Radiation testing of CCDs for space applications

This article reports the results of radiation resistance tests of fully depleted p-channel Charge Coupled Devices (CCDs) developed at the Lawrence Berkeley National Laboratory for imaging applications in space. Several such devices were irradiated by 12 MeV protons at the tandem accelerator at the Wright Nuclear Structure Laboratory at Yale University by doses up to 8 x 10¹⁰ protons/cm². The equivalent dose at an orbit near L2 for a six year mission in space was estimated to be an equivalent 7.3 x 10 ⁸ 12.5 MeV protons/cm². The performance of the CCDs was measured both before and after irradiation. The charge transfer efficiency CTE was degraded from 0.999999 before irradiation to 0.999996 after the expected six year dose. The dark current, which was 3 electrons/pixel/hour before irradiation, is degraded to an equilibrium rate of 15 electrons/pixel/hour in orbit. We conclude that the performance of these devices is quite acceptable for high precision imaging in a space mission.