Persistent currents in ceramic and evaporated thin film toroids of Ba sub 2 YCu sub 3 O sub 7.

We have demonstrated the existence of circumferential persistent currents in Ba sub 2 YBu sub 3 O sub 7 ceramic toroids at 77K and 4.2K and in thin films at 77K. The field dependence of the critical current densities obtained from these persistent current measurements at 77K is in fair agreement with that obtained from transport measurements. A long term experiment showed that the resistivity is less than 1.2x10 sup (-17) OMEGA cm at 77K.