Optimization of pick-up coils for weakly damped SQUID gradiometers

Yang Kang^{1, 2, 3}, Wang Jialei^{1, 2, 3}, Kong Xiangyan^{1, 2, 3, †}, Yang Ruihu^{1, 2, 3}, Chen Hua^{1, 2, 3}

Schematic of pickup coil of the first-order gradiometer. A current dipole source is placed at point . The vertical distance between the sensing loop of the pick-up coil and the dipole source is .