학술논문
Long pulse high performance discharges in the DIII-D tokamak
Document Type
article
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; Wong, K-L
Source
Nuclear Fusion. 41(11)
Subject
Language
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.