PARISROC, an autonomous front-end ASIC for triggerless acquisition in next generation neutrino experiments

International audience; PARISROC (Photomultiplier ARray Integrated in SiGe ReadOut Chip) is a complete readout chip in AustriaMicroSystems (AMS) SiGe 0.35 μm technology designed to read array of 16 Photomultipliers (PMTs). The ASIC is realized in the context of the PMm2 (square meter PhotoMultiplier) project that has proposed a new system of "smart photo-detectors" composed by sensor and read-out electronics dedicated to next generation neutrino experiments. The future water Cherenkov detectors will take place in megaton size water tanks then with a large surface of photo-detection. We propose to segment the large surface in arrays with a single front-end electronics and only the useful data send in surface to be stocked and analyzed. This paper describes the second version of the ASIC and illustrates the chip principle of operation and the main characteristics thank to a series of measurements. It is a 16-channel ASIC with channels that work independently, in triggerless mode and all managed by a common digital part. Then main innovation is that all the channels are handled independently by the digital part so that only channels that have triggered are digitized. Then the data are transferred to the internal memory and sent out in a data driven way. The ASIC allows charge and time measurement. We measured a charge measurement range starting from 160 fC (1 photoelectron-p.e., at PMT gain of 106) to 100 pC (around 600 p.e.) at 1% of linearity; time tagging at 1 ns thanks to a 24-bit counter at 10 MHz and a Time to Digital Converter (TDC) on a 100 ns ramp.