Magnetic shield of high-T/sub c/ Bi-Pb-Sr-Ca-Cu-O superconductors at 77 K for SQUID measurements

The authors have developed a relatively large high-T/sub c/ Bi-Pb-Sr-Ca-Cu-O superconducting magnetic shield vessel of 150 mm in inner diameter, 320 mm in depth, and 10 mm in thickness. It is applicable to biomagnetic measurements with a SQUID. Magnetic fields inside the vessel were measured by using a RF SQUID magnetometer or measuring induced voltages in a pickup coil. The shielding factors, defined as the ratio of the magnetic field at 290 K to that at 77 K, were around 10/sup 5/-10/sup 6/. The magnetic shielding of high-T/sub c/ superconductor is promising for neuromagnetic measurements with SQUIDs.