CALCULATION OF REALISTIC SNOWFLAKE EQUILIBRIA FOR NEXT-STEP DEVICES

Tokamak equilibria with a snowflake divertor configuration are studied using a wire current model in toroidal geometry. A set of conditions for the formation of a snowflake divertor that can also be applied in full equilibrium calculations using a Grad-Shafranov solver is presented. It is shown that by taking into account the vertical force balance of the plasma, previously obtained results using a simple wire model have to be corrected. For a reactor-type device with coils far away from the plasma to accommodate the shielding requirements, the poloidal field coil currents become so high that they will represent a major technological challenge.