Ultra-low-noise tunnel junction dc SQUID with a tightly coupled planar input coil
We present a new superconducting quantum interference device (SQUID) that combines ultra-low-noise performance with tight coupling to a useable input coil. The inductive loop of the SQUID consists of a superconducting square washer that is slit in a low inductance fashion from its central hole to an outside edge where two Josephson tunnel junctions are incorporated. The inductance of the SQUID is about 90 pH, and each junction has a critical current of 15 ..mu..A and a resistive shunt of 4.5 ..cap omega... The 190-nH input coil is a planar spiral of 50 turns situated immediately above the washer and coupled to the SQUID with a coupling constant k/sup 2/ of 0.86. The SQUID has a minimum coupled energy sensitivity of 19h at 4.2 K and 8h at 1.5 K, in good agreement with theory. The crossover between white and low frequency noise occurs at approx.250 Hz.
- Research Organization:
- IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598
- OSTI ID:
- 5658068
- Journal Information:
- Appl. Phys. Lett.; (United States), Journal Name: Appl. Phys. Lett.; (United States) Vol. 40:8; ISSN APPLA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMPARATIVE EVALUATIONS
CONFIGURATION
COUPLING
CRITICAL CURRENT
CURRENTS
DIRECT CURRENT
ELECTRIC COILS
ELECTRIC CURRENTS
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
EQUIPMENT
FLUXMETERS
JOSEPHSON JUNCTIONS
JUNCTIONS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
NOISE
SENSITIVITY
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTORS
TUNNEL EFFECT