the same axial height z 0 as the observed loop of radius r 2 analog for ri 1 summing over all windings of the shielding coil which are approximately all at the same radius r 2 results in a new mutual coupling of the additional field generating coil system with the shielding coil l 2 u2190 d l 2 u2190 d cl u03b1 ue89e ra 1 r 2 ue89e l 2 red ra 1 u2190 d cl l 2 red ri 1 u2190 d cl l 2 red ra 1 u2190 d cl therein designates the classical coupling of the additional field generating coil system with the shielding u201c reduced u201d to the radius ra 1 analogous for ri 1 as a result of this u201c reduction u201d together with the multiplicative factor ra 1 r 2 the coupling l 2 u2190 d is less attenuated with respect to the classical value l 2 u2190 d cl than is l 1 u2190 d with respect to l 1 u2190 d cl since the main and shielding coils are electrically connected in series the inductive reaction of the shielding coil exceeds the one of the main coil in the overall reaction of the magnet coil system to the small field change in total the new coupling of the additional field generating coil system d with the magnet coil system m is given by with l m u2190 d cor l 1 u2190 d cl l 1 red ri1 u2190 d cl ra 1 r 2 ue89e l 2 red ra 1 u2190 d cl l 2 red ri 1 u2190 d cl analogous to the main coil the disturbance flux is also expelled from the superconducting volume of the.