Abstract: Apparatus, consisting of a substrate and planar tapes which have respective mutually-opposing first and second faces. The tapes have edges connecting the faces, and each tape has a superconducting material on at least the first face thereof. The tapes may be arranged on the substrate so as to define at least a first set of at least one of the planar tapes overlying a surface of the substrate so that the edges of adjacent sections of the tapes in the first set butt together along a first direction over the surface. The tapes may also be arranged so that a second set of at least another one of the planar tapes overly the first set so that the edges of adjacent sections of the tapes in the second set butt together along a second direction that is different from the first direction.