Observation of Dynamic Interactions between Fundamental and Second-Harmonic Modes in a High-Power Sub-Terahertz Gyrotron Operating in Regimes of Soft and Hard Self-Excitation

Dynamic mode interaction between fundamental and second-harmonic modes has been observed in high-power sub-terahertz gyrotrons [T. Notake et al., Phys. Rev. Lett. 103, 225002 (2009); T. Saito et al. Phys. Plasmas 19, 063106 (2012)]. Interaction takes place between a parasitic fundamental or firstharmonic (FH) mode and an operating second-harmonic (SH) mode, as well as among SH modes. In particular, nonlinear excitation of the parasitic FH mode in the hard self-excitation regime with assistance of a SH mode in the soft self-excitation regime was clearly observed. Moreover, both cases of stable twomode oscillation and oscillation of the FH mode only were observed. These observations and theoretical analyses of the dynamic behavior of the mode interaction verify the nonlinear hard self-excitation of the FH mode

Formation of a laminar electron flow for 300 GHz high-power pulsed gyrotron

This paper describes the design of a triode magnetron injection gun for use in a 200 kW, 300 GHz gyrotron. As power and frequency increase, the performance of the gyrotron becomes quite sensitive to the quality of the electron beam. Formation of a laminar electron flow is essential for the realization of a high quality beam with a small velocity spread. In this study, a new method is developed for a quantitative evaluation of the laminarity and is applied to optimize the electrode design. The laminarity depends not only on conventional design parameters such as the cathode slant angle but also on the spatial distribution of the electric field along the beam trajectory. In the optimized design, the velocity pitch factors, a, larger than 1.2 are obtained at 65 kV, 10A with spreads, Da, less than 5%

Measurement of Radiation Power from the JIPP T-IIU Tokamak Plasma : JIPP T-IIUトカマクプラズマからの放射強度測定

名古屋大学Nagoya University理学博士Characteristics of a pyroelectric detector, a metal-film bolometer and a thermistor are investigated in order to attain high reliability or the bolometric measurement. The spurious signal which appears on a pyroelectric detector is efficiently eliminated by setting a mask close to the detector, which has a function of avoiding the direct incidence of photons on its electrode. This is verified with the consistency of integrated value of the signal. The detector is calibrated with a HeNe laser taking the reflection on the detector surface into account. No temporal change has been seen on the sensitivity or the detector calibrated by this method. We also developed a thin metal-film bolometer with high sensitivity (12.9Ω/mJ) , high time response (3 μs) and well defined thermal characteristics. The calibration of this detector was performed by supplying a bias current through its resistor. We constructed a bolometric system which consisted of twelve pyroelectric detectors and a metal-film bolometer with high time response and high spatial resolution. The radiation power measured with the pyroelectric detector agrees with that measured with the calibrated metal-film bolometer within 10 %. Spectroscopic and bolometric measurements with spatial and temporal resolution show that large radiation loss brings about the decrease in electron and ion temperature and plasma energy. Carbon limiters have an effect to suppress the radiation power for ohmic plasma, but are insufficient for ICRF heated plasma. The main contribution to radiation power may be attributed to Fe impurity released from the ICRF antennae, the Faraday shield and vacuum vessel. By making carbonization or the wall and in-vessel components, the Fe impurity is suppressed to a low level (nFe /ne　～ 0.04 %) and the radiation power is reduced to Prad /(PoH +P_rf )　~ 20 % and emissivity throughout the plasma region is reduced. This is clearly supported by the observation of Z_eff reduction (3.9→1.2).名古屋大学博士学位論文 学位の種類 : 理学博士(課程) 学位授与年月日 : 昭和62年3月25日doctoral thesi

Development of continuously frequency tunable Gyrotron for effective radiation source in the submillimeter wavelength range

研究種目:基盤研究(C) 研究期間:2008～2010 課題番号:20560320research repor

Observation of Simultaneous Oscillation of Multiple Modes in a CW 300 GHz Gyrotron

Multi-mode oscillation was observed in a 300 GHz fully CW gyrotron. It has been developed and installed in the Research Center for Development of Far-Infrared Region, University of Fukui as a power source of a submillimeter-wave material processing system. This gyrotron delivers 1.75 kW/CW at maximum. The radiation pattern is a Gaussian beam when the magnetic field strength Bc at the cavity is properly adjusted. However, within a range of Bc values, simultaneous oscillation of competing modes is observed, manifesting in radiation of the output power in multiple directions.othe

The ASTRO-H X-ray Observatory

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-2 keV with high spectral resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray

Measurement of Magnetic Field Intensity by Using Electron-Spin Resonance

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