<title>Characterization of the CCDs for the Joint European X-Ray Telescope</title>

Abstract

We present preliminary results from a comprehensive program to calibrate the CCDs to be used as the focal plane detectors on the Joint European X-ray telescope (JET-X). The goal of the program is to calibrate the response of the flight CCDs (efficiency and energy resolution) down to a limiting precision of 1%. In addition to using conventional characteristic X-ray emission line calibration techniques to quantify the broad-band response, the devices have also been taken to the Synchrotron Radiation Source (SRS) at the Daresbury Laboratory to map the detailed X-ray Absorption Fine Structure (XAFS) around the silicon K-edge. To carry out the latter measurements, the SRS had to be operated with a ring current reduced by 5 orders of magnitude so that individual photons could be recorded by the CCD. The data show considerable near edge structure which is similar in shape to pure Si XAFS obtained by photocurrent measurements, but modified by the presence of the various oxide insulation layers used in MOS construction. Lastly, an analysis oft he pulse height spectra obtained at the SRS, has demonstrated that the Fano factor and the energy to create an electron hole pair vary with energy in agreement with the photoionization theory of Fraser et al. and the semi- empirical analysis of Owens et al.