MEASURING THE SOFT-X-RAY QUANTUM EFFICIENCY OF CHARGE-COUPLED-DEVICESUSING CONTINUUM SYNCHROTRON-RADIATION

We have measured the soft X-ray (250-4500 eV) quantum efficiency of a charge-coupled device using continuum synchrotron radiation. The spect rum of the synchrotron radiation can be calculated accurately, so the observed pulse height spectrum is a direct measure of the detector eff iciency over the synchrotron bandpass. A key function in modeling the efficiency is the energy dependence of the fraction of detected single pixel events. We find that a model including the effects of charge dr ift and diffusion plus two different depletion depths (corresponding t o the collection and barrier phases under the gates) is required. With this model the absolute QE can be determined to within similar to 5% everywhere over the 500 to 4500 eV bandpass.