IEEE Transactions on Magnetics

Double transformer coupling to a very low noise SQUID

B. Muhlfelder, W. Johnson, Michael W. Cromar

Published May 1, 1983• 69 citations

Abstract

We demonstrate a new way to couple efficiently to a low-inductance, low-noise SQUID. We have built and tested a planar dc SQUID with an integral matching transformer. The measured coupling agrees with our calculations. We demonstrate that this configuration can efficiently couple a 1 μH signal source to a 16 pH SQUID loop. We have also built an uncoupled SQUID of this design that has an energy sensitivity, referred to the SQUID inductor, of 1.3 × 10-32J/Hz = 20 h over a flux range of about 0.15 φ0.

DOI: 10.1109/tmag.1983.1062527

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