paper presents a novel, straightforward technique for particle identification in $^3$He counters using risetime discrimination, enhancing background rejection capabilities.

Findings

Achieved 99% alpha-particle rejection efficiency.

Effectively rejected microdischarge noise events.

Demonstrated method's suitability for low-background neutron measurements.

Abstract

We present a straightforward method for particle identification and background rejection in $^3$He proportional counters for use in neutron detection. By measuring the risetime and pulse height of the preamplifier signals, one may define a region in the risetime versus pulse height space where the events are predominately from neutron interactions. For six proportional counters surveyed in a low-background environment, we demonstrate the ability to reject alpha-particle events with an efficiency of 99%. By applying the same method, we also show an effective rejection of microdischarge noise events that, when passed through a shaping amplifier, are indistinguishable from physical events in the counters. The primary application of this method is in measurements where the signal-to-background for counting neutrons is very low, such as in underground laboratories.