Characterizing hole trap production due to proton irradiation in germanium cross-strip detectors

TL;DR

This study investigates how high-energy proton irradiation causes hole trap production in germanium cross-strip detectors, quantifying trap formation rates and demonstrating calibration methods to mitigate spectral resolution degradation.

Contribution

It provides the first quantification of proton-induced hole trap production rates and develops calibration techniques to correct for trapping effects in germanium detectors.

Findings

Hole trap production rate is linearly related to proton fluence.

Calibration can effectively mitigate spectral resolution degradation.

Electron trapping dominates over hole trapping in undamaged detectors.

Abstract

We present an investigation into the effects of high-energy proton damage on charge trapping in germanium cross-strip detectors, with the goal of accomplishing three important measurements. First, we calibrated and characterized the spectral resolution of a spare COSI-balloon detector in order to determine the effects of intrinsic trapping, finding that electron trapping due to impurities dominates over hole trapping in the undamaged detector. Second, we performed two rounds of proton irradiation of the detector in order to quantify, for the first time, the rate at which charge traps are produced by proton irradiation. We find that the product of the hole trap density and cross-sectional area, $[n\sigma]_\mathrm{h}$ follows a linear relationship with the proton fluence, $F_\mathrm{p}$, with a slope of $(5.4\pm0.4)\times10^{-11}\,\mathrm{cm/p^{+}}$. Third, by utilizing our measurements of physical trapping parameters, we performed calibrations which corrected for the effects of trapping and mitigated degradation to the spectral resolution of the detector.