一种提高光电倍增器光电阴极量子效率的方法

A Method of Improving Quantum Efficiency of PMT’s Photocathode

摘要:

提出了一种可以提高光电倍增管光电阴极量子效率的方法。通过分析光电阴极的光电发射过程,从提高光子吸收率Pa和光电子迁移至真空一侧材料表面的几率Pe出发,确定可以在光电阴极膜层结构设计上增加合适的膜层,该膜层具有高带隙和减反射的作用。由于光电倍增管的外壳通常为细长的玻璃管,而常规的溅射设备为50mm的大靶,直接使用大靶对细管内部镀膜,效率低下且均匀性差。在常规大靶的基础上进行改造,成功实现了在细管内部快速均匀镀膜。使用分光设备测试光电阴极的光谱响应,结果表明,改进产品的光电阴极量子效率从常规的25%提高至35%。

Abstract:

A method for improving the quantum efficiency of PMT’s photocathode was proposed. By making analysis on the photoemission process of the photoelectric cathode, considering how to improve the probability of photons absorption and electrons migrating to the surface, it is determined to add a suitable film which has high band gap and reducing reflection. Because the shell of photomultiplier tube is usually long and thin, but the diameter of target is about 50mm in conventional sputtering equipment, so conventional equipment can not deposit films in the thin tube due to low deposition efficiency and non-uniformity. On the basis of conventional target, the sputtering equipment was reformed to achieve sputtering inside the thin tube successfully. Test results indicate that the quantum efficiency of the coating photocathode can reach 35%, which is much higher than that of the conventional photocathode of 25%.