Microinstability-based model for anomalous thermal confinement in tokamaks

This paper deals with the formulation of microinstability-based thermal transport coefficients (chi/sub j/) for the purpose of modelling anomalous energy confinement properties in tokamak plasmas. Attention is primarily focused on ohmically heated discharges and the associated anomalous electron thermal transport. An appropriate expression for chi/sub e/ is developed which is consistent with reasonable global constraints on the current and electron temperature profiles as well as with the key properties of the kinetic instabilities most likely to be present. Comparisons of confinement scaling trends predicted by this model with the empirical ohmic data base indicate quite favorable agreement. The subject of anomalous ion thermal transport and its implications for high density ohmic discharges and for auxiliary-heated plasmas is also addressed.

[1]  Tadashi Sekiguchi,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 1987 .

[2]  T. Hellsten.  Plasma physics and controlled nuclear fusion research 1978: vols. I and II, 7th Conf. Proc. Innsbruck, 23–30 August 1978, Nuclear Fusion, suppl. 1979 (IAEA, Vienna, 1979) vol. 1 pp. 828, Austrian Schillings 1160.-; vol. 2 pp. 671, Austrian Schillings 970.-. , 1979 .

[3]  P. Liewer.  Measurements of microturbulence in tokamaks and comparisons with theories of turbulence and anomalous transport , 1985 .

[4]  K. Razumova.  Results from T-7, T-10, T-11 and TM-4 Tokamaks , 1984 .

[5]  S. Kaye.  A review of energy confinement and local transport scaling results in neutral‐beam‐heated tokamaks , 1985 .

[6]  W. Tang,et al.  Residual trapped-ion instabilities in tokamaks , 1976 .

[7]  A. T. Ramsey,et al.  Evolution of the electron temperature profile of ohmically heated plasmas in TFTR , 1986 .

[8]  R. J. Fonck,et al.  Thermal energy confinement scaling in PDX limiter discharges , 1984 .

[9]  T. H. Dupree.  Nonlinear Theory of Drift‐Wave Turbulence and Enhanced Diffusion , 1967 .

[10]  M. S. Chance,et al.  Electromagnetic kinetic toroidal eigenmodes for general magnetohydrodynamic equilibria , 1982 .

[11]  R. Waltz,et al.  Tokamak transport code simulations with drift wave models , 1987 .

[12]  W. Tang,et al.  Destabilization of the trapped-electron mode by magnetic curvature drift resonances , 1976 .

[13]  F. Romanelli,et al.  Anomalous thermal confinement in ohmically heated tokamaks , 1986 .

[14]  Ballooning-mode theory of trapped-electron instabilities in tokamaks , 1981 .

[15]  R. Waltz,et al.  Determination of electron and ion thermal conductivities by analysis of Alcator‐A profile data , 1983 .

[16]  G. Rewoldt,et al.  Microinstabilities in weak density gradient tokamak systems , 1986 .

[17]  E. Ott,et al.  Anomalous electron‐ion energy exchange from the trapped electron mode , 1977 .

[18]  R. Groebner,et al.  Experimentally inferred ion thermal diffusivity profiles in the Doublet III tokamak: Comparison with neoclassical theory , 1986 .

[19]  F. Hinton,et al.  Theory of plasma transport in toroidal confinement systems , 1976 .

[20]  Robert James Goldston.  Energy confinement scaling in Tokamaks: some implications of recent experiments with Ohmic and strong auxiliary heating , 1984 .

[21]  R. E. Waltz,et al.  Empirical scaling laws for energy confinement in Ohmically-heated tokamaks , 1979 .

[22]  Robert J. Goldston,et al.  Theory of mode-induced beam-particle loss in tokamaks , 1983 .

[23]  G. Rewoldt,et al.  Kinetic analysis of MHD ballooning modes in tokamaks , 1985 .

[24]  R. Waltz,et al.  Maximum energy-confinement time in Joule-heated tokamaks , 1979 .

[25]  G. Rewoldt,et al.  Integral formulation for the two‐dimensional spatial structure of drift and trapped‐electron modes , 1978 .

[26]  W. Tang.  Microinstability theory in tokamaks , 1978 .

[27]  Equipe Tfr.  Tokamak scaling laws, with special emphasis on TFR experimental results , 1980 .

[28]  H. Knoepfel,et al.  Heating in Toroidal Plasmas (Report on the 4th International Symposium, Rome, 21–28 March, 1984) , 1984 .

[29]  Brian Labombard,et al.  Energy confinement of high-density pellet-fueled plasmas in the Alcator C tokamak , 1984 .

[30]  M. Dobrowolny,et al.  Drift wave anomalous transport in axisymmetric toroidal plasmas , 1974 .

[31]  T. Petrie,et al.  Scaling of energy confinement with minor radius, current and density in Doublet III Ohmically heated plasmas , 1982 .

[32]  W. Tang,et al.  Ion-temperature-gradient instability in toroidal plasmas , 1983 .