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  • Kinetic theory of convectiv...
    Gurevich, A.V; Dimant, Ya.S; Lebedev, P.N

    Nuclear fusion, 02/1981, Letnik: 21, Številka: 2
    Journal Article

    The ripple transport of fast (suprathermal) ions and electrons in tokamaks is analyzed. This transport, which arises from the drift motion of particles blocked in the ripple of a magnetic field, is of the convective type for particles whose energy exceeds a certain value. It is noted that for ions in real tokamaks, this energy region may be close to the bulk of ions having thermal energy. Kinetic equations for the particle distribution function are derived, with consideration given to the ripple drift motion through the magnetic surfaces. In the low-energy (diffusive) limit, the results are found to be in good agreement with the well-known ones; in the case of more energetic particles, convective transport dominates. In particular, a replacement (throught the ripple channel) of fast electrons from the hot periphery is possible; this results in a considerable rise there of the distribution function tail. The importance of the increase in the ripple depth from the chamber center to the periphery is stressed; it causes collisionless adiabatic capture of particles by ripples, which are held there, then drift, and finally escape from the plasma.