Microinstability-based model for anomalous thermal confinement in tokamaks

Abstract

The paper deals with the formulation of microinstability-based thermal transport coefficients (χ_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 χ_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 database indicate quite favourable agreement. The subject of anomalous ion thermal transport and its implications for high density Ohmic discharges and for auxiliary heated plasmas is also treated.