Magnetic Force Field Enhancement by Field Cooling of HTS Bulk Cylinder

In order to obtain a large magnetic force environment using a commercially available superconducting magnet with a room-temperature bore, a new cryostat cooling a high-temperature superconductor (HTS) bulk cylinder with a G-M cryocooler down to approximately 20 K was developed. The cryostat was inserted so that the bulk cylinder might be located at the mid-plane of a 12-T cryocooler-cooled magnet. In the first experiment, the cylinder was cooled from room temperature to 21 K at 5.0 T. The backup field was then decreased to 0 T. A field of 4.9 T was maintained along the Z-axis inside the cylinder. The second experiment was carried out from a backup field of 11.5 T. The HTS bulk cylinder maintained the magnetic flux down to about a backup field of 7.6 T, at which point the superconducting state of the cylinder was lost in a brief period. The experimental data exhibit good accordance with the calculation results. In the calculation, the minimum BdB /dz of -1029 T²/m was estimated to be generated along the Z-axis. As that of the magnet is -564 T²/m at 12 T, the enhancement of the magnetic force with the HTS bulk cylinder was confirmed.