基于表面等离激元的新型碲化铯光阴极研究  

Studies on Novel Cs_(2)Te Photocathode Based on Surface Plasmon Polaritons

作　　者：刘子硕 戴责已 关家宝 刘兰忻 钟建华 姜增公 王纪科 聂元存 LIU Zishuo;DAI Zeyi;GUAN Jiabao;LIU Lanxin;ZHONG Jianhua;JIANG Zenggong;WANG Jike;NIE Yuancun(The Institute for Advanced Studies,Wuhan University,Wuhan 430072,China;Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 201210,China)

机构地区：[1]武汉大学高等研究院,湖北武汉430072 [2]中国科学院上海高等研究院,上海201210

出　　处：《原子能科学技术》2024年第10期2220-2227,共8页Atomic Energy Science and Technology

基　　金：国家自然科学基金面上项目(12275196)。

摘　　要：目前已有研究将表面等离极化激元(SPPs)引入铜阴极和锑钾铯光阴极中,大幅提高其量子效率。碲化铯(Cs_(2)Te)光阴极是一种极佳的在紫外频段可应用于中高平均流强的光阴极材料,而常用贵金属介电函数在紫外频段过低无法满足SPPs激发要求。本研究通过微纳光栅结构将SPPs引入Cs_(2)Te光阴极,形成局域增强场以提高光子吸收率,并调节光电子初始激发分布。为探索SPPs对Cs_(2)Te光阴极性能的影响,使用蒙特卡罗方法模拟引入SPPs前后光阴极的光电发射过程。结果表明,引入SPPs会导致光电子数量增加,从而显著提高Cs_(2)Te光阴极的量子效率约60%,且增加的光电子大多数分布于深层界面附近,在逃逸过程中各类碰撞概率增加,使发射度基本保持不变。Cathodes serve as sources of electron beams,and their performance plays a great part of beam quality in electron accelerators.The introduction of surface plasmon polaritons(SPPs) into different photocathodes has been investigated to increase their quantum efficiency.Currently,the SPPs excitation is predominantly achieved in the infrared and visible bands due to limitations in the permittivity of common noble metals.Exciting SPPs in the ultraviolet band typically involve attaching aluminium nano-particles to the material surface,which can impact the optical properties of the material.Therefore,it is important to develop a method for exciting SPPs in the ultraviolet band without affecting optical properties of the material.The cesium telluride(Cs_(2)Te) photocathode represents a lifetime of several months,a quantum efficiency of up to 10%,a response time of less than 1 ps,a thermal emittance of less than 1 mm·mrad/mm,and moderate operating vacuum requirement of 10-7 Pa.These characteristics make Cs_(2)Te an exceptional photocathode material for generating high-current electron beams.However,a drawback of Cs_(2)Te photocathodes is that they need to be excited by highpower ultraviolet lasers,which are more challenging to obtain compared to green lasers.Consequently,there is a continued demand for increasing the quantum efficiency of Cs2Te to reduce the laser power requirements.In this paper,accuracy of the Monte Carlo model to simulate the Cs_(2)Te photoemission was verified.SPPs were introduced into Cs_(2)Te photocathode by means of micro-nano grating structure,which increases substantially the absorption of incident photons and hence form a local field enhancement to regulate initial photoelectrons distribution.The Monte Carlo model was modified according to the theory of SPPs to simulate the photoelectric emission process of the Cs_(2)Te photocathode after the introduction of SPPs.The simulation results show that the quantum efficiency of Cs_(2)Te photocathode increases by 60% while the thermal emittance is basic

关 键 词：碲化铯光阴极 紫外频段 表面等离极化激元 量子效率 热发射度 

分 类 号：TL99[核科学技术—核技术及应用] O462.3[理学—电子物理学]