CHARGE COUPLED DEVICES are the ideal detector for soft X rays (1 to 12 keV) in the high background environment of an accelerator.That is due to the manner in which X rays deposit energy in the detector material. The essential development in CCD detector technology was the reduction of the pixel size to approximately 22.5 x 22.5 µm2. Under this condition, charge deposited by a low energy X ray is mostly confined to a single pixel. Higher energy photons or charged particles have much more ionizing power and will deposit their charge over several pixels. By applying the "single pixel" criterion an enormous efficient background rejection has been achieved. This capability, in addition to the excellent energy resolution (150 eV FWHM for 6.5 keV X rays) is the key to success for many experiments.