Title :
Continuous feedback operation of a two-stage dc SQUID system
Author :
Jin, I. ; Wellstood, F.C.
Author_Institution :
Center for Supercond. Res., Maryland Univ., College Park, MD, USA
fDate :
6/1/1999 12:00:00 AM
Abstract :
We report on the continuous feedback operation of a two-stage dc Superconducting Quantum Interference Device (SQUID) system in which one SQUID works as a low-noise preamplifier to read out a second low-noise sensor SQUID. We first flux-locked the readout SQUID and measured the characteristics of the sensor SQUID, including its current-voltage characteristics, current-flux characteristics, and noise spectrum. We then investigated how the two SQUIDs could work together by simultaneously flux-locking both the sensor and the readout SQUIDs. With this two-SQUID flux-locking scheme, we recovered the noise spectrum of the sensor SQUID to within 4%. We discuss how to understand and optimize the two-stage SQUID feedback system.
Keywords :
SQUIDs; circuit feedback; preamplifiers; readout electronics; superconducting device noise; continuous feedback operation; current-flux characteristics; current-voltage characteristics; flux locking; noise spectrum; preamplifier; readout SQUID; sensor SQUID; two-stage DC SQUID system; Current measurement; Feedback; Interference; Noise measurement; Preamplifiers; SQUIDs; Sensor phenomena and characterization; Sensor systems; Superconducting device noise; Superconducting devices;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
