(FT/P2-25) Development of 1 MW Gyrotron and Progress of ECH System for the GAMMA 10 Tandem Mirror in Tsukuba

T. Imai1), T. Kariya1), R. Minami1), H. Shidara1), K. Sakamoto2), S. Kubo3), T. Shimozuma3), T. Mutoh3), H. Takahashi3), Y. Mitsunaka4), Y. Endo1), M. Harigae1), M. Nakamura1), Y. Sakagoshi1), N. Murofushi1), M. Ichimura1), Y. Nakashima1), M. Yoshikawa1), Y. Yamaguchi1)
1) Plasma Research Center, University of Tsukuba, Tsukuba, Japan
2) Japan Atomic Energy Agency, Naka, Ibaraki, Japan
3) National Institute for Fusion Science, Toki, Gifu, Japan
4) Toshiba Electron Tubes and Devices Co. Ltd, Otawara. Tochigi, Japan

Abstract.   An ECH is a reliable tool for the plasma heating, current drive and plasma control in the magnetic confinement fusion devices. It is especially essential for the tandem mirror machines to get high confining potential and high electron temperature. Power scaling of the ion confining potential predicts that further higher potential formation would be expected corresponding to the plug ECH power increase. Along this line, GAMMA 10 has started the ECH system upgrade program in collaboration with JAEA and NIFS High power gyrotrons with TE4,2 cavity at 28 GHz and with TE18,6 cavity and a diamond window at 77 GHz have been developed for GAMMA 10 and LHD in the joint program of NIFS and University of Tsukuba. The maximum outputs of 570 kW at 28 GHz and 1.1 MW at 77 GHz were obtained corresponding to each design. The calculated power profile at the window and the experimentally obtained burn pattern of the 77 GHz gyrotron agree well. The operations of 460 kW for 5 s and 810 kW for 3.5 s were achieved in the first test gyrotron at 77 GHz, which is the first high power-long pulse result of 77 GHz tube. The experimental simulation of the effect of the stray RF in the 28 GHz tube indicates the stray RF is the one of the major causes limiting gyrotron performance. Installation of the polarizer in the transmission line enhanced the performance of the ECH system in GAMMA 10, that is the first result which clearly showed 100% X mode excitation is a key to design the efficient fundamental ECH system in mirror devices.

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