Development of an X-ray Poralimeter Using Direct X-ray Imaging CCD with Position, Energy and Time Resolution

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The purpose of this research project is to improve not only the fundamental properties of X-ray CCD but also as an X-ray polarimeter. The research group consists of the member s in Hamamatsu photnonics (HPK) and the members in Osaka university. According to the specification determined by all the members, the CCD chips were fabricated at HPK,and the university side operated and examined those chips.Several kinds of CCD chips using different material and production methods have been made. We got eventually energy resolution of 140 eV for 5.9 keV X-rays with a CCD chip of which pixel size is 12 mum and pixel number is 512x512. Although the resolution was 160 eV at the end of the first year in the research term, reduction of the dark current by 1/50 lead to the better resolution. Using high registivity material, we got a CCD chip of which depletion layr is as thick as 20 mum.University side activities include the development of CCD operation and evaluation ; 1) spectrometer system for measuing the CCD detection efficiency for 0.4-2.2keV X-rays, 2) CCD drive clock to suppress spurious charge noise, 3) high speed read-out system using DSP,4) simulation code for X-ray absorption and charge collection process within CCD.Adding these, we invented a novel method for measuring detection efficiency for sub-pixel size structure by employing a mesh in front of the CCD chip. We also measured polarization degree of the X-ray beam from a laboratory X-ray generator. CCD chips with pixel size of 6 mum, which should be effective for X-ray polarimetry, were started to fabricate. The polarimeter-capability of those small pixel size CCD will be measured within the year of 1997.