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3. Recent diagnostic developments on LHD

Author

S Sudo, Y Nagayama, B J Peterson, K Kawahata, T Akiyama, N Ashikawa, M Emoto, M Goto, Y Hamada, K Ida, T Ido, H Iguchi, S Inagaki, M Isobe, T Kobuchi, A Komori, Y Liang, S Masuzaki, T Minami, T Morisaki, S Morita, S Muto, Y Nakamura, H Nakanishi, M Narushima, K Narihara, M Nishiura, A Nishizawa, S Ohdachi, M Osakabe, T Ozaki, R O Pavlichenko, S Sakakibara, K Sato, M Shoji, N Tamura, K Tanaka, K Toi, T Tokuzawa, K Y Watanabe, T Watanabe, H Yamada, I Yamada, M Yoshinuma, P Goncharov, D Kalinina, T Kanaba, T Sugimoto, A Ejiri, Y Ono, H Hojo, K Ishii, N Iwama, Y Kogi, A Mase, M Sakamoto, K Kondo, H Nagasaki, S Yamamoto, N Nishino, S Okajima, T Saida, M Sasao, T Takeda, S Tsuji-Iio, D S Darrow, H Takahashi, Y Liu, J F Lyon, A Yu Kostrioukov, V B Kuteev, V Sergeev, I Viniar, A V Krasilnikov, A Sanin, L N Vyacheslavov, D Stutman, M Finkenthal, O Motojima, and LHD Group

Subjects
Physics, Plasma parameters, business.industry, Divertor, Bolometer, Polarimeter, Condensed Matter Physics, Laser, Photon counting, law.invention, Large Helical Device, Optics, Nuclear Energy and Engineering, law, Plasma diagnostics, business
Abstract

Standard diagnostics for fundamental plasma parameters and for plasma physics are routinely utilized for daily operation and physics studies in the large helical device (LHD) with high reliability. Diagnostics for steady-state plasma are under intensive development, especially for Te, ne (yttrium–aluminium garnet (YAG) laser Thomson, CO2 laser polarimeter), data acquisition in steady-state and heat-resistant probes. To clarify the plasma properties of the helical structure, two- or three-dimensional diagnostics are being aggressively developed: tangential cameras (fast SX TV, photon counting CCD, Hα TV); tomography (tangential SX CCD, bolometer); imaging (bolometer, ECE, reflectometer). Divertor and edge physics are important key issues for steady-state operation. Diagnostics for neutral flux (Hα array, Zeeman spectroscopy) and ne (fast scanning probe, Li beam probe, pulsed radar reflectometer) are also in advanced stages of development. In addition to these, advanced diagnostics are being intensively developed in LHD through domestic and international collaborations.

Published
2003
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4. Experimental study on ion temperature behaviours in ECH, ICRF and NBI H2, He and Ne discharges of the Large Helical Device

Author

J. Miyazawa, Hisamichi Funaba, Osamu Motojima, M. Fujiwara, H. Nozato, Nobuyoshi Ohyabu, Hajime Suzuki, Keisuke Matsuoka, Tsuyoshi Akiyama, Kazuo Kawahata, Hideya Nakanishi, Masahiko Emoto, Atsushi J. Nishizawa, Masayuki Yokoyama, Hiroshi Yamada, T. Yamamoto, Kenji Tanaka, Mamiko Sasao, Naoko Ashikawa, H. Kawazome, Shigeru Sudo, Yasuo Yoshimura, Kazuo Toi, K. Yamazaki, Takashi Satow, Mitsutaka Isobe, N. Takeuchi, Takeshi Ido, A. Kostrioukov, N. Noda, Yunfeng Liang, T. Kobuchi, Hiroshi Idei, Takashi Minami, Naoki Tamura, Tetsuo Seki, T. Uda, S. Yamamoto, Yasuhiko Takeiri, Kunizo Ohkubo, T. Ozaki, P. Goncharov, T. Saida, Masaki Osakabe, Y. Nakamura, Byron J. Peterson, Yuki Torii, Takashi Notake, Shigeru Inagaki, Ryuichi Sakamoto, Osamu Kaneko, Katsuyoshi Tsumori, Kuninori Sato, Akio Sagara, K. Nishimura, Y. Xu, Takashi Shimozuma, Kazumichi Narihara, Yasuji Hamada, Ryuhei Kumazawa, Katsunori Ikeda, Tokihiko Tokuzawa, Takashi Mutoh, Shin Kubo, Tomohiro Morisaki, Akio Komori, S. Murakami, Mikiro Yoshinuma, M. Sato, Mamoru Shoji, Katsumi Ida, S. Morita, K.Y. Watanabe, Satoshi Ohdachi, Kimitaka Itoh, Sadatsugu Muto, Motoshi Goto, Satoru Sakakibara, Suguru Masuzaki, Yoshio Nagayama, K. Saito, Ichihiro Yamada, T. Watari, K. V. Khlopenkov, Yoshiro Narushima, and Yoshihide Oka

Subjects
Nuclear and High Energy Physics, Range (particle radiation), Materials science, chemistry.chemical_element, Magnetic confinement fusion, Condensed Matter Physics, Ion, Large Helical Device, chemistry, Plasma diagnostics, Atomic physics, Helium, Beam (structure), Doppler broadening
Abstract

Ion heating experiments have been carried out in the large helical device using ECH (82.5, 84.0, 168 GHz, ≤1 MW), ICRF (38.5 MHz, ≤2.7 MW) and NBI (H° beam: 160 keV, ≤9 MW). The central ion temperature has been observed from the Doppler broadening of Ti XXI (2.61 A) and Ar XVII (3.95 A) x-ray lines, which are measured using a newly installed crystal spectrometer with a charge-coupled device. Recently, in ECH discharges, on-axis heating became possible. As a result, a high Te(0) of 6–10 keV and a high ion temperature of 2.2 keV were obtained at ne = 0.6×1013 cm−3. A clear increment of Ti was also observed with the enhancement of the electron–ion energy flow when the ECH pulse was added to the NBI discharge. These results demonstrate the feasibility towards ECH ignition. A clear Ti increment was observed also in ICRF discharges at low density ranges of (0.4–0.6)×1013 cm−3 with appearance of a new operational range of Ti(0) = 2.8 keV > Te(0) = 1.9 keV. In low power ICRF heating (1 MW), the fraction of bulk ion heating is estimated to be 60% of the total ICRF input power, which means Pi>Pe. Higher Ti(0), up to 3.5 keV, was obtained for a combined heating of NBI ( Te(0), whereas the Ti(0) remained at relatively low values of 2 keV in H2 and He NBI discharges due to less Pi. The main reasons for the high Ti achievement in the Ne discharges are: (1) 30% increment of deposition power, (2) increase in Pi/ni (five times, Pi/niPe/ne, Pi

Published
2003
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5. Ion cyclotron range of frequencies heating and high-energy particle production in the Large Helical Device

Author

T Mutoh, R Kumazawa, T Seki, K Saito, T Watari, Y Torii, N Takeuchi, T Yamamoto, F Shimpo, G Nomura, M Yokota, M Osakabe, M Sasao, S Murakami, T Ozaki, T Saida, Y.P Zhao, H Okada, Y Takase, A Fukuyama, N Ashikawa, M Emoto, H Funaba, P Goncharov, M Goto, K Ida, H Idei, K Ikeda, S Inagaki, M Isobe, O Kaneko, K Kawahata, K Khlopenkov, T Kobuchi, A Komori, A Kostrioukov, S Kubo, Y Liang, S Masuzaki, T Minami, T Mito, J Miyazawa, T Morisaki, S Morita, S Muto, Y Nagayama, Y Nakamura, H Nakanishi, K Narihara, Y Narushima, K Nishimura, N Noda, T Notake, S Ohdachi, I Ohtake, N Ohyabu, Y Oka, B.J Peterson, A Sagara, S Sakakibara, R Sakamoto, K Sato, M Sato, T Shimozuma, M Shoji, H Suzuki, Y Takeiri, N Tamura, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K.Y Watanabe, Y Xu, H Yamada, I Yamada, S Yamamoto, M Yokoyama, Y Yoshimura, M Yoshinuma, K Itoh, K Ohkubo, T Satow, S Sudo, T Uda, K Yamazaki, K Matsuoka, O Motojima, Y Hamada, and M Fujiwara

Subjects
Nuclear and High Energy Physics, Range (particle radiation), High energy particle, Materials science, Cyclotron, Magnetic confinement fusion, Plasma, Condensed Matter Physics, law.invention, Large Helical Device, Helicon, Physics::Plasma Physics, law, Dielectric heating, Atomic physics
Abstract

Significant progress has been made with ion cyclotron range of frequencies (ICRF) heating in the Large Helical Device. This is mainly due to better confinement of the helically trapped particles and less accumulation of impurities in the region of the plasma core. During the past two years, ICRF heating power has been increased from 1.35 to 2.7 MW. Various wave-mode tests were carried out using minority-ion heating, second-harmonic heating, slow-wave heating and high-density fast-wave heating at the fundamental cyclotron frequency. This fundamental heating mode extended the plasma density range of effective ICRF heating to a value of 1×1020 m−3. This use of the heating mode was its first successful application in large fusion devices. Using the minority-ion mode gave the best performance, and the stored energy reached 240 kJ using ICRF alone. This was obtained for the inward-shifted magnetic axis configuration. The improvement associated with the axis-shift was common for both bulk plasma and highly accelerated particles. For the minority-ion mode, high-energy ions up to 500 keV were observed by concentrating the heating power near the plasma axis. The confinement properties of high-energy particles were studied for different magnetic axis configurations, using the power-modulation technique. It confirmed that with the inward-shifted configuration the confinement of high-energy particles was better than with the normal configuration. By increasing the distance of the plasma to the vessel wall to about 2 cm, the impurity influx was sufficiently reduced to allow sustainment of the plasma with ICRF heating alone for more than 2 min.

Published
2003
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6. Bolometer diagnostics for one- and two-dimensional measurements of radiated power on the Large Helical Device

Author

B J Peterson, A Yu Kostrioukov, N Ashikawa, Y Liu, Yuhong Xu, M Osakabe, K Y Watanabe, T Shimozuma, S Sudo, and the LHD Experiment Group

Subjects
Physics, Resistive touchscreen, Physics::Instrumentation and Detectors, business.industry, Bolometer, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Effective radiated power, Condensed Matter Physics, law.invention, Photodiode, Large Helical Device, Optics, Nuclear Energy and Engineering, law, Extreme ultraviolet, Plasma diagnostics, business
Abstract

Bolometer diagnostics are installed on the Large Helical Device (LHD) to provide measurements of the total (broad spectrum) electromagnetic radiation emitted by the plasma. Three types of detectors are used: resistive metal film bolometers, absolute extreme ultraviolet photodiodes and infrared imaging video bolometers. Details of the installation in LHD are given for each type of detector. The detector calibration, data analysis and tomography techniques are described and compared and sample results are shown.

