Characteristics of Signals Originating Near the Lithium-Diffused N+ Contact of High Purity Germanium P-Type Point Contact Detectors

TL;DR

This paper investigates signals near the lithium-diffused n+ contact of high purity germanium detectors, revealing partial charge collection in the transition region and introducing a new method to quantify related background contributions.

Contribution

It presents a novel technique to measure background signals from the transition region in germanium detectors, aiding low-energy threshold experiments.

Findings

Partial charge collection occurs in the transition region.

A new method quantifies background contributions from this region.

Implications for low-energy threshold detector experiments.

Abstract

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.