Improved pulse shape discrimination for high pressure 3He counters

The suppression of the internal detector background in 3He counters through pulse shape discrimination methods is becoming an area of interest for a growing number of experiments that want to detect low event rate signals. We discuss two discrimination methods for signals coming from high-pressure (thus high efficiency) 3He counters read out through charge sensitive preamplifiers. We present a digital filter to convert the integrated signal to a current pulse. The application of a discrimination method based on the peak shape suppresses the internal alpha-induced background by > 98.5%. In addition a semi-empirical model of the signal creation in 3He counters is presented and compared to experimental data.