Anomalous perturbative transport in tokamaks due to drift-wave turbulence

The authors calculate from first principles the incremental transport of particles and heat in the presence of electrostatic drift-wave turbulence in a tokamak plasma. The renormalized nonlinear plasma response function is derived using the Direct-Interaction Approximation (DIA). They obtain explicit expressions for all coefficients of the anomalous transport matrix relating particle and heat fluxes to density and temperature gradients in the plasma. The transport coefficients are about 2 to 4 times larger than predicted by the test-particle approximation. They find that, in the regime of interest, the trapped electrons contribute most to the transport. The anomalous transport matrix calculated in the DIA approximation does not have the Onsager symmetry. Using the parameters of the Texas Experimental Tokamak (TEXT), they evaluate all transport coefficients numerically, as well as the spectrum modulation. The relation between the theoretical results and the experiments is discussed. They also calculate the transport coefficients in the presence of drift-Alfven-wave turbulence, i.e., taking into account the magnetic field fluctuations. The magnetic terms are important for the transport by circulating electrons, but leave the transport by trapped electrons unaffected. Finally, they show that the transport of impurity particles is given, to first order in the impurity concentration, by the test-particle result