Proceedings of the 3^rd European Workshop on Low Temperature Electronics
WOLTE 3

J. Phys. IV France 08 (1998) Pr3-249-Pr3-252
DOI: 10.1051/jp4:1998355

Eddy-current nondestructive measurements with different HTS-SQUID spatial orientations

M. Valentino^{1, 2}, G. Pepe^{3, 2}, A. Ruosi² and G. Peluso<sup>3, 2

1</sup>  Università di Napoli Federico II, Dipartimento Ingegneria dei Materiali per la Produzione, Facoltà di Ingegneria, P.le Tecchio 80, 80125 Naples, ltaly
²  Istituto Nazionale per la Fisica della Materia, Unità di Ricerca di Napoli, Naples, Italy
³  Università di Napoli Federico II, Dipartimento Scienze Fisiche, Facoltà di Ingegneria, P. le Tecchio 80, 80125 Naples, ltaly

Abstract
Superconducting QUantum Interference Devices (SQUIDs) are extremely sensitive detectors for the measurement of magnetic flux. In particular the high critical temperature SQUIDs, which can be operated at liquid nitrogen temperature with easy cryogenic requirement, are well suited for nondestructive evaluation (NDE) of cracks and corrosion which result from the machining process or aging of electrically conductive structures. The main characteristics of SQUIDs as eddy-cunent NDE sensors are : high sensitivity even in unshielded environments, a large frequency range of operation which allows the detection of surface and subsurface flaws and high spatial resolution. We performed magnetic field measurements on the eddy-current double-D inducing coil, used in many NDE experimental systems, and on 200x100x4m m³ Al plates with a 6mm surface-breaking hole using high critical temperature SQUIDs in unshielded environments. The sensitivity to the anomalous magnetic field related to the defect along the three spatial directions is discussed in terms of unperturbed magnetic field distributions due to the eddy-current source.

© EDP Sciences 1998