高功率太赫兹回旋管准光模式变换器的研究
发布时间：2019-07-06 17:44
【摘要】：太赫兹(THz)科学技术是当前最受关注的国际学术前沿领域之一,为各国优争相抢占的科技制高点,它的发展对提高国家科技实力、促进国民经济发展、维护国土安全和社会安定都具有前瞻性、战略性和全局性的重大意义。近年来,THz回旋管作为THz频段高功率辐射源受到了广泛关注,它解决了THz科学技术的发展和应用受制于缺乏稳定高效高功率THz辐射源的问题。回旋管是一种典型的相对论电子学快波器件,它产生高功率THz波的原理是电子注在纵向磁场中回旋与高频角向电场互相作用后产生受激辐射,又称为电子回旋脉塞。在各国的努力下,回旋管朝着更高输出功率和频率的方向发展,它的工作模式通常要选用高阶模式以增加谐振腔的功率容量、减少欧姆损耗。这种高阶模式不利于THz波的远距离传输和应用,需要采用模式变换器将这些高阶波导模式转换成更利于传输的低阶波导模式或者是高斯波束。由于传统的波导模式变换器尺寸大不利于紧凑设计而且模式变换过程中模式竞争和损耗严重。而具有结构简单、设计紧凑和方便应用等优点的准光模式变换器现在已被广泛使用,所以研究用于高功率THz回旋管的准光模式变换器具有非常重要的意义。本文首先对应用于0.42THz-TE26模式和0.42THz-TE_(17,4)模式回旋管的准光模式变换器进行了理论和实验研究,然后设计了能够提高输出光斑质量的两级相位校正镜面,最后针对应用于双频工作同轴双电子注回旋管准光模式变换器进行了理论分析,并提出了运用基于频率选择表面(FSS)的空间滤波器能够实现输出功率双频分离的方法。具体的研究内容如下:1.从基本麦克斯韦方程组出发,基于导波场理论和几何光学近似,描述了回旋管工作模式在圆柱波导中的传输过程;结合矢量绕射理论和迭代方法,分析了应用于0.42THz-TE26模式回旋管准光模式变换器中Vlasov型辐射器场结构,数值计算结果与三维电磁场全波仿真软件—FEKO的模拟结果吻合良好。2.基于传输线理论和阻抗微扰理论,推导出考虑返波作用的耦合波方程,并分析了应用于0.42THz-TE_(17,4)模式回旋管准光模式变换器中Denisov型辐射器扰动段电磁波耦合情况及辐射器场结构,且数值计算结果与FEKO模拟结吻合良好。3.运用几何光学理论,推导了满足汇聚要求的准椭圆镜和抛物镜面在全局坐标系下镜面方程;基于矢量绕射理论,计算了各个规则镜面及输出窗处的场分布并与FEKO模拟结果进行对比验证;结合KSA算法和矢量绕射理论,设计出了能很大程度提高输出光斑质量的两级相位校正镜,且数值计算结果与FEKO模拟结吻合良好。4.对应用于0.42THz-TE26模式和0.42THz-TE_(17,4)模式回旋管的准光模式变换器进行了实验研究,其中辐射器分别为Vlasov型和Denisov型,实验测试所得结果与理论预测值吻合良好。5.首先介绍了双频工作同轴双电子注回旋管工作原理以及相应的模拟结果,并进行了相关实验测试,实验结果表明,基波和二次谐波同时工作的状态得到验证;然后针对双频工作同轴双电子注回旋振荡管同时输出的两个模式,分析了运用同一阶梯型准光模式变换器的模式转换情况;最后提出了运用基于频率选择表面空间滤波器能够实现输出功率双频分离的方法,运用THz时域光谱仪(TDS)对加工出的样品进行初步测试,并给出了透射系数的测量结果。
文内图片：
图片说明：电磁波谱分布图
[Abstract]:Terahertz (THz) science and technology is one of the most important international academic front areas of the world, and it is a high-tech high point for all countries to seize, and its development is forward-looking for improving the national scientific and technological strength, promoting the development of the national economy, safeguarding the homeland security and social stability, Strategic and global significance. In recent years, the THz gyrotron is widely concerned as the high-power radiation source in the THz frequency band, which solves the problems of the development and application of THz technology in the absence of a stable and high-power THz radiation source. The gyrotron is a typical relativistic electronic fast wave device. The principle of high power THz wave is that the electron injection generates excited radiation in the longitudinal magnetic field and the high-frequency angle to the electric field, and is also called electron cyclotron masse. In the efforts of all countries, the gyrotron is developed in the direction of higher output power and frequency, and its working mode is usually high-order mode to increase the power capacity of the resonant cavity and reduce the ohmic loss. This high-order mode is detrimental to the long-distance transmission and application of THz waves, and it is necessary to use a mode converter to convert these high-order waveguide modes into a low-order waveguide mode that is more favorable for transmission or a Gaussian beam. Due to the large size of the traditional waveguide mode converter, the mode competition and the loss are serious in the process of the compact design and the mode transformation process. The quasi-optical mode converter with the advantages of simple structure, compact design and convenient application has been widely used, so it is very important to study the quasi-optical mode converter for high power THz gyrotron. In this paper, the quasi-optical mode converter for 0.42 THz-TE26 and 0.42 THz-TE _ (17,4) mode gyrotron is studied theoretically and experimentally, and a two-stage phase correction mirror which can improve the quality of the output spot is designed. In the end, the theoretical analysis of the quasi-optical mode converter applied to the dual-frequency dual-frequency dual-electron-injection gyrotron is put forward, and the method of using the space filter based on the frequency selective surface (FSS) to realize double-frequency separation of the output power is put forward. The specific content of the study is as follows:1. Based on the theory of