Issue: Generic Control Issue

Background Problems of heat load handling in the DEMO may require use of new types of divertors that would allow reducing both steady-state heat fluxes and controlling episodic energetic events (ELMS, blobs). A recently proposed snowflake divertor [1] is aimed at solving all these problems by using a divertor configuration where the null of the poloidal magnetic field will be of the second order (not the first order as in a standard X-point divertor). The separatrix then acquires a characteristic hexagonal shape reminiscent of the snowflake, whence the name. The snowflake divertor has a higher flux expansion than the X-point divertor; this feature may allow the fraction of the radiated power to be increased by seeding impurities or using puff-and-pump approach. Simultaneously, by affecting the magnetic shear both inside and outside the separatrix, the snowflake configuration provides additional control over ELMs and blobs. The process of creating snowflake configuration can be considered as a process of merging of two closely separated X-points. As it turns out, exact merging is not necessary; the distance between two X-points should be simply small enough, at the level of 10 % of the minor radius. As explained, control of a snowflake configuration is control of tw