Development of frequency tunable gyrotrons as high power far-infrared wave sources and their applications to far-infrared spectroscopy

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(1) Development of submillimeter wave gyrotrons using a 17 T superconducting msgnet, whose wavelength is tunable down to 337 μm(2) Development of higher harmonic gyrotron with a 1 T permanent magnet. The 3 rd, the 4 th and the 5 th harmonic operations were realized successfully.(3) Frequency modulation of gyrotron output was achieved by modulation of beam electron energy, while amplitude modulation by modulation of velocity distribution function of beam electrons.(4) Frequency stabilization of gyrotron output was achieved by phase-lock control of beam electron energy, while amplitude stabilization by feed-back control of anode voltage of gun. The stabilities of frequency and amplitude were 3・10^<-10> and 10^<-3>, respectively.(5) Conversion of gyrotron output to Gaussian mode by a quasi-optical system and achievement of high efficiency transmission of the bi-Gaussian mode.(6) A plasma scattering measurement system with a gyrotron as a radiation source in a submillimeter wavelength range was designed and constructed. Its application to measurement of density fluctuation for CHS and LHD in National Institute for Fusion Science and a tokamak device NSTX in Princeton University was researched.(7) A high power ESR device with a gyrotron as a radiation source was constructed and already applied to ESR study in submillimeter wavelength range.