回旋管准光辐射器研究与设计

准光辐射器是高功率回旋管准光模式变换器的重要组成部分.采用几何光学理论分析圆波导准光辐射器,根据高斯波束(TEM00模)在辐射器切口处形成的原因,利用耦合波理论设计波纹波导准光辐射器.通过编写程序并进行数值优化完成140 GHz、TE28,8模式回旋管波纹波导准光辐射器的设计,结果表明波纹波导辐射器的总长度仅为205.2 mm,切口长度为47.2 mm,在辐射器螺旋切口Brillouin区内高斯模式标量相关系数大于98%.本文所用的方法也可用于其它频率和模式的回旋管准光辐射器设计.     

140 GHz回旋振荡管Denisov辐射器设计

根据几何光学和耦合波理论研究高功率回旋振荡管高阶模式在微扰圆波导中的准光传输特性,并编制出带有微扰结构辐射器准光模式变换系统的仿真程序,给出140 GHz回旋振荡管Denisov辐射器的设计方法及结果,分析其内部激励起的各模式的功率分布曲线和波导壁上的电流密度分布,得到扰动长度为60 mm,总长度为136.5 mm的Denisov辐射器结构,输出功率转换效率为99.1%,可满足140 GHz整管参数设计要求。并利用Feko软件对数值计算结果的可行性进行了有效验证,从而为热核聚变用回旋振荡管的研制打下技术基础。     

W波段回旋管准光模式变换器的研究

该文对W波段TE₆₂模回旋管准光模式变换器的辐射器和镜面系统进行了设计与实验验证。基于耦合模理论,采用两级微扰对辐射器进行了设计,获得了圆波导内壁上的类高斯束斑的场分布;基于惠更斯原理的矢量衍射积分理论,对准光模式变换器的镜面系统进行了优化设计,模拟与计算结果表明准光模式变换器的模式变换效率为92.3%。最后,通过热测实验,验证了输出模式为W波段类高斯模式。     

TE22,6模式—高斯波的准光模式转换器设计

准光模式转换器是高功率毫米波回旋管的重要组成部份,能够实现电磁波与电子注的分离、隔离波的反射,并实现回旋管的高斯波束输出。基于耦合波理论,分析设计出用于频率140 GHz、TE22.6模式回旋管的Denisov辐射器;基于几何光学理论,设计出准光反射镜面系统,并采用Feko软件进行优化。计算结果表明,所设计的准光模式转换器系统的转换效率约为97.3%,波束的高斯含量约为93.3%,达到了回旋管的应用需求。     

94GHz二次谐波回旋管波纹波导模式转换

在耦合波理论的基础上,详细讨论了3mm二次谐波渐变复合腔回旋管内置TE03—TE02—TE01模式转换器,并使模式转换器兼作回旋管的收集极.采用波纹波导结构和不同的相位重匹配技术进行优化分析,得到了可靠的最优几何参量.以此结果设计出了紧凑、高效的94GH z波纹波导模式转换器,并在回旋管的热测实验中测出模式样图.     

94GHzTE5,3准光辐射器

基于耦合波理论和相位匹配技术,对准光辐射器的传统设计方法进行了改进,使其适用于低阶模式的设计.通过调节耦合时模式间的相位,在切口处实现了具有高斯场分布的理想模式组合.利用这一方法,优化设计了一个94 GHz,TE5,3回旋管准光辐射器.数值模拟结果表明,设计的辐射器在切口处形成了一个良好的束斑,边馈电平达到-30 dB,口径场高斯含量高于98%.     

94 GHz回旋管准光模式变换器的数值模拟

对回旋管内置准光模式变换器进行了理论研究和数值模拟。基于几何光学理论和矢量绕射理论,编制了模拟电磁场行为的分析和优化程序,采用Vlasov辐射器和准光反射器实现了线极化准高斯模HE11。结果表明:在一级反射镜下的转换效率为88.3%,增加反射镜级数会降低转换效率。     

96GHz边廊模Denisov辐射器

介绍了采用Denisov辐射器将96 GHz边廊模式信号转换为高斯波束的设计、仿真及测试结果.基于耦合波理论给出Denisov辐射器的设计方法.根据96 GHz TE_(6,2)模式Denisov准光模式转换器结构布局的要求,优化得到Denisov辐射器,输入半径6.4 mm,长52 mm,辐射器切割边缘电流幅值为汇聚中心点的10%,输出准高斯能量转换效率达96.51%.由其组成的准光模式转换器冷测输出高斯波束束腰直径22.4 mm,矢量转换效率大于95%.     

170 GHz回旋管准光模式变换器的设计

针对170 GHz回旋管研究,设计了一种高效Denisov准光模式变换器,该回旋管工作在模式。模式变换器由微扰结构的辐射器和镜面系统组成。基于耦合模理论和矢量绕射理论,研究了两级微扰辐射器,优化设计了镜面系统。仿真结果显示,模式转换为高斯光束,其输出功率转换效率为93.7%。     

W波段准光模式变换器的设计

准光模式变换器是大功率输出回旋管的关键部件.采用高转换效率的准光模式变换器可以横向输出电磁波,增大收集极的尺寸,提高回旋管的输出功率,提高整管效率.该文设计的回旋管内置准光模式变换器由Denisov辐射器天线和四个反射镜组成,输入频率为94GHz,模式为TE_6,2模.采用耦合波理论分析和优化了Denisov辐射器内的场分布,并根据矢量绕射理论编制数值模拟程序计算了各个反射镜上的场分布,其输出功率转换效率达97.2%.利用三维全波仿真软件feko6.0进行对比分析,最后加工所设计的结构并内置于回旋振荡管进行热测实验,结果表明其输出场分布与理论计算结果基本一致.     

