Abstract: A primary current path (10) is defined by a thin film that spirals in a helix (14) around a central axis (16). A control path (12) extends peripherally around the helix to define a peripheral control coil (18). In this manner, the primary path and the control path each generate a magnetic flux parallel to the central axis. The primary and control paths are configured such that the magnetic flux density (B.sub.1) generated by the primary path is below a critical flux density (B.sub.c) of the superconducting material of the primary path. However, the sum of the magnetic flux densities from the primary and control paths exceeds the critical flux density (B.sub.1 +B.sub.2 >B.sub.c) quenching the superconductivity of the primary path. In the preferred embodiment, the superconducting film is anisotropic in that its critical flux density is smaller perpendicular to a plane of the film than parallel to the plane of the film.