SiPM behaviour under continuous light

TL;DR

This paper investigates the behavior of large-area SiPM detectors under continuous light, analyzing how voltage drops affect their electrical and optical properties, and proposes a model and correction methods for accurate operation in high-light environments.

Contribution

It introduces a comprehensive model to correct voltage drop effects in SiPMs under continuous illumination, validated through experiments and simulations.

Findings

Voltage drop significantly affects SiPM sensitivity and parameters.

A correction model effectively compensates for voltage drop effects.

Experimental results align with simulation, improving SiPM calibration.

Abstract

This paper reports on the behaviour of Silicon Photomultiplier (SiPM) detectors under continuous light. Usually, the bias circuit of a SiPM has a resistor connected in series to it, which protects the sensor from drawing too high current. This resistor introduces a voltage drop when a SiPM draws a steady current, when illuminated by constant light. This reduces the actual SiPM bias and then its sensitivity to light. As a matter of fact, this effect changes all relevant SiPM features, both electrical (i.e. breakdown voltage, gain, pulse amplitude, dark count rate and optical crosstalk) and optical (i.e. photon detection efficiency). To correctly operate such devices, it is then fundamental to calibrate them under various illumination levels. In this work, we focus on the large area ($\sim$1~cm$^{2}$) hexagonal SiPM S10943-2832(X) produced by Hamamatsu HPK for the camera of a gamma-ray telescope with 4 m-diameter mirror, called the SST-1M. We characterize this device under light rates raging from 3~MHz up to 5~GHz of photons per sensor at room temperature (T = 25 $^{\circ}$C). From these studies, a model is developed in order to derive the parameters needed to correct for the voltage drop effect. This model can be applied for instance in the analysis of the data acquired by the camera to correct for the effect. The experimental results are also compared with a toy Monte Carlo simulation and finally, a solution is proposed to compensate for the voltage drop.