Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD

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, Hiroshi Idei, J. Miyazawa, K. Y. Watanabe, K. Nishimura, A. Kostrioukov, H. Yamada & 3 others O. Kaneko, N. Ohyabu, K. Komori

Research output: Contribution to journalArticle

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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 n̄c for the collapse of RC plasmas is similar to the scaling laws obtained in other helical devices, i.e. n̄c ∝ (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.

Original languageEnglish
Pages (from-to)601-613
Number of pages13
JournalNuclear Fusion
Volume42
Issue number5
DOIs
Publication statusPublished - May 1 2002
Externally publishedYes

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decay
radiation
thermal instability
profiles
heating
asymmetry
temperature profiles
scaling laws
plasma density
contraction
causes
magnetic fields
temperature

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Xu, Y., Peterson, B. J., Sudo, S., Tokuzawa, T., Narihara, K., Osakabe, M., ... Komori, K. (2002). Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD. Nuclear Fusion, 42(5), 601-613. https://doi.org/10.1088/0029-5515/42/5/312

Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD. / Xu, Yuhong; Peterson, B. J.; Sudo, S.; Tokuzawa, T.; Narihara, K.; Osakabe, M.; Morita, S.; Goto, M.; Sakakibara, S.; Tanaka, K.; Kawahata, K.; Tsumori, K.; Ikeda, K.; Kubo, S.; Idei, Hiroshi; Miyazawa, J.; Watanabe, K. Y.; Nishimura, K.; Kostrioukov, A.; Yamada, H.; Kaneko, O.; Ohyabu, N.; Komori, K.

In: Nuclear Fusion, Vol. 42, No. 5, 01.05.2002, p. 601-613.

Research output: Contribution to journalArticle

Xu, Y, Peterson, BJ, Sudo, S, Tokuzawa, T, Narihara, K, Osakabe, M, Morita, S, Goto, M, Sakakibara, S, Tanaka, K, Kawahata, K, Tsumori, K, Ikeda, K, Kubo, S, Idei, H, Miyazawa, J, Watanabe, KY, Nishimura, K, Kostrioukov, A, Yamada, H, Kaneko, O, Ohyabu, N & Komori, K 2002, 'Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD', Nuclear Fusion, vol. 42, no. 5, pp. 601-613. https://doi.org/10.1088/0029-5515/42/5/312
Xu Y, Peterson BJ, Sudo S, Tokuzawa T, Narihara K, Osakabe M et al. Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD. Nuclear Fusion. 2002 May 1;42(5):601-613. https://doi.org/10.1088/0029-5515/42/5/312
Xu, Yuhong ; Peterson, B. J. ; Sudo, S. ; Tokuzawa, T. ; Narihara, K. ; Osakabe, M. ; Morita, S. ; Goto, M. ; Sakakibara, S. ; Tanaka, K. ; Kawahata, K. ; Tsumori, K. ; Ikeda, K. ; Kubo, S. ; Idei, Hiroshi ; Miyazawa, J. ; Watanabe, K. Y. ; Nishimura, K. ; Kostrioukov, A. ; Yamada, H. ; Kaneko, O. ; Ohyabu, N. ; Komori, K. / Properties of thermal decay and radiative collapse of NBI heated plasmas on LHD. In: Nuclear Fusion. 2002 ; Vol. 42, No. 5. pp. 601-613.
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AU - Xu, Yuhong

AU - Peterson, B. J.

AU - Sudo, S.

AU - Tokuzawa, T.

AU - Narihara, K.

AU - Osakabe, M.

AU - Morita, S.

AU - Goto, M.

AU - Sakakibara, S.

AU - Tanaka, K.

AU - Kawahata, K.

AU - Tsumori, K.

AU - Ikeda, K.

AU - Kubo, S.

AU - Idei, Hiroshi

AU - Miyazawa, J.

AU - Watanabe, K. Y.

AU - Nishimura, K.

AU - Kostrioukov, A.

AU - Yamada, H.

AU - Kaneko, O.

AU - Ohyabu, N.

AU - Komori, K.

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