Multispecies density and temperature gradient dependence of quasilinear particle and energy fluxes

The variations of the normalized quasilinear particle and energy fluxes with artificial changes in the density and temperature gradients, as well as the variations of the linear growth rates and real frequencies, for ion temperature gradient and trapped-electron modes, are calculated. The quasilinear fluxes are normalized to the total energy flux, summed over all species. Here, realistic cases for tokamaks and spherical torii are considered which have two impurity species, specifically cases for the Joint European Torus (JET) [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] and the National Spherical Torus Experiment (NSTX) [M. Ono, S. M Kaye, Y.-K. M. Peng, Nucl. Fusion 40, 557 (2000)]. For situations where there are substantial changes in the normalized fluxes, the "diffusive approximation," in which the normalized fluxes are taken to be linear in the gradients, is seen to be inaccurate. In the case of artificial changes in density or temperature gradients, changes in the fluxes of different species ("off-diagonal") generally are significant, or even dominant, compared to those for the same species ("diagonal").