A procedure for the design of snowflake magnetic configurations in tokamaks

This paper deals with the design of snowflake (SF) plasma configurations in tokamaks. The SF configuration represents a promising solution for the power exhaust and divertor design problem due to its ability to flare the scrape-off layer in the vicinity of the SF point. SF plasma configurations have been successfully achieved in tokamaks like Tokamak à Configuration Variable (TCV), DIII-D and National Spherical Torus Experiment (NSTX), and are under investigation for future tokamaks such as DEMO. The first attempts to determine such new plasma configurations have picked out the inherent difficulties in obtaining them with low coil currents and in controlling the associated equilibria against external disturbances and modeling errors. This paper presents a novel procedure based on the linearized model of the plasma for the design of an SF divertor configuration. Moreover, a procedure for the optimization of the poloidial field coil system is proposed. The effectiveness of the techniques is demonstrated with an application to DEMO. (paper)