Wall current compensation for rotating magnetic perturbations through the magnetic diagnostic response function

The method of magnetic diagnostic response function (MDRF) [1] is well suited to estimating the magnetic fields of wall currents induced by rotating resonant magnetic perturbations (RMP). The MDRF provides a set of time dependent Green’s functions for the magnetic diagnostics, obtained by fitting magnetic measurements with individual coils energized at varying frequencies. The wall current field from RMP is then predicted by the response functions when using the RMP coil currents with arbitrary waveforms. These predictions will be validated by vacuum shots with rotating RMP fields in DIII-D. The wall current field from the rotating RMP is separated in magnetic signals to evaluate the effect of the wall currents on electromagnetic torque analysis of magnetic islands. The present work can provide the wall currents compensation in error field identification experiments, which use a rotating RMP field to drive rotation of an n=1 magnetic island. Additionally, this work will benefit the analysis of other experiments with time-varying applied fields by accounting for the effects of induced currents in the wall and other conducting structures.

[1] Y. Jiang, RSI 2017