Investigation and reduction of excess low-frequency noise in rf superconducting quantum interference devices

Journal Article · Sun May 01 04:00:00 EDT 1994 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.355954· OSTI ID:5000379

Mueck, M; Heiden, C ^[1]; Clarke, J ^[2]

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1. Institut fuer Schicht und Ionentechnik, Forschungszentrum Juelich (KFA), 52425 Juelich (Germany)
2. Department of Physics, University of California and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley California 94720 (United States)

A detailed study has been made of the low-frequency excess noise of rf superconducting quantum interference devices (SQUIDs), fabricated from thin niobium films and operated at 4.2 K, with rf bias frequencies of 0.15, 1.7, and 3 GHz. When the SQUIDs were operated in an open-loop configuration in the absence of low-frequency flux modulation, the demodulated rf voltage exhibited a substantial level 1/[ital f] noise, which was essentially independent of the rf bias frequency. As the rf bias frequency was increased, the crossover frequency at which the 1/[ital f] noise power was equal to the white noise power moved to higher frequencies, because of the reduction in white noise. On the other hand, when the SQUID was flux modulated at 50 kHz and operated in a flux locked loop, no 1/[ital f] noise was observed at frequencies above 0.5 Hz. A detailed description of how the combination of rf bias and flux modulation removes 1/[ital f] noise due to critical current fluctuations is given. Thus, the results demonstrate that the 1/[ital f] noise observed in these SQUIDs is generated by critical current fluctuations, rather than by the hopping of flux vortices in the niobium films.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5000379
• Journal Information: Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 75:9; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

665412* -- Superconducting Devices-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ELECTRONIC EQUIPMENT
ELEMENTS
EQUIPMENT
FILMS
FLUCTUATIONS
FLUXMETERS
FREQUENCY DEPENDENCE
FREQUENCY RANGE
GHZ RANGE
GHZ RANGE 01-100
KHZ RANGE
KHZ RANGE 01-100
MEASURING INSTRUMENTS
METALS
MICROWAVE EQUIPMENT
MODULATION
NIOBIUM
NOISE
SQUID DEVICES
SUPERCONDUCTING DEVICES
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TRANSITION ELEMENTS
VARIATIONS