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Journal Articles

Development of a high power wideband polarizer for electron cyclotron current drive system in JT-60SA

Saigusa, Mikio*; Oyama, Gaku*; Matsubara, Fumiaki*; Takii, Keita*; Sai, Takuma*; Kobayashi, Takayuki; Moriyama, Shinichi

Fusion Engineering and Design, 96-97, p.577 - 582, 2015/10

 Times Cited Count:4 Percentile:32.14(Nuclear Science & Technology)

A wideband polarizer has been developed for an ECCD system in JT-60SA. The groove depth of the mirrors installed in miter bends were optimized for two frequencies (110 GHz and 138 GHz) by numerical simulations. All surfaces of Poincare spheres were covered at both of the frequencies in low power test. The thermal stress of polarizer were estimated by the numerical simulations. The twister polarizer has been tested up to 0.24 MW during 3 s at 110 GHz.

Journal Articles

Study of ohmic loss of high power polarizers at 170 GHz for ITER

Kashiwa, Yoshinori*; Saigusa, Mikio*; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi

Fusion Engineering and Design, 81(19), p.2249 - 2256, 2006/09

 Times Cited Count:2 Percentile:18.25(Nuclear Science & Technology)

High efficiency ECCD operations need an obliquely propagating electromagnetic wave with a specified elliptical polarization in magnetized plasma. The polarizer is necessary in order to excite the specified polarization. In the ITER design for ECCD system, the transmitted power per one waveguide is planned to be 1 MW as CW operation. The ohmic loss evaluation code for grooved mirror polarizers which calculates tangential magnetic field to the material at exterior to the groove and inside of that was developed. Calculation results were made sure of agreement with high power experiment qualitatively, and validity of the evaluation code has been confirmed.

Journal Articles

Polarizance of a synthetic mica crystal polarizer and the degree of linear polarization of an undulator beamline at 880eV evaluated by the rotating-analyzer method

Imazono, Takashi; Hirono, Toko*; Kimura, Hiroaki*; Saito, Yuji; Ishino, Masahiko; Muramatsu, Yasuji*; Koike, Masato; Sano, Kazuo*

Review of Scientific Instruments, 76(12), p.126106_1 - 126106_4, 2005/12

 Times Cited Count:14 Percentile:57.19(Instruments & Instrumentation)

Polarizance of a reflection-type polarizer made with a synthetic mica (fluorophlogopite) single crystal was evaluated at the photon energy of 880 eV by means of the rotating-analyzer method in conjunction with the evaluation of the degree of linear polarization of the insertion beamline, SPring-8 BL23SU, featuring an APPLE-2 type variably polarizing undulator. When the undulator was tuned to the horizontal linear polarization mode, the maximum reflectances for s- and p-polarization for a symmetric Bragg reflection of synthetic mica(002) were 2.6% and 0.013%, respectively, at incident angles of near 45$$^circ$$. Our analysis based on the rotating-analyzer method gave the polarizance of the polarizer of at least 0.997 $$pm$$ 0.002 and the degree of linear polarization of 0.993 $$pm$$ 0.004 in the linear polarization mode.

Journal Articles

Thermal analysis and Ohmic loss estimation of polarizer for ITER ECCD system

Saigusa, Mikio*; Takahashi, Koji; Kashiwa, Yoshinori*; Oishi, Shimpei*; Hoshi, Yuki*; Nakahata, Hiroyuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi*

Fusion Engineering and Design, 74(1-4), p.473 - 478, 2005/11

 Times Cited Count:4 Percentile:25.79(Nuclear Science & Technology)

The specification of an electron cyclotron current driving (ECCD) system in International Thermonuclear Experimental Reactor (ITER) demands severe operational conditions for transmission lines and polarizers. For evaluating Ohmic loss of a miter bend type polarizer, the six polarizers were made of chromium copper alloy, installed in miter bends and tested at a frequency of 170GHz, rf power of 441kW and pulse duration of 0.1-6 seconds. The increase in temperature on the back of the grooved mirrors has been measured with thermo couplers during high power rf pulses. The Ohmic loss of grooved mirrors strongly depends on the rotation angle of the polarization plane of the incident waves and the mirror rotation in high power experiments, for example the Ohmic loss distributed from 0.2% to1.6%. The thermal analysis of grooved mirror has been performed with the 3D FEM code: FEVA. The all strange behavior of Ohmic loss of polarizers could be explained, theoretically.

