Heps-Bpix3: A Fine Pitch Pixel Readout Chip Working In Single Photon Counting Mode For Synchrotron Radiation Applications

HEPS-BPIX3 is a hybrid pixel detector readout chip for X-ray applications for the High Energy Photon Source (HEPS) in China. The readout chip contains an array of 88 x 88 pixels with a pixel size of 55 mu m x 55 mu m, working in single photon counting mode. Each pixel handles both polarities of positive and negative input charge signals and has a counting depth of 11 bits. Using a clock with a frequency up to 160 MHz, the chip can read out serially with zero dead time. Designed in a 130 nm CMOS technology, the chip has been measured and given the CSA charge gain of 17.6 mV/ke(-) for electron collection and 13 mV/ke(-) for hole collection, respectively. Bump bonded detector modules with a 320-mu m-thick silicon sensor were also tested. The test results showed an equivalent input noise of 156 e(-) and a counting rate up to 2.2 Mcps. Besides, an image using an X-ray tube was demonstrated and a frame rate of 1.8 kHz could be guaranteed. Measured characteristics present the normal functionality of the HEPS-BPIX3 chip and prove that the chip satisfies the HEPS requirements.