本文介绍了一种基于光电倍增管的锁相放大光电探测系统, 并定量地对系统中光电倍增管、放大电路、高压电源的噪声特性进行研究, 发现高压电源的纹波对系统噪声的影响很大。实验利用三台不同纹波的高压电源测试系统噪声, 发现在无光条件下, 系统噪声以光电倍增管暗噪声为主, 高压纹波噪声近似线性地耦合进系统噪声中;在有光条件下, 系统噪声以阳极电流散粒噪声为主, 高压纹波贡献的噪声既随光电流增大而增大也与高压纹波正相关。基于以上研究, 分析了高压电源的传递函数并优化反馈系数, 设计了高稳定低纹波高压电源, 高压纹波小于 5 mV。系统整机信噪比测试表明, 使用自研高压可显著提升系统信噪比, 相比较于其他高压电源(纹波 15 mV, 50 mV), 最大信号下分别提升了 38%和 125%。

A photoelectric detection system based on a lock-in amplifier was developed. The noise charac. teristics of each part of the system, such as the photomultiplier, amplifier, and high-voltage power supply, were analyzed quantitatively. Research has shown that the ripple of the high-voltage power supply has a significant effect on system noise. Three high-voltage power supplies with different ripples were installed in the system, and the noise was analyzed. The results showed that in darkness, system noise was mainly contributed by photomultiplier anode dark noise and noise from the high-voltage power supply ripple linear. ly coupling into the system. In light, photomultiplier anode shot noise contributed the most to the system noise, and noise contributed by the high-voltage power supply ripple showed a positive correlation with both light current and ripple value. Based on the above findings, the transfer function of the high-voltage power supply was analyzed, and its feedback coefficient was optimized. A high-voltage power supply with high stability and low ripple(less than 5 mV)was designed. The signal-to-noise ratio test of the system showed that the signal-to-noise ratio could be significantly improved by applying self-developed high-voltage power supplies, which were 38% and 125% higher than those of other high-voltage power sources(ripples of 15 and 50 mV, respectively).