Well coupled, low noise, dc SQUIDs

• Published in: IEEE transactions on magnetics Vol. 21; no. 2; pp. 427 - 429
• Main Authors: Muhlfelder, B., Beall, J., Cromar, M., Ono, R., Johnson, W.
• Format: Journal Article
• Language: English
• Published: IEEE 01-03-1985
• Subjects: Computer simulation; Couplings; Model driven engineering; Resonance; SQUIDs; Superconducting device noise; Superconducting devices; Superconducting transmission lines; Testing; Voltage
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.1985.1063844

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.