Radiation effects on CCDs for spaceborne acquisition and tracking applications

The author reviews the results of recent Co⁶⁰ and proton testing of TH7863 and THX31160-1 CCDs. The Co⁶⁰ gamma ray tests were performed on devices both biased and unbiased during irradiation and at two dose rates (1 krad/hr and 50 rad/hr). In all cases the biased devices showed a threshold voltage shift of ~0.09 V/krad and significant increases in surface dark current (~10nA/cm² /krad at 22°C) which continued after irradiation had ceased. Both threshold voltage and dark current damage were reduced for unbiased devices. Power consumption, charge transfer efficiency (CTE), full well capacity and charge to voltage conversion factor were also measured but did not show large changes. Proton testing was carried out at 1.5 and 10 MeV again for biased and unbiased devices and dark current changes due to bulk damage were observed. These were bias independent. There was significant annealing of bulk damage after 3 months storage (this time the dark current reduced). After annealing a storage constant of roughly 2.4nA/cm² per MeV of damage energy at 22°C was found