.170 Ghz Gyrotron Quasi-optical Mode Converters Preliminary Study

In recent years,the international academic reserch on the built-in quasi-optical moder converter has gradually been warming up,almost 70% of the gyrotron use this power transmission structure,and gyrotron oscillator outputs the quasi-optical Gaussian beam from the horizontal direction.This Internal Installed quasi-optical mode converter has the following advantages:1. The converter separates the electron beam form the RF-wave path, so that the electron collector is no longer part of the output waveguide as in the case of a tube with an asial output .Hence, the collector can be designed especially for handling the high-electron-bean power.In addition,energy recovery with a depressed collector becomes possible,and improves the efficiency of the entire tube.2. Wave reflection is isolated. As a result of the adoption of high-power microwave from the horizontal output mirror, reflection of electromagnetic waves to the resonant cavity will be greatly reduced, especially in the output window slightly tilted, this reflection will be greatly weakened.3. The linearly polarazed TEM00 mode is directly usable for low-loss transmission, as well as for effective antanna feeding and no furture mode converters are needed. therefore,QO mode converter is for relatively modestly overmode systems when a very compact mode converter to the TEM00 mode is required.The purpose of this article gets some useful attempts to realize the progress of the QO mode converter.1. Providing an interview of the development of high-power microwave and its application, as well as the progress of 170GHz gyrotron oscillator.then introduce and derive the theory that the design of quasi-optical mode converter needed.2. Using the method of geometrical optics to discribe the microwave transmission in the waveguide, using the coupled-wave theory analysis the coupling between modes in the corrugated waveguide. A specific length of corrugated waveguide is designed including amplitude perturbation parameters. 3. Determining the length of the launcher cut, then using the method of vector diffraction theory and mirror imagine method to determine the field distribution, finally I modify the cylindrical parabolic reflector, and compare the field distribution between the radiation field and the Gaussian beam.The conclusion and prospect of the future work are made at last.