Published
2003
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7. Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

Author

Byron J. Peterson, Takashi Notake, Akio Komori, Mikiro Yoshinuma, M. Sato, Hideya Nakanishi, Hiroshi Idei, Y. Nakamura, Shigeru Inagaki, Masahiko Emoto, K. Yamazaki, Satoshi Ohdachi, Kimitaka Itoh, Tokihiko Tokuzawa, Takashi Mutoh, Ichihiro Yamada, T. Watari, K.Y. Watanabe, Mamoru Shoji, Katsumi Ida, Yunfeng Liang, N. Noda, T. Kobuchi, P. R. Goncharov, Y. Xu, Tsuyoshi Akiyama, Hisamichi Funaba, Shin Kubo, Hiroshi Yamada, Yasuo Yoshimura, Kenji Tanaka, H. Kawazome, Naoko Ashikawa, M. Fujiwara, Takashi Satow, Kazuo Toi, N. Takeuchi, Motoshi Goto, Satoru Sakakibara, S. Murakami, Yoshihide Oka, K. V. Khlopenkov, Yoshiro Narushima, Kazuo Kawahata, Kunizo Ohkubo, Y. Takeiri, Sadatsugu Muto, Katsuyoshi Tsumori, Takashi Minami, Hajime Suzuki, Mamiko Sasao, Tomohiro Morisaki, Yuki Torii, S. Yamamoto, Akio Sagara, Keisuke Matsuoka, Osamu Kaneko, K. Saito, Ryuhei Kumazawa, T. Ozaki, Katsunori Ikeda, J. Miyazawa, Osamu Motojima, Nobuyoshi Ohyabu, A. Kostrioukov, Masayuki Yokoyama, Kuninori Sato, H. Nozato, Kazumichi Narihara, Yasuji Hamada, Shigeru Sudo, Mitsutaka Isobe, Tetsuo Seki, S. Morita, Naoki Tamura, K. Nagaoka, Ryuichi Sakamoto, T. Uda, Takashi Shimozuma, T. Saida, T. Yamamoto, K. Nishimura, Yoshio Nagayama, M. Osakabe, and Suguru Masuzaki

Subjects
Physics, Ambipolar diffusion, chemistry.chemical_element, Electron, Plasma, Condensed Matter Physics, Neutral beam injection, Electron cyclotron resonance, Neon, Large Helical Device, chemistry, Physics::Plasma Physics, Electron temperature, Atomic physics
Abstract

An internal transport barrier (ITB) was observed in the electron temperature profile in the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)] with a centrally focused intense electron cyclotron resonance microwave heating. Inside the ITB the core electron transport was improved, and a high electron temperature, exceeding 10 keV in a low density, was achieved in a collisionless regime. The formation of the electron-ITB is correlated with the neoclassical electron root with a strong radial electric field determined by the neoclassical ambipolar flux. The direction of the tangentially injected beam-driven current has an influence on the electron-ITB formation. For the counter-injected target plasma, a steeper temperature gradient, than that for the co-injected one, was observed. As for the ion temperature, high-power NBI (neutral beam injection) heating of 9 MW has realized a central ion temperature of 5 keV with neon injection. By introducing neon gas, the NBI absorption power was increased in low-density plasmas and the direct ion heating power was much enhanced with a reduced number of ions, compared with hydrogen plasmas.

Published
2003
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8. Plasma emission tomographic reconstruction in the large helical device

Author

Yi Liu, B.J. Peterson, and A.Yu. Kostrioukov

Subjects
Physics, Tomographic reconstruction, business.industry, Plasma, Magnetic flux, Large Helical Device, Cross section (physics), Optics, Physics::Plasma Physics, Harmonics, Extreme ultraviolet, Plasma diagnostics, business, Instrumentation
Abstract

Both one-dimensional (1D) and two-dimensional (2D) tomographic reconstruction of the total radiation power distribution from the large helical device (LHD) was based on the data obtained from absolute extreme ultraviolet silicon photodiodes. Two arrays (16 and 19 channels) installed in the normal LHD cross section (constant toroidal angle) provided simple and reliable 1D poloidally symmetric radiation profile reconstruction. The data obtained from two other arrays (20 and 20 channels) were used for 2D reconstruction of the radiation distribution in a semitangential plasma cross section. Using a 2D peeling away algorithm, improved by a feedback procedure, enabled reconstruction of several Fourier harmonics at each magnetic flux surface. These measurement and analysis techniques have enabled us to visualize asymmetries in plasma emission due to pellet and gas fueling.

Published
2003
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9. Plasma performance and impurity behaviour in long pulse discharges on LHD

Author

M. Fujiwara, Kazuo Kawahata, Takashi Shimozuma, Ichihiro Yamada, T. Watari, Ryuhei Kumazawa, J. Miyazawa, Osamu Motojima, Shigeru Inagaki, T. Kobuchi, Nobuyoshi Ohyabu, K. Saito, Byron J. Peterson, Takashi Notake, Katsunori Ikeda, T. Uda, Suguru Masuzaki, S. Morita, T. Saida, Yasuo Yoshimura, Tsuyoshi Akiyama, Sadatsugu Muto, Hiroshi Idei, N. Noda, T. Yamamoto, Takashi Satow, Hisamichi Funaba, Satoshi Ohdachi, Takashi Minami, I. Ohtake, S. Okamura, Shigeru Sudo, Mamoru Shoji, Katsumi Ida, A. Kostrioukov, Mitsutaka Isobe, Masayuki Yokoyama, S. Yamamoto, Kimitaka Itoh, Y. Nakamura, Keisuke Matsuoka, Ryuichi Sakamoto, Y. Xu, Osamu Kaneko, Akio Komori, Toshiyuki Mito, Hideya Nakanishi, K. V. Khlopenkov, Mikiro Yoshinuma, Yoshiro Narushima, M. Sato, Masahiko Emoto, Naoki Tamura, Shinji Yoshimura, T. Ozaki, Satoru Sakakibara, Yuki Torii, Hajime Suzuki, Tetsuo Seki, H. Nozato, K.Y. Watanabe, K. Nishimura, Masaki Osakabe, Kuninori Sato, M. Y. Tanaka, Akio Sagara, K. Nagaoka, S. Murakami, Yoshihide Oka, Kazumichi Narihara, Yasuji Hamada, Shinsaku Imagawa, Tomohiro Morisaki, Yunfeng Liang, Yoshio Nagayama, Mamiko Sasao, K. Yamazaki, Yasuhiko Takeiri, P. R. Goncharov, Shin Kubo, Motoshi Goto, Hiroshi Yamada, Naoko Ashikawa, Kazuo Toi, Kunizo Ohkubo, Katsuyoshi Tsumori, Kenji Tanaka, H. Kawazome, N. Takeuchi, Tokihiko Tokuzawa, and Takashi Mutoh

Subjects
Convection, Superconductivity, Nuclear and High Energy Physics, Long pulse, Materials science, Hydrogen, chemistry.chemical_element, Plasma, Condensed Matter Physics, Neon, chemistry, Physics::Plasma Physics, Impurity, Condensed Matter::Superconductivity, Electric field, Atomic physics
Abstract

The superconducting machine LHD has conducted long pulse experiments for four years to achieve long-duration plasmas with high performance. The operational regime was largely extended in discharge duration and plasma density. In this paper, the plasma characteristics, in particular, plasma performance and impurity behaviour in long pulse discharges are described. Confinement studies show that global energy confinement times are comparable to those in short pulse discharges. Long sustainment of high performance plasma, which is equivalent to the previous achievement in other devices, was demonstrated. Long pulse discharges enabled us to investigate impurity behaviour in a long timescale. Intrinsic metallic impurity accumulation was observed in a narrow density window (2–3×1019 m−3) only for hydrogen discharges. Impurity transport study by using active impurity pellet injection shows a long impurity confinement time and an inward convection in the impurity accumulation window, which is consistent with the intrinsic impurity behaviour. The pulsed neon gas injection experiment shows that the neon penetration into the plasma core is caused by the inward convection due to radial electric field. Finally, impurity accumulation control with an externally induced magnetic island at the plasma edge was demonstrated.

Published
2003
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10. Bolometric images of the three-dimensional structure of asymmetric radiative collapse in LHD

Author

S. Morita, B.J. Peterson, N. Ashikawa, Masaki Osakabe, Tsuguhiro Watanabe, A.Yu. Kostrioukov, S. Sudo, Mamoru Shoji, Motoshi Goto, and Y. Xu

Subjects
Physics, Nuclear and High Energy Physics, Infrared, business.industry, Bolometer, Collapse (topology), Plasma, Fusion power, Radiation, law.invention, Nuclear physics, Large Helical Device, Optics, Nuclear Energy and Engineering, law, Radiative transfer, General Materials Science, business
Abstract

The infrared (IR) imaging bolometer has the merit of being able to measure wide two-dimensional images of the plasma radiation. Two IR imaging video bolometers (IRVB, one type of IR imaging bolometer system) were installed on the large helical device (LHD). Using these IRVBs, the asymmetric radiation collapse that is similar to the multifaceted asymmetric radiation from the edge was measured in LHD. From the results of the asymmetric collapse study in LHD, the high radiation region is localized on the inboard side and under the midplane on the vacuum vessel, but this region is not the nearest point from the plasma to the first wall. From other reports on LHD, it is written that the wall recycling is not a trigger for the asymmetric radiation onset, which is confirmed by this new result.

Published
2003
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11. Impurity radiation during ‘breathing’-like oscillations in LHD discharges using a wall limiter

Author

S. Sudo, Y. Xu, N. Ashikawa, T. Tokuzawa, Osamu Kaneko, A. Komori, Kenji Tanaka, Y. Nakamura, Satoru Sakakibara, Hiroshi Yamada, Kuninori Sato, A.Yu. Kostrioukov, S. Morita, K. Yamazaki, Motoshi Goto, Kazuo Kawahata, John Rice, Masaki Osakabe, N. Noda, B.J. Peterson, and Suguru Masuzaki

Subjects
Nuclear and High Energy Physics, Materials science, Oscillation, Divertor, Plasma, Radiation, Fusion power, Large Helical Device, Nuclear Energy and Engineering, Physics::Plasma Physics, Impurity, Limiter, General Materials Science, Atomic physics
Abstract

By changing the distribution of the coil currents in the helical coils of the large helical device (LHD) the plasma could be scraped off on the stainless steel inboard wall at the last closed flux surface, eliminating the ergodic edge region and helical divertor (HD) plasmas. During such NBI-heated discharges slow oscillations (1–2.5 Hz) have been observed in the major global parameters. These oscillations exhibit many similarities to the ‘breathing’ relaxation phenomenon observed during long pulse experiments in LHD when the divertor material was stainless steel. These similarities include a large core radiation fraction, significant radiation from the metallic impurities and dependence of the oscillation frequency on density. In contrast, discharges using the graphite HD show hollow radiation profiles and reduced levels of radiation from heavy impurities. Modeling shows that differences in the density dependence of the oscillation frequency between the wall limiter and HD cases can be attributed to differences in the impurity diffusion between the core and ergodic edge regions.

