Orbit-Like Proton Radiation Sensitivity of CdTe Detectors: Evaluation of Mobility-Lifetime Products and Spectroscopic Properties

Abstract

This article reports the proton radiation sensitivity of two 1.0-mm-thick EURORAD ohmic CdTe detectors, irradiated with a low energy proton beam generated in a positron emission tomography (PET) cyclotron facility. The CdTe crystals were exposed to a proton radiation field composed of energies of $\approx 13.8$ , $\approx 9.7$ , $\approx 5.7$ , and $\approx 3.3$ MeV, at an average flux of ~ $10^{8}$ protons cm−2s−1, a total fluence from $\approx 2.1 \times 10^{9}$ up to $\approx 4.5 \times 10^{10}$ protons cm−2, and an average dose from $\approx 5.9$ up to $\approx 130$ Gy, equivalent to the proton fluence accumulated in ~1 up to ~20 years in a low earth orbit (LEO). The impact of the proton radiation field was analyzed through its charge transport properties—the mobility-lifetime product for electrons, ( $\mu \tau $ ) e , and holes, ( $\mu \tau $ ) h ,—and spectroscopic properties—the energy resolution and the peak-to-valley ratio, for $\gamma $ -ray lines within 60–662 keV. The tested CdTe detectors, with ( $\mu \tau $ ) $_{e} \sim 5 \times 10^{-4}$ cm2V−1 and ( $\mu \tau $ ) $_{h} \sim 3\times \,\,10^{-5}$ cm2 V−1, showed good radiation hardness, with the measured upper-limit of ( $\mu \tau $ ) e and ( $\mu \tau $ ) h proton fluence (average dose) sensitivity of $\sim 2\times 10^{-15}$ cm2V−1/protons cm−2 ( $\sim 7 \times 10^{-7}$ cm2 V−1/Gy) and $\sim 3 \times 10^{-16}$ cm2 V−1/protons cm−2 ( $\sim 1 \times 10^{-7}$ cm2 V−1/Gy), respectively. Up to $\approx 130$ Gy, no significant degradation of the energy resolution and the peak-to-valley ratio was observed.