The...

We have been developing a monolithic active pixel sensor with silicon-on-insulator technology for use in X-ray astronomical satellite missions. Our aim is to replace the X-ray charge-coupled device—which is the standard detector in the field—with a device that exhibits a high-coincidence time resolution (i.e.,∼1 µs), superior hit-position readout time (i.e.,∼10 µs), and wider bandpass (i.e., 0.3–40 keV), in addition to having comparable performance in imaging spectroscopy. To realize this detector, we have developed prototype detectors called the “XRPIX ” series. XRPIX contains a comparator circuit in each pixel to detect an X-ray photon, and it offers an intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. Therefore, XRPIX is capable of direct access to selected pixels to read out the signal amplitude. X-ray signal readout by this function is called an “event-driven readout. ” In our previous study, we successfully demonstrated the X-ray spectra acquisition by the event-driven readout. However, there were some problems in the circuit operation. Recently, these investigations progressed because of many evaluation tests. In this paper, we describe the development and the evaluation of the event-driven readou