Published
2003
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12. Calibration and sensitivity of the infrared imaging video bolometer

Author

N. Ashikawa, S. Sudo, B.J. Peterson, A.Yu. Kostrioukov, and Masaki Osakabe

Subjects
Materials science, business.industry, Infrared, Bolometer, Thermal diffusivity, law.invention, Optics, law, Emissivity, Calibration, Optoelectronics, Plasma diagnostics, business, Instrumentation, Noise-equivalent power, FOIL method
Abstract

The infrared (IR) imaging video bolometer (IRVB) is an imaging bolometer which uses a large (9?cm×9?cm) thin (1 μm) gold foil and an IR camera to provide images of radiation from the plasma. Calibration of the IRVB using a lamp has been performed to compensate for any nonuniformities in the foil’s thickness and its thermal properties due to blackening of the foil with graphite to improve the IR emissivity. This calibration revealed close to expected values for the calibration coefficient proportional to the product of the thermal conductivity and the foil thickness in the central region of the foil, while these values were anomalously high near the foil edge. The calibration coefficient proportional to the thermal diffusivity is a factor of 2 smaller than the expected value at the center and drops further at the edge of the foil. Using a derived expression for the IRVB noise equivalent power, a sensitivity comparison shows the IRVB using current IR technologies to be ? 200 times less sensitive than an equivalent conventional resistive bolometer operating under ideal conditions.

Published
2003
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13. Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD

Author

Yuhong Xu, B.J. Peterson, S. Sudo, T. Tokuzawa, K. Narihara, M. Osakabe, S. Morita, M. Goto, S. Sakakibara, K. Tanaka, K. Kawahata, K. Tsumori, K. Ikeda, S. Kubo, H. Idei, J. Miyazawa, K.Y. Watanabe, K. Nishimura, A. Kostrioukov, H. Yamada, O. Kaneko, N. Ohyabu, K. Komori, and the LHD Experimental Group

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Magnetic confinement fusion, Plasma, Radiation, Condensed Matter Physics, Instability, law.invention, law, Radiative transfer, Plasma diagnostics, Atomic physics, Stellarator
Abstract

In LHD discharges, the NBI heated plasmas are terminated in two ways: (a) thermal decay (TD) after the termination of NBI and (b) radiative collapse (RC) during the NBI heating. The basic characteristics of the TD and RC discharges are compared. It is found that the decay and collapse of the plasma are mainly governed by the heating power and the plasma density. The critical density c for the collapse of RC plasmas is similar to the scaling laws obtained in other helical devices, i.e. c∝(PB/V)0.5, where P, B and V denote heating power, magnetic field and plasma volume, respectively. Moreover, measurements using multichannel bolometric diagnostics indicate that the total radiation profiles in TD and RC plasmas are usually inboard-outboard symmetric and asymmetric, respectively, at the end of the discharge. In RC discharges, the total radiation profile develops in several phases. Before the onset of the thermal instability (TI), the radiation profile is rather symmetric, while after that, the radiation profile evolves from being symmetric in the initial period towards being asymmetric eventually with high radiation on the inboard side. Corresponding variations are shown in the time evolutions of the density and temperature profiles, and a substantial contraction of the plasma column is observed immediately after TI onset. The spatial and temporal coincidence of the asymmetries in the radiation, density and temperature is similar to that observed with multifaceted asymmetric radiation from the edge (MARFE) in tokamaks. But, unlike MARFEs, the asymmetric radiation (AR) in LHD is rather transient since it appears just before the end of RC discharges. The underlying cause for the development of radiation asymmetry was investigated and compared with existing instability models. The result suggests that the high inboard radiation is a manifestation of an enhanced local thermal instability, and the AR results from asymmetric developments of TI on the inboard-outboard sides during the final stage of RC discharges.

Published
2002
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14. Role of Radial Electric Field Shear at the Magnetic Island in the Transport of Plasmas

Author

K., IDA, N., OHYABU, T., MORISAKI, Y., NAGAYAMA, S., INAGAKI, M., YOKOYAMA, K., ITOH, M., YOSHIMURA, Y., LIANG, K., NARIHARA, A.Yu., KOSTRIOUKOV, B.J., PETERSON, K., TANAKA, T., TOKUZAWA, K., KAWAHATA, H., SUZUKI, A., KOMORI, and Experimental Group, LHD

Subjects
radial electric field, spontaneous poloidal flow, transport, magnetic island, flow shear
Abstract

The structures of radial electric field and transport at the magnetic island are investigated using n/m=1/1 external perturbation coils in the Large Helical Device (LHD). The radial profiles of plasma potential, as well as the electron temperature and density, shows flattening inside the magnetic island and the large shear of the radial electric field is observed at the boundary of the magnetic island. When the current of n/m=1/1 external perturbation coils becomes large enough, the finite radial electric field appears inside the magnetic island. The abrupt appearance of plasma flow inside the magnetic island suggests the non-linearity of the viscous force at the boundary of the magnetic island. The thermal diffusivity perpendicular to the magnetic filed inside the magnetic island is estimated with the cold pulse propagation, which is produced by a tracer-encapsulated solid pellet (TESPEL). The time delay and amplitude of the electron temperature of the cold pulse show much lower thermal diffusivity inside the magnetic island (0.16 m2ls; than that outside the magnetic island (2 m2ls;, which is a clear evidence for the significant reduction of heat transport inside the magnetic island.

Published
2002

15. Local Impurity Deposition in a Magnetic Island by Means of a Tracer-Encapsulated Solid Pellet in the LHD

Author

Lhd experimental groups, Akio Komori, K. V. Khlopenkov, Yoshio Nagayama, Shigeru Sudo, Kazuo Kawahata, Hajime Suzuki, Naoki Tamura, A. Kostrioukov, Tomohiro Morisaki, Shigeru Inagaki, Byron J. Peterson, Nobuyoshi Ohyabu, and Katsumi Ida

Subjects
Large Helical Device, Materials science, Radiometer, Nuclear magnetic resonance, Physics::Instrumentation and Detectors, Impurity, TRACER, Pellet, Silicon photodiode, Ultra violet, Molecular physics
Abstract

Local impurity deposition in the n/m = 1/1 magnetic island, which is expanded by the external perturbation coils, has been obtained by means of the tracer-encapsulated solid pellet in the Large Helical Device. The differences of the local deposition of the tracer between inside the magnetic island and outside that were clearly observed by both the absolute extreme ultra violet silicon photodiode arrays and the ECE radiometer.

Published
2002
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16. Analysis of images of radiation due to plasma-limiter interaction

Author

Peterson, Byron J., Ashikawa, Naoko, Kostrioukov, Artem Yu., Nishimura, Kiyohiko, Kojima, Haruki, and Sudo, Shigeru

Subjects
Infrared imaging -- Research, Plasma confinement -- Research, Radiation -- Measurement, Business, Chemistry, Electronics, Electronics and electrical industries
Abstract

Images of radiation due to plasma interaction with limiting surfaces in the Large Helical Device are presented with an explanation of the diagnostic and the data analysis technique. The images are made using an 10 x 14 pixel infrared imaging video bolometer with a 15-Hz frame rate and a sensitivity of 0.5 mW/[cm.sup.2]. Data from experiments using a wall limiter and an insertable limiter show the localization of the radiation source near the limiting surface. Index Terms--Bolometer, imaging bolometer, infrared camera, large helical device, limiter, plasma radiation.

Published
2002

17. Plasma bolometry using a multislit shutter with piezoelectric actuator

Author

Andrew A. Outkine, P. G. Gabdullin, B.V. Kuteev, Artem Yu. Kostrioukov, and V. G. Kapralov

Subjects
Materials science, business.industry, Amplifier, Bolometer, Piezoelectricity, law.invention, Optics, law, Modulation, Shutter, Plasma diagnostics, business, Actuator, Instrumentation, Frequency modulation
Abstract

We offer to apply a shutter with a piezoelectric bimorph actuator as a modulator of radiation and particle fluxes. Such shutters may be useful to provide measurements in steady state regimes of tokamaks and stellarators because they allow one to avoid amplifier drifts and to simplify diagnostics calibration. Signal modulation makes it possible to apply the lock-in amplification technique, increasing the sensitivity and reducing the neutron doze collected by sensors. Experiments with pyroelectric sensors (LiTaO3) at 350 Hz modulation frequency have demonstrated the detection limit at 30 Hz equal to 15 μW/cm2, which is comparable to metallic bolometers.

Published
2004
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18. Analysis of images of radiation due to plasma-limiter interaction

Author

K. Nishimura, A.Yu. Kostrioukov, B.J. Peterson, S. Sudo, N. Ashikawa, and H. Kojima

Subjects
Physics, Nuclear and High Energy Physics, business.industry, Infrared, Bolometer, Plasma, Radiation, Condensed Matter Physics, Frame rate, law.invention, Large Helical Device, Optics, law, Limiter, Plasma diagnostics, business
Abstract

Images of radiation due to plasma interaction with radiation due to plasma-limiter interaction limiting surfaces in the Large Helical Device are presented with an explanation of the diagnostic and the data analysis technique. The images are made using an 10/spl times/14 pixel infrared imaging video bolometer with a 15-Hz frame rate and a sensitivity of 0.5 mW/cm/sup 2/. Data from experiments using a wall limiter and an insertable limiter show the localization of the radiation source near the limiting surface.

