A hybrid SQUID gradiometer with 3-dimensional thin-film pick-up coils fabricated using an excimer laser

A compact hybrid superconducting quantum interference device (SQUID) gradiometer consisting of a coaxial pick-up coil with a superconducting Nb thin-film and a square double-washer dc-SQUID is developed. To make the pick-up coils, a 3-dimensional thin-film patterning technique is developed using an excimer laser. The gradiometer operates with flux locked loop electronics, a low-noise amplifier, and a high-speed (1 MHz) phase-sensitive detector. This gradiometer is sensitive to levels as low as 9 fT//spl radic/Hz.<
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