An improved design for quasi-optical mode conversion of whispering gallery mode gyrotron radiation

Results are reported of a theoretical and experimental investigation of a quasi-optical mode converter for the transformation of whispering gallery mode gyrotron output into a linearly polarized Gaussian like beam. The mode converter consists of a helically cut waveguide launcher, similar to that originally proposed by Vlasovet al, followed by a focusing mirror. Theoretical results using aperture field methods indicate that the length of the waveguide launcher is of critical importance in providing a confined radiation pattern. Experimental results on the radiation pattern were obtained for several launcher lengths using a 0.6 MW, 149 GHz pulsed gyrotron operating in the TE_16,2 mode. Radiation pattern results for the optimum launcher length agree well with theoretical calculations using the Stratton-Chu aperture radiation theory for unperturbed waveguide modes. A mirror focusing in the azimuthal direction was designed by a geometrical optics approach to focus the radiation coming from the launcher. Good focusing with 91.4% efficiency (power in the focused beam divided by gyrotron power) was found experimentally using the combined launcher and mirror with the pulsed gyrotron. These results indicate that quasi-optical antennas are useful for transforming high order, high frequency gyrotron modes into directed beams in free space.     

Calculation of Radiation from a Helically Cut Waveguide for a Gyrotron Mode Converter in the Quasi-Optical Approximation

We present results of calculations of the radiation from a helically cut waveguide launcher, a so-called Vlasov launcher, which is commonly used either internal or external to a gyrotron for purposes of mode conversion. A gyrotron internal mode converter consists of such a launcher that radiates the waveguide mode as a nearly Gaussian beam in free space followed by a set of mirrors to focus and direct the radiation. The radiation from the launcher is first calculated using a geometric optics representation of the waveguide mode. Then the radiation is calculated in the quasi-optical limit, including diffraction. These analytic results are compared to a rigorous calculation using the computer code SURF3D, which uses an electric field integral equation (EFIE) approach. Good agreement is obtained between the quasi-optical theory and the SURF3D calculation. The present results provide new insights into the accuracy of the quasi-optical theory and may be useful for the design and improvement of Vlasov-type mode converters.     

Experimental study of a high efficiency quasi-optical mode converter for whispering gallery mode gyrotrons

A mode converter for whispering gallery mode gyrotrons has been designed and experimentally demonstrated. Experiments were performed on a megawatt power level, 3μs pulsed gyrotron operating in the TE_16,2,1 whispering gallery mode at 146 GHz. The gyrotron cavity employs a non-linear uptaper to minimize radial mode conversion. About 99% of the output power is in the TE_16,2 mode. The quasi-optical converter consists of a helically cut Vlasov-type waveguide launcher and a reflector. The doubly curved reflector, designed using geometric optics and vector diffraction theory, was built to focus the full radiation pattern to a small, gaussian-like focal spot. Of the power incident in the TE_16,2 mode, 96% is directed by the launcher and reflector to a gaussian-like focal spot in the far field. Small fractions of other modes were found to form distinct focal spots in the far field. Analysis of the power in the other focal spots allows for a good quantitative measurement of gyrotron output mode content, potentially on a single shot basis.     

太赫兹宽带Denisov型准光模式变换器的设计分析

研究并设计了一种具有宽频带工作能力的太赫兹准光模式变换器。该准光模式变换器采用具有高效率特性的Denisov 辐射器,工作在TE_6,2模式,用于实现回旋管内的模式变换。由于Denisov 辐射器的参数是影响准光模式变换器宽带性能的主要因素,因此通过对辐射器参数的优化设计,达到增大模式变换器带宽的效果。使用自主开发的准光学模拟程序进行仿真,模式变换器中心频率为94 GHz,带宽达2 GHz。     

A high-efficiency quasi-optical mode converter for a 140-GHz 1-MW CW gyrotron

A highly efficient quasi-optical mode converter system with several novel features has been designed and tested at Forschungszentrum Karlsruhe (FZK). The converter consists of a dimpled-wall waveguide launcher, one quasi-elliptical mirror and two toroidal mirrors. The coupled-mode theory has been used to analyze the operation of the prebunching waveguide launcher; the radiated fields from the cut of the launcher have been calculated by the scalar diffraction integral. Simulation results show that the advanced dimpled-wall launcher generates a well-focused Gaussian radiation pattern with low diffraction losses. In this case, toroidal mirrors are sufficient to obtain a desired output beam pattern. An efficiency of more than 98% has been achieved to convert the rotating TE/sub 28,8/ cavity mode at 140 GHz into a fundamental Gaussian beam. Experimental measurements show close agreement with theoretical predictions.     

Highly Efficient Quasi-Optical Mode Converter for a Multifrequency High-Power Gyrotron

A highly efficient quasi-optical mode converter with a bandwidth of 38 GHz has been designed and tested. The mode converter combines low-diffraction losses and a Gaussian mode content up to 97% for a set of nine modes in the range of 105 to 143 GHz for a 1-MW CW gyrotron. This was achieved using a dimpled-wall waveguide antenna (launcher), one quasi-elliptical mirror, and two toroidal mirrors. The optimization of the launcher was done using coupled-mode theory. The simulation results show a well-focused Gaussian beam for all nine operating modes. The curvature radii of the toroidal mirrors were determined by Gaussian mode transformation (ABCD-law) and subsequently optimized for a multimode operation. The simulations of the quasi-optical mode converter are based on the electric field integral equation and, thus, are 3-D. Experimental low-power measurements show close agreement with predictions.