Published
2002
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19. ICRF Heating and High Energy Particle Production in the Large Helical Device

Author

Mutoh, T., Kumazawa, R., Seki, T., Saito, K., Watari, T., Torii, Y., Takeuchi, N., Yamamoto, T., Osakabe, M., Sasao, M., Murakami, S., Ozaki, T., Saida, T., Zhao, Y. P., Okada, H., Takase, Y., Fukuyama, A., Ashikawa, N., Emoto, M., Funaba, H., Goncharov, P., Goto, M., Ida, K., Idei, H., Ikeda, K., Inagaki, S., Isobe, M., Kaneko, O., Kawahata, K., Khlopenkov, K., Kobuchi, T., Komori, A., Kostrioukov, A., Kubo, S., Liang, Y., Masuzaki, S., Minami, T., Mito, T., Miyazawa, J., Morisaki, T., Morita, S., Muto, S., Nagayama, Y., Nakamura, Y., Nakanishi, H., Narihara, K., Narushima, Y., Nishimura, K., Noda, N., Notake, T., Ohdachi, S., Ohtake, I., Ohyabu, N., Oka, Y., Peterson, B. J., Sagara, A., Sakakibara, S., Sakamoto, R., Sato, K., Sato, M., Shimozuma, T., Shoji, M., Suzuki, H., Takeiri, Y., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Tsumori, K., Watanabe, K. Y., Xu, Y., Yamada, H., Yamada, I., Yamamoto, S., Yokoyama, M., Yoshimura, Y., Yoshinuma, M., Itoh, K., Ohkubo, K., Satow, T., Sudo, S., Uda, T., Yamazaki, K., Matsuoka, K., Motojima, O., Hamada, Y., Fujiwara, M., Mutoh, T., Kumazawa, R., Seki, T., Saito, K., Watari, T., Torii, Y., Takeuchi, N., Yamamoto, T., Osakabe, M., Sasao, M., Murakami, S., Ozaki, T., Saida, T., Zhao, Y. P., Okada, H., Takase, Y., Fukuyama, A., Ashikawa, N., Emoto, M., Funaba, H., Goncharov, P., Goto, M., Ida, K., Idei, H., Ikeda, K., Inagaki, S., Isobe, M., Kaneko, O., Kawahata, K., Khlopenkov, K., Kobuchi, T., Komori, A., Kostrioukov, A., Kubo, S., Liang, Y., Masuzaki, S., Minami, T., Mito, T., Miyazawa, J., Morisaki, T., Morita, S., Muto, S., Nagayama, Y., Nakamura, Y., Nakanishi, H., Narihara, K., Narushima, Y., Nishimura, K., Noda, N., Notake, T., Ohdachi, S., Ohtake, I., Ohyabu, N., Oka, Y., Peterson, B. J., Sagara, A., Sakakibara, S., Sakamoto, R., Sato, K., Sato, M., Shimozuma, T., Shoji, M., Suzuki, H., Takeiri, Y., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Tsumori, K., Watanabe, K. Y., Xu, Y., Yamada, H., Yamada, I., Yamamoto, S., Yokoyama, M., Yoshimura, Y., Yoshinuma, M., Itoh, K., Ohkubo, K., Satow, T., Sudo, S., Uda, T., Yamazaki, K., Matsuoka, K., Motojima, O., Hamada, Y., and Fujiwara, M.

Abstract

Significant progress has been made with lon-Cyclotron Range-of-Frequencies (lCRF) heating in the Large Helical Device (LHD). This is mainly due to better confinement of the helically trapped particles, and less accumulation of impurities in the region of the plasma core. During the past two years, ICRF heating power has been increased from 1.35 MW to 2.7 MW. Various wave-mode tests were carried out using minority-ion heating, second-harmonic heating, slow-wave heating, and high-density fast-wave heating at the fundamental cyclotron frequency. This fundamental heating mode extended the plasma-density range of effective ICRF heating to a value of 1 x 10^20 m^-3. This was the first successful result of this geating mode in large fusion devices. Using the minority-ion mode gave the best performance, and the stored energy reached 240 kJ using ICRF alone. This was obtained for the inward-shifted magnetic axis configuration. The improvement associated with the axis shift was common to both bulk plasma and highly accelerated particles. For the minority-ion mode, high-energy ions up to 500 keV were observed by concentrating the heating power near the plasma axis. The confinement properties of high-energy particles were studied for different magnetic axis configurations using the power-modulation technique. It confirmed that the confimement of high-energy particles with the inward-shifted configuration was better than that with the normal configuration. The impurity problem was not serious when the plasma boundary was sufficiently far from the chamber wal1. By reducing the impurity problem, it was possible to sustain the plasma for more than two minutes using ICRF alone.

Published
2002

20. Radiation Losses Studies with Pyroelectric Bolometer

Author

Kapralov, V.G., primary, Smirnov, A.S., additional, Kuteev, B.V., additional, Gusev, V.K., additional, Dyachenko, V.V., additional, Gabdullin, P.G., additional, Kostrioukov, A.Yu., additional, Lashkul, S.I., additional, Minaev, V.B., additional, Mineev, A.B., additional, Sakharov, N.V., additional, Voronin, A.V., additional, Shesterikov, I.N., additional, and Moseev, D.S., additional

Published
2005
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21. Radial electric field and transport near the rational surface and the magnetic island in LHD

Author

Ida, K, primary, Inagaki, S, additional, Tamura, N, additional, Morisaki, T, additional, Ohyabu, N, additional, Khlopenkov, K, additional, Sudo, S, additional, Watanabe, K, additional, Yokoyama, M, additional, Shimozuma, T, additional, Takeiri, Y, additional, Itoh, K, additional, Yoshinuma, M, additional, Liang, Y, additional, Narihara, K, additional, Tanaka, K, additional, Nagayama, Y, additional, Tokuzawa, T, additional, Kawahata, K, additional, Suzuki, H, additional, Komori, A, additional, Akiyama, T, additional, Ashikawa, N, additional, Emoto, M, additional, Funaba, H, additional, Goncharov, P, additional, Goto, M, additional, Idei, H, additional, Ikeda, K, additional, Isobe, M, additional, Kaneko, O, additional, Kawazome, H, additional, Kobuchi, T, additional, Kostrioukov, A, additional, Kubo, S, additional, Kumazawa, R, additional, Masuzaki, S, additional, Minami, T, additional, Miyazawa, J, additional, Morita, S, additional, Murakami, S, additional, Muto, S, additional, Mutoh, T, additional, Nakamura, Y, additional, Nakanishi, H, additional, Narushima, Y, additional, Nishimura, K, additional, Noda, N, additional, Notake, T, additional, Nozato, H, additional, Ohdachi, S, additional, Oka, Y, additional, Osakabe, M, additional, Ozaki, T, additional, Peterson, B.J, additional, Sagara, A, additional, Saida, T, additional, Saito, K, additional, Sakakibara, S, additional, Sakamoto, R, additional, Sasao, M, additional, Sato, K, additional, Sato, M, additional, Seki, T, additional, Shoji, M, additional, Takeuchi, N, additional, Toi, K, additional, Torii, Y, additional, Tsumori, K, additional, Watari, T, additional, Xu, Y, additional, Yamada, H, additional, Yamada, I, additional, Yamamoto, S, additional, Yamamoto, T, additional, Yoshimura, Y, additional, Ohtake, I, additional, Ohkubo, K, additional, Mito, T, additional, Satow, T, additional, Uda, T, additional, Yamazaki, K, additional, Matsuoka, K, additional, Motojima, O, additional, and Fujiwara, M, additional

Published
2004
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22. Recent advances in the LHD experiment

Author

Motojima, O, primary, Ohyabu, N, additional, Komori, A, additional, Kaneko, O, additional, Yamada, H, additional, Kawahata, K, additional, Nakamura, Y, additional, Ida, K, additional, Akiyama, T, additional, Ashikawa, N, additional, Cooper, W.A, additional, Ejiri, A, additional, Emoto, M, additional, Ezumi, N, additional, Funaba, H, additional, Fukuyama, A, additional, Goncharov, P, additional, Goto, M, additional, Idei, H, additional, Ikeda, K, additional, Inagaki, S, additional, Isobe, M, additional, Kado, S, additional, Kawazome, H, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Kondo, K, additional, Kostrioukov, A, additional, Kubo, S, additional, Kumazawa, R, additional, Liang, Y, additional, Lyon, J.F, additional, Mase, A, additional, Masuzaki, S, additional, Minami, T, additional, Miyazawa, J, additional, Morisaki, T, additional, Morita, S, additional, Murakami, S, additional, Muto, S, additional, Mutoh, T, additional, Nagaoka, K, additional, Nagayama, Y, additional, Nakajima, N, additional, Nakamura, K, additional, Nakanishi, H, additional, Narihara, K, additional, Narushima, Y, additional, Nishimura, K, additional, Nishino, N, additional, Noda, N, additional, Notake, T, additional, Nozato, H, additional, Ohdachi, S, additional, Oka, Y, additional, Okada, H, additional, Okamura, S, additional, Osakabe, M, additional, Ozaki, T, additional, Peterson, B.J, additional, Sagara, A, additional, Saida, T, additional, Saito, K, additional, Sakakibara, S, additional, Sakamoto, M, additional, Sakamoto, R, additional, Sasao, M, additional, Sato, K, additional, Sato, M, additional, Seki, T, additional, Shimozuma, T, additional, Shoji, M, additional, Suzuki, H, additional, Takeiri, Y, additional, Takeuchi, N, additional, Tamura, N, additional, Tanaka, K, additional, Tanaka, M.Y, additional, Teramachi, Y, additional, Toi, K, additional, Tokuzawa, T, additional, Tomota, Y, additional, Torii, Y, additional, Tsumori, K, additional, Watanabe, K.Y, additional, Watari, T, additional, Xu, Y, additional, Yamada, I, additional, Yamamoto, S, additional, Yamamoto, T, additional, Yokoyama, M, additional, Yoshimura, S, additional, Yoshimura, Y, additional, Yoshinuma, M, additional, Asakura, N, additional, Fujita, T, additional, Fukuda, T, additional, Hatae, T, additional, Higashijima, S, additional, Isayama, A, additional, Kamada, Y, additional, Kubo, H, additional, Kusama, Y, additional, Miura, Y, additional, Nakano, T, additional, Ninomiya, H, additional, Oikawa, T, additional, Oyama, N, additional, Sakamoto, Y, additional, Shinohara, K, additional, Suzuki, T, additional, Takenaga, H, additional, Ushigusa, K, additional, Hino, T, additional, Ichimura, M, additional, Takase, Y, additional, Sano, F, additional, Zushi, H, additional, Satow, T, additional, Imagawa, S, additional, Mito, T, additional, Ohtake, I, additional, Uda, T, additional, Itoh, K, additional, Ohkubo, K, additional, Sudo, S, additional, Yamazaki, K, additional, Matsuoka, K, additional, Hamada, Y, additional, and Fujiwara, M, additional

Published
2003
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23. Recent diagnostic developments on LHD

