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Summary
Digital Photon Counter (DPC) developed by Philips Digital Photon Counting combines array of Geiger-mode avalanche photodiodes and readout electronics on a silicon die using convetional CMOS process technology. Readout chain includes TDC with 20 ps bin and 4 counters for measurement of fired cells numbers as well as logic for event trigger. An array of 4x4 dies is mounted on a tile PCB equipped with an FPGA for event processing and an SPI flash memory for storage of calibration parameters. One of the main advantages of the DPC is a possibility to disable noisy cells.
We consider DPC as a promising photon sensor for aerogel RICH detectors for the Forward spectrometer of the PANDA experiment at FAIR and for the Super Charm-Tau factory project at BINP (Novosibirsk). Known issue of Geiger-mode APDs is an increase of dark counting rate under irradiation. We tested radiation hardness of DPC using a proton beam facility at the COSY accelerator.
Two DPC-3200-22-44 tiles were irradiated by protons with 800 MeV/c momenta up to the fluence of 4*10^11 protons per square cm. Increase of dark counting rate by 4 orders of magnitude has been observed. The dependencies of dark counting rate on the temperature before and after irradiation have been compared. A probability of readout errors induced by radiation (single event effects) has been measured.
