1. Long pulse high performance discharges in the DIII-D tokamak
- Author
-
Luce, TC, Wade, MR, Politzer, PA, Allen, SL, Austin, ME, Baker, DR, Bray, B, Brennan, DP, Burrell, KH, Casper, TA, Chu, MS, DeBoo, JC, Doyle, EJ, Ferron, JR, Garofalo, AM, Gohil, P, Gorelov, IA, Greenfield, CM, Groebner, RJ, Heidbrink, WW, Hsieh, C-L, Hyatt, AW, Jayakumar, R, Kinsey, JE, La Haye, RJ, Lao, LL, Lasnier, CJ, Lazarus, EA, Leonard, AW, Lin-Liu, YR, Lohr, J, Mahdavi, MA, Makowski, MA, Murakami, M, Petty, CC, Pinsker, RI, Prater, R, Rettig, CL, Rhodes, TL, Rice, BW, Strait, EJ, Taylor, TS, Thomas, DM, Turnbull, AD, Watkins, JG, West, WP, and Wong, K-L
- Subjects
Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Fluids & Plasmas - 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.
- Published
- 2001