Measurement and calculation of the radial electric field in the stellarator W7-AS

At the advanced stellarator W7-AS, active charge exchange recombination spectroscopy (CXRS) is used to measure the toroidal and poloidal impurity rotation velocity. The radial electric field is determined experimentally from the radial force balance equation. In parallel, is calculated by means of the neoclassical drift kinetic equation solver (DKES) transport code. Neoclassical calculation and measurement are, in general, in good agreement. A selection of discharges is presented in this paper which shows typical properties of at W7-AS, and which highlights the mutual relationship between and transport.