针对一种由Denisov型辐射器和第一面镜为准抛物镜的四级反射镜面系统组成的准光模式变换器开展了详细的研究和设计。利用耦合模理论和矢量绕射理论设计了波纹波导准光模式变化器,通过编写仿真程序进行数值优化完成了140 GHz,TE28,8回旋管准光模式变换器的设计。仿真结果表明,抛物面反射镜的焦距对矢量高斯效率影响较大,输出窗口处得到了较好的高斯波束,标量高斯效率达到98%,矢量高斯效率达到90%。

This paper presents a high efficiency Denisov quasi-optical mode converter for 140 GHz, TE28,8 mode gyrotron. The mode converter includes a dimpled wall launcher and a mirror system. The mirror system consists of four mirrors, of which the first mirror is a quasi-parabolic one. A simulation code is developed based on the coupled mode theory and the vector diffraction theory. The simulation results show that the focal length of the parabolic mirror has a great effect on the vector Gaussian correlation coefficient. Therefore, it is important to select an appropriate focal length for the mirror system. The simulation results show that the scalar Gaussian correlation coefficient of the operating cavity mode to a fundamental Gaussian distribution on the window plane is about 98%, and the corresponding vector correlation coefficient is more than 90%.