arXiv subjects

Sophia E. Haight

Publications and source records attributed to Sophia E. Haight.

4 recordsLinked to original sources

arXiv2026

Depth Calibration of Double-sided Strip Germanium Detectors for the Compton Spectrometer and Imager Satellite

Double-sided strip high-purity germanium detectors with three-dimensional position reconstruction capability have been developed over three decades, with space-based applications in high-energy astrophysics and heliophysics. Position resolution in three dimensions is key to reconstruction of Compton scattering events, including for the upcoming Compton Spectrometer and Imager (COSI) satellite mission. Two-dimensional position reconstruction is enabled by segmentation of the two detector faces into orthogonal strip contacts, enabling a pixelized analysis. The depth of an interaction cannot be measured directly but must be inferred from the charge collection time difference between the two faces of the detector. Here, we demonstrate for the first time the depth calibration of a detector with the COSI satellite geometry read out using an application specific integrated circuit (ASIC) developed for the COSI mission. In this work, we map collection time difference to depth using the Julia-based simulation package SolidStateDetectors$.$jl and validate it with comparison to the timing distributions observed in data. We also use simulations and data to demonstrate the depth resolution on a per-pixel basis, with >90% of pixels having <0.9 mm (FWHM) resolution at 59.5 keV and <0.6 mm (FWHM) resolution at 122.1 keV.

astro-ph.IM↗

arXiv2025

Characterizing, correcting, and repairing the effects of radiation damage in the COSI germanium cross-strip detectors

The Compton Spectrometer and Imager (COSI) is a gamma-ray survey telescope utilizing a compact Compton imager design, enabled by an array of 16 high-resolution germanium cross-strip detectors. After its launch into an equatorial Low Earth Orbit (LEO) in 2027, COSI will experience radiation damage primarily due to energetic protons, with the proton fluence dominated by the passage of COSI through the edge of the South Atlantic Anomaly (SAA) for a few minutes each orbit. We have developed a comprehensive program focused on the modeling, characterization, data correction, and physical repair of radiation damage effects in the COSI detectors. We have performed energetic proton beam irradiations of a spare COSI detector at a proton synchrotron, with proton fluences consistent with multiple years of exposure to the COSI space radiation environment. These exposures allow us to characterize the relationship between proton fluence and induced charge trapping. We demonstrate our techniques to correct for trapping effects, as well as characterize the effectiveness of high-temperature annealing on correcting this damage, as characterized by the resulting spectral performance of the detector. We will present our efforts to characterize the effects of radiation damage in the COSI detectors, as well as our techniques for correcting these effects in the data analysis pipeline and ultimately repairing the detectors on orbit every few years through high-temperature annealing.

astro-ph.IM↗

arXiv2025

Proton Radiation Damage and Annealing of COSI p-type Cross-strip HPGe Detectors

In order to understand the effects of a space radiation environment on cross-strip germanium detectors, we investigated the effects of high-energy proton damage on a COSI detector and the capabilities of high-temperature annealing in repairing detector spectral resolution. We irradiated a COSI-balloon cross-strip high-purity germanium (HPGe) detector with 150 MeV protons resulting in a net fluence of $4.95\times10^8$ p$^+$/cm$^2$ and corresponding to ~10 years in COSI's space radiation environment. We repaired the resulting degradation in spectral resolution through a series of high-temperature anneals to obtain a final FWHM of 4.08 keV, within 37% of its preradiation value (2.98 keV FWHM). We characterized the repair of charge traps with time spent under high-temperature anneal to inform an annealing procedure for long-term maintenance of COSI's spectral resolution.

physics.ins-det↗

arXiv2025

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

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, $[nσ]_\mathrm{h}$ 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.

physics.ins-det↗