Improvement of plasma Core confinement via electron-root realization by strongly focused ECRH in LHD

Core electron-root confinement

T. Shimozuma, M. Yokoyama, K. Ida, Y. Takeiri, S. Kubo, S. Murakami, A. Wakasa, Hiroshi Idei, Y. Yoshimura, T. Notake, Inagaki Shigeru, N. Tamura, K. Toi, N. Ohyabu, M. Osakabe, K. Ikeda, K. Tsumori, Y. Oka, K. Nagaoka, O. Kaneko & 16 others I. Yamada, K. Narihara, Y. Nagayama, S. Muto, K. Tanaka, T. Tokuzawa, S. Morita, M. Goto, M. Yoshinuma, H. Funaba, T. Morisaki, K. Y. Watanabe, J. Miyazawa, T. Mutoh, T. Watari, K. Ohkubo

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Core electron-root confinement (CERC), observed in the Large Helical Device as well as in other helical devices, is an improved electron energy confinement mode. It is characterized by a highly peaked electron temperature profile in the core region and appears when the centrally focused electron cyclotron resonance heating power exceeds a certain threshold value. This threshold value has been clarified to associate with the transition of the radial electric field (Er) from the ion root (small negative value) to the electron root (large positive value greater than a few kV/m), based on the bifurcation nature of Er due to the ambipolarity condition of neoclassical transport fluxes that is specific in nonaxisymmetric configurations. It has been experimentally recognized that a steeper Te gradient is realized with a clear transition (power threshold nature) in target plasmas with counter neutral beam injection (NBI) than ones with codirectional NBI. It has been interpreted, based on the heat pulse propagation experiment, to be related to the rational surface or the island induced by the NBI-driven current. Transport analyses have shown that the incremental thermal diffusivity of electron heat transport becomes lower, and the standard thermal diffusivity decreases with the increase of heating power in CERC plasmas.

Original languageEnglish
Pages (from-to)38-45
Number of pages8
JournalFusion Science and Technology
Volume58
Issue number1
DOIs
Publication statusPublished - Jan 1 2010

Fingerprint

Plasma confinement
beam injection
neutral beams
Plasmas
Electrons
thermal diffusivity
Thermal diffusivity
thresholds
electrons
electron energy
heat
heating
plasma control
Heating
electron cyclotron resonance
Electron cyclotron resonance
temperature profiles
Electron temperature
counters
gradients

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Materials Science(all)
  • Mechanical Engineering

Cite this

Improvement of plasma Core confinement via electron-root realization by strongly focused ECRH in LHD : Core electron-root confinement. / Shimozuma, T.; Yokoyama, M.; Ida, K.; Takeiri, Y.; Kubo, S.; Murakami, S.; Wakasa, A.; Idei, Hiroshi; Yoshimura, Y.; Notake, T.; Shigeru, Inagaki; Tamura, N.; Toi, K.; Ohyabu, N.; Osakabe, M.; Ikeda, K.; Tsumori, K.; Oka, Y.; Nagaoka, K.; Kaneko, O.; Yamada, I.; Narihara, K.; Nagayama, Y.; Muto, S.; Tanaka, K.; Tokuzawa, T.; Morita, S.; Goto, M.; Yoshinuma, M.; Funaba, H.; Morisaki, T.; Watanabe, K. Y.; Miyazawa, J.; Mutoh, T.; Watari, T.; Ohkubo, K.

In: Fusion Science and Technology, Vol. 58, No. 1, 01.01.2010, p. 38-45.

