Electricity: measuring and testing – Magnetic – Magnetometers
Patent
1995-06-07
1997-08-12
Snow, Walter E.
Electricity: measuring and testing
Magnetic
Magnetometers
505846, G01R 3302, G01R 33035, H01L 2100, H01L 3922
Patent
active
056569378
ABSTRACT:
A multiple loop dc SQUID configuration with input and modulation circuitry configured for high-symmetry and low-noise operation is disclosed. The configuration is adaptable to implementation using standard thin film circuit fabrication technology. The SQUID inductance is defined by a plurality of washer-shaped thin superconducting films symmetrically oriented on a substrate and connected in series through a pair of Josephson junctions to form a multiple-washer gradiometric structure. The series connection arrangement also minimizes the number of required input and output terminal pads. Bias and modulation conductors are configured so as to prevent magnetic fields produced by currents flowing therethrough from coupling to the SQUID, and the modulation and input coil portions of the SQUID circuit are symmetrically configured to minimize signal coupling therebetween. A method of parameter selection for the input and modulation circuit portions of the SQUID configuration is disclosed which establishes a well-defined resonance point for the SQUID, within which low-noise operation is possible.
REFERENCES:
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patent: 5219826 (1993-06-01), Kapitulnik
Clarke, J. "SQUIDS: Theory & Practice" (1993) New Superconductivity Electronics, Kluwer Academic Publishers.
Knuutila, J., et al., "Design, Optimization, and Construction of a DC SQUID with Complete Flux Transformer Circuits," (1988) J. Low Temp. Phys. 71:(5/6)369-391.
Yamasaki, et al., "Design and Fabrication of Multichannel DC SQUIDS for Biomagnetic Applications" (1993) IEEE Transactions on Applied Superconductivity 3:(1) 1887-1889.
Foglietti, et al., "A Double dc-SQUID Device for Flux Locked Loop Operation" (1991) IEEE Transactions on Magnetics 27:(2)2989-2992.
Cantor, et al., "Design and Optimization of DC SQUIDS Fabricated Using a Simplified Four-Level Process" (1991) IEEE Transactions on Magnetics 27:(2)2927-2931.
Ryhanen, T. and Seppa, H., "Effect of Parasitic Capacitance and Inductance on the Dynamics and Noise of dc Superconducting Quantum Interference Devices" (1992) J. Appl. Phys. 71:(12)6150-6166.
Conductus, Inc.
Snow Walter E.
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