The design of a new concept HTSC axial gradiometer

The design of a new-concept axial gradiometer is discussed, which employs a gradiometric pick-up loop formed by etching a transformer loop structure on flexible superconducting tape. The pick-up loop is inductively coupled to a SQUID magnetometer. Sensitivity to the magnetic field in the direction transverse to the gradiometer axis is problematic in some applications and can be reduced by matching the mutual inductance between the secondary loop of the flux transformer and the magnetometer to establish a condition of shielding. The conditions for optimum magnetic effective volume are discussed and it is shown that a gradient resolution better than 0.01 nT/(m√Hz) is achievable for a reasonable choice of device parameters