Shielding of pulsed magnetic fields with already sintered 1 mu m sized powder-pressed Bi-based superconducting rings

To confirm a ferrite-core model for the superconducting rings (supertrons) to focus and guide electron current beams, we examined a bismuth-based ring into the configuration of which already sintered 1 mum sized 2223-phase po wders were cold-isostatic pressed, No additional sintering was performed on the ring. Although the four-probe dc electric resistance of the ring incre ased with decreasing temperatures down to 77 K, the ring effectively shield ed the self-magnetic field of single pulsed nanosecond-order electron curre nts (similar to 340 keV, similar to1 kA, similar to 10 ns), below the T-c. These results certainly support the model, and provide a clue useful in app lications of bulk superconductors. (C) 2001 American Institute of Physics.