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Journal Articles

Performance of the LH antenna with carbon grill in JT-60U

Seki, Masami; Moriyama, Shinichi; Shinozaki, Shinichi; Hasegawa, Koichi; Hiranai, Shinichi; Yokokura, Kenji; Shimono, Mitsugu; Terakado, Masayuki; Fujii, Tsuneyuki

Fusion Engineering and Design, 74(1-4), p.273 - 277, 2005/11

 Times Cited Count:3 Percentile:24.34(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Recent RF experiments and application of RF waves to real-time control of safety factor profile in JT-60U

Suzuki, Takahiro; Isayama, Akihiko; Ide, Shunsuke; Fujita, Takaaki; Oikawa, Toshihiro; Sakata, Shinya; Sueoka, Michiharu; Hosoyama, Hiroki*; Seki, Masami; JT-60 Team

AIP Conference Proceedings 787, p.279 - 286, 2005/09

A real-time control system of safety factor (q) profile was developed in JT-60. This system, for the first time, enables 1) real time evaluation of q profile using local magnetic pitch angle measurement by motional Stark effect (MSE) diagnostic and 2) control of current drive (CD) location (rhoCD) by adjusting the parallel refractive index $$N_{rm //}$$ of lower-hybrid (LH) waves through the change of phase difference (dphi) of LH waves between multi-junction launcher modules. The method for q profile evaluation was newly developed, without time-consuming reconstruction of equilibrium, so that the method requires less computational time. The system evaluates q profile within every 10ms, which is much faster than current relaxation time, typically order of 1s. Safety factor profile by the real-time calculation agreed well with that by equilibrium reconstruction with MSE. From temporal evolution of q (or current) profile, we evaluate CD location in real-time, too. The control system controls rhoCD through $$N_{rm //}$$ (or directly dphi) in such a way to minimize difference between the real-time evaluated q profile and its reference profile. The real-time control system was applied to positive shear plasmas ($$q(0)sim 1$$), having plasma current of 0.6MA, toroidal field of 2.3T, and electron density of $$0.5times 10^{19}{rm m}^{-3}$$. In order to keep good coupling of LH waves to the plasma, gap between the launcher and the plasma surface was controlled to about 0.1m. The reference q profile was set to q(0)=1.3. The real-time q profile approached to the reference after application of real-time control; the controlled q profile was sustained for 3s, which was limited by injected LH power. RF experiments in JT-60U, such as stabilization of neo-classical tearing modes, plasma startup experiments, etc., are also presented.

Journal Articles

Outgassing of lower hybrid antenna modules during high-power long-pulse transmission

Goniche, M.*; Kazarian, F.*; Bibet, P.*; Maebara, Sunao; Seki, Masami; Ikeda, Yoshitaka; Imai, Tsuyoshi*

Journal of Vacuum Science and Technology A, 23(1), p.55 - 65, 2005/01

 Times Cited Count:2 Percentile:9.33(Materials Science, Coatings & Films)

Outgassing rates have been measured for long duration (100-4700 seconds) of RF transmission at high power density (50-200 MW/m$$^{2}$$) for waveguides made of OFHC copper, dispersoid copper, copper-coated carbon fiber composite and copper-coated graphite. The measurements were performed on multi-waveguide(2 to 8)mockups, using a test bed facility equipped with a 3.7 GHz klystron. The effect on the outgassing rate of waveguide surface temperature and of initial wall gas loading('conditioning'), is examined. It is concluded that an outgassing rate of 1$$times$$10$$^{-5}$$ Pam$$^{3}$$s$$^{-1}$$m$$^{-2}$$ and 5$$times$$10$$^{-5}$$ Pam$$^{3}$$s$$^{-1}$$m$$^{-2}$$ at 300$$^{circ}$$C and 400$$^{circ}$$C respectively, can be expected for the tested material. Based on these measurement results, it is further concluded that no additional pumping will be needed for the LHRF antenna proposed for ITER.

Journal Articles

Evolution of lower hybrid driven current during the formation of an internal transport barrier

Naito, Osamu; Cui, Z.*; Ide, Shunsuke; Suzuki, Takahiro; Oikawa, Toshihiro; Seki, Masami; Hatae, Takaki; Fujita, Takaaki; Kondoh, Takashi; Shirai, Hiroshi; et al.

Physical Review Letters, 89(6), p.065001_1 - 065001_4, 2002/08

 Times Cited Count:9 Percentile:52.7(Physics, Multidisciplinary)

Evolution of lower hybrid (LH) driven current profile was measured during the formation of internal transport barrier (ITB) in a reversed magnetic shear discharge. As the ITB developed, initially centrally peaked LH driven current profile gradually turned hollow and was sometimes accompanied by an off-axis peak in electron temperature profile followed by a sawtooth-like instability localized to the ITB. These observations indicate the concentration of LH power deposition at the ITB and suggest the difficulty of current profile control by LH waves once the ITB is established.

Journal Articles

Large current drive experiments by using simplified multijunction lower hybrid wave launcher in JT-60U

Kondoh, Takashi; Ikeda, Yoshitaka; Ushigusa, Kenkichi; Seki, Masami; Ide, Shunsuke; Naito, Osamu;

Nihon Genshiryoku Gakkai-Shi, 37(2), p.124 - 132, 1995/00

 Times Cited Count:1 Percentile:17.57(Nuclear Science & Technology)

no abstracts in English

Journal Articles

High performance and current drive experiments in the JAERI Tokamak-60 Upgrade

Kondoh, Takashi; JT-60 Team

Physics of Plasmas, 1(5), p.1489 - 1496, 1994/05

 Times Cited Count:19 Percentile:57.36(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Numerical investigation of current profile flattening during lower hydrid current drive in JT-60

Yoshino, Ryuji; Ushigusa, Kenkichi; Imai, Tsuyoshi; Shirai, Hiroshi; Shimizu, Katsuhiro

JAERI-M 89-116, 12 Pages, 1989/09

JAERI-M-89-116.pdf:0.46MB

no abstracts in English

Journal Articles

Optimization of OH coil recharging scenario of quasi-steady operation in tokamak fusion reactor by lower hybrid wave current drive

; ; ; ; *; ; *; *

Nucl.Eng.Des./Fusion, 1, p.265 - 277, 1984/00

 Times Cited Count:2 Percentile:30.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Parametric absorption of lower hybrid wave in the boundary plasma of JFT-2 tokamak

; ; ; ; ; ;

Journal of the Physical Society of Japan, 49(6), p.2364 - 2370, 1980/00

 Times Cited Count:6 Percentile:52.06(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Effect of finite wavelength of the pump on the parametric threshold of lower hybrid wave

Journal of the Physical Society of Japan, 43(3), p.1105 - 1106, 1977/03

 Times Cited Count:0

no abstracts in English

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