Journal Articles

Performance of a reflection-type polarizer by use of muscovite mica crystal in the soft X-ray region of 1 keV

Imazono, Takashi; Ishino, Masahiko; Koike, Masato; Kimura, Hiroaki*; Hirono, Toko*; Sano, Kazuo*

Review of Scientific Instruments, 76(2), p.023104_1 - 023104_4, 2005/02

 Times Cited Count:13 Percentile:55.26(Instruments & Instrumentation)

To develop the polarizer functioning in the soft X-ray region of 1 keV, the polarization performance of muscovite mica has been investigated theoretically with simulation code based on dynamical theory. As the result of calculation, muscovite mica is found to be promising candidate as a reflection-type polarizer with the reflectivity for s-polarization of 0.03 at approximately 0.9 keV at the angle of incidence of 45$$^circ$$. In order to verify the polarization performance of muscovite mica experimentally, a symmetric Bragg reflection measurement of muscovite mica(002) was carried out using a linearly polarized undulator radiation. As the result, the maximum reflectivity for s-polarization and the extinction ratio of muscovite mica were approximately 0.018 and 200 at 878 eV, respectively. This result indicates that muscovite mica works as a practical polarizer in the soft X-ray region.

Journal Articles

Study of ohmic loss of high power polarizers at 170 GHz for ITER

Kashiwa, Yoshinori*; Saigusa, Mikio*; Takahashi, Koji; Oishi, Shimpei*; Hoshi, Yuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi

Proceedings of 2004 International Symposium on Microwave Science and Its Application to Related Fields (Microwave 2004), p.527 - 530, 2004/07

An electron cyclotron current drive (ECCD) system is, especially, necessary to suppress the neoclassical tearing mode instability in ITER. The polarizers are one of the important components in the ECCD system, to generate optimum polarization for an efficient ECCD. An ohmic loss of the polarizers is evaluated, when 170GHz, high power RF wave taransmits, in oreder to investigate its performance. The maximum temperature increase on the back plate of the deep grooved and the conventinal type were 65$$^{circ}$$C and 30$$^{circ}$$C, respectively. RF power and pulse were 441kW and 6sec, respectively. The dependence of temperature increase on the plolarizer angle obtained in the experiment agrees with the calculation, qualitatively. It was also found that the significant reduction of ohmic loss on the polarizers was achievable with the optimized rotation angle of the linearly polarized incident wave.

JAEA Reports

Injection control development of the JT-60U electron cyclotron heating system

Hiranai, Shinichi; Shinozaki, Shinichi; Sato, Fumiaki*; Suzuki, Yasuo*; Yokokura, Kenji; Moriyama, Shinichi; Ikeda, Yoshitaka

JAERI-Tech 2003-038, 39 Pages, 2003/03


The JT-60U electron cyclotron heating (ECH) System injects a millimeteric wave at 110 GHz (EC beam) into the JT-60 Plasma, and heats the plasma or drives a current locally to enhance the confinement performance of the JT-60 plasma. The system consists of four sets of high power gyrotrons, high voltage power supplies and transmission lines, and two antennas that launch electron cyclotron (EC) beams toward the plasma. The key features of the injection control system are steering of the direction of the EC beam by driving the movable mirror in the antenna, and capability to set any combination of polarization angle and ellipticity by rotating the two grooved mirrors in the polarizers. This report represents the design, fabrication and improvements of the injection control system.

Journal Articles

Study of Joule loss of grooved mirror polarizers

Saigusa, Mikio*; Takahashi, Koji; Oishi, Shimpei*; Kashiwa, Yoshitada*; Hoshi, Yuki*; Kobayashi, Yuki*; Kasugai, Atsushi; Sakamoto, Keishi; Imai, Tsuyoshi

Proceedings of IAEA TM on ECRH Physics and Technology for ITER (CD-ROM), 7 Pages, 2003/00

The specified elliptical polarization which is necessary to excite a pure ordinary or extraordinary mode, when rf waves obliquely propagate in plasma, for electron cyclotron current drive(ECCD) can be produced by a grooved mirror polarizer. The Joule loss of deeped groove mirrors has been experimentally investigated at a frequency of 170 GHz. The strange dependence of the Joule loss of groove mirror on the mirror rotation angle was obtained. In addition, maximum loss of 0.8% in regard to the injection rf power to the mirrors was estimated. The calculation code to estimate the Joule loss of grooved mirror is developed for the structure analysis. The dependence of the mirror on its rotation angle can be explained by the calculation results, clearly.

Journal Articles

Beam combiner for transient phenomena measurement in the JT-60 Thomson scattering diagnostic

Yoshida, Hidetoshi; Naito, Osamu; Yamashita, Osamu; Kitamura, Shigeru; Nagashima, Akira; Matoba, Toru

Review of Scientific Instruments, 66(1), p.143 - 147, 1995/01

 Times Cited Count:23 Percentile:84.08(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Progress in development of a wide band polarizer for ECCD system in JT-60SA

Horie, Naoyuki*; Sai, Takuma*; Omori, Kohei*; Saigusa, Mikio*; Kobayashi, Takayuki; Moriyama, Shinichi; Arata, Hiroshi*; Uno, Tsuyoshi*

no journal, , 

no abstracts in English

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