Author

Sudo, S, primary, Nagayama, Y, additional, Peterson, B J, additional, Kawahata, K, additional, Akiyama, T, additional, Ashikawa, N, additional, Emoto, M, additional, Goto, M, additional, Hamada, Y, additional, Ida, K, additional, Ido, T, additional, Iguchi, H, additional, Inagaki, S, additional, Isobe, M, additional, Kobuchi, T, additional, Komori, A, additional, Liang, Y, additional, Masuzaki, S, additional, Minami, T, additional, Morisaki, T, additional, Morita, S, additional, Muto, S, additional, Nakamura, Y, additional, Nakanishi, H, additional, Narushima, M, additional, Narihara, K, additional, Nishiura, M, additional, Nishizawa, A, additional, Ohdachi, S, additional, Osakabe, M, additional, Ozaki, T, additional, Pavlichenko, R O, additional, Sakakibara, S, additional, Sato, K, additional, Shoji, M, additional, Tamura, N, additional, Tanaka, K, additional, Toi, K, additional, Tokuzawa, T, additional, Watanabe, K Y, additional, Watanabe, T, additional, Yamada, H, additional, Yamada, I, additional, Yoshinuma, M, additional, Goncharov, P, additional, Kalinina, D, additional, Kanaba, T, additional, Sugimoto, T, additional, Ejiri, A, additional, Ono, Y, additional, Hojo, H, additional, Ishii, K, additional, Iwama, N, additional, Kogi, Y, additional, Mase, A, additional, Sakamoto, M, additional, Kondo, K, additional, Nagasaki, H, additional, Yamamoto, S, additional, Nishino, N, additional, Okajima, S, additional, Saida, T, additional, Sasao, M, additional, Takeda, T, additional, Tsuji-Iio, S, additional, Darrow, D S, additional, Takahashi, H, additional, Liu, Y, additional, Lyon, J F, additional, Kostrioukov, A Yu, additional, Kuteev, V B, additional, Sergeev, V, additional, Viniar, I, additional, Krasilnikov, A V, additional, Sanin, A, additional, Vyacheslavov, L N, additional, Stutman, D, additional, Finkenthal, M, additional, Motojima, O, additional, and Group, LHD, additional

Published
2003
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24. Experimental study on ion temperature behaviours in ECH, ICRF and NBI H2, He and Ne discharges of the Large Helical Device

Author

Morita, S, primary, Goto, M, additional, Takeiri, Y, additional, Miyazawa, J, additional, Murakami, S, additional, Narihara, K, additional, Osakabe, M, additional, Yamazaki, K, additional, Akiyama, T, additional, Ashikawa, N, additional, Emoto, M, additional, Fujiwara, M, additional, Funaba, H, additional, Goncharov, P, additional, Hamada, Y, additional, Ida, K, additional, Idei, H, additional, Ido, T, additional, Ikeda, K, additional, Inagaki, S, additional, Isobe, M, additional, Itoh, K, additional, Kaneko, O, additional, Kawahata, K, additional, Kawazome, H, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Komori, A, additional, Kostrioukov, A, additional, Kubo, S, additional, Kumazawa, R, additional, Liang, Y, additional, Masuzaki, S, additional, Matsuoka, K, additional, Minami, T, additional, Morisaki, T, additional, Motojima, O, additional, Muto, S, additional, Mutoh, T, additional, Nagayama, Y, additional, Nakamura, Y, additional, Nakanishi, H, additional, Narushima, Y, additional, Nishimura, K, additional, Nishizawa, A, additional, Noda, N, additional, Notake, T, additional, Nozato, H, additional, Ohdachi, S, additional, Ohkubo, K, additional, Ohyabu, N, additional, Oka, Y, additional, Ozaki, T, additional, Peterson, B.J, additional, Sagara, A, additional, Saida, T, additional, Saito, K, additional, Sakakibara, S, additional, Sakamoto, R, additional, Sasao, M, additional, Sato, K, additional, Sato, M, additional, Satow, T, additional, Seki, T, additional, Shimozuma, T, additional, Shoji, M, additional, Sudo, S, additional, Suzuki, H, additional, Takeuchi, N, additional, Tamura, N, additional, Tanaka, K, additional, Toi, K, additional, Tokuzawa, T, additional, Torii, Y, additional, Tsumori, K, additional, Uda, T, additional, Watanabe, K.Y, additional, Watari, T, additional, Xu, Y, additional, Yamada, H, additional, Yamada, I, additional, Yamamoto, S, additional, Yamamoto, T, additional, Yokoyama, M, additional, Yoshimura, Y, additional, and Yoshinuma, M, additional

Published
2003
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25. Ion cyclotron range of frequencies heating and high-energy particle production in the Large Helical Device

Author

Mutoh, T, primary, Kumazawa, R, additional, Seki, T, additional, Saito, K, additional, Watari, T, additional, Torii, Y, additional, Takeuchi, N, additional, Yamamoto, T, additional, Shimpo, F, additional, Nomura, G, additional, Yokota, M, additional, Osakabe, M, additional, Sasao, M, additional, Murakami, S, additional, Ozaki, T, additional, Saida, T, additional, Zhao, Y.P, additional, Okada, H, additional, Takase, Y, additional, Fukuyama, A, additional, Ashikawa, N, additional, Emoto, M, additional, Funaba, H, additional, Goncharov, P, additional, Goto, M, additional, Ida, K, additional, Idei, H, additional, Ikeda, K, additional, Inagaki, S, additional, Isobe, M, additional, Kaneko, O, additional, Kawahata, K, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Komori, A, additional, Kostrioukov, A, additional, Kubo, S, additional, Liang, Y, additional, Masuzaki, S, additional, Minami, T, additional, Mito, T, additional, Miyazawa, J, additional, Morisaki, T, additional, Morita, S, additional, Muto, S, additional, Nagayama, Y, additional, Nakamura, Y, additional, Nakanishi, H, additional, Narihara, K, additional, Narushima, Y, additional, Nishimura, K, additional, Noda, N, additional, Notake, T, additional, Ohdachi, S, additional, Ohtake, I, additional, Ohyabu, N, additional, Oka, Y, additional, Peterson, B.J, additional, Sagara, A, additional, Sakakibara, S, additional, Sakamoto, R, additional, Sato, K, additional, Sato, M, additional, Shimozuma, T, additional, Shoji, M, additional, Suzuki, H, additional, Takeiri, Y, additional, Tamura, N, additional, Tanaka, K, additional, Toi, K, additional, Tokuzawa, T, additional, Tsumori, K, additional, Watanabe, K.Y, additional, Xu, Y, additional, Yamada, H, additional, Yamada, I, additional, Yamamoto, S, additional, Yokoyama, M, additional, Yoshimura, Y, additional, Yoshinuma, M, additional, Itoh, K, additional, Ohkubo, K, additional, Satow, T, additional, Sudo, S, additional, Uda, T, additional, Yamazaki, K, additional, Matsuoka, K, additional, Motojima, O, additional, Hamada, Y, additional, and Fujiwara, M, additional

Published
2003
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26. Impact of heat deposition profile on global confinement of NBI heated plasmas in the LHD

Author

Yamada, H, primary, Murakami, S, additional, Yamazaki, K, additional, Kaneko, O, additional, Miyazawa, J, additional, Sakamoto, R, additional, Watanabe, K.Y, additional, Narihara, K, additional, Tanaka, K, additional, Sakakibara, S, additional, Osakabe, M, additional, Peterson, B.J, additional, Morita, S, additional, Ida, K, additional, Inagaki, S, additional, Masuzaki, S, additional, Morisaki, T, additional, Rewoldt, G, additional, Sugama, H, additional, Nakajima, N, additional, Cooper, W.A, additional, Akiyama, T, additional, Ashikawa, N, additional, Emoto, M, additional, Funaba, H, additional, Goncharov, P, additional, Goto, M, additional, Idei, H, additional, Ikeda, K, additional, Isobe, M, additional, Kawahata, K, additional, Kawazome, H, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Komori, A, additional, Kostrioukov, A, additional, Kubo, S, additional, Kumazawa, R, additional, Liang, Y, additional, Minami, T, additional, Muto, S, additional, Mutoh, T, additional, Nagayama, Y, additional, Nakamura, Y, additional, Nakanishi, H, additional, Narushima, Y, additional, Nishimura, K, additional, Noda, N, additional, Notake, T, additional, Nozato, H, additional, Ohdachi, S, additional, Ohyabu, N, additional, Oka, Y, additional, Ozaki, T, additional, Sagara, A, additional, Saida, T, additional, Saito, K, additional, Sasao, M, additional, Sato, K, additional, Sato, M, additional, Seki, T, additional, Shimozuma, T, additional, Shoji, M, additional, Suzuki, H, additional, Takeiri, Y, additional, Takeuchi, N, additional, Tamura, N, additional, Toi, K, additional, Tokuzawa, T, additional, Torii, Y, additional, Tsumori, K, additional, Watanabe, T, additional, Watari, T, additional, Xu, Y, additional, Yamada, I, additional, Yamamoto, S, additional, Yamamoto, T, additional, Yokoyama, M, additional, Yoshimura, Y, additional, Yoshinuma, M, additional, Mito, T, additional, Itoh, K, additional, Ohkubo, K, additional, Ohtake, I, additional, Satow, T, additional, Sudo, S, additional, Uda, T, additional, Matsuoka, K, additional, and Motojima, O, additional

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2003
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28. Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device

Author

Takeiri, Y., primary, Shimozuma, T., additional, Kubo, S., additional, Morita, S., additional, Osakabe, M., additional, Kaneko, O., additional, Tsumori, K., additional, Oka, Y., additional, Ikeda, K., additional, Nagaoka, K., additional, Ohyabu, N., additional, Ida, K., additional, Yokoyama, M., additional, Miyazawa, J., additional, Goto, M., additional, Narihara, K., additional, Yamada, I., additional, Idei, H., additional, Yoshimura, Y., additional, Ashikawa, N., additional, Emoto, M., additional, Funaba, H., additional, Inagaki, S., additional, Isobe, M., additional, Kawahata, K., additional, Khlopenkov, K., additional, Kobuchi, T., additional, Komori, A., additional, Kostrioukov, A., additional, Kumazawa, R., additional, Liang, Y., additional, Masuzaki, S., additional, Minami, T., additional, Morisaki, T., additional, Murakami, S., additional, Muto, S., additional, Mutoh, T., additional, Nagayama, Y., additional, Nakamura, Y., additional, Nakanishi, H., additional, Narushima, Y., additional, Nishimura, K., additional, Noda, N., additional, Ohdachi, S., additional, Ozaki, T., additional, Peterson, B. J., additional, Sagara, A., additional, Saito, K., additional, Sakakibara, S., additional, Sakamoto, R., additional, Sasao, M., additional, Sato, K., additional, Sato, M., additional, Seki, T., additional, Shoji, M., additional, Suzuki, H., additional, Tamura, N., additional, Tanaka, K., additional, Toi, K., additional, Tokuzawa, T., additional, Watanabe, K. Y., additional, Watari, T., additional, Xu, Y., additional, Yamada, H., additional, Yoshinuma, M., additional, Itoh, K., additional, Ohkubo, K., additional, Satow, T., additional, Sudo, S., additional, Uda, T., additional, Yamazaki, K., additional, Hamada, Y., additional, Matsuoka, K., additional, Motojima, O., additional, Fujiwara, M., additional, Notake, T., additional, Takeuchi, N., additional, Torii, Y., additional, Yamamoto, S., additional, Yamamoto, T., additional, Akiyama, T., additional, Goncharov, P., additional, Saida, T., additional, Kawazome, H., additional, and Nozato, H., additional

