First Performance Evaluation of an X-Ray SOI Pixel Sensor for Imaging Spectroscopy and Intra-Pixel Trigger

We have been developing a monolithic active pixel sensor with the 0.2 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for the wide-band X-ray imaging spectroscopy on future astronomical satellites. SOIPIX includes a thin CMOS-readout-array layer and a thick high-resistivity Si-sensor layer stacked vertically on a single chip. This arrangement allows for fast and intelligent readout circuitries on-chip, providing advantages over the charge-coupled device (CCD). We have designed and built a new SOIPIX prototype XRPIX1 for X-ray detection. XRPIX1 implements a correlated double sampling (CDS) readout circuit in each pixel to suppress the reset noise. We obtained an energy resolution of full width at half maximum of 1.2 keV (5.4%) at 22 keV with a chip having a 147 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> sensor depletion at a back bias of 100 V cooled to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-50^{\circ}{\rm C}$</tex></formula> . Moreover, XRPIX1 offers intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. We also confirmed the trigger capability by irradiating a single pixel with laser light.