Quasi-optical mode convertor is an important component for a high-power gyrotron.The transverse area of collector in gyrotron can be increased and the wave beam can be separated from the electron beam with a high conversion efficiency quasi optical mode convertor.To improve the conversion efficiency of the whole gyrotron

a quasi optical mode convertor with small size must be used to high-efficiently convert the cavity mode to fundamental Gaussian beam.This paper presents a quasi-optical mode convertor for TE

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94GHz gyrotron.The converter consists of a dimpled-wall Denisov launcher

a quasi-elliptical mirror

two parabolic mirrors and a plane mirror.The coupled-mode theory is used to analyze the operation of the pre-bunching wav

eguide launcher.The code of the vector diffraction theory is used to calculate the radiate fields of the mirrors.The efficiency of more than 97.2% is achieved for converting the rotating TE

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mode at 94GHz into a fundamental Gaussian beam.Simulations with feko 6.0 are done to compare with the calculation result.The structures is fabricated and placed in the 94GHz gyrotron.Experimental measurements show that close agreement with theoretical predictions is obtained.