Current profile modeling to extend the duration of high performance advanced Tokamak modes in DIII-D

Conference · Thu Jun 25 04:00:00 EDT 1998

OSTI ID:302859

We use a model for negative central shear (NCS) heat transport which has a parametric dependence on the plasma conditions with a transport barrier dependence on the minimum of the safety factor profile, 4, qualitatively consistant with experimental observations. Our 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. We adjust free parameters (c, cl 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, we use the measured density profiles rather than self- consistently solve for particle sources and particle transport at this time In these results, we employ a simple model for the ECH power deposition by providing an externally supplied heat source for the electrons. The heating deposition location and profile are specified as a function of the toroidal flux coordinate to allow us to independently vary the heating dynamics For the results shown here, we assume a Gaussian profile, typically using a width of {delta}{rho}=O.O5 ({delta}r-3 cm in minor radius), with {rho} defined as the square root of toroidal flux All powers are interpreted as that absorbed by the plasma Similarly, the current drive location and profile are specified with the total current (integrated over the assumed profile) modeled as I{sub EccD}={Gamma}PEcH/neR with {Gamma}=0 005T{sub e}, providing current drive efficiency consistent with earlier experiments [6] with a dependence on T{sub e}, but fixed Z{sub eff} and trapped particle effects in these simulations Future work will integtate the existing TORCH [7] code into this ECH modeling effort.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 302859
• Report Number(s): UCRL-JC--131088; CONF-980678--; ON: DE98058892; BR: AT5010200
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPUTERIZED SIMULATION
CURRENT-DRIVE HEATING
DOUBLET-3 DEVICE
ECR HEATING
ELECTRIC CURRENTS
ELECTRIC DISCHARGES
TRANSPORT THEORY