High-speed x-ray imaging spectroscopy by CCD-CMOS hybrid sensor

Le résumé fourni par la source

Current x-ray astronomical satellites carry CCD cameras that have moderate performance in imaging, spectroscopy and timing. Future x-ray telescopes with large effective areas and sharp point spread functions require quick readout of focal plane sensors to realize imaging spectroscopy without photon pile-up nor intermittency of exposure time. To fulfill the requirements we are developing a hybrid sensor of CCD and CMOS. The former has readout nodes for every columns and the latter equips corresponding readout ICs including analog-to-digital converters. Both parts are implemented in the same package. Vertical transfer frequency of 100kHz enables us to readout the whole frame within 10ms even with 1k by 1k pixel format. Our first test device with pixel format of 128×1024 and pixel size of 11μm square has been evaluated with monochromatic x-rays from 109Cd. X-ray events are successfully detected and the energy resolution is 1.43keV (full width at half maximum) at 22keV for the events whose signal charges are concentrated in a single pixel. Approximately 30% of charges are lost for the multi-pixel events, which implies that there might exist non-depleted region in the wafer. Pulse height comparison among the split pattern of the events indicated non-uniformity of the electric field in horizontal axis. As a next step We will adopt the CCD wafer that has been used for XRISM/Xtend in order to realize the optimum electric field.

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