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Well coupled, low noise, dc SQUIDs

1985; IEEE Magnetics Society; Volume: 21; Issue: 2 Linguagem: Inglês

10.1109/tmag.1985.1063844

1941-0069

B. Muhlfelder, James A. Beall, M. W. Cromar, R.H. Ono, W. Johnson,

Advanced Electrical Measurement Techniques

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.