A 0.4-THz Second Harmonic Gyrotron with Quasi-Optical Confocal Cavity
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Mode density is very relevant for harmonic gyrotron cavity. Theoretical investigations suggest that quasi-optical confocal waveguide performs low mode density and good mode-selective character. By selecting the appropriate mode and optimizing the cavity parameters, the quasi-optical confocal cavity is suitable for high-harmonic terahertz gyrotron without mode competition. In order to verify the theoretical analysis, a 0.4-THz second harmonic gyrotron has been designed and experimented. Driven by a 40-kV, 4.75-A electron beam and 7.51-T magnetic field, the gyrotron prototype could generate 6.44 kW of output power at 395.35 GHz, which corresponds to an electron efficiency of 3.4%. There is no mode competition between the second harmonic and fundamental observed in the experiments.
KeywordsTHz Harmonic gyrotron Quasi-optical cavity Cylindrical confocal waveguide Mode selection
We gratefully acknowledge the assistance of Yin Huang and Weirong Deng. This work is supported by the National Natural Science Foundation of China under Grant No. 61401064, National Natural Science Foundation of China under Grant No. 61771096, National Basic Research Program of China under Grant No. 2013CB933603, and by CAEP THz Science and Technology Foundation under Grant No. CAEPTHZ201403.
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