SOFT-X-RAY CCD IMAGERS FOR AXAF

We describe the key features and performance data of a 1024 x 1026-pix el frame-transfer imager for use as a soft-X-ray detector on the NASA X-ray observatory Advanced X-ray Astrophysics Facility (AXAF), The fou r-port device features a floating-diffusion output circuit with a resp onsivity of 20 mu V/e(-) and noise of about 2 e(-) at a 100-kHz data r ate, Techniques for achieving the low sense-node capacitance of 5 fF a re described, The CCD is fabricated on high-resistivity p-type silicon for deep depletion and includes narrow potential troughs for transfer inefficiencies of around 10(-7), To achieve good sensitivity at energ ies below 1 keV, we have developed a back-illumination process that fe atures low recombination losses at the back surface and has produced q uantum efficiencies of about 0.7 at 277 eV (carbon K alpha).