Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device

K. Toi; M. Takechi; M. Isobe; N. Nakajima; M. Osakabe; S. Takagi; T. Kondo; G. Matsunaga; K. Ohkuni; M. Sasao; S. Yamamoto; S. Ohdachi; S. Sakakibara; H. Yamada; K. Y. Watanabe; D. S. Darrow; A. Fujisawa; M. Goto; K. Ida; H. Idei; H. Iguchi; S. Lee; S. Kado; S. Kubo; O. Kaneko; K. Kawahata; K. Matsuoka; T. Minami; S. Morita; O. Motojima; K. Narihara; S. Nishimura; N. Ohyabu; Y. Oka; S. Okamura; T. Ozaki; K. Sato; M. Sato; A. Shimizu; T. Shimozuma; Y. Takeiri; K. Tanaka; T. Tokuzawa; K. Tsumori; I. Yamada; Y. Yoshimura

doi:10.1088/0029-5515/40/7/306

Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device

K. Toi, M. Takechi, M. Isobe, N. Nakajima, M. Osakabe, S. Takagi, T. Kondo, G. Matsunaga, K. Ohkuni, M. Sasao, S. Yamamoto, S. Ohdachi, S. Sakakibara, H. Yamada, K. Y. Watanabe, D. S. Darrow, A. Fujisawa, M. Goto, K. Ida, H. IdeiH. Iguchi, S. Lee, S. Kado, S. Kubo, O. Kaneko, K. Kawahata, K. Matsuoka, T. Minami, S. Morita, O. Motojima, K. Narihara, S. Nishimura, N. Ohyabu, Y. Oka, S. Okamura, T. Ozaki, K. Sato, M. Sato, A. Shimizu, T. Shimozuma, Y. Takeiri, K. Tanaka, T. Tokuzawa, K. Tsumori, I. Yamada, Y. Yoshimura

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Abstract

Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfven eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfven eigenmodes (TAEs) and global Alfven eigenmodes (GAEs), where the identified toroidal mode numbers are n = 1 and 2 for TAEs and n = 0 for GAEs. The frequencies of the FBs are less than, at most, half of the minimum TAE gap frequency and do not exhibit the obvious density dependence related to Alfven velocity. The modes have characteristic features of the energetic particle modes or the resonant TAEs excited by circulating energetic beam ions produced by NBI. Bursting amplitude modulation is observed in TAEs as well as in FBs. Rapid frequency chirping is observed in each burst, by a factor of 2-6 in FBs and about 25% in TAEs. In several shots, the power spectrum of the TAEs is split into multiple peaks having the same toroidal mode number through non-linear evolution of TAEs. A pulsed increase in energetic ion loss towards the wall is induced by m = 3/n = 2 FBs, but so far not by m = 2/n = 1 FBs, TAEs and GAEs, where m is the poloidal mode number. This research has been extended to LHD plasmas heated by neutral hydrogen beams with about 130 keV energy. Similar to CHS, TAEs and FBs were observed in relatively low density plasmas at low toroidal magnetic field (B_t = 1.5 T).

Original language	English
Pages (from-to)	1349-1362
Number of pages	14
Journal	Nuclear Fusion
Volume	40
Issue number	7
DOIs	https://doi.org/10.1088/0029-5515/40/7/306
Publication status	Published - Jul 2000
Externally published	Yes

All Science Journal Classification (ASJC) codes

Nuclear and High Energy Physics
Condensed Matter Physics

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10.1088/0029-5515/40/7/306

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Toi, K., Takechi, M., Isobe, M., Nakajima, N., Osakabe, M., Takagi, S., Kondo, T., Matsunaga, G., Ohkuni, K., Sasao, M., Yamamoto, S., Ohdachi, S., Sakakibara, S., Yamada, H., Watanabe, K. Y., Darrow, D. S., Fujisawa, A., Goto, M., Ida, K., ... Yoshimura, Y. (2000). Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device. Nuclear Fusion, 40(7), 1349-1362. https://doi.org/10.1088/0029-5515/40/7/306

Toi, K, Takechi, M, Isobe, M, Nakajima, N, Osakabe, M, Takagi, S, Kondo, T, Matsunaga, G, Ohkuni, K, Sasao, M, Yamamoto, S, Ohdachi, S, Sakakibara, S, Yamada, H, Watanabe, KY, Darrow, DS, Fujisawa, A, Goto, M, Ida, K, Idei, H, Iguchi, H, Lee, S, Kado, S, Kubo, S, Kaneko, O, Kawahata, K, Matsuoka, K, Minami, T, Morita, S, Motojima, O, Narihara, K, Nishimura, S, Ohyabu, N, Oka, Y, Okamura, S, Ozaki, T, Sato, K, Sato, M, Shimizu, A, Shimozuma, T, Takeiri, Y, Tanaka, K, Tokuzawa, T, Tsumori, K, Yamada, I & Yoshimura, Y 2000, 'Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device', Nuclear Fusion, vol. 40, no. 7, pp. 1349-1362. https://doi.org/10.1088/0029-5515/40/7/306

