Temporal Stabilization of Magnetic Flux Focused by Superconducting Magnetic Lens

Two methods for stabilizing magnetic fields focused by a magnetic lens that uses high-temperature superconducting bulks were proposed and verified experimentally in this paper. One is a method for reducing the temperature of the magnetic lens during the energization of a surrounding coil that generates a background magnetic field. The other is a method that combines this temperature reduction method with a method for overshooting the background magnetic field. A magnetic lens was fabricated with high-temperature superconducting bulks. It was inserted into the bore of an MgB2 coil with an inner diameter of 220 mm. The coil was energized up to a constant current, and the magnetic field was measured. The two methods effectively stabilized the focused magnetic field. The temperature reduction method and the combination of the two methods reduced the decay rate of -6500 ppm/h to -1300 and -30 ppm/h, respectively. This rate is small enough for some accelerator applications, but further studies are needed to expand on applications of magnetic lenses.