Tokamak Operation with Safety Factor q95<2 via Control of MHD Stability

P. Piovesan, J. M. Hanson, P. Martin, G. A. Navratil, F. Turco, J. Bialek, N. M. Ferraro, R. J. La Haye, M. J. Lanctot, M. Okabayashi, C. Paz-Soldan, E. J. Strait, A. D. Turnbull, P. Zanca, M. Baruzzo, T. Bolzonella, A. W. Hyatt, G. L. Jackson, L. Marrelli, L. Piron, and D. Shiraki
Phys. Rev. Lett. 113, 045003 – Published 24 July 2014

Abstract

Magnetic feedback control of the resistive-wall mode has enabled the DIII-D tokamak to access stable operation at safety factor q95=1.9 in divertor plasmas for 150 instability growth times. Magnetohydrodynamic stability sets a hard, disruptive limit on the minimum edge safety factor achievable in a tokamak, or on the maximum plasma current at a given toroidal magnetic field. In tokamaks with a divertor, the limit occurs at q95=2, as confirmed in DIII-D. Since the energy confinement time scales linearly with current, this also bounds the performance of a fusion reactor. DIII-D has overcome this limit, opening a whole new high-current regime not accessible before. This result brings significant possible benefits in terms of fusion performance, but it also extends resistive-wall mode physics and its control to conditions never explored before. In present experiments, the q95<2 operation is eventually halted by voltage limits reached in the feedback power supplies, not by intrinsic physics issues. Improvements to power supplies and to control algorithms have the potential to further extend this regime.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Received 18 September 2013

DOI:https://doi.org/10.1103/PhysRevLett.113.045003

© 2014 American Physical Society

Authors & Affiliations

P. Piovesan1, J. M. Hanson2, P. Martin1, G. A. Navratil2, F. Turco2, J. Bialek2, N. M. Ferraro3, R. J. La Haye3, M. J. Lanctot3, M. Okabayashi4, C. Paz-Soldan5, E. J. Strait3, A. D. Turnbull3, P. Zanca1, M. Baruzzo1, T. Bolzonella1, A. W. Hyatt3, G. L. Jackson3, L. Marrelli1, L. Piron1, and D. Shiraki2

  • 1Consorzio RFX, Corso Stati Uniti 4, 35127 Padova, Italy
  • 2Columbia University, New York, New York 10027, USA
  • 3General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA
  • 4Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451, USA
  • 5Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831, USA

  • paolo.piovesan@igi.cnr.it

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 113, Iss. 4 — 25 July 2014

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review Letters

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×