HIGH T-C SUPERCONDUCTING 2ND-ORDER GRADIOMETER

A planar, second-order gradiometer was fabricated from single-layer YB a2Cu3O7-x films. The gradiometer consists of a symmetric flux transfor mer with an overall length of 80 mm inductively coupled to a directly coupled magnetometer, and has a baseline of 31 mm. The mutual inductan ce between the flux transformer and the magnetometer is adjusted mecha nically to reduce the response to a uniform magnetic field applied per pendicularly to the plane of the gradiometer to typically 50 ppm. From an independent measurement, the residual first-order gradient respons e was determined to be at most 1.4% relative to the second-order gradi ent response. (C) 1998 American Institute of Physics. [S0003-6951(98)0 3641-9].