ECRH and ECCD scenarios for W7-X

The main ECRH scenarios for the W7-X Stellarator are described. Both X2 (low and moderate densities) and O2 scenarios (high density) have been studied. Since O2 scenario cannot be realized without pre-heating, transition from X2 to O2 scenarios has been discussed. Due to a lack of Ohmic transformer, only ECCD is available for compensating the bootstrap current and for controlling the edge rotational transform value. The efficiency of ECCD for all main scenarios has been estimated. All simulations have been performed by a 1D transport code coupled self-consistently with ray-tracing code.