Edge Plasma in Snowflake Divertor

Abstract The snowflake divertor (Ryutov 2007, Phys. Plasmas 14, 064502) uses a 2nd order null of the poloidal magnetic field instead of the 1st order null used in the standard divertor. This leads to a number of interesting geometric properties such as stronger fanning of the poloidal flux, stronger magnetic shear in the edge region, larger radiating volume, and larger connection length in the scrape‐off layer. These can potentially lead to new ways for alleviating heat loads on the divertor target plates. Discussion of properties of snowflake is presented, along with results of numerical modeling. Divertor leg volume is larger in snowflake than in the standard x‐point configuration, which leads to larger fraction of radiated power in the divertor. This allows the snowflake to transition to a strongly detached plasma regime more easily than for the standard x‐point. Besides, stronger shearing of the magnetic field in snowflake may be beneficial for controlling magneto‐hydrodynamic instabilities in the edge (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)