Prof. Kohmura present findings at iWoRiD 2019 [Performance Improvement of the Event-Driven SOI Pixel Detectors for X-ray Astronomy]


From 7th ~12th July, 21st International Workshop on Radiation Imaging Detectors (iWoRiD 2019) was held in Greek. Professor Kohmura present findings at iWoRiD 2019.

Performance Improvement of the Event-Driven SOI Pixel Detectors for X-ray Astronomy

■Primary author
Dr Ayaki Takeda (University of Miyazaki)

Dr Koji Mori (University of Miyazaki)
Mr Yusuke Nishioka (University of Miyazaki)
Mr Masataka Yukumoto
Mr Takahiro Hida (University of Miyazaki)
Prof. Takeshi Tsuru (Kyoto University)
Dr Takaaki Tanaka (Kyoto University)
Dr Hiroyuki Uchida (Kyoto University)
Mr Kazuho Kayama (Kyoto University)
Mr Yuki Amano (Kyoto University)
Dr Hideaki Matsumura (Kavli IPMU, The University of Tokyo)
Prof. Yasuo Arai (High Energy Accelerator Research Organization (JP))
Prof. Ikuo Kurachi (High Energy Accelerator Research Organization)
Dr Takayoshi Kohmura (Tokyo University of Science)
Dr Kouichi Hagino (Tokyo University of Science)
Mr Mitsuki Hayashida (Tokyo University of Science)
Prof. Shoji Kawahito (Shizuoka University)
Dr Keiichiro Kagawa (Shizuoka University)
Dr Keita Yasutomi (Shizuoka University)
Mr Syunta Nakanishi (Shizuoka University)
Dr Hiroki Kamehama (Okinawa College)

Future X-ray astronomical satellite missions will require a new type of a detector that can distinguish X-rays and charged particle tracks, so as to reduce the background level. In order to realize these demands, we have been developing monolithic active pixel detectors, named “XRPIX,” based on the silicon-on-insulator (SOI) CMOS technology. XRPIX offers high coincidence time resolution (∼50 ns), superior hit-position readout time (∼10 μs), wide bandpass (1–40 keV), and comparable performances in imaging spectroscopy. XRPIX contains a comparator circuit in each pixel to detect particles; it offers an intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. Therefore, XRPIX can directly access the selected pixels to readout the signal amplitude. One of our key development items is the improvement of the energy resolution for the event-driven readout mode. We have observed that the logic inversion of the intra-pixel comparator circuit affects the analog signal at the time of event detection and causes the degradation of the energy resolution. This phenomenon can be attributed to the capacitive coupling between the CMOS circuit and the sensor layer. Recently, two sensor structures have been introduced to reduce capacitive coupling. One is a Double-SOI (D-SOI) structure which contains a middle-silicon layer within the buried oxide (BOX) layer. The other is a pinned depleted diode (PDD) structure which contains a fixed potential layer at the interface between the BOX layer and the sensor layer. We succeeded in improving the spectral performance of the event-driven readout mode for both the D-SOI and PDD structures. In case of the D-SOI structure, we achieved an energy resolution of 410 eV in full width at half maximum for the 6.4-keV X-rays. Furthermore, the peripheral digital circuit of the hit-pattern processing was improved to enhance the functionality of the event-driven readout mode. In this presentation, we report the recent status and evaluation results of our developed XRPIXs.