A compensation circuit for the gain temperature drift of silicon photomultiplier tube

Background Silicon photomultiplier tube(SiPM)has been widely applied in high energy physics experiments.The wide field of view Cherenkov telescope array of Large High Altitude Air Shower Observatory(LHAASO)consists of 12 arrays of SiPMs.Each of the array includes 32*32 pixels.Large Array of imaging atmospheric Cherenkov Telescopes(LACT),the next generation of particle astrophysics experiment,will also adopt SiPM arrays.Purpose LACT will located at a high altitude,leading to a significant operating temperature variation of the SiPM.Since the gain of SiPM is temperature-sensitive,in order to keep it stable,compensation for the gain is necessary by adjusting the bias voltage of SiPM.Methods The compensation circuit provides the bias voltage of SiPM by using a high-voltage output Digital-to-Analog Converter and several high-voltage output amplifiers.To reduce the temperature drift of the gain,the compensation circuit adjust the bias voltage of SiPM according to the operating temperature.Results The compensation circuit supplies SiPM with an adjustable bias voltage from 0 to 80 V,and the adjustment step is 1.22 mV.When the output voltage of the compensation circuit is 64 V,the voltage ripple is 2.59 mV,and the temperature drift is 0.17 mV/℃.In the temperature range from−20 to 30℃,the compensation circuit reduces the gain temperature drift of SiPM to within 2%.

Characterization of FEEWAVE,a low‑power waveform digitizer ASIC with 15‑ps time resolution

Purpose FEEWAVE is a chip with a waveform digitizer based on a switched capacitor array(SCA).A SCA uses capacitor arrays to store waveforms and exhibits low-power consumption and high time resolution performance.However,the limitations of the chip manufacturing process induce sampling interval and digitization deviations between different cells,which affects the performance of the chip.Methods Calibration was performed on the SCA sampling part on the FEEWAVE chip to obtain more accurate digitized output and time intervals between the sampling cells.Experiments were carried out according to the proposed amplitude and time calibration methods,and the time resolution of the chip was further improved by a fitting algorithm.Results and conclusion Through the calibration algorithm,the time resolution of the SCA sampling part of the chip reached 9.0 ps after calibration.In the self-test of the electronics time performance,the time measurement after leading-edge fitting and calibration was approximately 12.3 ps.In the joint test with silicon photomultiplier detectors,the time resolution of the SCA part was low and comparable to the resolution of the oscilloscope after calibration algorithm and waveform fitting.