PLANAR HTS GRADIOMETERS WITH LARGE BASE-LINE

We have designed an HTS single-layer planar rf double-hale gradiometer with long and well defined baseline up to 5 mm and small washer areas . We measured a gradient field resolution of about 1, pT/(cm.root Hz) above 10 Hz in unshielded environment. The gradiometer could be operat ed placed on a swinging pendulum in the geomagnetic field. This permit ted a simple demonstration of a movable SQUID system. We placed a SQUI D system on a scanning table and performed two-dimensional eddy-curren t nondestructive evaluation measurements an realistic samples.