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A novel high power sub-terahertz gyrotron operating at second harmonic resonance was designed. This gyrotron is intended for use as a probe beam source for collective Thomson scattering diagnostics in nuclear fusion plasma research. The resonant cavity mode, cavity radius, and its length were optimized from various aspects such as resonant frequency, coupling between the electron beam and the RF-electric...
High power THz radiation sources - gyrotrons are being applied to high power THz technologies including enhancement of NMR sensitivity by a dynamic nuclear polarization, direct measurement of hyperfine structure of positronium, X-ray detected magnetic resonance measurement, sub-THz ESR echo spectroscopy and new medical technology. In this paper, such applications of THz gyrotrons are presented.
We have developed the Gyrotron FU CW VII for 300 MHz and 600 MHz DNP-NMR spectroscopy. For high frequency DNP-NMR experiment, high power sub-THz radiation sources are required. Gyrotron is able to emit enough power and appropriate frequency in sub-THz region for DNP. This Gyrotron emits electromagnetic waves with high power and appropriate frequency for each DNP-NMR spectroscopy (used cavity modes...
The latest gyrotron included Gyrotron FU CW Series, Gyrotron FU CW III is introduced in detail. It consists of a 20T superconducting magnet, a demountable gyrotron tube, a 30 kV, 0.5 A, CW power supply for electron gun and additional coils in a gun region. The gyrotron has achieved the breakthrough of 1 THz and frequency step tunability up to around 540 GHz for fundamental operations and up to 1.08...
The experimental tests of a gyrotron using a 21 T pulse magnet have achieved 1 THz at second harmonic operation. The operation conditions of the gyrotron at the THz regime are investigated. The single mode operation at second harmonic and frequency of 1 THz has been clarified with the theoretical results. This achievement and understanding of operating condition of gyrotron at 1 THz will be useful...
A gyrotron with a 21 T pulse magnet achieved the breakthrough of 1 THz. This is the first result of high frequency operation in the world beyond 1 THz. In addition, new gyrotron series in FIR FU, University of Fukui, so-called Gyrotron FU CW Series is being developed. Such a present status of high frequency gyrotron in FIR FU will be introduced.
A high power sub terahertz pulse gyrotron with a frequency around 400 GHz and the output power of tens of kW is under development in FIR-FU. Use of this gyrotron as a power source of collective Thomson scattering from a high density fusion plasma will reduce the plasma dispersion effect and the background ECE. As the first step of this development, a 200 GHz, TE03 mode pulse gyrotron operating at...
For application of high frequency gyrotrons to high power THz technologies, CW operation is needed. In FIR FU, we have developed Gyrotron FU CW Series which consists of three gyrotrons. In this presentation, The present status of Gyrotron FU CW Series is summarized.
For application of high frequency gyrotrons to high power THz technologies, we are developing THz CW gyrotron, FU CW Series. Gyrotron FU CW I with 12 T liquid He free superconducting magnert has already been developed applied for material processing, for example, ceramics sintering. The second gyrotron of the series, Gyrotron FU CW II with an 8 T superconducting magnet has been constructed and the...
Simulation results of a CW 1 THz gyrotron operates at second harmonic are described. Gyrotron utilize a newly obtained 20 T superconducting magnet. Mode competition analysis is employed to investigate operation conditions for excitation of the second harmonic cavity modes in a single mode operation. Simulation results shows frequency tunability of 22.9 percent with frequency ranging from 781.6 to...
A computational code for design of terahertz-frequency-range tapers has been developed by using the taper synthesis method. It was applied to designing an output taper for extraction of a terahertz wave from the cavity of Gyrotron FU CW II. The power transmission rates 99.7 % and 96.2 % of the main mode, TE26, are obtained for the taper length 300 and 150 mm, respectively. These values are high enough...
Application of an intense, high quality, well-collimated probe beam is effective in improving the performance of the measurement. Such probe beam is produced by stabilization of the high frequency gyrotron output and its conversion into a Gaussian beam.
We developed the material heating system by using a 300 GHz gyrotron. This system are consisted of a 300 GHz, 3.5 kW, CW gyrotron with a cryogen free 12 T superconducting magnet (Gyrotron FU CW I), a corrugated circular waveguide and an applicator. The circular corrugated waveguide ( i.d. = 6.35 cm) with a corrugated period and depth of 254mum have been designed. The applicator has been designed for...
The design of a gyrotron for continuous wave operation at 395 GHz at a power level from several watts to 2 kilowatts is presented. The gyrotron oscillator will be used for development of high sensitive NMR with dynamic nuclear polarization (DNP) method. The gyrotron design is optimized for single mode operation at second harmonic of the electron cyclotron frequency, omega=2omegac by removing the mode...
A gyrotron with a 21 T pulse magnet achieved the breakthrough of 1 THz. This is the first result of high frequency operation in the world beyond 1 THz. In addition, new gyrotron series in FIR FU, University of Fukui, so-called gyrotron FU CW series is being developed. Such a present status of high frequency gyrotron in FIR FU will be introduced.
A CW 300 GHz gyrotron has been developed and installed in University of Fukui. A quasi-Gaussian beam is delivered through the vacuum window after mode conversion from the TE22.8 cavity mode with a complex of an internal radiator and beam shaping mirrors. Performance test has been carried out and the maximum CW output power of 1.75 kW has been attained at the beam voltage of 15 kV and the beam current...
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