Parametric dependence of particle pinch coefficients for electron particle transport in linear gyrokinetic theory

Peaked density profiles are observed in the core of Tokamak plasmas in regimes where the core particle sources and neoclassical transport are negligible. Gyrokinetic theory predicts that microinstabilities can produce a net inward particle convection balancing outward diffusion and thus explaining the experimental observations. In this work we present a general methodology that allows to calculate the particle pinch coefficients, i.e. the off-diagonal elements of the transport matrix. We adopt this procedure to perform a systematic study of the parametric dependence of these coefficients for electron particle transport in different plasma conditions. Once the coefficients are computed, one can reconstruct the predicted gradient and compare with the experimental observations in regimes with parameters similar to the ones employed in these calculations. The procedure can predict the density logarithmic gradient at zero particle flux in a self-consistent way, based on first principles. The results can be helpful in understanding the possible range of variation of the predicted gradients as a function of the main plasma parameters and in clarifying the relevant dependencies for electrons. Finally, as instructive example, we discuss how this procedure can effectively help to interpret measurements of peaked density profiles in TCV electron Internal Transport Barriers and the significant thermodiffusive inward convection that is observed.