Plasma diffusion in an ergodic magnetic limiter

Creation of an ergodic volume of magnetic field lines by means of a single external helical magnetic field in toroidal geometry is briefly discussed. The enhanced heat conductivity in the ergodic magnetic limiter has been calculated taking into account the cubic coherent nonlinearity of perturbations including the effect of plasma current within the limit of MHD approximation. Plasma diffusion coefficients have also been evaluated based on the two fluid model. In the quasilinear theory, without the radial electric field, the radial ion flux is found to be small. In the presence of a radial electric field under the ambipolar condition, an enhanced ion diffusion is possible.