Miniature Planar Self-Shielded Coil for Suppressing Crosstalk of Optically Pumped Magnetometer Arrays*

The multi-channel optically pumped magnetometer (OPM) array has been considered as a new generation of equipment used in the magnetoencephalography (MEG), due to its high sensitivity, flexibility, no cryogenic cooling required, and multi-axis measurement capability. Reducing the volume of the magnetometer probe and increasing the spatial density of the array can improve the measurement spatial resolution of the whole-head MEG system, which is the future development trend. However, due to the need for magnetic field modulation and compensation based on the coils inside the OPM probe, reducing the probe spacing will exacerbate the adverse effect of the magnetic field outside the coil on adjacent probes, resulting in a magnetic field crosstalk. Here, we present a design method for planar self-shielded uniform magnetic field coils suitable for commonly used miniaturized triaxial atomic magnetometers. The proposed method constructs the multiple coil pairs with the same number of turns in a square planar configuration facilitating the process into flexible printed circuits and the installation on six faces of the cubic structure. The coil structure parameters and current directions are optimized based on the Taylor expansion method and magnetic field characteristics of the target field points to ensure the required uniform interior and rapidly decaying exterior magnetic field. The coils designed by the proposed method can effectively improve the crosstalk problem and support probe spacing reduced in magnetometer arrays.