Optimization of pick-up coils for weakly damped SQUID gradiometers

Abstract

The performance of a superconducting quantum interference device (SQUID) gradiometer is always determined by its pick-up coil geometry, such as baseline and radius. In this paper, based on the expressions for the coupled flux threading a magnetometer obtained by Wikswo, we studied how the gradiometer performance parameters, including the current dipole sensitivity, spatial resolution and signal-to-noise ratio (SNR), are affected by its pick-up coil via MatLab simulation. Depending on the simulation results, the optimal pick-up coil design region for a certain gradiometer can be obtained. To verify the simulation results, we designed and fabricated several first-order gradiometers based on the weakly damped SQUID with different pick-up coils by applying superconducting connection. The experimental measurements were conducted on a simple current dipole in a magnetically shielding room. The measurement results are well in coincidence with the simulation ones, indicating that the simulation model is useful in specific pick-up coil design.

Residual field suppression for magnetocardiography measurement inside a thin magnetically shielded room using bi-planar coil

“…And the reference magnetometer is placed above the sensing magnetometer coaxially with a distance of 7 cm, which refers to the baseline of a hardware gradiometer we optimized before. [19] Moreover, this thin MSR is manufactured by two layers of permalloy plates and one layer of Al. The thickness of each permalloy plate is 1.75 mm and these two plates are separated by a 100 mm distance.…”