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

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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 ... continued below

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7 p.

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Casper, T. A. June 25, 1998.

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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.

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7 p.

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OSTI as DE98058892

Other: FDE: PDF; PL:

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  • 25. European Physical Society conference on controlled fusion and plasma physics, Prague (Czech Republic), 29 Jun - 3 Jul 1998

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  • Other: DE98058892
  • Report No.: UCRL-JC--131088
  • Report No.: CONF-980678--
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 302859
  • Archival Resource Key: ark:/67531/metadc674974

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  • June 25, 1998

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  • July 25, 2015, 2:20 a.m.

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  • April 6, 2017, 6:02 p.m.

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Casper, T. A. Current profile modeling to extend the duration of high performance advanced Tokamak modes in DIII-D, article, June 25, 1998; California. (digital.library.unt.edu/ark:/67531/metadc674974/: accessed October 16, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.