Multi-loop 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 coil, which show promise both for LTc and HTc biomagnetic measuring systems. 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 with a resolution of the order of 3-4 fT/spl radic/Hz. A multiloop SQUID may be used with a flux transformer in the form of a first-order gradiometer free from conductor crossings. Such a gradiometer has a single-layer design and can be easily fabricated from HTc materials.<
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