Novel superconductor/magnet resonant configurations: Exact analytic representations of the Meissner state and the critical state

We derive exact analytic representations of the Meissner state and the critical state of a current-carrying superconductor strip located inside a cylindrical magnetic cavity. Our results show that, when the distance between the superconductor and the magnet is small, the penetration of magnetic flux fronts is strongly reduced as compared to the respective situation in an isolated strip. Even for total currents almost matching the critical current of the strip, the major part of the superconductor remains flux free, so that AC losses in it are greatly depressed; a fact which facilitates the use of such a configuration as a coaxial-type transmission line. From our generic representation it is possible to derive current profiles in cavities of various other closed geometries too by means of conformal mapping of the basic configuration addressed.