Magnetic field interference suppression for minimized SERF atomic magnetometer

The spin-exchange relaxation-free (SERF) atomic magnetometer (AM) has become popular for the non-invasive, low-cost, wearable bio-magnetic measurement and imaging. While in the real medical environment, the magnetic field interferences that are diverse and complex can introduce output errors of SERF AM and degrade location accuracy of bio-magnetic source. In this study, an effective method for magnetic field interference suppression based on PI closed-loop control is proposed to suppress and alleviate three foremost magnetic field interferences. We construct a magnetic field closed-loop SERF AMs system with the single axis modulation field applied and the gain errors caused by the low-frequency residual magnetic field along three axes are mitigated effectively. This magnetic field interference along x axis is zeroed in real time and the corresponding gain error is suppressed from 16.5% to 1.8%. The crosstalk caused by the modulation fields of adjacent SERF AMs is alleviated from 10% to 4.5%, which is especially advantageous for the integration of more channels of magnetometers. The third type of magnetic field interference due to the output of PI controller is taken into account and we demonstrate that it is fixed when the positions of SERF AMs and control parameters are determined. Our method that improves the stability of magnetic field measurements dramatically has potential to enhance bio-magnetic imaging quality and pave the way for the application of wearable multi-channel closed-loop SERF AMs arrays.