SQUID magnetometers for low-frequency applications

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Journal of Low Temperature Physics; (USA)

DOI:https://doi.org/10.1007/BF00681735· OSTI ID:6253068

Ryhaenen, T; Seppae, H ^[1]; Ilmoniemi, R; Knuutila, J ^[2]

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1. Helsinki Univ. of Technology and Technical Research Centre of Finland, Espoo (Finland)
2. Helsinki Univ. of Technology, Espoo (Finland)

The authors present a novel formulation for SQUID operation, which enables them to evaluate and compare the sensitivity and applicability of different devices. SQUID magnetometers for low-frequency applications are analyzed, taking into account the coupling circuits and electronics. They discuss nonhysteretic and hysteretic single-junction rf SQUIDs, but the main emphasis is on the dynamics, sensitivity, and coupling considerations of dc-SQUID magnetometers. A short review of current ideas on thin-film, dc-SQUID design presents the problems in coupling and the basic limits of sensitivity. The fabrication technology of tunnel-junction devices is discussed with emphasis on how it limits critical current densities, specific capacitances of junctions, minimum linewidths, conductor separations, etc. Properties of high-temperature superconductors are evaluated on the basis of recently published results on increased flux creep, low density of current carriers, and problems in fabricating reliable junctions. The optimization of electronics for different types of SQUIDs is presented. Finally, the most important low-frequency applications of SQUIDs in biomagnetism, metrology, geomagnetism, and some physics experiments demonstrate the various possibilities that state-of-the-art SQUIDs can provide.

• OSTI ID: 6253068
• Journal Information: Journal of Low Temperature Physics; (USA), Vol. 76:5-6; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

47 OTHER INSTRUMENTATION
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MAGNETOMETERS
USES
SQUID DEVICES
CARRIER DENSITY
COMPARATIVE EVALUATIONS
CRITICAL CURRENT
CURRENT DENSITY
DEPOSITION
ELECTRONIC CIRCUITS
FABRICATION
HEAT FLUX
HYSTERESIS
JOSEPHSON JUNCTIONS
MAGNETIC FLUX
MATHEMATICAL MODELS
NOISE
OPERATION
OPTIMIZATION
PERFORMANCE TESTING
QUANTIZATION
REVIEWS
RF SYSTEMS
SENSITIVITY
SUPERCONDUCTING FILMS
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THIN FILMS
TUNNEL EFFECT
CURRENTS
DOCUMENT TYPES
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
ELECTRONIC EQUIPMENT
EQUIPMENT
FILMS
FLUXMETERS
JUNCTIONS
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
PHYSICAL PROPERTIES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TESTING
440800* - Miscellaneous Instrumentation- (1990-)
420201 - Engineering- Cryogenic Equipment & Devices