Gyrokinetic calculations of diffusive and convective transport of α particles with a slowing-down distribution function

Quasilinear gyrokinetic calculations of the transport of fast α particles with a slowing-down equilibrium distribution function in the trace limit are presented. Diffusive and convective contributions to the total flux are separated and their dependence on the ratio of the fast particle energy to the background plasma temperature is investigated. The results are compared with those obtained in the case an equivalent Maxwellian distribution function is assumed for the fast particles. On the basis of the gyrokinetic results, simple models for α particle transport are proposed for transport modeling purposes.