【作者】 任玲；

【导师】 常本康； 郭晖；

【作者基本信息】 南京理工大学 ， 光学工程， 2013， 博士

【摘要】 本文围绕均匀掺杂和指数掺杂GaAs光电阴极电子输运、分辨力及GaAs光电阴极在微光像增强器中的应用展开了研究。通过建立均匀掺杂GaAs光电阴极原子基本结构单元和电离杂质散射公式,模拟了光电子在均匀掺杂GaAs光电阴极体内的输运轨迹,分析了电子扩散长度、掺杂浓度和发射层厚度等因素对光电阴极的弥散圆斑和到达阴极出射面的光电子数与激发光电子总数之比的影响,讨论了发射层厚度、掺杂浓度以及电子扩散长度的最佳值。考虑了GaAlAs窗口层和GaAs发射层的反射率、透射率和吸收系数等参数的影响,计算了均匀掺杂GaAs光电阴极调制传递函数,分析了光电阴极的结构参数对调制传递函数的影响。在均匀掺杂GaAs光电阴极光电子输运理论模型的基础上,建立了指数掺杂GaAs光电阴极原子基本结构单元和电场作用下的电离杂质散射公式,考虑了400-900nm波段光在光电阴极体内不同位置激发的光电子,模拟了光电子在光电阴极体内的输运轨迹,比较分析了指数掺杂对GaAs光电阴极出射面的电子能量分布、出射角分布、光电发射效率和MTF等的影响。建立了场渗透模型,分析了场渗透强度对光电子落点分布、光电发射效率和调制传递函数的影响,研究了GaAs光电阴极在微光像增强器工作时的光电发射性能。考虑了GaAs光电阴极出射电子的能量与角度分布,设GaAs光电阴极出射电子的能量分布服从Beta分布,角度分布服从Lambert分布,研究了前近贴聚焦系统的调制传递函数,分析了近贴电压和距离对近贴聚焦系统分辨力的影响。根据次级电子发射理论,建立了MCP通道内壁发射次级电子的能量分布与角度分布,研究了MCP开口面积比、斜切角、末端电极深度和通道板长径比等参数对微光像增强器光电子输运和MTF的影响,建立了较为完善的GaAs光电阴极微光像增强器分辨力理论。为了验证理论模型,开展了GaAs光电阴极微光像增强器halo效应和分辨力测试研究工作,比较了超二代和三代微光像增强器halo效应,分析了采集的halo图像的灰度值分布曲线。构建了高压脉冲电源,通过调节前近贴脉冲信号的高低电平电压幅值和占空比,研究了前近贴脉冲电压对三代微光像增强器halo效应和分辨力的影响。另外,对比分析了不同掺杂方式下的GaAs光电阴极微光像增强器halo效应,理论研究了均匀掺杂和指数掺杂GaAs光电阴极微光像增强器的分辨力,分析了GaAs光电阴极对微光像增强器分辨力的影响,间接验证了GaAs光电阴极微光像增强器分辨力理论模型的可用性。更多还原

【Abstract】 The researches on the electron transport and resolution of uniform-doping and exponential-doping GaAs photocathode, and the application of GaAs photocathode in image intensifier were carried out in this thesis.By establishing the atomic fundamental structure unit and ionized impurity scattering formula, the transport of photoelectrons in the uniform-doping transmission-mode GaAs photocathode was simulated. The influence of the electron diffusion length, the doping concentration, and the photocathode thickness on the dispersive spot and the ratio of the number of photoelectrons reaching the emission surface to the number of exited photoelectrons at the emission surface of GaAs photocathode were analyzed. The optimum values of the photocathode thickness, the doping concentration, and the electron diffusion length were explored. Considering the factors of reflectivity, transmisstivity, and absorption coefficient of GaAlAs window-layer and GaAs active-layer, the modulation transfer function of uniform-doping GaAs photocathode was calculated, and the influence of photocathode structure parameters on modulation transfer function was analyzed.Based on the photoelectron transport model of uniform-doping transmission-mode GaAs photocathode, the atomic fundamental structure unit and ionized impurity scattering formula of exponential-doping GaAs photocathode were established. Considering the different positions of excitated photoelectrons in the radiation range of400-900nm, the trajectories of photoelectrons in photocathode were simulated, and the influence of exponential-doping structure on the energy spread, emergence angle spread, the modulation transfer function and the photoemission efficiency of GaAs photocathode was analyzed. By establishing the electric field penetration model, the influence of electric field penetration on the electron distribution, the photoemission efficiency, and the modulation transfer function were analyzed. The photoemission performance of GaAs photocathode operating in low light level image intensifier was researched.Considering the energy spread and emergence angle spread of photoelectrons, the modulation transfer function of pre-proximity focusing system was researched assuming that the initial energy distribution and angle distribution of photoelectrons escaped from GaAs photocathode obey Beta distributions and Lambert distributions respectively. The influence of proximity voltage and distance on the pre-proximity focusing system was analyzed. According to the theory of secondary electron emission, the energy spread and angle spread of secondary electron in microchannel plate were established. The influences of microchannel plate opening area ratio, oblique angle, ending spoiling electrode depth, and thickness on the resolution and modulation transfer function of the low light level image intensifier were researched. A perfect resolution theory of GaAs photocathode low light level image intensifier was established consequently.In order to verify the theoretical model, the halo effect and resolution of low light level image intensifier with GaAs photocathode were investigated. The halo effects of super second-and third-generation image intensifier were tested and compared by analyzing the gray value curves of the collected halo effect. The influence of pro-proximity pulse voltage on image intensifiers halo effect was researched by respectively changing the high and low level voltage and duty ratio. Besides, the halo effects of low light level image intensifiers with different doping GaAs photocathode were analyzed. Moreover, the resolutions of low light level image intensifiers consisting of uniform-doping and exponential-doping GaAs photocathode were calculated respectively. Then the influence of GaAs photocathode on image intensifier resolution was analyzed, and the availability of the resolution theory model of low light level image intensifier with GaAs photocathode was verified indirectly.更多还原