Operation of HTS SQUIDs with a portable cryostat: a SQUID system in conjunction with eddy current technique for non-destructive evaluation

Author

Lucia, M.L. ; Hohmann, R. ; Soltner, H. ; Krause, H.-J. ; Wolf, W. ; Bousack, H. ; Faley, M.I. ; Sporl, G. ; Binneberg, A.

Author_Institution

Dept. de Fisica Aplicada III, Univ. Complutense de Madrid, Spain

Volume

7

Issue

2

fYear

1997

fDate

6/1/1997 12:00:00 AM

Firstpage

2878

Lastpage

2881

Abstract

We present a new design of a portable nitrogen cryostat for operation of moving SQUIDs. A mixture of liquid and gaseous nitrogen fills a reservoir in direct contact with a copper part for the SQUID integration. The temperature at the SQUID position is 77.8 K or 78.8 K depending on orientation, and varies within /spl plusmn/10 mK during lateral movement. The cryostat can operate as a portable system for 7 hours without refilling. Washer rf SQUIDs and dc gradiometers were integrated with the cryostat. We proved the operation of the system as a moving magnetometer in an unshielded laboratory environment. Noise spectra in shielding and outside were independent of orientation. The system was equipped with a differential eddy current excitation. We show the first non-destructive material evaluation results for fatigue crack detection on stationary samples with moving SQUID sensors.

Keywords

SQUID magnetometers; crack detection; cryostats; eddy current testing; high-temperature superconductors; portable instruments; superconducting device noise; 7 hour; 77.8 K; 78.8 K; HTS SQUIDs; N/sub 2/; SQUID integration; dc gradiometers; differential eddy current excitation; eddy current technique; fatigue crack detection; liquid/gaseous N/sub 2/ mixture; moving SQUID sensors; moving magnetometer; noise spectra; nondestructive evaluation; portable cryostat; shielding; stationary samples; unshielded laboratory environment; washer rf SQUIDs; Copper; Eddy currents; Fatigue; High temperature superconductors; Magnetic materials; Nitrogen; Reservoirs; SQUID magnetometers; Temperature dependence; Working environment noise;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.621892

Filename

621892