(E)over-right-arrow x (B)over-right-arrow motion of test ion in spatially periodical structures of potential

We study the motion of test ions in the spatially periodical electrostatic field which is perpendicular to the homogeneous magnetic field. We show tha t the ion motion in such structures scales with a single dimensionless para meter R, which is a combination of amplitude and dimension of potential str uctures, magnetic field intensity and ion charge/mass ratio. We show that, for sufficiently large values of R, the ions are able to diffuse in space d ue to their chaotic scattering with the periodical lattice of the electric field. This approach is used for description of ion diffusion in potential structu res formed in the edge plasma of tokamaks due to the plasma turbulence. The diffusion coefficient, calculated by the Monte-Carlo method for magnetic f ields typical for tokamaks, was found to be sufficiently high for heavy imp urities even for modest amplitudes and dimensions of the potential structur es.