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2003
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29. Recent results from the Large Helical Device

Author

Komori, A, primary, Ohyabu, N, additional, Yamada, H, additional, Kaneko, O, additional, Kawahata, K, additional, Ida, K, additional, Nakamura, Y, additional, Akiyama, T, additional, Ashikawa, N, additional, Emoto, M, additional, Funaba, H, additional, Goncharov, P, additional, Goto, M, additional, Idei, H, additional, Ikeda, K, additional, Inagaki, S, additional, Isobe, M, additional, Kawazome, H, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Kostrioukov, A, additional, Kubo, S, additional, Kumazawa, R, additional, Liang, Y, additional, Masuzaki, S, additional, Minami, T, additional, Miyazawa, J, additional, Morisaki, T, additional, Morita, S, additional, Murakami, S, additional, Muto, S, additional, Mutoh, T, additional, Nagayama, Y, additional, Nakanishi, H, additional, Narihara, K, additional, Narushima, Y, additional, Nishimura, K, additional, Noda, N, additional, Notake, T, additional, Nozato, H, additional, Ohdachi, S, additional, Oka, Y, additional, Osakabe, M, additional, Ozaki, T, additional, Peterson, B J, additional, Sagara, A, additional, Saida, T, additional, Saito, K, additional, Sakakibara, S, additional, Sakamoto, R, additional, Sasao, M, additional, Sato, K, additional, Sato, M, additional, Seki, T, additional, Shimozuma, T, additional, Shoji, M, additional, Suzuki, H, additional, Takeiri, Y, additional, Takeuchi, N, additional, Tamura, N, additional, Tanaka, K, additional, Toi, K, additional, Tokuzawa, T, additional, Torii, Y, additional, Tsumori, K, additional, Watanabe, K Y, additional, Watari, T, additional, Xu, Y, additional, Yamada, I, additional, Yamamoto, S, additional, Yamamoto, T, additional, Yokoyama, M, additional, Yoshimura, Y, additional, Yoshinuma, M, additional, Itoh, K, additional, Matsuoka, K, additional, Ohkubo, K, additional, Satow, T, additional, Sudo, S, additional, Uda, T, additional, Yamazaki, K, additional, Motojima, O, additional, and Fujiwara, M, additional

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2003
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30. Plasma performance and impurity behaviour in long pulse discharges on LHD

Author

Nakamura, Y, primary, Takeiri, Y, additional, Kumazawa, R, additional, Osakabe, M, additional, Seki, T, additional, Peterson, B.J, additional, Ida, K, additional, Funaba, H, additional, Yokoyama, M, additional, Tamura, N, additional, Komori, A, additional, Morita, S, additional, Sato, K, additional, Narihara, K, additional, Inagaki, S, additional, Tokuzawa, T, additional, Masuzaki, S, additional, Miyazawa, J, additional, Noda, N, additional, Mutoh, T, additional, Shimozuma, T, additional, Kawahata, K, additional, Oka, Y, additional, Suzuki, H, additional, Ohyabu, N, additional, Akiyama, T, additional, Ashikawa, N, additional, Emoto, M, additional, Goncharov, P, additional, Goto, M, additional, Idei, H, additional, Ikeda, K, additional, Imagawa, S, additional, Isobe, M, additional, Kaneko, O, additional, Kawazome, H, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Kostrioukov, A, additional, Kubo, S, additional, Liang, Y, additional, Minami, T, additional, Morisaki, T, additional, Murakami, S, additional, Muto, S, additional, Nagaoka, K, additional, Nagayama, Y, additional, Nakanishi, H, additional, Narushima, Y, additional, Nishimura, K, additional, Notake, T, additional, Nozato, H, additional, Ohdachi, S, additional, Okamura, S, additional, Ozaki, T, additional, Sagara, A, additional, Saida, T, additional, Saito, K, additional, Sakakibara, S, additional, Sakamoto, R, additional, Sasao, M, additional, Sato, M, additional, Shoji, M, additional, Takeuchi, N, additional, Tanaka, K, additional, Tanaka, M.Y, additional, Toi, K, additional, Torii, Y, additional, Tsumori, K, additional, Watanabe, K.Y, additional, Watari, T, additional, Xu, Y, additional, Yamada, H, additional, Yamada, I, additional, Yamamoto, S, additional, Yamamoto, T, additional, Yoshimura, S, additional, Yoshimura, Y, additional, Yoshinuma, M, additional, Itoh, K, additional, Mito, T, additional, Ohkubo, K, additional, Ohtake, I, additional, Satow, T, additional, Sudo, S, additional, Uda, T, additional, Yamazaki, K, additional, Matsuoka, K, additional, Motojima, O, additional, Hamada, Y, additional, and Fujiwara, M, additional

Published
2003
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32. Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD

Author

Xu, Yuhong, primary, Peterson, B.J., additional, Sudo, S., additional, Tokuzawa, T., additional, Narihara, K., additional, Osakabe, M., additional, Morita, S., additional, Goto, M., additional, Sakakibara, S., additional, Tanaka, K., additional, Kawahata, K., additional, Tsumori, K., additional, Ikeda, K., additional, Kubo, S., additional, Idei, H., additional, Miyazawa, J., additional, Watanabe, K.Y., additional, Nishimura, K., additional, Kostrioukov, A., additional, Yamada, H., additional, Kaneko, O., additional, Ohyabu, N., additional, Komori, K., additional, and Group, the LHD Experimental, additional

Published
2002
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33. Island Dynamics in the Large-Helical-Device Plasmas

Author

Ohyabu, N., primary, Ida, K., additional, Morisaki, T., additional, Narihara, K., additional, Komori, A., additional, Watanabe, K., additional, Narushima, Y., additional, Nagayama, Y., additional, Shoji, M., additional, Ashikawa, N., additional, Emoto, M., additional, Funaba, H., additional, Goto, M., additional, Idei, H., additional, Ikeda, K., additional, Inagaki, S., additional, Inoue, N., additional, Isobe, M., additional, Khlopenkov, K., additional, Kobuchi, T., additional, Kostrioukov, A., additional, Kubo, S., additional, Kumazawa, R., additional, Liang, Y., additional, Masuzaki, S., additional, Minami, T., additional, Miyazawa, J., additional, Morita, S., additional, Muto, S., additional, Mutoh, T., additional, Murakami, S., additional, Nakamura, Y., additional, Nakanishi, H., additional, Nishimura, K., additional, Noda, N., additional, Notake, T., additional, Ohkubo, K., additional, Ohdachi, S., additional, Oka, Y., additional, Osakabe, M., additional, Ozaki, T., additional, Peterson, B. J., additional, Sakamoto, R., additional, Sakakibara, S., additional, Sagara, A., additional, Saito, K., additional, Sasao, M., additional, Sato, K., additional, Sato, M., additional, Seki, T., additional, Shimozuma, T., additional, Sudo, S., additional, Suzuki, H., additional, Takeiri, Y., additional, Tanaka, K., additional, Tamura, N., additional, Toi, K., additional, Tokuzawa, T., additional, Torii, Y., additional, Tsumori, K., additional, Watanabe, T., additional, Yamazaki, K., additional, Yamada, I., additional, Yamamoto, S., additional, Yokoyama, M., additional, Yoshimura, Y., additional, Watari, T., additional, Xu, Y., additional, Kaneko, O., additional, Kawahata, K., additional, Yamada, H., additional, and Motojima, O., additional

Published
2002
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34. Observation of Plasma Flow at the Magnetic Island in the Large Helical Device

Author

Ida, K., primary, Ohyabu, N., additional, Morisaki, T., additional, Nagayama, Y., additional, Inagaki, S., additional, Itoh, K., additional, Liang, Y., additional, Narihara, K., additional, Kostrioukov, A. Yu., additional, Peterson, B. J., additional, Tanaka, K., additional, Tokuzawa, T., additional, Kawahata, K., additional, Suzuki, H., additional, and Komori, A., additional

Published
2001
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35. Configuration flexibility and extended regimes in Large Helical Device

Author

Yamada, H, primary, Komori, A, additional, Ohyabu, N, additional, Kaneko, O, additional, Kawahata, K, additional, Watanabe, K Y, additional, Sakakibara, S, additional, Murakami, S, additional, Ida, K, additional, Sakamoto, R, additional, Liang, Y, additional, Miyazawa, J, additional, Tanaka, K, additional, Narushima, Y, additional, Morita, S, additional, Masuzaki, S, additional, Morisaki, T, additional, Ashikawa, N, additional, Baylor, L R, additional, Cooper, W A, additional, Emoto, M, additional, Fisher, P W, additional, Funaba, H, additional, Goto, M, additional, Idei, H, additional, Ikeda, K, additional, Inagaki, S, additional, Inoue, N, additional, Isobe, M, additional, Khlopenkov, K, additional, Kobuchi, T, additional, Kostrioukov, A, additional, Kubo, S, additional, Kuroda, T, additional, Kumazawa, R, additional, Minami, T, additional, Muto, S, additional, Mutoh, T, additional, Nagayama, Y, additional, Nakajima, N, additional, Nakamura, Y, additional, Nakanishi, H, additional, Narihara, K, additional, Nishimura, K, additional, Noda, N, additional, Notake, T, additional, Ohdachi, S, additional, Oka, Y, additional, Osakabe, M, additional, Ozaki, T, additional, Peterson, B J, additional, Rewoldt, G, additional, Sagara, A, additional, Saito, K, additional, Sasao, H, additional, Sasao, M, additional, Sato, K, additional, Sato, M, additional, Seki, T, additional, Sugama, H, additional, Shimozuma, T, additional, Shoji, M, additional, Suzuki, H, additional, Takeiri, Y, additional, Tamura, N, additional, Toi, K, additional, Tokuzawa, T, additional, Torii, Y, additional, Tsumori, K, additional, Watanabe, T, additional, Yamada, I, additional, Yamamoto, S, additional, Yokoyama, M, additional, Yoshimura, Y, additional, Watari, T, additional, Xu, Y, additional, Itoh, K, additional, Matsuoka, K, additional, Ohkubo, K, additional, Satow, T, additional, Sudo, S, additional, Uda, T, additional, Yamazaki, K, additional, Motojima, O, additional, and Fujiwara, M, additional

Published
2001
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36. Plasma emission tomographic reconstruction in the large helical device.

