Measured Temperature Dependence of High Tc SQUIDs and Magnetometers.
Abstract
We have made a systematic study of the temperature dependence of the (flux-locked) output of high Tc SQUIDs and SQUID magnetometers for small changes in temperature around the 77 K operating point. In zero magnetic field, we find typical temperature dependences of 4 to 60 ; mΦ _ 0 / K for bare SQUIDs and 10 to 100 ; mΦ _ 0 / K for 1 by 1 cm direct coupled magnetometers. In the Earth's field, both numbers increase significantly. At least two mechanisms contribute to the temperature dependence: the change in junction critical current and the change in magnetic penetration depth. Bias-reversing the SQUID can reduce the contribution of the former mechanism significantly. However, the contribution of the latter mechanism greatly increases in an applied magnetic field, particularly in the case of a magnetometer. For many proposed applications, small changes in temperature resulting from cryogen sloshing and/or cryocooler temperature fluctuations will hence result in changes in output of the SQUID that are larger than its self noise.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1996
- Bibcode:
- 1996APS..MAR.M1012M