Kinetic effects of magnetic turbulence in tokamaks
The electron kinetic theory in tokamak plasmas in the presence of magnetic turbulence is investigated. The evolution of the electron distribution function under the effect of turbulent magnetic fields, a dc electric field, and Coulomb collisions is governed by a 3-dimensional kinetic equation (2-D in velocity space and 1-D in ordinary space). The turbulence is described by a radial diffusion operator, coupled to slowing-down in energy due to ambipolar fields. The resulting kinetic equation is solved numerically, by means of a new fully 3-D Fokker-Planck code. It is shown that, in a turbulent plasma, the central equilibrium electron distribution function is nearly Maxwellian, but in the temperature gradient region an anisotropic superthermal tail develops, due to radial diffusion of hot electrons. This affects the local electrical conductivity and the global plasma resistance. An analytical expression for this turbulent conductivity is derived.
Bibliographic Reference: Article: Nuclear Fusion (1992)
Record Number: 199210133 / Last updated on: 1994-12-02
Original language: en
Available languages: en