Achievement of robust high-efficiency 1 MW oscillation in the hard-self-excitation region by a 170 GHz continuous-wave gyrotron

Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Minami, Ryutaro*; Kobayashi, Noriyuki; Kajiwara, Ken

The first 1 MW quasi-continuous wave generation is demonstrated at 170 GHz gyrotron of TE31,8 resonator mode with outstanding efficiency of greater than 55 percent. The robust high efficiency oscillation is obtained in a hard self-excitation region with an active control of gyrotron parameters. Furthermore, a novel nonlinear process is found that the desired TE31,8 mode is excited as a parasitic mode of an adjacent TE30,8 mode and finally the TE31,8 dominates a system. This effect extends a substantial soft self-excitation region of the desired mode significantly.