Quantum Efficiency Improvement Scheme for High-Voltage Power Supplies of Photomultiplier Tubes (PMTs)

Photomultiplier Tubes (PMTs) are widely used in low-light detection fields such as 光谱分析 (spectral analysis), radiation detection, and astronomical observation. Their quantum efficiency (QE), which refers to the ratio of detected photons to incident photons, is highly dependent on the stability and precision of the associated high-voltage power supply. Traditional PMT HVPS often has voltage ripple of 0.1-0.3% and temperature drift of ±200mV/°C, leading to QE fluctuations of up to 15%.
The quantum efficiency improvement scheme focuses on three core optimizations. First, a closed-loop feedback control system with dual sensors is designed. A high-precision voltage sensor (accuracy ±0.01%) and a current sensor monitor the output in real time, and the feedback signal is processed by a 32-bit MCU to adjust the HVPS output via a digital-to-analog converter (DAC) with 16-bit resolution. This reduces voltage ripple to less than 0.02%. Second, a temperature compensation module is integrated. A platinum resistance temperature detector (PT1000) with an accuracy of ±0.1°C is used to collect the HVPS internal temperature, and a compensation circuit adjusts the reference voltage to offset temperature drift, reducing it to ±30mV/°C. Third, the HVPS output voltage is calibrated according to the PMT spectral response. For PMTs used in visible light detection (400-700nm), the output voltage is fine-tuned in 1V increments to match the PMT's optimal gain at different wavelengths, maximizing QE at each spectral band.
Experimental results show that after optimization, the QE of a PMT at 550nm (peak wavelength) increased from 78% to 86%, and QE fluctuations over a temperature range of -20°C to 60°C were reduced to less than 3%. This scheme has been successfully applied in a portable radiation detector, improving its minimum detectable dose rate by 40%.