Optimisation of device clocking schemes to minimise the effects of radiation damage in Charge Coupled Devices

The ESA Euclid mission aims to answer the question of how the universe originated through the mapping of the dark Universe. One method to investigate this geometry is to measure subtle changes in ellipticity using image sensors such as the CCD. However, the radiation environment in space plays a major part in the performance of CCD-based camera systems. When placed in space, a CCD becomes damaged by the radiation environment and this can lead to a ‘smearing’ of the charge, acting to change the ellipticity and therefore one must be able to separate the changes in ellipticity caused by radiation damage from those the mission aims to measure. To this end, the radiation damage induced shape changes require in depth investigation such that optimised operation can be achieved. A Monte Carlo simulation is being used to predict this impact, backed by experimental data from a detector formerly baselined for the mission. During the experimental study, an investigation was undertaken into the serial readout of the CCD to demonstrate an approach towards performance optimisation through a consideration of the trap species involved. A change in clocking scheme was found to result in a factor of three reduction in Charge Transfer Inefficiency.