Title :
Characteristics of the relaxation oscillating SQUID with tunnel junctions
Author :
Uehara, G. ; Morooka, T. ; Kawai, J. ; Mizutani, N. ; Kado, H.
Author_Institution :
Superconducting Sensor Lab., Chiba, Japan
fDate :
3/1/1993 12:00:00 AM
Abstract :
The authors describe a relaxation oscillating superconducting quantum interference device (SQUID) fabricated using the Nb/AlO/sub x//Nb Josephson tunnel junction technique. It is demonstrated that this SQUID transfers flux changes into frequency changes. The relative linewidth of the frequency spectrum is on the order of 10/sup -5/. The spectral density of frequency fluctuations is 2*10/sup 4/ Hz/sup 2//Hz at both 10 kHz and 100 kHz. A method to evaluate the flux resolution of relaxation oscillating SQUIDs without a flux-locked loop is also proposed; the result is S/sub phi /(f)=2.1*10/sup -14/ phi /sub 0//sup 2//Hz at both 10 kHz and 100 kHz. The advantage of the relaxation oscillating SQUID is that it does not suffer from amplifier noise as long as the signal is treated in the frequency domain.<>
Keywords :
SQUIDs; aluminium compounds; electron device noise; niobium; relaxation oscillators; 10 kHz; 100 kHz; Josephson tunnel junction technique; Nb-AlO/sub x/-Nb; amplifier noise; flux noise; flux resolution; frequency spectrum linewidth; relaxation oscillating SQUID; spectral density of frequency fluctuations; Critical current; Fluctuations; Frequency domain analysis; Josephson junctions; Microwave frequencies; Niobium; Resistors; SQUIDs; Temperature sensors; Voltage;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
