Two-stream cyclotron radiative instabilities due to the marginally mirror-trapped fraction of fusion alphas in tokamaks

It is shown here that the marginally mirror-trapped fraction of newly born fusion alpha particles in deuterium-tritium (DT) reaction-dominated tokamak plasmas can induce a two-stream cyclotron radiative instability for fast Alfven waves propagating near harmonics of the alpha-particle cyclotron frequency ωcα. This can explain both the experimentally observed temporal behaviour and spatially localized origin of the fusion-product ion cyclotron emission (ICE) in TFTR at frequencies ω''appro='' mωcα. (Author)