Ion orbit loss effects on radial electric field in tokamak edge for standard and snowflake divertor configurations

Neoclassical orbits and related non-ambipolar losses in tokamak edge are sensitive to the radial electric field Er; therefore an electric field in the edge may be affected by the ion orbit prompt loss at the null point [1]. This effect may be sensitive to the details of magnetic field near the null-point. In the snowflake divertor configuration [2], the prompt loss is quite different from that in the standard X-point configuration since the zone affected by the prompt loss in snowflake geometry is significantly larger than that for the standard X-point [3]. Here we extend the analytic study in [3] by including the effects of electric field and collisions using numerical calculation of drift orbits. Radial electric field induced by the prompt loss is compared for otherwise similar standard x-point configuration and a snowflake. \\[4pt] [1] C.S. Chang, S. Kue, H. Weitzner, Phys. Plasmas, 9, 3854 (2002).\\[0pt] [2] D.D. Ryutov, Phys. Plasmas, 14, 064502, June 2007.\\[0pt] [3] D.D. Ryutov and M.V. Umansky, Phys. Plasmas, 17, 014501 (2009)