Development and Application of a Frequency-Tunable, Submillimeter Wave Gyrotron

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A gyrotron is a high power source covering millimeter and submillimeter wavelength ranges. We are planning the development of high frequency, cyclotron harmonic gyrotorns and their application to a spectroscopy in the submillimeter wavelength range.I) Development of a gyrotron covering a submillimeter wavelength rangeWe have made up a 8-12 T superconducting magnet which is optimized for a gyrotron and designed an electron gun and a cylindrical cavity to construct the gyrotron tube. We have tested the gyrotrons made on the basis of the designs and obtained following results.1. A new harmonic gyrotron has produced a submillimeter wave, output power at the 2nd harmonic resonance, in Fukui University. Its frequency is 404 GHz (the corresponding wavelength is 0.75 mm) and its power is several kw. Gyrotron IVA of University of Sydney has achieved high frequency operations up to 516 GHz, which is the world record for a stable gyrotron. The work was done under collaboration with Fukui University.2. An operation of the whispering gallery mode has been observed. The output power can be used to develop a quasi-optical antenna for its conversion to a linearly poralized mode.3. Cyclotron harmonic operations up to 3rd have been observed, which are necessary for a high frequency gyrotron. Our gyto-peniotron has produced a high power (-3.3kW) at a high frequensy (-140 GHz) under the 3rd harmonic resonance.II) Application of a submillimeter wave gyrotron1. We have constructed the scattering measurement system for plasmas and applied it to WT-3 Tokamak of Kyoto University and TORTUS Tokamak of University of Sydney and succeeded to observe a spontaneously excited, low frequency drift wave and an externally excited Alfen wave.2. We have developed elements for quasi-optical circuit, using outputs of our gyrotrons.3. We have begun to use a gyrotron as a power source for spectroscopy in the millimeter and submillimeter wavelength ranges, to study the properties of condensed matters.