Robust Correction of 3D Error Fields in Tokamaks including ITER

Full text: Important progress has been made in the correction of 3D fields, based on the improved understanding of plasma response using the Ideal Perturbed Equilibrium Code (IPEC). The key to error field correction is to reduce the dominant distribution of 3D fields that is stronger often by an order of magnitude than any other distribution in breaking magnetic surfaces. The important validation is achieved in presently the most extreme case, the DIII-D mock-up experiments for the ITER Test Blanket Modules (TBMs). Although the TBM 3D fields are highly localized and can not be controlled by typical error field correction coils, the optimal operation could be restored using I-coils by minimizing the dominant part in the TBM 3D fields as IPEC prediction. Including TBM experiments, various experimental results in error field correction and locking in tokamaks have been successfully understood and quantified based on the dominant 3D fields, as can be summarized in the robust parametric scaling of the locking threshold across many different plasma configurations. The implications are favorable for ITER, since the highly reliable 3D field compensation can be provided for a wide range of different plasmas if the correction coil is designed based on the robust patterns of the dominant 3D fields. Present Error Field Correction Coil (EFCC) in ITER is under active investigations using IPEC to revise their capabilities. This research was supported by U.S. DOE contracts DE-AC02-76-CH03073, DE-FG02-03ERS496 and DE-FC02-04ER54698. (author)