High-resolution magnetic imaging with an array of flux guides

Potential applications in neuroscience, such as recordings of neural electrical activity at a microscopic scale, set demanding requirements on both high-resolution and high-sensitivity magnetic imaging. Optically pumped magnetometers (OPMs) based on lasers and alkali-metal vapor cells are the most sensitive magnetic field sensors that do not require cryogenic cooling. Recently, we constructed and tested an ultra-sensitive magnetic microscope by combining a cm-size spin-exchange relaxation-free (SERF) OPM with a pair of flux guides (FGs). The FGs served to direct the magnetic flux from a microscopic source of magnetic field to the OPM to improve simultaneously the spatial resolution and the magnetic field sensitivity. The specific demonstrated performance of the FG-OPM device was resolution 250 mu m and sensitivity 23 pT/Hz(1/2), with potential for further improvement according to numerical simulations to the level that a single neuron could be detected. Our previous demonstration and simulations were done for a single pair of FGs. In this work, we numerically investigated the performance of a parallel multi-FG system and show that similar high resolution and high sensitivity are feasible. Many applications such as the neuronal direct magnetic imaging, non-destructive tests, and detection of magnetic particles with high throughput are anticipated.