本文選題：像增強器 + 負(fù)電子親和勢光電陰極　； 參考：《南京理工大學(xué)》2015年博士論文

【摘要】：像增強器是構(gòu)成微光夜視系統(tǒng)與成像型紫外探測系統(tǒng)的核心部件,其分辨力和信噪比是決定像增強器探測能力和成像質(zhì)量的主要性能參數(shù)。光電子在陰極及MCP內(nèi)的輸運特性與像增強器的分辨力密切相關(guān),而像增強器的噪聲特性又是通過信噪比來表征的。因此,本文圍繞像增強器的電子輸運與噪聲特性開展了深入研究�；诰鶆驌诫sGaAs陰極的原子結(jié)構(gòu)單元和電離雜質(zhì)散射的理想模型,定性分析了透射式GaAs陰極的摻雜濃度、電子擴(kuò)散長度對其體內(nèi)電子輸運的影響。同時,利用電子輸運方程分別推導(dǎo)了指數(shù)摻雜GaAs、GaAlAs及GaN陰極的MTF表達(dá)式,并據(jù)此研究了光電陰極的電子擴(kuò)散長度、發(fā)射層厚度、吸收系數(shù)以及后界面復(fù)合速率對分辨力和量子效率的影響。計算結(jié)果表明,與均勻摻雜結(jié)構(gòu)相比,指數(shù)摻雜結(jié)構(gòu)不僅能獲得高量子效率,更能提升陰極的分辨力。利用數(shù)值方法對MCP的電子輸運及分辨力特性進(jìn)行了仿真研究。首先計算了 MCP的電場分布;其次通過求解電子輸運軌跡方程模擬了電子在MCP倍增過程中的輸運軌跡;最后繪制了相應(yīng)的MTF特性曲線。進(jìn)而分析了 MCP的斜切角θt、通道直徑D、工作電壓VM以及末端電極深度h對其電子輸運及MTF特性的影響。仿真結(jié)果顯示,當(dāng)VM=900V、θt=14°、D=5.0μm以及h=10μm時,MCP具有良好的電子輸運及分辨力特性。通過評價MCP的噪聲因子研究了 MCP的噪聲特性。首先從理論上分析了影響MCP噪聲因子的主要因素,然后采用以服從泊松分布的正弦隨機(jī)信號作為電子源的噪聲激勵的方法實現(xiàn)了對MCP噪聲因子的評價。評價結(jié)果顯示,鍍膜MCP的噪聲因子低于1.8,且比無膜MCP的噪聲因子增大了約14.7%;同時當(dāng)開口面積比為72%時,無膜MCP的噪聲因子低于1.3,且比開口面積比為64%的MCP噪聲因子減小了約8.9%。此外,對MCP進(jìn)行適度地電子清刷處理可在一定程度上降低噪聲因子,而離子阻擋膜在延長像增強器壽命的同時也惡化了 MCP的噪聲特性,故需考慮最佳膜厚的選取。通過測試微光像增強器的輸出信噪比與halo效應(yīng)對其電子輸運與噪聲特性開展了研究。主要研究了前近貼脈沖電壓對三代微光像增強器輸出信噪比與halo效應(yīng)的影響,同時測試分析了直流電壓對超二代和三代微光像增強器輸出信噪比的影響。測試結(jié)果表明,當(dāng)前近貼脈沖電壓高、低電平分別為-300V和0.2V時,占空比大于60%后對三代微光像增強器的輸出信噪比與halo效應(yīng)幾乎沒有影響。另外,超二代和三代微光像增強器的輸出信噪比均隨陰極電壓的升高而增大,當(dāng)陰極電壓達(dá)到一定值后,二者的輸出信噪比趨于飽和。當(dāng)MCP工作電壓在700V-800V范圍內(nèi)逐步增大時,超二代微光像增強器的輸出信噪比有較大幅度地提高,繼續(xù)升高電壓則會導(dǎo)致信噪比的增長趨勢放緩甚至降低。本文的研究工作可為研制低噪聲、高分辨力像增強器提供理論指導(dǎo)、實驗支撐以及評價手段。
[Abstract]:Image intensifier is the core component of LLL night vision system and imaging ultraviolet detection system. Its resolution and signal-to-noise ratio (SNR) are the main performance parameters that determine the detection ability and imaging quality of image intensifier. The transport characteristics of photoelectron in cathode and MCP are closely related to the resolution of image intensifier, and the noise characteristics of image intensifier are characterized by signal-to-noise ratio (SNR). Therefore, the electronic transport and noise characteristics of image intensifier are studied in this paper. Based on the atomic structure unit of uniformly doped GaAs cathode and the ideal model of ionizing impurity scattering, the effects of doping concentration and electron diffusion length on electron transport in transmission GaAs cathode are qualitatively analyzed. At the same time, the MTF expressions of exponentially doped GaAs-GaAlAs and GaN cathodes are derived by using the electron transport equation, and the electron diffusion length and emission layer thickness of photocathode are studied accordingly. The influence of absorption coefficient and post interface recombination rate on resolution and quantum efficiency. The calculated results show that the exponential doping structure can not only achieve high quantum efficiency, but also improve the resolution of the cathode. The characteristics of electron transport and resolution of MCP are simulated by numerical method. First, the electric field distribution of MCP is calculated; secondly, the electron transport trajectory in the MCP multiplication process is simulated by solving the electron transport trajectory equation; finally, the corresponding MTF characteristic curve is drawn. Furthermore, the effects of oblique angle 胃 t, channel diameter D, working voltage VM and terminal electrode depth h on the electron transport and MTF characteristics of MCP are analyzed. The simulation results show that the MCP has good electron transport and resolution characteristics when VM900 V, 胃 t0 14 擄DX 5.0 渭 m and HG 10 渭 m. The noise characteristics of MCP are studied by evaluating the noise factor of MCP. In this paper, the main factors affecting MCP noise factor are analyzed theoretically, and then the MCP noise factor is evaluated by using the sine random signal distributed from Poisson distribution as the electron source. The results show that the noise factor of coated MCP is lower than 1.8, and the noise factor of MCP without film increases about 14.70.When the ratio of opening area to area is 72, the noise factor of MCP without film is lower than 1.3, and the noise factor of MCP with 64% ratio of specific opening area decreases by 8.9. In addition, the proper electronic cleaning of MCP can reduce the noise factor to a certain extent, and the ion barrier membrane not only prolongs the life of image intensifier, but also deteriorates the noise characteristics of MCP, so it is necessary to consider the selection of optimum film thickness. The characteristics of electron transport and noise are studied by measuring the output signal-to-noise ratio (SNR) and halo effect of the LLL image intensifier. In this paper, the influence of the front and near pulse voltage on the output signal-to-noise ratio (SNR) and halo effect of the third generation LLL image intensifier is studied, and the effect of DC voltage on the output SNR of the super second generation and the third generation LLL image intensifier is tested and analyzed. The test results show that the output SNR and halo effect of the third generation LLL image intensifier are almost unaffected when the duty cycle is greater than 60% when the near pasted pulse voltage is high and the low level is -300V and 0.2V, respectively. In addition, the output signal-to-noise ratio of the super-second generation and the third generation low-light level image intensifier increases with the increase of cathode voltage. When the cathode voltage reaches a certain value, the output signal to noise ratio tends to saturation. When the operating voltage of MCP increases gradually in the range of 700V-800V, the output SNR of the super-second generation LLL image intensifier is greatly improved, and the increasing voltage will lead to the slowdown or even decrease of the SNR growth trend. The research work in this paper can provide theoretical guidance, experimental support and evaluation method for the development of low noise and high resolution image intensifier.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TN144

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