guided wave field and the geometrical optics approximation, the transmission process of the working mode of the gyrotron in the cylindrical waveguide is described from the basic Maxwell equations, and the vector diffraction theory and the iterative method are combined. The Vlasov type radiator field structure in a 0.42 THz-TE26 mode gyrotron quasi-optical mode converter is analyzed, and the numerical results are in good agreement with the simulation results of the three-dimensional electromagnetic field full-wave simulation software. Based on the theory of transmission line and the theory of impedance perturbation, the coupling wave equation considering the function of the return wave is derived, and the electromagnetic coupling and the structure of the radiator field of the Denisov type radiator in the quasi-optical mode converter with the mode of 0.42 THz-TE _ (17,4) are analyzed. And the numerical results are in good agreement with the FEKO simulation. The mirror equation of the quasi-elliptical mirror and the parabolic mirror in the global coordinate system is derived by using the geometrical optics theory, and the field distribution at each regular mirror and the output window is calculated based on the vector diffraction theory and compared with the FEKO simulation result. Combined with the KSA algorithm and the vector diffraction theory, a two-stage phase correction mirror which can improve the output spot quality is designed to a great extent, and the numerical results are in good agreement with the FEKO analog junction. The quasi-optical mode converter for 0.42 THz-TE26 mode and 0.42 THz-TE _ (17,4) mode gyrotron has been experimentally studied, in which the radiators are Vlasov type and Denisov type, and the results of the experimental test are in good agreement with the theoretical predicted value. In this paper, the working principle and the corresponding simulation results of the dual-frequency working coaxial double-electron beam-injection tube are introduced. The experimental results show that the state of the simultaneous operation of the fundamental wave and the second harmonic is verified. then the mode conversion of the same step-type quasi-optical mode converter is analyzed for two modes simultaneously output by the dual-frequency working coaxial dual-electron beam-injection rotary oscillation tube, and finally, a method for realizing double-frequency separation of the output power by using a frequency-based selection surface spatial filter is proposed, The processed samples were tested with a THz time-domain spectrometer (TDS), and the results of the measurements were given.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN12
文内图片：
图片说明：电磁波谱分布图
[Abstract]:Terahertz (THz) science and technology is one of the most important international academic front areas of the world, and it is a high-tech high point for all countries to seize, and its development is forward-looking for improving the national scientific and technological strength, promoting the development of the national economy, safeguarding the homeland security and social stability, Strategic and global significance. In recent years, the THz gyrotron is widely concerned as the high-power radiation source in the THz frequency band, which solves the problems of the development and application of THz technology in the absence of a stable and high-power THz radiation source. The gyrotron is a typical relativistic electronic fast wave device. The principle of high power THz wave is that the electron injection generates excited radiation in the longitudinal magnetic field and the high-frequency angle to the electric field, and is also called electron cyclotron masse. In the efforts of all countries, the gyrotron is developed in the direction of higher output power and frequency, and its working mode is usually high-order mode to increase the power capacity of the resonant cavity and reduce the ohmic loss. This high-order mode is detrimental to the long-distance transmission and application