HTS SQUID NDE of Curved Surfaces Using Background Field Cancellation Techniques

Single-layer high-temperature superconducting SQUID gradiometers are well established for measuring small localized magnetic fields in the presence of much larger background interference. Such sensors have proved extremely useful for eddy-current nondestructive evaluation (NDE) of aircraft and other metallic structures. Most applications to date have involved either the sensor remaining stationary or being moved in a straight line in an unshielded environment. However it is desirable for many field mapping applications for the sensor to be rotated or tilted in the Earth´s field whilst retaining full device sensitivity. We report on the development and performance of a portable NDE scanning system which uses background field cancellation techniques to allow the device orientation to change whilst mapping the surface of a curved wing structure.