Ion cyclotron heating scenarios for NET revisited

A critical review is made of the different possible ion cyclotron resonance heating (ICRH) scenarios to be envisaged for NET. Their relevance is examined with respect to both physical requirements, reactor applicability and specific NET constraints. The impact of the presence of fusion products on these methods is discussed. It is found that larger aspect ratio and operation at higher magnetic field can strongly reduce alpha particle effects. New dielectric tensor expressions relevant to such particle populations are derived; first estimates show that wave damping for realistic distribution functions can be much reduced with respect to Maxwellian results. It is concluded that the most attractive scheme is 2nd harmonic tritium heating rather than 2nd harmonic deuterium heating which is strongly modified by the presence of residual hydrogen and fusion produced alpha particles in the machine.