Use of superconducting self-correcting harmonic coils for pulsed superconducting dipole or multipole magnets

Thanks to the zero resistance of a superconducting wire, an induced current in a closed superconducting circuit is continuously exactly opposed to its cause. This phenomenon has been applied to the correction of the field harmonics of a pulsed magnet by putting short-circuited superconducting coils of particular symmetry in the useful aperture of the magnet. After a recall of the choices to be done for the main characteristics of such devices [1], the construction of two correcting coils (quadrupole and sextupole) is described. Experimental results about magnetic efficiency and time behaviour are given; they are quite encouraging since the field harmonicshave been reduced by one or two orders of magnitude.