IEEE Transactions on Magnetics

Well coupled, low noise, dc SQUIDs

B. Muhlfelder, James A. Beall, Michael W. Cromar, Ronald H. Ono, W. W. Johnson

Published Mar 1, 1985• 21 citations

Abstract

We have designed, fabricated, and tested a Double Transformer (DT) coupled dc SQUID (Superconducting Quantum Interference Device) with low noise, an input inductance of 1μH and a smooth input-output characteristic. A transmission line model is presented to explain a resonance in the input-output characteristic of early versions of this device. Guided by the results of numerical simulations a new version of this device has been built and tested. Experimental results are presented that show that the resonance can be moved to a higher voltage by reducing the area of the SQUID loop. The voltage-external flux characteristic of some of these new devices agrees to within 10% with computer simulations. The minimum detectable energy per unit bandwidth (MDE) referred to the SQUID loop, is 10h, where h is Planck's constant. Computer simulations indicate an MDE of 6h.

DOI: 10.1109/tmag.1985.1063844

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