Advanced ST Plasma Scenario Simulations for NSTX
Authors: C.E. Kessel, E.J. Synakowski, D.A. Gates, R.W. Harvey, S.M. Kaye, T.K. Mau, J. Menard, C.K. Phillips, G. Taylor, R. Wilson, and the NSTX Research Team
Date of PPPL Report: October 2004
Pubished in: Nuclear Fusion 45:8 (August 2005) 814-824
Presented at: the 20th IAEA Fusion Energy Conference, 1-6 November 2004, Vilamoura, Portugal. The papers will be published by the IAEA as unedited proceedings in electronic format on CD-ROM and on the IAEA Physics Section web site as soon as possible after the conference.
Integrated scenario simulations are done for NSTX [National Spherical Torus Experiment] that address four primary milestones for developing advanced ST configurations: high β and high βN inductive discharges to study all aspects of ST physics in the high-beta regime; non-inductively sustained discharges for flattop times greater than the skin time to study the various current-drive techniques; non-inductively sustained discharges at high β for flattop times much greater than a skin time which provides the integrated advanced ST target for NSTX; and non-solenoidal start-up and plasma current ramp-up.
The simulations done here use the Tokamak Simulation Code (TSC) and are based on a discharge 109070. TRANSP analysis of the discharge provided the thermal diffusivities for electrons and ions, the neutral-beam (NB) deposition profile, and other characteristics. CURRAY is used to calculate the High Harmonic Fast Wave (HHFW) heating depositions and current drive. GENRAY/CQL3D is used to establish the heating and CD [current drive] deposition profiles for electron Bernstein waves (EBW). Analysis of the ideal-MHD stability is done with JSOLVER, BALMSC, and PEST2.
The simulations indicate that the integrated advanced ST plasma is reachable, obtaining stable plasmas with β ≈ 40% at βN's of 7.7-9, IP = 1.0 MA, and BT = 0.35 T. The plasma is 100% non-inductive and has a flattop of 4 skin times. The resulting global energy confinement corresponds to a multiplier of H98(y,2) = 1.5. The simulations have demonstrated the importance of HHFW heating and CD, EBW off-axis CD, strong plasma shaping, density control, and early heating/H-mode transition for producing and optimizing these plasma configurations.