超二代微光像增强器多碱光电阴极膜厚测量研究

介绍了多碱光电阴极的光学性能和光谱反射率特性,测量了多碱阴极的光谱反射率曲线.该曲线与普通光学膜层光谱反射率曲线相比,形状较不规则,原因是多碱阴极膜层存在光吸收.光谱反射率曲线上的干涉峰是入射光在玻璃与阴极膜层界面反射和在阴极膜层与真空的界面反射的两束光发生干涉的结果.根据干涉的原理,如果阴极膜层所反射的两束光的光程差为二分之一波长的偶倍数时,光谱反射将出现干涉加强峰；如果阴极膜层所反射的两束光的光程差为二分之一波长的奇倍数时,光谱反射将出现干涉减弱峰.根据超二代像增强器光谱反射干涉峰对应的波长,可以计算出其阴极膜层的厚度约为191 nm,比二代像增强器阴极膜层的厚度增加了38％.多碱阴极膜层厚度是影响多碱阴极灵敏度的一个关键参量,仅仅靠人眼观察阴极膜层颜色的方法不准确.实践证明,利用光谱反射的方法来计算阴极膜层厚度的方法简单有效.如果在多碱阴极的制作过程中进行光谱反射率的监控,那么将可以精确控制阴极膜层的厚度,对多碱阴极的研究将会更加深入,多碱阴极的灵敏度也将会得到进一步的提升.

Thickness Measurement of Multi-alkali Photocathode

In this paper the optical properties and spectral reflectance characteristics of multi alkali photocathode were illustrated and spectral reflectance curve of multi alkali photocathode were measured. The shape of spectral reflectance curve is irregular compared with ordinary optical film. The reason is that the cathode layer absorbs light. Interference peak of spectral reflectance curve is the results that the reflection light on the interface between the glass and the cathode layer and the reflection light on the interface between the cathode layer and vacuum interference together. According to interference theory, if two beam light reflected by the cathode film have the optical path difference of even times the λ/2, interference enhancement peak on spectral reflection cure will appear. Similarly, if two beam light reflected by the cathode film have the optical path difference of odd times the λ/2, interference decreased peak on spectral reflection cure will appear. According to the interference theory and peak wavelength on spectral reflection interference curve the cathode film thickness of the super second generation image intensifier can be calculated out. The thickness is about 191nm, and increased by 38% compared with the second generation image intensifier. Determination of thickness simply by observing cathode film color was not an accurate method. Practice has proved that, the method to calculate the cathode film thickness by using spectral reflectance method is simple and effective. If the spectral reflectance were monitored during the process of cathode production, then the thickness of cathode layer would be able to control precisely, and the cathode study would be more in-depth, cathode sensitivity would be further improved.