Optimization design of a single-layer self-shielded coil in a nanocrystalline magnetic shielding helmet for wearable magnetoencephalography

Magnetoencephalography (MEG) technology relies on a near-zero magnetic environment to achieve high-sensitivity measurements. However, conventional permalloy shielding chambers are cumbersome and costly, hindering the development of wearable systems. This paper proposes a cooperative design and optimization method for an open-ended single-layer self-shielded coil (OSSC) targeting a flexible nanocrystalline magnetic shielding helmet (NMSH). A forward model for the surface current density of the coil is established using the target field method (TFM). To simultaneously optimize both the internal magnetic field (MF) uniformity and external attenuation performance, a multi-objective particle swarm optimization (MOPSO) algorithm is employed for the global optimization of coil parameters. This approach enables a single-layer structure to generate a highly uniform MF within a target region while ensuring its rapid decay outside. Simulations show a maximum field uniformity error of only 0.94% in the target region, which is an 85.39% improvement over traditional designs. Active experiments further confirmed the coil's effectiveness in suppressing residual MF. This work presents a key technical advancement toward developing wearable, high-performance magnetoencephalography (MEG) systems.