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Kawano, Yasunori; Nakano, Tomohide; Asakura, Nobuyuki; Tamai, Hiroshi; Isayama, Akihiko; Kondoh, Takashi; Hatae, Takaki; Takenaga, Hidenobu; Ide, Shunsuke
Purazuma, Kaku Yugo Gakkai-Shi, 81(10), p.743 - 744, 2005/10
Electron density of post-disruption runaway plasmas in JT-60U has been measured by the tangential CO
laser interferometer. Increases in electron density after the first drop of runaway plasma current have been observed during a fast termination phase of the runaway plasma. At the second current drop, an increase in electron density with multiple spikes or oscillation with the period of 1 ms has been found. It is suggested that the increased electron density seems to take part in the shorter current decay time after the second current drop.
Kondoh, Takashi; Costley, A. E.*; Sugie, Tatsuo; Kawano, Yasunori; Malaquias, A.*; Walker, C. I.*
Review of Scientific Instruments, 75(10), p.3420 - 3422, 2004/10
Times Cited Count：23 Percentile：71.61(Instruments & Instrumentation)In order to measure the line average electron density on ITER, a CO laser interferometer/polarimeter system is being developed. The design of the interferometer/polarimeter is improved from the previous design, which uses CO and CO laser, on the basis of experience gained with a dual CO system on JT-60U in which good reliability was confirmed for both interferometry and polarimetry operation. The performance of the dual CO laser meets requirements for ITER (accuracy; 1%, time resolution; 1 ms).
Oyama, Naoyuki; Miura, Yukitoshi; Chankin, A. V.; Takenaga, Hidenobu; Asakura, Nobuyuki; Kamada, Yutaka; Oikawa, Toshihiro; Shinohara, Koji; Takeji, Satoru
Nuclear Fusion, 43(10), p.1250 - 1257, 2003/10
Times Cited Count：16 Percentile：45.80(Physics, Fluids & Plasmas)no abstracts in English
Kondoh, Takashi; Kawano, Yasunori; Costley, A. E.*; Malaquias, A.*; Sugie, Tatsuo; Walker, C.*
Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/07
In order to measure line average electron density for long pulse operation on ITER, a CO laser interferometer/polarimeter system has being selected. High reliability is necessary because the measurements will be used as a reference signal for real time control of the density during long plasma pulses. The design of the interferometer/polarimeter is improved from the previous design because of an input from experiences gained on JT-60U. A dual CO laser interferometer/polarimeter was chosen in order to improve reliability. The proof-of-principle test of the dual CO laser interferometer/polarimeter has been demonstrated and the system is operating routinely on JT-60U. Five tangential sight lines are designed near the midplane of ITER. The laser beams will be transmitted to the plasma through shielding labyrinths in an equatorial port and reflected by retroreflectors. Position of the laser beams will be remotely controlled by steering mirrors outside the port plug because the vacuum vessel of ITER will move due to change in temperature during long plasma pulses.
Kotaki, Hideyuki
JAERI-Research 2002-031, 88 Pages, 2002/12
JAERI-Research-2002-031.pdf:3.33MB
We investigate a nonlinear phenomena in laser-plasma interaction, a wakefield excited by intense laser pulses, and a possibility of generating an electron beam by an intense laser pulse. Ionization of gas with a self-focusing causes a broad continuous spectrum with blueshift. The normal blueshift depends on the laser intensity and the plasma density. We have found the spectrum shifts to fixed wavelength independent of the laser power and gas pressure. We call the phenomenon "anomalous blueshift". An intense laser pulse excites a wakefield in plasma. The wakefield excited by 2TW, 50fs laser pulses in a gas-jet plasma is measured with a time-resolved frequency domain interferometer (FDI). This is the first time-resolved measurement of the wakefield of 20GeV/m in a gas-jet plasma. The FDI and the anomalous blueshift will be modified to an optical injection system as an electron beam injector. In a simulation we obtain a high quality intense electron beam. The result illuminates the possibility of a high energy and a high quality electron beam acceleration.
Hatae, Takaki; JT-60 Team
Proceedings of 6th Japan-Australia Workshop on Plasma Diagnostics (CD-ROM), 16 Pages, 2002/00
The diagnostic system of JT-60U is composed of about 50 individual diagnostic devices. Recently, the detailed radial profile measurements of plasma parameters such as electron temperature, electron density, ion temperature, plasma rotation, and plasma current (safety factor q) have been improved. As a result, the understanding of internal structure of plasmas has advanced. In particular, detailed studies of the internal transport barrier could be performed in reversed magnetic shear plasmas. Furthermore, a "current hole" or a nearly zero current density at the plasma center was discovered in JT-60U plasmas by using a motional stark effect (MSE) system. Several diagnostic signal have been linked to actuators such as neutral beam injectors, the gas feed system, and the electron cyclotron heating system establishing the real-time control of electron temperature, neutron yield, radiated power, and electron temperature gradient, and thus improving plasma performance.
Department of Fusion Plasma Research
JAERI-Conf 2000-007, p.161 - 0, 2000/03
JAERI-Conf-2000-007.pdf:9.11MB
no abstracts in English
Tomimitsu, Hiroshi; ; Aizawa, Kazuya; Kikuta, Seishi*
Nuclear Instruments and Methods in Physics Research A, 420(3), p.453 - 466, 1999/00
Times Cited Count：2 Percentile：27.41(Instruments & Instrumentation)no abstracts in English
Dewa, Hidenori*; H.Ahn*; Harano, Hideki*; Kando, Masaki*; Kinoshita, Kenichi*; Kondo, Shuji; Kotaki, Hideyuki; Nakajima, Kazuhisa*; Nakanishi, Hiroshi*; Ogata, Atsushi*; et al.
Nuclear Instruments and Methods in Physics Research A, 410(3), p.357 - 363, 1998/00
Times Cited Count：42 Percentile：93.09(Instruments & Instrumentation)no abstracts in English
laser interferometer for large tokamakNagashima, Akira; Kawano, Yasunori; Hatae, Takaki;
Diagnostics for Experimental Thermonuclear Fusion Reactors, 0, p.235 - 243, 1996/00
no abstracts in English
