Tunnel junction dc SQUID: fabrication, operation, and performance

Journal Article · Fri Oct 01 04:00:00 EDT 1976 · J. Low Temp. Phys.; (United States)

DOI:https://doi.org/10.1007/BF00654826· OSTI ID:7214804

Clarke, J; Goubau, M; Ketchen, M B

A description is given of the theory, fabrication, operation, and performance of a cylindrical dc SQUID made with shunted Nb-NbO/sub x/-Pb Josephson tunnel junctions. The SQUID is current-biased at a nonzero voltage and modulated with a 100 kHz flux. The 100 kHz voltage developed across the SQUID is amplified by a cooled resonant LC circuit that optimally couples the SQUID impedance to the input of a room temperature FET preamplifier. A typical flux noise power spectrum for a SQUID at 4.2K in a superconducting shield is presented. At lower frequencies, the power spectrum is approximately 10/sup -10/ (1 Hz/F)phi/sub 0//sup 2/ Hz/sup -1/, where F is the frequency. This value is approximately two orders of magnitude greater than the calculated I/F noise in the tunnel junctions. A detailed description is given of the coupling efficiency of various input coils wound on the SQUID. The effects of coupling between the input coil, the SQUID, and the feedback (modulation) coil are described and measurements of the coupling parameters reported.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 7214804
• Journal Information: J. Low Temp. Phys.; (United States), Journal Name: J. Low Temp. Phys.; (United States) Vol. 25:1/2; ISSN JLTPA
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COUPLING
CURRENTS
DIRECT CURRENT
ELECTRIC CURRENTS
ELECTRONIC CIRCUITS
ELECTRONIC EQUIPMENT
FABRICATION
FLUXMETERS
FREQUENCY DEPENDENCE
JOSEPHSON JUNCTIONS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
NOISE
OPERATION
PERFORMANCE
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TANK CIRCUITS