Studies of high power oscillation source with frequency tunability in the millimeter and sub-millimeter waves

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The output power and pulse duration of previous gyrotron for fusion reactor were 0.5MW and 100s or 0.2MWand 550s in the frequency range of 0.17 THz, respectively. However, a continuous-wave gyrotron is required for academic research and industrial application even if some output power decreased. For this purpose, suppression of outgases due to overheating inside the gyrotron and instabilities, which limit the pulse duration of the gyrotron, is indispensable.In this study, the parameters of the 0.17T gyrotron for fusion research, which is modified in a mode converter, an electron gun and control circuit, are optimized in the oscillation experiment in 2006. As a result, demonstration of 0.6MW output power, 46% efficiency and 1 hour (3600s) operation were carried out because the vacuum pressure in the gyrotron was stabilized in the low level of l×10-8 torr in the long pulse operation.Furthermore, the demonstrations of 1MW-800s-55% and 0.8MW-2000s-57% were successful and high power, high efficiency and steady state operation were also accomplished. This result shows the high reliability of the gyrotron because total output energy exceed more than 150GJ.High-speed sweep experiment of magnetic field of 7T-SCM for gyrotron oscillation was also carried out as a start-up of frequency tenability of the gyrotron. The sweep rate of 02T/5s was checked. As a result, the preparation of the experiment for the fast frequency tunability has been accomplished and an outlook for research to high frequency and tunability gyrotron has been also obtained.