Statistical analysis of expected error fields in tokamaks and their correction

摘要

Error fields in tokamak magnet systems are primarily associated with displacements of toroidal field and poloidal field coils, arising during their manufacture and assembly. The Fourier analysis of error fields on a rational magnetic flux surface, anticipated in the ITER machine, exhibited the lower-order modes ((m,n) = (1, 1), (2,1), (3,1)) of error fields as the most crucial ones. A statistical study using the Monte Carlo simulations has demonstrated that an averaged three-mode error field from the superposition of coil displacements can be two to three times higher than the acceptable level. The estimates obtained have been used to assess the capability of the correction coil system.