High-energy components and collective modes in thermonuclear plasmas

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Abstract
The theory of a class of collective modes of a thermonuclear magnetically confined plasma, with frequencies in the range of the ion‐cyclotron frequency and of its harmonics, is presented. These modes can be excited by their resonant cyclotron interaction with a plasma component of relatively high‐energy particles characterized by a strongly anisotropic distribution in velocity space. Normal modes that are spatially localized by the inhomogeneity of the plasma density are found. This ensures that the energy gained by their resonant interaction is not convected away. The mode spatial localization can be significantly altered by the magnetic field inhomogeneity for a given class of plasma density profiles. Special attention is devoted to the case of a spin polarized plasma, where the charged products of fusion reactions are anisotropically distributed. It is shown that for the mode of polarization that enhances nuclear reaction rates the tritium will be rapidly depolarized for toroidal configurations with relatively mild gradients of the confining magnetic field.