Transition from chirping to steady NBI-driven Alfvén modes caused by magnetic configuration variations in the TJ-II stellarator

A. V. Melnikov, L. G. Eliseev, E. Ascasíbar, A. Cappa, F. Castejón, C. Hidalgo, T. Ido, J. A. Jiménez, A. S. Kozachek, L. I. Krupnik, M. Liniers, S. E. Lysenko, K. Nagaoka, J. L. De Pablos, A. Shimizu, S. E. Sharapov, M. V. Ufimtsev, S. Yamamoto

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13 Citations (Scopus)

Abstract

Beam-driven Alfvén eigenmodes (AEs) have been studied in the TJ-II low-magnetic-shear flexible heliac (B 0 = 0.95 T, R = 1.5 m, a = 0.22 m), in L-mode hydrogen plasmas with hydrogen NBI and ECR heating (P NBI 1.0 MW, E NBI = 32 keV, P ECRH 0.6 MW). In low-density plasmas in the range = (0.3-1.5) ×1019 m-3, a large variety of AEs have been observed in the plasma core with the heavy ion beam probe diagnostic and Mirnov coils, in the frequency range 50 kHz < f AE < 380 kHz. In experiments in which the vacuum rotational transform is varied during the shot (dynamic configuration scan), some AEs exhibit changes in their nonlinear evolution from bursting-amplitude AEs with chirping frequency to steady-frequency AEs, and back. The range of intervals within which the AEs studied are chirping or steady-state is determined.

Original languageEnglish
Article number076001
JournalNuclear Fusion
Volume56
Issue number7
DOIs
Publication statusPublished - Jun 3 2016
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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