The sub-millimetre non-uniformity measurement of residual and coil-generated field in the magnetic shield using atomic vapor cell

TL;DR

This paper demonstrates a high-resolution, sensitive atomic vapor cell method for measuring sub-millimeter non-uniform magnetic fields within shields, enabling detailed 3D magnetography at small scales.

Contribution

It introduces a novel measurement approach combining atomic vapor cells, FID scheme, and DMD scanning for precise magnetic field mapping at sub-millimeter scales.

Findings

Achieved 109.6 μm spatial resolution and 10 pT/√Hz sensitivity.

Successfully mapped residual and coil-generated fields within a magnetic shield.

Showed the impact of shield holes on magnetic field distribution.

Abstract

Magnetic field source localization and imaging happen at different scales. The sensing baseline ranges from meter scale such as magnetic anomaly detection, centimeter scale such as brain field imaging to nanometer scale such as the imaging of magnetic skyrmion and single cell. Here we show how atomic vapor cell can be used to realize a baseline of 109.6 {\mu}m with a magnetic sensitivity of 10pT/sqrt(Hz)@0.6-100Hz and a dynamic range of 2062-4124nT.We use free induction decay (FID) scheme to suppress low-frequency noise and avoid scale factor variation for different domains due to light non-uniformity. The measurement domains are scanned by digital micro-mirror device (DMD). The currents of 22mA, 30mA, 38mA and 44mA are applied in the coils to generate different fields along the pumping axis which are measured respectively by fitting the FID signals of the probe light. The residual fields of every domain are obtained from the intercept of linearly-fitting of the measurement data corresponding to these four currents. The coil-generated fields are calculated by deducting the residual fields from the total fields. The results demonstrate that the hole of shield affects both the residual and the coil-generated field distribution. The potential impact of field distribution measurement with an outstanding comprehensive properties of spatial resolution, sensitivity and dynamic range is far-reaching. It could lead to capability of 3D magnetography for small stuffs and/or organs in millimeter or even smaller scale.