Study of maintaining stable SSPM-based detector gain by active bias control

It is well known that the gain and noise of solid-state photomultiplier (SSPM) is sensitive to the temperature, which is a big concern for its practical applications. In this study, we tested a simple method to maintain the overall detector signal output level (namely detector gain which includes factors of photon intensity, wavelength and SSPM gain) at different temperatures by active bias control (ABC), which measures the SSPM bias voltage as a function of temperature under the same detector output gain and uses it as a calibration for gain stability control. The experiment setup includes a laser LED (US-Lasers D650-5) as an input light source, a SSPM (Hammatsu MPPC), a enclosure box for the temperature control from 25 C to 37 C, a temperature sensor at the precision of 0.25 C, a bias control power supply with precision 0.01V and the dedicated detector readout electronics with an ASIC and FPGA-based signal processing and acquisition. All measurements, calibration, and control were automated with LabView based software. The measured bias-temperature relationship under the same detector gain shows a linear curve with a slop of 0.0565 V/C, matching with the vendor's specification. The results show that ABC can achieve high precision for detector gain stability control: the measured gain variations were within 1% with gain stability control and ∼70% without gain stability control, over the temperature ranging from 25 C to 37 C. In summary, the method is simple, straightforward for implementation, and effective to control the gain variations for SSPM-based detector.