High-speed back-illuminated CMOS sensor for photon-counting-type imaging-spectroscopy in the soft X-ray range

Abstract

Abstract Using a high-speed CMOS sensor, we realized a photon-counting-type imaging-spectrometer in the soft X-ray range for studying the solar corona. The key technology enabling this observation is a sensor with the following capabilities. The sensor is pixelized with a pixel size of 11 μ m and a pixel array of 2048 pixels × 2048 pixels. Furthermore, the sensor is sensitive to X-rays ranging from ∼ 0.5 keV to ∼ 5 keV. The sensor outputs a signal that is proportional to the energy of the incident X-rays. The signal generated by a single X-ray photon does not spread across an area of more than 3 pixels × 3 pixels, in which case signal loss does not occur. The readout noise of the sensor is 2.1 electrons at the 1-sigma level. The sensor can perform continuous exposure at a rate of 1000 times per second for an area of 100 pixels × 2048 pixels. This high-speed readout capability is a special requirement for observation of the solar corona, because energetic solar phenomena, e.g., solar flares, have lifetimes ranging from several minutes to several tens of minutes. We evaluated the above capabilities for the back-illuminated Complementary Metal-Oxide Semiconductor (CMOS) sensor developed by Gpixel, “GSENSE400-BSI UV” using an 55Fe X-ray source, and confirmed the capability of this CMOS sensor to be sufficient for observations of the solar corona.