MAGNETIC SHIELDING STUDIES USING CYLINDERS OF YBA2CU3O7-X PREPARED BYISOSTATIC COMPRESSION

The shielding properties of cylindrical pots of YBa2Cu3O7-x (YBCO) pre pared by isostatic compression were measured at 77 K for d.c. magnetic fields as well as a.c. magnetic fields in the range of frequencies fr om 100 Hz to 5 KHz. The critical penetration field (H), defined as th e value of the applied magnetic field, at which a detectable field was observed inside the cylinder was 16 Gauss for isostatically compresse d cylinders. The H values decreased as a function of frequency of the applied field was increased. The waveform of the field inside the cyl inder for a sinusoidal applied field was highly distorted and showed t he presence of higher harmonics with appreciale amplitude. The additio n of 10% Ag seems to improve shielding at higher fields. The results a re compared with that of a shield prepared by uniaxial compression.