Low noise charge injection in the CCD22

The inclusion of a charge injection structure on a charge coupled device (CCD) allows for the mitigation of charge transfer losses caused by radiation induced charge trapping defects. Any traps present in the pixels of the CCD are filled by the injected charge as it is swept through the device improving the charge transfer efficiency in the subsequent acquired images. To date, a number of CCD types have been manufactured featuring different methods of charge injection. The e2v Technologies CCD22, used in the EPIC MOS focal plane instruments of XMM-Newton, is one such device and is the subject of this paper. A detailed understanding of charge injection operation and the use of charge injection to mitigate charge transfer losses due to radiation damage in CCDs will benefit a number of planned future space projects, including the ESA GAIA and X-ray Evolving Universe Spectrometry (XEUS) missions. The charge injection structure and mode of operation in the CCD22 are presented, followed by a detailed analysis of the uniformity and repeatability of the charge injection amplitude across the columns of the device. The effects of proton irradiation on the charge injection characteristics are also presented, in particular the effect of radiation induced bright pixels on the injected charge level.