Development and Application of a Medium Power, High Quality, Submillimeter Wave Gyrotron

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1. Development of High Frequency Gyrotrons Using the Second and the Third Harmonic Operations(1) A demountable gyrtron using a 12 T superconducting magnet has been constructed and operated under the second and the third harmonic resonances. The maximum frequencies of 636 GHz and 444 GHz at the second and the third harmonic resonances, respectively. The output powers lie in the range from 100 to 700 W.The gyrotron is useful for plasma diagnostics and studies of materials.(2) A high frequency gyrotron consisting of a 17 T superconducting magnet and a tipped-off tube has been constructed and tested. The gyrotron has attained frequency tunabilities from 159 to 430 GHz at the fundamental operations and from 336 to 850 GHz at the second harmonic operations. The maximum frequency of 850 GHz is the new world record for high frequency operation of gyrotron.2. Amplitude and Frequency Modulations of Submillimeter Wave GyrotronsBoth modulations of gyrotrons are important for applications to wide fields as radiation sources. Our submillimeter wave gyrotrons have achieved both sinusoidal-wave and square-wave modulations in the frequency range from 1 kHz to 600 kHz. The gyrotrons also have achieved frequency step switchings between 257 GHz and 260 GHz (switching between two fundamental modes) and between 223 GHz and 444 GHz (switching between a fundamental mode and a second mode). This is the first experiment of frequency switching of gyrotron.We have applied our gyrotrons to submillimeter wave spectroscopy and studied on the following fields.3. Mode competitions and cooperations between the fundamental and the harmonic mode operations, 4. Quasi-optical devices applied for submillimeter wave gyrotrons, 5. Plasma scattering measurement using a gyrotron as a power source, 6. Millimeter wave ESR experiment using a gyrotron as a power source.