Current profile modeling to extend the duration of high performance advanced tokamak modes in DIII-D
- Lawrence Livermore National Lab., CA (United States)
- Univ. of California, Berkeley, CA (United States)
- General Atomics, San Diego, CA (United States)
In DIII-D, as in a number of tokamaks, high performance is obtained with various optimized magnetic shear configurations that exhibit internal transport barriers. Negative central shear (NCS) discharges are created transiently during the current ramp-up by auxiliary heating and current drive from neutral beam injection. Both q{sub min} and the radius at which it occurs, {rho}{sub qmin}, decrease with time as the Ohmic current diffuses inward. The q-profiles calculated using EFIT with external magnetic and Motional Stark Effect (MSE) measurements as constraints are comparable to those calculated with the Corsica code, a time-dependent, 2D equilibrium and 1D transport modeling code. Corsica is used to predict the temporal evolution of the current density from a combination of measured profiles, transport models and neoclassical resistivity. Using these predictive capabilities, the authors are exploring methods for increasing the duration and {rho}{sub qmin} of the NCS configuration by local control of the current density profile with simulations of the possible control available from the electron cyclotron heating and current drive system currently being upgraded on DIII-D. Their intention is not to do a detailed investigation of transport models but rather to provide a reasonable model of heat conductivity to be able to simulate effects of electron cyclotron heating (ECH) and current drive (ECCD) on confinement in NCS configurations. The authors adjust free parameters (c, c1 and c2) in the model to obtain a reasonable representation of the temporal evolution of electron and ion temperature profiles consistent with those measured in selected DIII-D shots. In all cases, they use the measured density profiles rather than self-consistently solve for particle sources and particle transport at this time.
- Research Organization:
- General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC03-89ER51114; FG03-89ER51116; W-7405-ENG-48
- OSTI ID:
- 638251
- Report Number(s):
- GA-A22914; CONF-980678-; ON: DE98007255; TRN: 98:007913
- Resource Relation:
- Conference: 25. European Physical Society conference on controlled fusion and plasma physics, Prague (Czech Republic), 29 Jun - 3 Jul 1998; Other Information: PBD: Jul 1998
- Country of Publication:
- United States
- Language:
- English
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