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title = "Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device",

abstract = "Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfven eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfven eigenmodes (TAEs) and global Alfven eigenmodes (GAEs), where the identified toroidal mode numbers are n = 1 and 2 for TAEs and n = 0 for GAEs. The frequencies of the FBs are less than, at most, half of the minimum TAE gap frequency and do not exhibit the obvious density dependence related to Alfven velocity. The modes have characteristic features of the energetic particle modes or the resonant TAEs excited by circulating energetic beam ions produced by NBI. Bursting amplitude modulation is observed in TAEs as well as in FBs. Rapid frequency chirping is observed in each burst, by a factor of 2-6 in FBs and about 25% in TAEs. In several shots, the power spectrum of the TAEs is split into multiple peaks having the same toroidal mode number through non-linear evolution of TAEs. A pulsed increase in energetic ion loss towards the wall is induced by m = 3/n = 2 FBs, but so far not by m = 2/n = 1 FBs, TAEs and GAEs, where m is the poloidal mode number. This research has been extended to LHD plasmas heated by neutral hydrogen beams with about 130 keV energy. Similar to CHS, TAEs and FBs were observed in relatively low density plasmas at low toroidal magnetic field (Bt = 1.5 T).",

author = "K. Toi and M. Takechi and M. Isobe and N. Nakajima and M. Osakabe and S. Takagi and T. Kondo and G. Matsunaga and K. Ohkuni and M. Sasao and S. Yamamoto and S. Ohdachi and S. Sakakibara and H. Yamada and Watanabe, {K. Y.} and Darrow, {D. S.} and A. Fujisawa and M. Goto and K. Ida and H. Idei and H. Iguchi and S. Lee and S. Kado and S. Kubo and O. Kaneko and K. Kawahata and K. Matsuoka and T. Minami and S. Morita and O. Motojima and K. Narihara and S. Nishimura and N. Ohyabu and Y. Oka and S. Okamura and T. Ozaki and K. Sato and M. Sato and A. Shimizu and T. Shimozuma and Y. Takeiri and K. Tanaka and T. Tokuzawa and K. Tsumori and I. Yamada and Y. Yoshimura",

year = "2000",

month = jul,

doi = "10.1088/0029-5515/40/7/306",

language = "English",

volume = "40",

pages = "1349--1362",

journal = "Nuclear Fusion",

issn = "0029-5515",

publisher = "IOP Publishing Ltd.",

number = "7",

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TY - JOUR

T1 - Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device

AU - Toi, K.

AU - Takechi, M.

AU - Isobe, M.

AU - Nakajima, N.

AU - Osakabe, M.

AU - Takagi, S.

AU - Kondo, T.

AU - Matsunaga, G.

AU - Ohkuni, K.

AU - Sasao, M.

AU - Yamamoto, S.

AU - Ohdachi, S.

AU - Sakakibara, S.

AU - Yamada, H.

AU - Watanabe, K. Y.

AU - Darrow, D. S.

AU - Fujisawa, A.

AU - Goto, M.

AU - Ida, K.

AU - Idei, H.

AU - Iguchi, H.

AU - Lee, S.

AU - Kado, S.

AU - Kubo, S.

AU - Kaneko, O.

AU - Kawahata, K.

AU - Matsuoka, K.

AU - Minami, T.

AU - Morita, S.

AU - Motojima, O.

AU - Narihara, K.

AU - Nishimura, S.

AU - Ohyabu, N.

AU - Oka, Y.

AU - Okamura, S.

AU - Ozaki, T.

AU - Sato, K.

AU - Sato, M.

AU - Shimizu, A.

AU - Shimozuma, T.

AU - Takeiri, Y.

AU - Tanaka, K.

AU - Tokuzawa, T.

AU - Tsumori, K.

AU - Yamada, I.

AU - Yoshimura, Y.

PY - 2000/7

Y1 - 2000/7

N2 - Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfven eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfven eigenmodes (TAEs) and global Alfven eigenmodes (GAEs), where the identified toroidal mode numbers are n = 1 and 2 for TAEs and n = 0 for GAEs. The frequencies of the FBs are less than, at most, half of the minimum TAE gap frequency and do not exhibit the obvious density dependence related to Alfven velocity. The modes have characteristic features of the energetic particle modes or the resonant TAEs excited by circulating energetic beam ions produced by NBI. Bursting amplitude modulation is observed in TAEs as well as in FBs. Rapid frequency chirping is observed in each burst, by a factor of 2-6 in FBs and about 25% in TAEs. In several shots, the power spectrum of the TAEs is split into multiple peaks having the same toroidal mode number through non-linear evolution of TAEs. A pulsed increase in energetic ion loss towards the wall is induced by m = 3/n = 2 FBs, but so far not by m = 2/n = 1 FBs, TAEs and GAEs, where m is the poloidal mode number. This research has been extended to LHD plasmas heated by neutral hydrogen beams with about 130 keV energy. Similar to CHS, TAEs and FBs were observed in relatively low density plasmas at low toroidal magnetic field (Bt = 1.5 T).

AB - Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfven eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfven eigenmodes (TAEs) and global Alfven eigenmodes (GAEs), where the identified toroidal mode numbers are n = 1 and 2 for TAEs and n = 0 for GAEs. The frequencies of the FBs are less than, at most, half of the minimum TAE gap frequency and do not exhibit the obvious density dependence related to Alfven velocity. The modes have characteristic features of the energetic particle modes or the resonant TAEs excited by circulating energetic beam ions produced by NBI. Bursting amplitude modulation is observed in TAEs as well as in FBs. Rapid frequency chirping is observed in each burst, by a factor of 2-6 in FBs and about 25% in TAEs. In several shots, the power spectrum of the TAEs is split into multiple peaks having the same toroidal mode number through non-linear evolution of TAEs. A pulsed increase in energetic ion loss towards the wall is induced by m = 3/n = 2 FBs, but so far not by m = 2/n = 1 FBs, TAEs and GAEs, where m is the poloidal mode number. This research has been extended to LHD plasmas heated by neutral hydrogen beams with about 130 keV energy. Similar to CHS, TAEs and FBs were observed in relatively low density plasmas at low toroidal magnetic field (Bt = 1.5 T).

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JO - Nuclear Fusion

JF - Nuclear Fusion

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ER -

Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device

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