Development of Mega-Watt Gyrotrons for Fusion Research

At the Plasma Research Center (PRC) in University of Tsukuba, development of Mega-Watt Gyrotrons is performed for fusion research. We are developing a new 28 GHz 1 MW and a 77 GHz 1.5 MW gyrotron for ECRH system of tandem mirror GAMMA10 and Large Helical Device (LHD), respectively. In the short pulse test of 77 GHz gyrotron, the maximum output power of 1.6 MW and the maximum total efficiency of 49.4% with CPD were obtained. In the long pulse test, the pulse length extended to 5 sec. with 1 MW and 4500 sec. with 0.2 MW. The design study of 154 GHz 1MW gyrotron for LHD has been started. For each cavity oscillation mode, TE_28,8, TE_28,12 and TE_31,8, cavity, electron gun (MIG), mode converter, collector and SCM design are being examined.