Energetic-Electron-Driven Instability in the Helically Symmetric Experiment

C. B. Deng, D. L. Brower, B. N. Breizman, D. A. Spong, A. F. Almagri, D. T. Anderson, F. S. B. Anderson, W. X. Ding, W. Guttenfelder, K. M. Likin, and J. N. Talmadge

Phys. Rev. Lett. 103, 025003 – Published 10 July 2009

Abstract

Energetic electrons generated by electron cyclotron resonance heating are observed to drive instabilities in the quasihelically symmetric stellarator device. The coherent, global fluctuations peak in the plasma core and are measured in the frequency range of 20–120 kHz. Mode propagation is in the diamagnetic drift direction of the driving species. When quasihelical symmetry is broken, the mode is no longer observed. Experimental observations indicate that the unstable mode is acoustic rather than Alfvénic.

Received 18 February 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.025003

Authors & Affiliations

C. B. Deng¹, D. L. Brower¹, B. N. Breizman², D. A. Spong³, A. F. Almagri⁴, D. T. Anderson⁴, F. S. B. Anderson⁴, W. X. Ding¹, W. Guttenfelder⁴, K. M. Likin⁴, and J. N. Talmadge⁴

¹Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095, USA
²Institute for Fusion Studies, University of Texas, Austin, Texas 78712, USA
³Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
⁴Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA

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Vol. 103, Iss. 2 — 10 July 2009

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