超二代像增强器多碱阴极电子逸出机理研究  

Study on Electron Escaping Mechanism of Multi-alkali Photocathode in the Super Gen.Ⅱ Image Intensifier

作　　者：李晓峰[1,2] 瞿利平 黄建民[2] 张云昆[2] 

机构地区：[1]微光夜视技术重点实验室,陕西西安710065 [2]北方夜视科技集团有限公司,云南昆明650114

出　　处：《红外技术》2012年第12期729-733,共5页Infrared Technology

基　　金：微光夜视技术重点实验室基金;编号:J2011016

摘　　要：测量了超二代像增强器多碱阴极的光谱反射率和透射率,计算了多碱阴极的光谱吸收率。从光谱吸收率看出,当波长大于850 nm以后,多碱阴极的吸收率下降很快,但当波长大于915 nm之后,吸收率的下降变慢,同时吸收率低于5%。这说明多碱阴极的Na2KSb膜层存在一个915 nm的长波吸收限,入射光的波长如果大于该吸收限,多碱阴极将不吸收。多碱阴极在吸收光子之后的电子跃迁过程中,跃迁电子的能量增加小于所吸收的光子能量,即存在"能量损失"。光子的能量越高,跃迁电子的能级越高,能量损失越大。超二代像增强器Na2KSb阴极膜层在Cs激活之后,荧光的峰值波长向短波方向移动,发生"蓝移"现象,表明多碱阴极Na2KSb膜层在进行表面Cs激活之后,跃迁电子的能级有所升高。多碱阴极无论是单独采用Cs激活还是采用Cs、Sb同时激活,光谱响应的长波阈值基本相同,但光谱响应却不相同,原因是采用Cs、Sb同时激活时,Na2KSb阴极膜层存在"体积"效应。由于Na2KSb阴极存在长波吸收限,对应的光子能量为1.35 eV,因此如果多碱阴极的逸出功进一步降低并且低于1.35 eV时,尽管多碱阴极的光谱响应会进一步提高,但光谱响应的长波阈并不会向长波方向延伸,此时多碱阴极光谱响应的长波阈值由其长波吸收限所决定。By measuring the multi-alkali cathode spectral reflectance and transmittance of super gen. II image intensifier, the spectral absorption was obtained through calculating by the energy conservation law. The spectral absorption indicates that, when the wavelength is greater than 850 nm, the absorption of the multi-alkali cathodes drops quickly, but when the wavelength is greater than 915 nm, the absorption drops slowly, and is less than 5%. This shows that the multi-alkali cathode spectral absorption has a long wavelength absorption limit of 915 nm. If the wavelength of the incident light is greater than the absorption limit, it will not be absorbed by multi-alkali cathode. During the electronic transition process of multi-alkali cathodes after the absorption of a photon, the energy increases of transition electron is less than the energy of the incident photons, i.e. there is an ＂energy loss＂. The higher the photon energy and the higher transition electron＇s energy level are, the greater the energy loss is. After Na2KSb cathode film of super gen. II image intensifier was activated by Cs, the peak wavelength of the fluorescence is shift toward blue, i.e. ＂blue shift＂ phenomenon was occurred. This indicated that transition electron energy levels of NazKSb cathode film was promoted because of surface Cs activation. Weather Na2KSb cathode was activated by Cs alone or by Cs and Sb simultaneously, their long wavelength threshold are substantially same, but spectral response are not same.The reason is that there is a kind of ＂volume effect＂ in Na2KSb layer. The. Na2KSb layer has a long wave absorption limit corresponding to photon energy of 1.35 eV. When work function is low than 1.35 eV, the long wavelength threshold of spectral response would not stretch toward long wavelength although spectral response would increase further. On this occasion, the long wavelength threshold of spectral response would be determined by long wavelength absorption limit.

关 键 词：多碱阴极 光电发射 电子跃迁 逸出功 

分 类 号：O462.3[理学—电子物理学]