Charge Transfer Efficiency in Proton Damaged CCDs

We have performed detailed measurements of the charge transfer efficiency (CTE) in a thinned, backside-illuminated imaging CCD. The device had been damaged in three separate sections by proton radiation typical of that which a CCD would receive in space-borne experiments, nuclear imaging or particle detection. We examined CTE as a function of temperature, clock rate and radiation dose.The dominant factor affecting the CTE in radiation-damaged CCDs is seen to be trapping by bulk states. We present a simple physical model for trapping as a function of transfer rate, trap concentration and temperature. We have made calculations using this model and arrived at predictions that closely match the measured results.