of THz waves, and it is necessary to use a mode converter to convert these high-order waveguide modes into a low-order waveguide mode that is more favorable for transmission or a Gaussian beam. Due to the large size of the traditional waveguide mode converter, the mode competition and the loss are serious in the process of the compact design and the mode transformation process. The quasi-optical mode converter with the advantages of simple structure, compact design and convenient application has been widely used, so it is very important to study the quasi-optical mode converter for high power THz gyrotron. In this paper, the quasi-optical mode converter for 0.42 THz-TE26 and 0.42 THz-TE _ (17,4) mode gyrotron is studied theoretically and experimentally, and a two-stage phase correction mirror which can improve the quality of the output spot is designed. In the end, the theoretical analysis of the quasi-optical mode converter applied to the dual-frequency dual-frequency dual-electron-injection gyrotron is put forward, and the method of using the space filter based on the frequency selective surface (FSS) to realize double-frequency separation of the output power is put forward. The specific content of the study is as follows:1. Based on the theory of guided wave field and the geometrical optics approximation, the transmission process of the working mode of the gyrotron in the cylindrical waveguide is described from the basic Maxwell equations, and the vector diffraction theory and the iterative method are combined. The Vlasov type radiator field structure in a 0.42 THz-TE26 mode gyrotron quasi-optical mode converter is analyzed, and the numerical results are in good agreement with the simulation results of the three-dimensional electromagnetic field full-wave simulation software. Based on the theory of transmission line and the theory of impedance perturbation, the coupling wave equation considering the function of the return wave is derived, and the electromagnetic coupling and the structure of the radiator field of the Denisov type radiator in the quasi-optical mode converter with the mode of 0.42 THz-TE _ (17,4) are analyzed. And the numerical results are in good agreement with the FEKO simulation. The mirror equation of the quasi-elliptical mirror and the parabolic mirror in the global coordinate system is derived by using the geometrical optics theory, and the field distribution at each regular mirror and the output window is calculated based on the vector diffraction theory and compared with the FEKO simulation result. Combined with the KSA algorithm and the vector diffraction theory, a two-stage phase correction mirror which can improve the output spot quality is designed to a great extent, and the numerical results are in good agreement with the FEKO analog junction. The quasi-optical mode converter for 0.42 THz-TE26 mode and 0.42 THz-TE _ (17,4) mode gyrotron has been experimentally studied, in which the radiators are Vlasov type and Denisov type, and the results of the experimental test are in good agreement with the theoretical predicted value. In this paper, the working principle and the corresponding simulation results of the dual-frequency working coaxial double-electron beam-injection tube are introduced. The experimental results show that the state of the simultaneous operation of the fundamental wave and the second harmonic is verified. then the mode conversion of the same step-type quasi-optical mode converter is analyzed for two modes simultaneously output by the dual-frequency working coaxial dual-electron beam-injection rotary oscillation tube, and finally, a method for realizing double-frequency separation of the output power by using a frequency-based selection surface spatial filter is proposed, The processed samples were tested with a THz time-domain spectrometer (TDS), and the results of the measurements were given.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN12
【参考文献】
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