Long pulse high performance discharges in the DIII-D tokamak

T. C. Luce, M. R. Wade, P. A. Politzer, S. L. Allen, M. E. Austin, D. R. Baker, B. Bray, D. P. Brennan, K. H. Burrell, T. A. Casper, M. S. Chu, J. C. DeBoo, E. J. Doyle, J. R. Ferron, A. M. Garofalo, P. Gohil, I. A. Gorelov, C. M. Greenfield, R. J. Groebner, W. W. HeidbrinkC. L. Hsieh, A. W. Hyatt, R. Jayakumar, J. E. Kinsey, R. J. La Haye, L. L. Lao, C. J. Lasnier, E. A. Lazarus, A. W. Leonard, Y. R. Lin-Liu, J. Lohr, M. A. Mahdavi, M. A. Makowski, M. Murakami, C. C. Petty, R. I. Pinsker, R. Prater, C. L. Rettig, T. L. Rhodes, B. W. Rice, E. J. Strait, T. S. Taylor, D. M. Thomas, A. D. Turnbull, J. G. Watkins, W. P. West, K. L. Wong

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70 Citations (Scopus)

Abstract

Significant progress in obtaining high performance discharges lasting many energy confinement times in the DIII-D tokamak has been realized in recent experimental campaigns. Normalized performance ∼10 has been sustained for more than 5>E with qmin > 1.5. (The normalized performance is measured by the product βNH89, indicating the proximity to the conventional β limits and energy confinement quality, respectively.) These H mode discharges have an ELMing edge and β < 5%. The limit to increasing β is a resistive wall mode, rather than the tearing modes as previously observed. Confinement remains good despite qmin > 1. The global parameters were chosen to optimize the potential for fully non-inductive current sustainment at high performance, which is a key program goal for the DIII-D facility. Measurement of the current density and loop voltage profiles indicate that ≈75% of the current in the present discharges is sustained non-inductively. The remaining ohmic current is localized near the half-radius. The electron cyclotron heating system is being upgraded to replace this remaining current with ECCD. Density and β control, which are essential for operating advanced tokamak discharges, were demonstrated in ELMing H mode discharges with βNH89 ≈ 7 for up to 6.3 s or ≈34τE. These discharges appear to have stationary current profiles with qmin ≈ 1.05 in agreement with the current profile relaxation time ≈1.8 s.

Original languageEnglish
Pages (from-to)1585-1599
Number of pages15
JournalNuclear Fusion
Volume41
Issue number11
DOIs
Publication statusPublished - 2001 Nov

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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