Toroidal Alfvén eigenmodes driven with ICRF accelerated protons in JT-60U negative shear discharges

Y. Kusama; H. Kimura; T. Ozeki; M. Saigusa; G. J. Kramer; T. Oikawa; S. Moriyama; M. Nemoto; T. Fujita; K. Tobita; G. Y. Fu; R. Nazikian; C. Z. Cheng

doi:10.1088/0029-5515/38/8/308

Toroidal Alfvén eigenmodes driven with ICRF accelerated protons in JT-60U negative shear discharges

Y. Kusama, H. Kimura, T. Ozeki, M. Saigusa, G. J. Kramer, T. Oikawa, S. Moriyama, M. Nemoto, T. Fujita, K. Tobita, G. Y. Fu, R. Nazikian, C. Z. Cheng

ENG - Quantum Science and Energy Engineering

Research output: Contribution to journal › Article › peer-review

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Abstract

On JT-60U, for the first time in negative shear plasmas, toroidicity induced Alfvén eigenmodes (TAEs) with frequencies in the range of 90 to 110 kHz and toroidal mode numbers n = 5-8 were observed after a broadening of the density profile due to sequential partial collapses during ion cyclotron range of frequency (ICRF) heating. TAEs are more stable in negative shear plasmas than plasmas with a monotonically increasing q profile. The TAE stability was analysed with the NOVA-K code. It was found that the stability is highly sensitive to the gap alignment just inside q_min and that the theoretical results are consistent with the experimental results. In a weak central magnetic shear discharge, modes with very rapid frequency chirping were observed during ICRF heating. The frequencies of these modes rapidly increased from ∼30 kHz up to ∼110 kHz in a period of ∼150 ms. The large frequency chirping is not well understood by the present theory.

Original language	English
Pages (from-to)	1215-1223
Number of pages	9
Journal	Nuclear Fusion
Volume	38
Issue number	8
DOIs	https://doi.org/10.1088/0029-5515/38/8/308
Publication status	Published - 1998

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@article{e96c208a51384f8087ed658a540ef111,

title = "Toroidal Alfv{\'e}n eigenmodes driven with ICRF accelerated protons in JT-60U negative shear discharges",

abstract = "On JT-60U, for the first time in negative shear plasmas, toroidicity induced Alfv{\'e}n eigenmodes (TAEs) with frequencies in the range of 90 to 110 kHz and toroidal mode numbers n = 5-8 were observed after a broadening of the density profile due to sequential partial collapses during ion cyclotron range of frequency (ICRF) heating. TAEs are more stable in negative shear plasmas than plasmas with a monotonically increasing q profile. The TAE stability was analysed with the NOVA-K code. It was found that the stability is highly sensitive to the gap alignment just inside qmin and that the theoretical results are consistent with the experimental results. In a weak central magnetic shear discharge, modes with very rapid frequency chirping were observed during ICRF heating. The frequencies of these modes rapidly increased from ∼30 kHz up to ∼110 kHz in a period of ∼150 ms. The large frequency chirping is not well understood by the present theory.",

author = "Y. Kusama and H. Kimura and T. Ozeki and M. Saigusa and Kramer, {G. J.} and T. Oikawa and S. Moriyama and M. Nemoto and T. Fujita and K. Tobita and Fu, {G. Y.} and R. Nazikian and Cheng, {C. Z.}",

year = "1998",

doi = "10.1088/0029-5515/38/8/308",

language = "English",

volume = "38",

pages = "1215--1223",

journal = "Nuclear Fusion",

issn = "0029-5515",

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TY - JOUR

T1 - Toroidal Alfvén eigenmodes driven with ICRF accelerated protons in JT-60U negative shear discharges

AU - Kusama, Y.

AU - Kimura, H.

AU - Ozeki, T.

AU - Saigusa, M.

AU - Kramer, G. J.

AU - Oikawa, T.

AU - Moriyama, S.

AU - Nemoto, M.

AU - Fujita, T.

AU - Tobita, K.

AU - Fu, G. Y.

AU - Nazikian, R.

AU - Cheng, C. Z.

PY - 1998

Y1 - 1998

N2 - On JT-60U, for the first time in negative shear plasmas, toroidicity induced Alfvén eigenmodes (TAEs) with frequencies in the range of 90 to 110 kHz and toroidal mode numbers n = 5-8 were observed after a broadening of the density profile due to sequential partial collapses during ion cyclotron range of frequency (ICRF) heating. TAEs are more stable in negative shear plasmas than plasmas with a monotonically increasing q profile. The TAE stability was analysed with the NOVA-K code. It was found that the stability is highly sensitive to the gap alignment just inside qmin and that the theoretical results are consistent with the experimental results. In a weak central magnetic shear discharge, modes with very rapid frequency chirping were observed during ICRF heating. The frequencies of these modes rapidly increased from ∼30 kHz up to ∼110 kHz in a period of ∼150 ms. The large frequency chirping is not well understood by the present theory.

AB - On JT-60U, for the first time in negative shear plasmas, toroidicity induced Alfvén eigenmodes (TAEs) with frequencies in the range of 90 to 110 kHz and toroidal mode numbers n = 5-8 were observed after a broadening of the density profile due to sequential partial collapses during ion cyclotron range of frequency (ICRF) heating. TAEs are more stable in negative shear plasmas than plasmas with a monotonically increasing q profile. The TAE stability was analysed with the NOVA-K code. It was found that the stability is highly sensitive to the gap alignment just inside qmin and that the theoretical results are consistent with the experimental results. In a weak central magnetic shear discharge, modes with very rapid frequency chirping were observed during ICRF heating. The frequencies of these modes rapidly increased from ∼30 kHz up to ∼110 kHz in a period of ∼150 ms. The large frequency chirping is not well understood by the present theory.

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U2 - 10.1088/0029-5515/38/8/308

DO - 10.1088/0029-5515/38/8/308

M3 - Article

AN - SCOPUS:0032131557

SN - 0029-5515

VL - 38

SP - 1215

EP - 1223

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 8

ER -

Toroidal Alfvén eigenmodes driven with ICRF accelerated protons in JT-60U negative shear discharges

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