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Current resolution, noise, and inductance measurements on high-<i>T</i> <i>c</i> dc SQUID galvanometers
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1996
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Superconducting MaterialEngineeringMeasurementTemperature DependenceEducationInstrumentation EngineeringQuantum EngineeringElectromagnetic CompatibilityJosephson JunctionsNovel SuperconductorsInductance MeasurementsCalibrationSuperconductivityQuantum MaterialsHigh Tc SuperconductorsInstrumentationSuperconducting DevicesElectrical EngineeringPrecision MeasurementHigh-tc SuperconductivityPhysicsQuantum DeviceQuantum Interference DevicesSquid InductanceMicroelectronicsHigh-frequency MeasurementQuantum TechnologyApplied PhysicsQuantum DevicesElectronic InstrumentationQuantum SuperconductivityCurrent Resolution
Single layer autonomous high-Tc dc superconducting quantum interference devices (SQUIDs) have been fabricated and tested. The SQUIDs were designed for application as a galvanometer. The current to be measured is injected directly in a microstrip segment of the SQUID loop. Step-edge as well as bicrystal YBCO Josephson junctions were used. We consider two aspects: (i) optimization of the noise properties with respect to current resolution, and (ii) temperature dependence of the period of voltage-flux relation. The SQUID inductance was calculated numerically taking into account the magnetic field penetration depth λ. The temperature dependence of λ(T) was obtained from experimental results and is found to be in good agreement with λ(T)≊λ(0)[1−(T/TC)2]−1/2.