Title :
A SQUID picovoltmeter working at 77 K
Author :
Eriksson, T. ; Blomgren, J. ; Winkler, D. ; Holst, T. ; Shen, Y.Q.
Author_Institution :
ABB Corp. Res., Vasteras, Sweden
fDate :
6/1/1999 12:00:00 AM
Abstract :
A SQUID picovoltmeter working at 77 K has been constructed with a bandwidth of 37 kHz. The white noise of the picovoltmeter was 32 pV//spl radic/Hz with the input shorted. For an optimal source resistance of 0.8 /spl Omega/ the noise temperature was 46 K. The picovoltmeter was constructed from a multilayer high-T/sub c/ SQUID-magnetometer coupled to the signal source via a 10-turn copper coil. The mutual inductance between the coil and the SQUID washer was 0.7 nH. To reduce the noise contributions of the first-stage room temperature amplifier, additional positive feedback (APF) was used together with direct read-out electronics. As a demonstration, the current-voltage characteristics of another SQUID was measured with the picovoltmeter.
Keywords :
SQUIDs; high-temperature superconductors; superconducting device noise; voltmeters; white noise; 37 kHz; 77 K; SQUID picovoltmeter; additional positive feedback; current-voltage characteristics; direct readout electronics; multilayer high-T/sub c/ SQUID magnetometer; white noise; Bandwidth; Coils; Copper; Feedback; Inductance; Noise reduction; Nonhomogeneous media; SQUIDs; Temperature; White noise;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
