Progress in Snowflake Divertor Studies on TCV

Since pioneering the alternative “snowflake”(SF) divertor, TCV research has concentrated on understanding its usefulness and applicability for a fusion reactor. It was first demonstrated that this divertor configuration is compatible with the high confinement H-mode regime on TCV and other machines. Since the main hope for this configuration is to lower the peak power incident on the divertor, and in particular near the strike points, this paper presents a résumé of experiments on TCV that seek to understand and model the particle and energy flows of a SF divertor configuration. The variety of possible snowflake configurations are presented and compared with, for reference, a similarly shaped (and in use on many machines), single-null configuration. The resulting heat and particle flows to the divertor strike plates are compared to each-other and with the first results from physics based numerical modelling. Most recently, initial experiments with wide density scans and impurity injection, designed to test possible advantages of a SF in increasing the radiated fraction or facilitating divertor detachment are reported.