Author

Liu, Y., Kostrioukov, A. Yu., and Peterson, B. J.

Subjects
*PHOTODIODES, *MAGNETIC flux
Abstract

Both one-dimensional (1D) and two-dimensional (2D) tomographic reconstruction of the total radiation power distribution from the large helical device (LHD) was based on the data obtained from absolute extreme ultraviolet silicon photodiodes. Two arrays (16 and 19 channels) installed in the normal LHD cross section (constant toroidal angle) provided simple and reliable 1D poloidally symmetric radiation profile reconstruction. The data obtained from two other arrays (20 and 20 channels) were used for 2D reconstruction of the radiation distribution in a semitangential plasma cross section. Using a 2D peeling away algorithm, improved by a feedback procedure, enabled reconstruction of several Fourier harmonics at each magnetic flux surface. These measurement and analysis techniques have enabled us to visualize asymmetries in plasma emission due to pellet and gas fueling. [ABSTRACT FROM AUTHOR]

Published
2003

37. Configuration flexibility and extended regimes in Large Helical Device

Author

Suguru Masuzaki, Y. Nakamura, Hiroshi Idei, Masayuki Yokoyama, Masahide Sato, K. V. Khlopenkov, T. Tokuzawa, Hajime Suzuki, T. Uda, B.J. Peterson, Osamu Kaneko, Y. Narushima, Mamiko Sasao, Tsutomu Kuroda, Larry R. Baylor, Ichihiro Yamada, K. Yamazaki, Kuninori Sato, Masami Fujiwara, T. Watari, Yuki Torii, O. Motojima, A. Kostrioukov, K. Narihara, Hideo Sugama, Motoshi Goto, Shin Kubo, Ken Matsuoka, W. A. Cooper, S. Sudo, S. Murakami, Akio Sagara, Satoru Sakakibara, T. Ozaki, M. Emoto, K. Nishimura, Hiroshi Yamada, Ryuichi Sakamoto, P. W. Fisher, Ryuhei Kumazawa, N. Inoue, K. Toi, Takashi Notake, Satoshi Ohdachi, Katsunori Ikeda, Mitsutaka Isobe, Kimitaka Itoh, S. Morita, Sadatsugu Muto, Kenji Tanaka, Yunfeng Liang, Noriyoshi Nakajima, Yoshihide Oka, Y. Takeiri, K.Y. Watanabe, Takashi Shimozuma, T. Kobuchi, Mamoru Shoji, Katsumi Ida, N. Ashikawa, Shigeru Inagaki, N. Noda, Yoshio Nagayama, Kazuo Kawahata, H. Sasao, Tsuguhiro Watanabe, T. Minami, Naoki Tamura, Takashi Mutoh, Kunizo Ohkubo, G Rewoldt, Katsuyoshi Tsumori, Masaki Osakabe, Tetsuo Seki, A. Komori, H Funaba, Kenji Saito, S. Yamamoto, Y. Xu, Tomohiro Morisaki, Hideya Nakanishi, J. Miyazawa, Nobuyoshi Ohyabu, Yasuo Yoshimura, and Takashi Satow

Subjects
Physics, Stability criterion, Ripple, Mechanics, Condensed Matter Physics, law.invention, Large Helical Device, Nuclear Energy and Engineering, law, ITER, Beta (plasma physics), Atomic physics, Magnetohydrodynamics, Scaling, Stellarator, Pressure gradient
Abstract

Recent experimental results in the Large Helical Device have indicated that a large pressure gradient can be formed beyond the stability criterion for the Mercier (high-n) mode. While the stability against an interchange mode is violated in the inward-shifted configuration due to an enhancement of the magnetic hill, the neoclassical transport and confinement of high-energy particle are, in contrast, improved by this inward shift. Mitigation of the unfavourable effects of MHD instability has led to a significant extension of the operational regime. Achievements of the stored energy of I MJ and the volume-averaged beta of 3% are representative results from this finding. A confinement enhancement factor above the international stellarator scaling ISS95 is also maintained around 1.5 towards a volume-averaged beta, (beta), of 3%. Configuration studies on confinement and MHD characteristics emphasize the superiority of the inward-shifted geometry to other geometries. The emergence of coherent modes appears to be consistent with the linear ideal MHD theory; however, the inward-shifted configuration has reduced heat transport in spite of a larger amplitude of magnetic fluctuation than the outward-shifted configuration. While neoclassical helical ripple transport becomes visible for the outward-shifted configuration in the collisionless regime, the inward-shifted configuration does not show any degradation of confinement deep in the collisionless regime (nu* < 0.1). The distinguished characteristics observed in the inward-shifted configuration help in creating a new perspective of MHD stability and related transport in net current-free plasmas. The first result of the pellet launching at different locations is also reported.

38. Radial electric field and transport near the rational surface and the magnetic island in LHD

Author

Y. Xu, Tsuyoshi Akiyama, S. Murakami, Kazumichi Narihara, T. Uda, Akio Komori, Keisuke Matsuoka, Takashi Minami, M. Sato, Sadatsugu Muto, N. Noda, Ryuichi Sakamoto, T. Yamamoto, K. Saito, Y. Nakamura, Mikirou Yoshinuma, S. Yamamoto, Hisamichi Funaba, Tokihiko Tokuzawa, Takashi Mutoh, K.Y. Watanabe, Masayuki Yokoyama, Hajime Suzuki, T. Saida, Shigeru Sudo, K. V. Khlopenkov, Motoshi Goto, Yoshiro Narushima, M. Fujiwara, T. Kobuchi, I. Ohtake, Ryuhei Kumazawa, Mitsutaka Isobe, Satoru Sakakibara, Mamiko Sasao, Toshiyuki Mito, Kunizo Ohkubo, Katsunori Ikeda, Mamoru Shoji, Kazuo Kawahata, Osamu Kaneko, Katsumi Ida, K. Yamazaki, T. Ozaki, J. Miyazawa, A. Kostrioukov, Osamu Motojima, Katsuyoshi Tsumori, Naoki Tamura, Tomohiro Morisaki, Ichihiro Yamada, T. Watari, Tetsuo Seki, H. Nozato, Satoshi Ohdachi, Kimitaka Itoh, Nobuyoshi Ohyabu, Hiroshi Yamada, Yoshihide Oka, Masaki Osakabe, Shigeru Inagaki, Hiroshi Idei, Naoko Ashikawa, Kenji Tanaka, H. Kawazome, Kazuo Toi, S. Morita, N. Takeuchi, Byron J. Peterson, Takashi Notake, Kuninori Sato, Suguru Masuzaki, Hideya Nakanishi, Masahiko Emoto, Yasuo Yoshimura, Takashi Satow, K. Nishimura, Yoshio Nagayama, Yuki Torii, Akio Sagara, Yunfeng Liang, P. R. Goncharov, Shin Kubo, Takashi Shimozuma, and Yasuhiko Takeiri

Subjects
Convection, Physics, Nuclear and High Energy Physics, Condensed matter physics, Magnetic energy, business.industry, Magnetic confinement fusion, Condensed Matter Physics, Magnetic flux, L-shell, Optics, Electric field, Magnetic pressure, Electric potential, business
Abstract

The structure of the radial electric field and heat transport at the magnetic island in the large helical device (LHD) are investigated by measuring the radial profile of the poloidal flow with charge exchange spectroscopy and measuring the time evolution of the electron temperature with ECE. A vortex-like plasma flow along the magnetic flux surface inside the magnetic island is observed when the n/m = 1/1 external perturbation field becomes large enough to increase the magnetic island width above a critical range (15–20% of minor radius) in LHD. This convective poloidal flow results in a non-flat space potential inside the magnetic island. The sign of the curvature of the space potential (∂2Φ/∂r2, where Φ is the space potential) depends on the radial electric field at the boundary of the magnetic island. The heat transport inside the magnetic island is studied with a cold pulse propagation technique. The experimental results show the existence of radial electric field shear at the boundary of the magnetic island and a reduction in heat transport at the boundary and inside the magnetic island.

39. Recent advances in the LHD experiment

Author

Tsuyoshi Akiyama, Makoto Ichimura, T. Uda, T. Saida, Nobuhiro Nishino, Mizuki Sakamoto, Motoshi Goto, N. Ashikawa, N. Noda, Kazuo Kawahata, S. Morita, Shinji Yoshimura, J. Miyazawa, Nobuyoshi Ohyabu, Hidenobu Takenaga, H. Nozato, Fumimichi Sano, O. Motojima, Satoru Sakakibara, T. Yamamoto, Shinichiro Kado, Masami Fujiwara, Takaki Hatae, Yuki Torii, H. Ninomiya, Nobuyuki Asakura, Y. Teramachi, Hideya Nakanishi, T. Tokuzawa, T. Kobuchi, Mikiro Yoshinuma, Naomichi Ezumi, K. Saito, Osamu Kaneko, B.J. Peterson, H. Kubo, Kenkichi Ushigusa, Akio Sagara, Satoshi Ohdachi, Kimitaka Itoh, T. Fukuda, H. Funaba, Atsushi Fukuyama, Ryuichi Sakamoto, Mitsutaka Isobe, Y. Hamada, S. Okamura, Yoshihide Oka, Shinsaku Imagawa, Masayuki Yokoyama, Yukio Sakamoto, Sadatsugu Muto, Masahide Sato, Akihiko Isayama, Naoki Tamura, Ryuhei Kumazawa, K. V. Khlopenkov, S. Murakami, A. Kostrioukov, A. Komori, Y. Narushima, Y. Nakamura, Katsunori Ikeda, Yunfeng Liang, Mamoru Shoji, Katsumi Ida, Hajime Suzuki, W. A. Cooper, S. Sudo, M. Y. Tanaka, Hideki Zushi, Masaki Osakabe, Y. Tomota, P. R. Goncharov, Ichihiro Yamada, Mamiko Sasao, Shin Kubo, K. Matsuoka, T Oikawa, K. Nagaoka, Atsushi Mase, Tomohiro Morisaki, Tetsuo Seki, T. Nakano, Yutaka Kamada, Yasuo Yoshimura, T. Watari, T. Suzuki, Takashi Satow, K. Narihara, Hiroshi Yamada, K.Y. Watanabe, Hiroyuki Okada, Suguru Masuzaki, S. Yamamoto, S. Higashijima, K. Toi, Y. Xu, Noriyoshi Nakajima, K. Shinohara, Tomoaki Hino, I. Ohtake, Toshiyuki Mito, Shigeru Inagaki, Takashi Shimozuma, T. Minami, Takashi Mutoh, Naoyuki Oyama, Kenji Tanaka, H. Kawazome, Kuninori Sato, N. Takeuchi, Katsumasa Nakamura, Kunizo Ohkubo, Katsuyoshi Tsumori, Takashi Notake, J. F. Lyon, K. Nishimura, Yoshio Nagayama, Takaaki Fujita, Y. Kusama, Hiroshi Idei, K. Yamazaki, Y. Miura, Akira Ejiri, Y. Takeiri, M. Emoto, Yuichi Takase, Katsumi Kondo, and T. Ozaki

