A Novel Technique for the Stabilization of SiPM Gain Against Temperature Variations

In several applications of Silicon Photo-Multipliers (SiPM), drifts of the detector gain with the temperature represent a severe drawback which prevents from achieving optimal performance. We propose an original technique to address this issue, based upon the use of a SiPM not exposed to the light as a temperature sensor. The average amplitude of the dark pulses produced by this detector is measured and controlled to a constant reference value by means of a negative feedback loop, which automatically varies the bias voltage of the SiPM. The same bias voltage variations generated by the feedback loop are also applied to the sensitive SiPMs used in the specific application, thus making constant their gain. The effectiveness of the proposed compensation scheme has been experimentally demonstrated by using two SiPMs from FBK-irst (1mm x 1 mm, 400 micro-cells, breakdown voltage V-br congruent to 29V), one as temperature sensor involved in the negative feedback loop and the other as light sensitive device. Both detectors have been enclosed in a thermally isolated box with temperature varied in the interval between 20 degrees C and 30 degrees C: the variation of the SiPM gain can be reduced from more than 20%, without compensation, to about 2%.