Radiation effects on Silicon Drift Detector based X-ray spectrometer on-board Chandrayaan-2 mission

The space radiation damage effects on the Silicon Drift Detector (SDD) has been studied by measuring the leakage current and the energy resolution for various gamma (Co-60) and X-ray (Fe-55) doses. It is observed that there is no significant change in the leakage current and the energy resolution for the gamma ray dose up to 3 krad. The energy resolution is degraded from similar to 160 eV to similar to 210 eV at 5.89 keV for the gamma ray dose of similar to 10 krad for the detector operating temperature of similar to-40 degrees C. This meets the requirement of Chandrayaan-2 payload performance for the mission life of 2 years. Irradiation tests were also carried out using Fe-55 X-ray source for the doses up to 64 krad and it is observed that there is no significant change in the leakage current and the energy resolution. The radiation damage to the electronic components such as internal JFET (specifically transconductance-g(m)) and the change in the total input capacitance are quantified by measuring the energy resolution for various pulse shaping time constants, before and after irradiation. In this paper, we present a summary of the irradiation measurements and their effects on the SDD devices.