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 ≈13.8, ≈9.7, ≈5.7, and ≈3.3 MeV, at an average flux of ~10 8 protons cm -2 s -1 , a total fluence from ≈2.1×10 9 up to ≈4.5×10 10 protons cm -2 , and an average dose from ≈5.9 up to ≈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, (μτ)e, and holes, (μτ)h,- and spectroscopic properties-the energy resolution and the peak-to-valley ratio, for y-ray lines within 60-662 keV. The tested CdTe detectors, with (μτ)e~5 × 10 -4 cm 2 V -1 and (μτ)h~3× 10 -5 cm 2 V -1 , showed good radiation hardness, with the measured upper-limit of (μτ)e and (μτ)h proton fluence (average dose) sensitivity of ~2 × 10 -15 cm 2 V -1 /protons cm -2 (~7×10 -7 cm 2 V -1 /Gy) and ~3×10 -16 cm 2 V -1 /protons cm -2 (~1×10 -7 cm 2 V -1 /Gy), respectively. Up to ≈130 Gy, no significant degradation of the energy resolution and the peak-to-valley ratio was observed.