The effects of 199 MeV proton radiation damage on CdZnTe photon detectors

Four CdZnTe detectors were irradiated with 199 MeV protons to simulate the damaging radiation in space. The gamma-ray spectra of ²⁴¹Am and ⁵⁷Co as well as the detector leakage currents were monitored at room temperature to assess the effects of radiation damage. Surprisingly, after a fluence of a few ×10⁸ p/cm², gamma-ray peak shifts and resolution degradation became visible. After a fluence of 5×10⁹ p/cm² the degradation was quite dramatic. An analysis of these effects clearly demonstrates that radiation damage causes electron trapping in CdZnTe detectors. No increase in leakage current or electronic noise was observed. Radiation damage effects in CdZnTe and germanium detectors are compared. CdZnTe detectors are ~250 times more sensitive to radiation damage than germanium detectors per unit charge-drift distance