Plasma effect on error fields correction at high βN in ASDEX Upgrade

Tokamak plasmas can amplify very small resonant components of error fields (EFs) when operating close to the ideal magneto-hydrodynamic (MHD) limits. Such EFs are well diagnosed in ASDEX Upgrade tokamak (Igochine V et al 2017 Nucl. Fusion 57 116027, Maraschek M et al 40th EPS Conf. on Plasma Physics 2013 P4.127), which allows to model EF as well as the correction required for the optimal compensation. Experiments on ASDEX Upgrade show that EF correction considering the plasma effect, as it is foreseen for ITER, is necessary even in the case of small resonant EF. Such correction improves the achievable ss N by 10% and makes discharges more stable with respect to ideal modes.

Automated summary

Tokamak plasmas can amplify small resonant components of error fields near the ideal MHD limits. ASDEX Upgrade experiments demonstrate the necessity of EF correction considering plasma effect for optimal compensation, even for small resonant EFs. Such correction improves the achievable characteristics and stability of discharges.