Operating space of the Dynamic Ergodic Divertor for TEXTOR-94

Abstract

The Dynamic Ergodic Divertor (DED) is under construction as a novel tool for TEXTOR-94 to control transport at the plasma edge and possibly also plasma rotation. The DED has been laid out for the plasma reference conditions rres(q = 3) and βpol = 1. The operational space of DED is analysed here. It has been shown that a sufficient edge ergodization can be reached for all relevant βpol values (0 ⩽ βpol ⩽ 2). By shifting the resonance layer close to the edge, the degree of ergodization can be substantially increased (by about a factor of 4). The power supplies allow a superposition of the base n = 4 mode with the n = 2 mode at arbitrary amplitude ratios, providing a partial decoupling of the perturbation amplitude and its penetration; by an admixture of 20% of the n = 2 mode, the diffusion coefficient for the magnetic field lines is significantly increased. Analyses of the operational space are carried out by using both novel asymptotic and mapping methods.