Research output: Contribution to journalArticle

Shimozuma, T, Yokoyama, M, Ida, K, Takeiri, Y, Kubo, S, Murakami, S, Wakasa, A, Idei, H, Yoshimura, Y, Notake, T, Shigeru, I, Tamura, N, Toi, K, Ohyabu, N, Osakabe, M, Ikeda, K, Tsumori, K, Oka, Y, Nagaoka, K, Kaneko, O, Yamada, I, Narihara, K, Nagayama, Y, Muto, S, Tanaka, K, Tokuzawa, T, Morita, S, Goto, M, Yoshinuma, M, Funaba, H, Morisaki, T, Watanabe, KY, Miyazawa, J, Mutoh, T, Watari, T & Ohkubo, K 2010, 'Improvement of plasma Core confinement via electron-root realization by strongly focused ECRH in LHD: Core electron-root confinement', Fusion Science and Technology, vol. 58, no. 1, pp. 38-45. https://doi.org/10.13182/FST10-A10791
Shimozuma, T. ; Yokoyama, M. ; Ida, K. ; Takeiri, Y. ; Kubo, S. ; Murakami, S. ; Wakasa, A. ; Idei, Hiroshi ; Yoshimura, Y. ; Notake, T. ; Shigeru, Inagaki ; Tamura, N. ; Toi, K. ; Ohyabu, N. ; Osakabe, M. ; Ikeda, K. ; Tsumori, K. ; Oka, Y. ; Nagaoka, K. ; Kaneko, O. ; Yamada, I. ; Narihara, K. ; Nagayama, Y. ; Muto, S. ; Tanaka, K. ; Tokuzawa, T. ; Morita, S. ; Goto, M. ; Yoshinuma, M. ; Funaba, H. ; Morisaki, T. ; Watanabe, K. Y. ; Miyazawa, J. ; Mutoh, T. ; Watari, T. ; Ohkubo, K. / Improvement of plasma Core confinement via electron-root realization by strongly focused ECRH in LHD : Core electron-root confinement. In: Fusion Science and Technology. 2010 ; Vol. 58, No. 1. pp. 38-45.
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abstract = "Core electron-root confinement (CERC), observed in the Large Helical Device as well as in other helical devices, is an improved electron energy confinement mode. It is characterized by a highly peaked electron temperature profile in the core region and appears when the centrally focused electron cyclotron resonance heating power exceeds a certain threshold value. This threshold value has been clarified to associate with the transition of the radial electric field (Er) from the ion root (small negative value) to the electron root (large positive value greater than a few kV/m), based on the bifurcation nature of Er due to the ambipolarity condition of neoclassical transport fluxes that is specific in nonaxisymmetric configurations. It has been experimentally recognized that a steeper Te gradient is realized with a clear transition (power threshold nature) in target plasmas with counter neutral beam injection (NBI) than ones with codirectional NBI. It has been interpreted, based on the heat pulse propagation experiment, to be related to the rational surface or the island induced by the NBI-driven current. Transport analyses have shown that the incremental thermal diffusivity of electron heat transport becomes lower, and the standard thermal diffusivity decreases with the increase of heating power in CERC plasmas.",
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AU - Shimozuma, T.

AU - Yokoyama, M.

AU - Ida, K.

AU - Takeiri, Y.

AU - Kubo, S.

AU - Murakami, S.

AU - Wakasa, A.

AU - Idei, Hiroshi

AU - Yoshimura, Y.

AU - Notake, T.

AU - Shigeru, Inagaki

AU - Tamura, N.

AU - Toi, K.

AU - Ohyabu, N.

AU - Osakabe, M.

AU - Ikeda, K.

AU - Tsumori, K.

AU - Oka, Y.

AU - Nagaoka, K.

AU - Kaneko, O.

AU - Yamada, I.

AU - Narihara, K.

AU - Nagayama, Y.

AU - Muto, S.

AU - Tanaka, K.

AU - Tokuzawa, T.

AU - Morita, S.

AU - Goto, M.

AU - Yoshinuma, M.

AU - Funaba, H.

AU - Morisaki, T.

AU - Watanabe, K. Y.

AU - Miyazawa, J.

AU - Mutoh, T.

AU - Watari, T.

AU - Ohkubo, K.

PY - 2010/1/1

Y1 - 2010/1/1

N2 - Core electron-root confinement (CERC), observed in the Large Helical Device as well as in other helical devices, is an improved electron energy confinement mode. It is characterized by a highly peaked electron temperature profile in the core region and appears when the centrally focused electron cyclotron resonance heating power exceeds a certain threshold value. This threshold value has been clarified to associate with the transition of the radial electric field (Er) from the ion root (small negative value) to the electron root (large positive value greater than a few kV/m), based on the bifurcation nature of Er due to the ambipolarity condition of neoclassical transport fluxes that is specific in nonaxisymmetric configurations. It has been experimentally recognized that a steeper Te gradient is realized with a clear transition (power threshold nature) in target plasmas with counter neutral beam injection (NBI) than ones with codirectional NBI. It has been interpreted, based on the heat pulse propagation experiment, to be related to the rational surface or the island induced by the NBI-driven current. Transport analyses have shown that the incremental thermal diffusivity of electron heat transport becomes lower, and the standard thermal diffusivity decreases with the increase of heating power in CERC plasmas.

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