Ion cyclotron and spin-flip emissions from fusion products in tokamaks

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Power emission by fusion products (i.e. protons and/or alpha particles) of tokamak plasmas in their ion cyclotron range of frequencies (ICRF) and at their spin-flip resonance frequency is calculated for some specific model fusion product velocity space distribution functions. Single 'dressed' test particle spontaneous emission calculations are presented first and the radiation temperature for ion cyclotron emission (ICE) is analysed both for black body emission and non-equilibrium conditions. Thresholds for instability and overstability (i.e. negative radiation temperature) conditions are then examined and quasi-linear and non-linear theories of the electromagnetic ion cyclotron modes are discussed. Some numerical estimates are presented for typical tokamak parameters. Semiquantitative remarks are offered on wave accessibility, mode conversion and parametric decay instabilities as possible mechanisms for spatially localized ICE. Calculations are carried out both for k|| = 0 and for k|| not= 0. The effects of the temperature anisotropy (i.e. T⊥ not= T||) and large drift velocities in the parallel direction are also examined. Finally, proton spin-flip resonance emission and absorption calculations are also presented both for thermal equilibrium conditions and for an 'inverted' population of states. Reasonably good agreement is obtained between theory and experiment. Distinctions between 'kinetic or causal instabilities' and 'hydrodynamic instabilities' are drawn in the Appendix