Radiation Damage of $2 \times 2 \times 1 \ \mathrm{cm}^3$ Pixelated CdZnTe Due to High-Energy Protons

TL;DR

This study investigates how high-energy protons damage pixelated CdZnTe detectors used in space gamma-ray imaging, revealing degradation effects, bias dependency, and recovery methods through irradiation experiments.

Contribution

It provides the first detailed quantification of proton-induced radiation damage on pixelated CdZnTe detectors, including bias effects and annealing recovery strategies.

Findings

Proton irradiation degrades energy resolution and centroid accuracy.

Bias during irradiation influences damage severity.

Annealing at room temperature and 60°C aids recovery.

Abstract

Pixelated CdZnTe detectors are a promising imaging-spectrometer for gamma-ray astrophysics due to their combination of relatively high energy resolution with room temperature operation negating the need for cryogenic cooling. This reduces the size, weight, and power requirements for telescope-based radiation detectors. Nevertheless, operating CdZnTe in orbit will expose it to the harsh radiation environment of space. This work, therefore, studies the effects of $61 \ \mathrm{MeV}$ protons on $2 \times 2 \times 1 \ \mathrm{cm}^3$ pixelated CdZnTe and quantifies proton-induced radiation damage of fluences up to $2.6 \times 10^8 \ \mathrm{p/cm^2}$. In addition, we studied the effects of irradiation on two separate instruments: one was biased and operational during irradiation while the other remained unbiased. Following final irradiation, the $662 \ \mathrm{keV}$ centroid and nominal $1\%$ resolution of the detectors were degraded to $642.7 \ \mathrm{keV}, 4.9 \% \ ( \mathrm{FWHM})$ and $653.8 \ \mathrm{keV}, 1.75 \% \ (\mathrm{FWHM})$ for the biased and unbiased systems respectively. We therefore observe a possible bias dependency on proton-induced radiation damage in CdZnTe. This work also reports on the resulting activation and recovery of the instrument following room temperature and $60^{\circ}\mathrm{C}$ annealing.