Design of Coaxial Resonator in TE28, 8 Mode Generator

In this paper, a three-stage coaxial cavity mode generator for the cold measurement of gyrotron is studied in detail, which uses the mode selection characteristics of the coaxial cavity to convert the input 140 GHz Gaussian mode into the high purity TE28,8 mode. Based on the first-order transmission line equation and its boundary conditions, we describe the design the structural parameters of the coaxial cavity and verify it by simulation. The TE28,8 mode generator consists of a Gaussian horn, a convex lens, a quasi-parabolic cylindrical lens, and a coaxial cavity. After numerical programming, the diffraction quality factor of the resonator is 872, and the mode purity is 93.2%.