The development of a high-T/sub c/ magnetocardiography system for unshielded environment

A modular, 9-channel high-T/sub c/ SQUID system for magnetocardiography (MCG) was developed and tested in an unshielded environment. Galvanically-coupled magnetometers made from Y-Ba-Cu-O films, with intrinsic white noise levels as low as 70 fT//spl radic/Hz, are used as SQUID sensors. In an unshielded environment, a noise level of about 1 pT//spl radic/Hz for each channel was achieved using an active noise compensation system. A new digital planar gradiometer is proposed. First magnetocardiograms recorded in an unshielded environment are presented.