Development of Medium Power, High Quality, Submillimeter Wave Gyrotron and Its Application to Plasma Measurement

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Objectives of the project are as follows, 1. Development of medium power, high quality, submillimeter wave gyrotron, and 2. Its application to plasma scattering measurement as a submillimeter wave source.Main results obtained through the term (1991-1993) are as follows,1. Development of high frequency gyrotron using the second and the third harmonic operationsHigh frequency, submillimeter wave gyrotrons are developed in both universities using 12 T superconducting magnets. In Fukui, a frequency tunable gyrotron (GYROTRON FU III) up to 636 GHz is realized by the fundamental, the second and the third harmonics of electron cyclotron resonance. Output powers are several hundred watts. In Sydney, a frequency tunability from 150 GHz to 615 GHz is attained by introducing the second harmonic operation developed in Fukui.The gyrotron has a important advantage of continuous operation, while output power is low, that is, several milliwatt to several ten watts.2. Long pulse operation of a submilli … More meter wave gyrotronGyrotrons in Fukui are pulsed. Long pulse operation is necessary for its application to plasma scattering measurement. Using GYROTRON FU II, 0.6 msec, TE_<161> mode operation at the second harmonic (frequency is 352 GHz) has been achieved. The output power is 150 W, which is applicable to plasma measurement as a power source.3. Amplitude modulation and frequency modulation of a submillimeter wave gyrotronBoth modulations of a gyrotron are important for its application to wider fields. Such modulations have been achieved by modulating anode voltage and cathode voltage of electron gun, respectively.4. Mode competition and cooperation between the fundamental and the second harmonic operationsSingle mode operations at the second harmonic which are necessary for development of high frequency gyrotron have been achieved by suppressing mode competition with the fundamental operations. On the other hand, under some operation condition, the second harmonic operation triggers a fundamental operation (a kind of mode cooperation). As the results, a starting current of the fundamental decreases and total energy extracted from the electron beam increases.5. Plasma scattering measurement using a gyrotron as a power sourceUsing GYROTRON FU II as a submillimeter wave source, a scattering measurement of a drift wave in CHS device is successfully done under collaboration with National Institute of Fusion Science. In Sydney, a scattering measurement of Alfven wave in TORTUS Tokamak is also done in the plasma heating experiment. Less