Future X-ray astronomical satellite missions will require a new type of detector that offers a lower non-X-ray background (NXB) rate. To realize this, we have been developing a series of monolithic active pixel detectors, named “XRPIX,” based on silicon-on-insulator (SOI) complementary metal-oxide-semiconductor technology. The XRPIX series offers higher coincidence time resolution (< 10 μs) and wider energy range (1–40 keV) compared to the currently used charge-coupled devices. The XRPIX includes a comparator circuit within each pixel, and can output information of the hit trigger (timing) and the two-dimensional hit pattern (position). Therefore, it is possible to read only the fired pixels, driven by the event. The X-ray readout method using this function is called event-driven mode. This is a key technique in realizing an effective anti-coincidence system. In a previously reported study, we improved the spectroscopic performance by introducing a pinned depleted diode (PDD) structure (Harada et al. 2018, NIMA). The readout noise was measured to be ~10 e- (rms). The energy resolution was ~240 eV (FWHM) in the frame-readout mode at 6.4 keV. However, in this device, an unexpected current path from under the peripheral circuit to the pixel sensing node was observed. We designed a new prototype that improved the structure under the peripheral circuit. In this presentation, we report the recent status and evaluation results of the developed detector with PDD structure.
|Submission declaration||Original and unpublished|