Error field measurements with rotating RMP fields

This poster presents a method for error field measurement by injecting a short burst of rotating resonant magnetic perturbation (RMP) to entrain a saturated island at the end phase of the plasma current flattop. Minimizing error fields (EF) is important for improving fusion performance and avoiding disruptions. This work shows that 3D magnetic sensors can identify the error field’s amplitude and toroidal phase by analyzing of the torque balance on the island, including the electromagnetic (EM) torque from the wall, error field, rotating RMP, and the neutral beam injection (NBI) torque. The plasma response to the RMP is obtained by compensating magnetic data for the pickups from the RMP field and induced vessel field using the magnetic diagnostic response function [1]. Additionally, the field of the island is separated from the field of its induced wall currents using 2-axis measurements of the non-axisymmetric field [2]. This method has been recently tested in both L-mode and H-mode plasma on DIII-D. It can be used as a fast error field measurement technique during operation for various plasma conditions, efficiently enabling customized error field correction for a broad range of scenarios.