Optimization of Flux Transformer for Optically Pumped Atomic Magnetometer in Ultra-Low Field MRI Systems

An ultra-low field (ULF) magnetic resonance imaging (MRI) system with an optically pumped atomic magnetometer (AM) has recently been proposed. Because AM does not require cryogenic cooling, it can easily measure extremely small magnetic fields. However, to measure magnetic resonance (MR) signals with high sensitivity in ULF-MRI systems with AMs, the resonant frequencies of the sample and alkali metal in the AM must be same. To satisfy this requirement, a flux transformer (FT) has been proposed to detect MR signals. In this study, the simulations in the output coil of the FT and pseudo-MR signal measurements were performed to improve the signal-to-noise ratio (SNR) in the remote detection of MR signals by using AM with FT. The simulations and measurement results indicate that, to improve the SNR of the detector, the output coil of the FT should be placed in the vicinity of a glass cell, and the number of turns and radius of the output coil need to be optimized.