多碱光电阴极膜厚对阴极灵敏度的影响研究

叙述了多碱光电阴极光谱反射的特点,测量了超二代微光像增强器多碱光电阴极的光谱反射曲线,分析了光谱响应曲线产生干涉加强峰和干涉减弱峰的原因,比较了不同膜层厚度多碱阴极光谱反射曲线的区别。根据能量守恒定律,利用实测的多碱光电阴极光谱反射率和光谱透过率,计算出多碱光电阴极的光谱吸收曲线,通过研究不同厚度多碱阴极的光谱吸收,发现多碱光电阴极膜层厚度加厚并不会提高其对所有波段光吸收率的特点。厚度增加只会增加短波和长波的光吸收率,但中波的光吸收率不会增加反而下降,这是由于受到光谱反射的影响。阴极膜层的厚度既影响光谱反射和光谱透过,又会影响光谱吸收,因此也影响多碱阴极的光谱响应,所以多碱光电阴极的膜层厚度是影响多碱光电阴极灵敏度的一个关键参数。实践证明,转移式技术制作的多碱光电阴极膜层厚度也存在一个最佳值,超过这一最佳厚度,阴极的灵敏度不增反降,这是因为红外光谱响应增加不多,但中波光谱响应下降很多。所以对转移式多碱光电阴极而言,实践证明当膜层厚度达到最佳厚度时,膜层呈现淡红色,在制作过程中要控制好阴极膜层的厚度,这样才可能获得较高的阴极灵敏度。

Study on Sensitivity of Different Thickness of Multi-Alkali Photocathode

This paper described the spectral reflectance characteristic of multi-alkali photocathode, measured the spectral reflectance curve of multi-alkali photocathode on the second generation image intensifier, analyzed the reason of both interference peak and valley on spectral response curves, and compared the difference of spectral reflectance curve between different photocathode film thicknesses. According to the law of conservation of energy, the spectral absorption curve of multi-alkali photocathode is calculated by the spectral reflectance and transmittance measured on multi-alkali photocathode. Through the research of different thickness cathode absorption spectrum, the characteristic that the film thickness of multi-alkali photocathode does not improve light absorption of all wave bands was found. Thickness increases will only increase the short wavelength and long wavelength optical absorption rate, but the middle wavelength band light absorption rate does not increase but declined. This is due to the influence of spectral reflectance. Cathodes film thickness affects both the spectral reflectance and the spectral transmission, and then affects the absorption spectrum, thus also affect spectral response of multi-alkali photocathode. So the film thickness of multi-alkali photocathode is the key parameter for sensitivity. Experiments proved that the thickness of multi-alkali photocathode produced by transfer technology has an optimum value, exceeding the optimum thickness, the cathode sensitivity falling instead of rising. The reason is that the IR spectral response increases not much, but the short wavelength spectral response decreased a lot. So for multi-alkali photocathode produced by the transfer technology, practice has proved that the cathode film will take the color of pale red when the optimal film thickness is got. In the production process of multi-alkali photocathode to obtain higher cathode sensitivity, it is a key to control the cathode film thickness.