Subjects
Nuclear and High Energy Physics, Materials science, Physics::Plasma Physics, Beta (plasma physics), Divertor, Electric field, Magnetic confinement fusion, Electron temperature, Electron, Plasma, Atomic physics, Condensed Matter Physics, Magnetic field
Abstract

In the first four years of the LHD experiment, several encouraging results have emerged, the most significant of which is that MHD stability and good transport are compatible in the inward shifted axis configuration. The observed energy confinement at this optimal configuration is consistent with ISS95 scaling with an enhancement factor of 1.5. The confinement enhancement over the smaller heliotron devices is attributed to the high edge temperature. We find that the plasma with an average beta of 3% is stable in this configuration, even though the theoretical stability conditions of Mercier modes and pressure driven low-n modes are violated. In the low density discharges heated by NBI and ECR, internal transport barrier (ITB) and an associated high central temperature (> 10 keV) are seen. The radial electric field measured in these discharges is positive (electron root) and expected to play a key role in the formation of the ITB. The positive electric field is also found to suppress the ion thermal diffusivity as predicted by neoclassical transport theory. The width of the externally imposed island (n/m = 1/1) is found to decrease when the plasma is collisionless with finite beta and increase when the plasma is collisional. The ICRF heating in LHD is successful and a high energy tail (up to 500 keV) has been detected for minority ion heating, demonstrating good confinement of the high energy particles. The magnetic field line structure unique to the heliotron edge configuration is confirmed by measuring the plasma density and temperature profiles on the divertor plate. A long pulse (2 min) discharge with an ICRF power of 0.4 MW has been demonstrated and the energy confinement characteristics are almost the same as those in short pulse discharges.

40. Recent results from the large helical device

Author

Mamoru Shoji, Katsumi Ida, Kunizo Ohkubo, Y. Xu, Hideya Nakanishi, Kazuo Kawahata, Katsuyoshi Tsumori, Tetsuo Seki, Takashi Notake, J. Miyazawa, K. Yamazaki, H. Nozato, Hajime Suzuki, Nobuyoshi Ohyabu, Kuninori Sato, K. V. Khlopenkov, Naoki Tamura, Suguru Masuzaki, S. Murakami, Mamiko Sasao, T. Minami, Y. Nagayama, T. Tokuzawa, M. Emoto, Takashi Mutoh, Masaki Osakabe, Masami Fujiwara, Takashi Shimozuma, Masayuki Yokoyama, Sadatsugu Muto, Motoshi Goto, Kenji Saito, Osamu Kaneko, K. Matsuoka, Yasuo Yoshimura, Masahide Sato, Shin Kubo, Takashi Satow, Kenji Tanaka, H. Kawazome, Shigeru Inagaki, Y. Nakamura, Ryuhei Kumazawa, T. Uda, N. Takeuchi, Hiroshi Idei, Tomohiro Morisaki, Katsunori Ikeda, S. Morita, N. Noda, Satoru Sakakibara, O. Motojima, Y. Takeiri, Yunfeng Liang, B.J. Peterson, Tsuyoshi Akiyama, A. Kostrioukov, S. Yamamoto, P. Goncharov, T. Ozaki, T. Kobuchi, N. Ashikawa, Akio Komori, K.Y. Watanabe, Hiroshi Yamada, Mikiro Yoshinuma, T. Saida, K. Narihara, H. Funaba, K. Toi, S. Sudo, Y. Narushima, Ichihiro Yamada, Satoshi Ohdachi, Kimitaka Itoh, T. Watari, Yuki Torii, Yoshihide Oka, Ryuichi Sakamoto, Mitsutaka Isobe, T. Yamamoto, K. Nishimura, and Akio Sagara

Subjects
Tokamak, Materials science, Magnetic confinement fusion, Plasma, Condensed Matter Physics, Neutral beam injection, Electron cyclotron resonance, law.invention, Large Helical Device, Nuclear Energy and Engineering, Physics::Plasma Physics, law, Physics::Space Physics, Electron temperature, Magnetohydrodynamics, Atomic physics
Abstract

The most important finding in the Large Helical Device (LHD) experiments so far is that an inward-shifted configuration exhibits good plasma performance with a scaling similar to that of ELMy H-mode tokamaks. The inward-shifted configuration has been predicted to have unfavourable magnetohydrodynamic (MHD) properties, even though it has significantly better particle-orbit properties. However, no serious confinement degradation due to the MHD activities was observed, resolving favourably the potential conflict between stability and confinement. Neoclassical transport loss can be suppressed even in a low-collisionality regime, and in this way the inward-shifted configuration was shown to make the LHD plasma properties favourable. Then, it is very important to realize more improved plasma performance and higher temperature plasmas for extending the plasma-parameter regime in order to obtain data that can be extrapolated to a reactor. In the fifth campaign in 2001–2002, an increase in the heating power achieved an electron temperature Te of over 10 keV and an ion temperature Ti of 5 keV. A Te profile, which is characteristic of internal transport barriers, was also observed when the electron cyclotron resonance heating power was highly focused on the centre of the plasma sustained by neutral beam injection.

41. Recent diagnostic developments on LHD

Author

Sudo, S., Nagayama, Y., Peterson, B. J., Kawahata, K., Akiyama, T., Ashikawa, N., Emoto, M., Goto, M., Hamada, Y., Ida, K., Ido, T., Iguchi, H., Inagaki, S., Isobe, M., Kobuchi, T., Komori, A., Liang, Y., Masuzaki, S., Minami, T., Morisaki, T., Morita, S., Muto, S., Nakamura, Y., Nakanishi, H., Narushima, M., Narihara, K., Nishiura, M., Nishizawa, A., Ohdachi, S., Osakabe, M., Ozaki, T., Pavlichenko, R. O., Sakakibara, S., Sato, K., Shoji, M., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Watanabe, K. Y., Watanabe, T., Yamada, H., Yamada, I., Yoshinuma, M., Pavel Goncharov, Kalinina, D., Kanaba, T., Sugimoto, T., Ejiri, A., Ono, Y., Hojo, H., Ishii, K., Iwama, N., Kogi, Y., Mase, A., Sakamoto, M., Kondo, K., Nagasaki, H., Yamamoto, S., Nishino, N., Okajima, S., Saida, T., Sasao, M., Takeda, T., Tsuji-Iio, S., Darrow, D. S., Takahashi, H., Liu, Y., Lyon, J. F., Kostrioukov, A. Yu, Kuteev, V. B., Sergeev, V., Viniar, I., Krasilnikov, A. V., Sanin, A., Vyacheslavov, L. N., Stutman, D., Finkenthal, M., and Motojima, O.

42. Island dynamics in the large-helical-device plasmas

Author

Ichihiro Yamada, T. Watari, Satoru Sakakibara, Naoki Tamura, Hisamichi Funaba, Ryuhei Kumazawa, K. V. Khlopenkov, Katsunori Ikeda, Satoshi Ohdachi, Yoshiro Narushima, Masaki Osakabe, J. Miyazawa, Osamu Motojima, Sadatsugu Muto, Yasuhiko Takeiri, Kuninori Sato, Ryuichi Sakamoto, S. Morita, Takashi Minami, Nobuyoshi Ohyabu, Shigeru Sudo, N. Noda, Tetsuo Seki, K. Saito, S. Murakami, Mitsutaka Isobe, Y. Torii, Mamoru Shoji, Katsumi Ida, Tokihiko Tokuzawa, Takashi Mutoh, Tsuguhiro Watanabe, Suguru Masuzaki, K. Nishimura, Osamu Kaneko, Shin Kubo, T. Ozaki, Masayuki Yokoyama, Hiroshi Yamada, Yunfeng Liang, T. Kobuchi, Yoshihide Oka, K.Y. Watanabe, Naoko Ashikawa, Yasuo Yoshimura, Kazuo Toi, Kunizo Ohkubo, Yoshio Nagayama, Katsuyoshi Tsumori, Kazuo Kawahata, Byron J. Peterson, Kenji Tanaka, Kazumichi Narihara, Akio Sagara, Takashi Notake, Akio Komori, Tomohiro Morisaki, M. Sato, Y. Xu, Hiroshi Idei, Takashi Shimozuma, A. Kostrioukov, Hajime Suzuki, Hideya Nakanishi, Masahiko Emoto, Mamiko Sasao, Shigeru Inagaki, N. Inoue, Y. Nakamura, K. Yamazaki, S. Yamamoto, and Motoshi Goto

Subjects
Mode number, Physics, Large Helical Device, Beta (plasma physics), General Physics and Astronomy, Plasma confinement, Electron temperature, Plasma, Atomic physics, Magnetic field
Abstract

In the Large Helical Device plasma discharges, the size of an externally imposed island with mode number ( $n/m\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/1$) decreases substantially when the plasma is collisionless ( ${\ensuremath{\nu}}^{*}l\ensuremath{\sim}1$) and the beta is finite ( $g\ensuremath{\sim}0.1%$) at the island location. For the collisional plasmas with finite beta, on the other hand, the size of the island increases. However, there is a threshold in terms of the vacuum island size below which the island enlargement is not seen.

43. Observation of plasma flow at the magnetic island in the Large Helical Device

Author

K., Ida, N., Ohyabu, T., Morisaki, Y., Nagayama, S., Inagaki, K., Itoh, Y., Liang, K., Narihara, A.Yu., Kostrioukov, B.J., Peterson, K., Tanaka, T., Tokuzawa, K., Kawahata, H., Suzuki, A., Komori, and Experimental Group, LHD

Subjects
Physics, Maple, Condensed matter physics, General Physics and Astronomy, Perturbation (astronomy), Ion temperature, engineering.material, Magnetic flux, Physics::Fluid Dynamics, Plasma flow, Large Helical Device, Nuclear magnetic resonance, Physics::Plasma Physics, Electric field, engineering
Abstract

Radial profiles of ion temperature and plasma flow are measured at the n/m = 1/1 magnetic island produced by external perturbation coils in the Large Helical Device. The sheared poloidal flows and sheared radial electric field are observed at the boundaries of the magnetic island, because the poloidal flow vanishes inside the static magnetic island. When the width of the magnetic island becomes large, the flow along the magnetic flux surface inside the magnetic island appears around the O point in the direction which reduces the shear of the poloidal flow at the boundary of the magnetic island.

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