Dielectric tensor expression for non-Maxwellian distribution functions and applications to α-particle damping in ICRH

A general expression of the dielectric tensor of a non-Maxwellian plasma is derived. Parasitic damping of the fast wave by fusion-generated alpha particles in ion cyclotron heating scenarios is investigated using a realistic slowing down distribution function. This indicates that despite the large birth velocity of α-particles their cyclotron damping is as small as the one of an equivalent Maxwellian with the temperature of 0.6 MeV. This reduces significantly the impact of α-particle absorption on the fundamental D and second harmonic T scenarios in D-T plasmas.