Principles and applications of SQUIDs

Journal Article · Tue Aug 01 04:00:00 EDT 1989 · Proceedings of the IEEE (Institute of Electrical and Electronics Engineers); (USA)

DOI:https://doi.org/10.1109/5.34120· OSTI ID:5648917

Clarke, J ^[1]

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1. California Univ., Berkeley, CA (USA). Dept. of Physics

Superconducting quantum interference devices (SQUIDs) combine flux quantization and Josephson tunneling to produce an output voltage that is periodic in the applied magnetic flux with a period of one flux quantum Phi/sub o/. SQUIDs are thus flux-to-voltage transducers, and are able to detect changes in flux much smaller that Phi/sub o/. Using Nb-based thin-film technology, a number of groups can now routinely fabricate dc SQUIDs with input circuits integrated on the same chip. At 4.2 {Kappa} the dc SQUID, which operates with a constant bias current, can detect signals with an equivalent energy per unit bandwidth of a few hundred h-bar. At low frequencies, the SQUID exhibits l/f noise that originates in fluctuations in the critical current of the junctions and in the motion of magnetic flux trapped in the thin films. RF SQUIDs, which operate with an RF flux bias, are usually machined from bulk Nb, and have a typical energy sensitivity per unit bandwidth of 10/sup 5/ to 10/sup 6/ h-bar. Both types of SQUID can be used in a wide variety of applications, including magnetometers, gradiometers, susceptometers, voltmeters, RF amplifiers, gravity wave antennas, and gravity gradiometers.

• OSTI ID: 5648917
• Journal Information: Proceedings of the IEEE (Institute of Electrical and Electronics Engineers); (USA), Journal Name: Proceedings of the IEEE (Institute of Electrical and Electronics Engineers); (USA) Vol. 77:8; ISSN IEEPA; ISSN 0018-9219
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
656100 -- Condensed Matter Physics-- Superconductivity
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMPLIFIERS
ANTENNAS
CRITICAL CURRENT
CURRENTS
ELECTRIC CURRENTS
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
EQUIPMENT
FABRICATION
FILMS
FLUCTUATIONS
FLUXMETERS
HIGH TEMPERATURE
JOSEPHSON EFFECT
MAGNETIC FLUX
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
QUANTUM ELECTRONICS
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING FILMS
VARIATIONS