SOFT-X-RAY RESPONSE OF CHARGE-COUPLED-DEVICES

The charge coupled device (CCD) is useful as an imaging detector in the X-ray waveband, and when used to detected single photon events can simultaneously provide spatial imaging and energy resolution. This capability is important in the field of X-ray astronomy. With radiation focussed onto the front electrodes, the CCD suffers from reduced response below 1 keV due to absorption in the electrode structure; the same process that limits the blue response in the optical band. Two alternative developments are described that extend the soft X-ray and blue responses of the CCD. Experimental data are presented for these two configurations of CCD and their performance characteristics as X-ray images are compared.