MULTILOOP SELF-SHIELDED DC-SQUID WITH MEANDER-SHAPED INPUT COIL

A multi-loop design insensitive to external uniform magnetic fields is suggested for a dc SQUID. The SQUID has a meander-shaped coupling coi l, which show promise both for LTc and HTc biomagnetic measuring syste ms. The 16- and 32-loop versions of the SQUID were manufactured using niobium technology and were tested experimentally. On the basis of the experimental data it was shown that the use of LTc multi-loop SQUIDs makes it possible to develop biomagnetic measuring gradiometers ,vith a resolution of the order of 3-4 fT/root Hz. A multiloop SQUID may be used,vith a flux transformer in the form of a first-order gradiometer free from conductor crossings. Such a gradiometer has a single-layer d esign and can be easily fabricated from HTc materials.