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Physics of Plasmas / Volume 16 / Issue 10 / ARTICLES / Magnetically Confined Plasmas, Heating, Confinement

Phys. Plasmas 16, 102502 (2009); http://dx.doi.org/10.1063/1.3232325 (14 pages)

Advanced techniques for neoclassical tearing mode control in DIII-D a

a This paper is based on an invited presentation at the 2008 APS DPP Meeting in Dallas in 2008. Paper VI2 4, Bull. Am. Phys. Soc. 53, 318 (2008).
F. A. G. Volpe1, M. E. Austin2, R. J. La Haye3, J. Lohr3, R. Prater3, E. J. Strait3, and A. S. Welander3

1Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
2University of Texas-Austin, Austin, Texas 78712, USA
3General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA

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(Received 21 May 2009; accepted 28 August 2009; published online 6 October 2009)

Two techniques were developed at DIII-D [ J. L. Luxon, Nucl. Fusion 42, 64 (2002) ] to tackle ITER-specific aspects of neoclassical tearing mode (NTM) control, namely, (1) the relatively small size of the rotating islands, smaller than the electron cyclotron current drive (ECCD) deposition region, and (2) the increased tendency of the islands, compared to present devices, to lock to the wall or to the residual error field, in a position not necessarily accessible to ECCD. Modulated ECCD is known to suppress small islands more efficiently, when “broad,” than continuous ECCD. At DIII-D, a NTM of poloidal/toroidal mode numbers m/n = 3/2 was completely stabilized by a new technique where oblique electron cyclotron emission acted at the same time as an indicator of good alignment between ECCD and the island, and as a waveform generator, for modulation in synch and in phase with the island O-point. In another experiment, after locking in an unfavorable position, a 2/1 island was steered by externally generated magnetic perturbations, brought in the view of the gyrotrons and partly stabilized by ECCD in the island O-point. Magnetic perturbations were also used to sustain and control the mode rotation, which has the potential for an easier ECCD modulation.

© 2009 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. PRINCIPLE OF OBLIQUE-ECE-ASSISTED ALIGNMENT OF ECCD
  3. MOTIVATION FOR AND PRINCIPLE OF OBLIQUE-ECE-DRIVEN MODULATION OF ECCD
  4. EXPERIMENTAL SETUP FOR OBLIQUE-ECE-ASSISTED EXPERIMENTS
  5. ALIGNMENT RESULTS
  6. MODULATION RESULTS
  7. NEED FOR MAGNETIC STEERING IN CASE OF LOCKING
  8. EXPERIMENTAL SETUP FOR DETECTION AND CONTROL OF LOCKED MODES
  9. INITIAL PART OF THE DISCHARGES: NTM ONSET AND LOCKING
  10. SLOW ENTRAINMENT, PREFERENTIAL LOCKING, AND CW ECCD RESULTS
    1. ECCD turn-off experiment
    2. Prospects for unlocking by ECCD
  11. FAST ENTRAINMENT RESULTS
  12. MODE ROTATION OPPOSITE TO APPLIED ROTATION
  13. CONCLUSIONS

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KEYWORDS and PACS

Keywords

plasma radiofrequency heating, tearing instability, Tokamak devices

PACS

  • 52.55.Fa

    Tokamaks, spherical tokamaks

  • 52.50.Sw

    Plasma heating by microwaves; ECR, LH, collisional heating

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.3232325

PUBLICATION DATA

ISSN

1070-664X (print)  
1089-7674 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

For access to fully linked references, you need to log in.
    R. J. La Haye, Phys. Plasmas 13, 055501 (2006)PHPAEN000013000005055501000001.

    M. Maraschek, G. Gantenbein, Q. Yu, H. Zohm, S. Günter, F. Leuterer, and A. Manini, Phys. Rev. Lett. 98, 025005 (2007).

    A. Pletzer and F. W. Perkins, Phys. Plasmas 6, 1589 (1999)PHPAEN000006000005001589000001.

    C. C. Hegna and J. D. Callen, Phys. Plasmas 4, 2940 (1997)PHPAEN000004000008002940000001.

    H. Zohm, Phys. Plasmas 4, 3433 (1997)PHPAEN000004000009003433000001.

    G. Ramponi, E. Lazzaro, and S. Nowak, Phys. Plasmas 6, 3561 (1999)PHPAEN000006000009003561000001.


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