Compensation of 1/1 and 2/2 error field in Wendelstein 7-X via divertor heat load symmetrization

Recent experiments with the water-cooled, high-heat-flux divertor of the Wendelstein 7-X
(W7-X) stellarator demonstrate substantial progress in error-field compensation. Numerical
simulations reveal a pronounced sensitivity of divertor heat load distributions to error fields.
Experimentally, wide-angle infrared cameras monitoring all ten divertor units show significant
improvements in the symmetry of divertor thermal footprints when trim coils and control coils
are employed to compensate intrinsic 1/1 and 2/2 error fields, respectively. The experimentally
determined amplitude of the intrinsic 1/1 error field is consistent with results obtained seven
years ago, despite different diagnostics, divertor components, and slight variation in magnetic
configurations. For the first time, the intrinsic 2/2 error field has been compensated through a
phase-scan experiment using control coil currents, supported and validated by simulations.