Inflight proton activation and damage on a CdTe detection plane

摘要

Future high-energy space telescope missions require further analysis of orbital environment induced activation and radiation damage on main instruments. A scientific satellite is exposed to the charged particles harsh environment, mainly geomagnetically trapped protons (up to ~300 MeV) that interact with the payload materials, generating nuclear activation background noise within instruments' operational energy range and causing radiation damage in detector material. As a consequence, instruments' performances deteriorate during the mission time-frame. In order to optimize inflight operational performances of future CdTe high-energy telescope detection planes under orbital radiation environment, we measured and analyzed the effects generated by protons on CdTe ACRORAD detectors with 2.56 cm2 sensitive area and 2 mm thickness. To carry-out this study, several sets of measurements were performed under a ~14 MeV cyclotron proton beam. Nuclear activation radionuclides' identification was performed. Estimation of activation background generated by short-lived radioisotopes during one day was less than ~1.3x10~(-5) counts cm~(-2) s~(-1) keV~(-1) up to 800 keV. A noticeable gamma-rays energy resolution degradation was registered (~60% @ 122 keV, ~14% @ 511 and ~2.2% @ 1275 keV) after an accumulated proton fluence of 4.5X10~(10) protons cm~(-2), equivalent to ~22 years in-orbit fluence. One year later, the energy resolution of the irradiated prototype showed a good level of performance recovery.