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Abstract: Atomic magnetometers are emerging as an alternative to SQUID magnetometers for detection of biological magnetic fields. They have been used to measure both the magnetocardiography (MCG) and magnetoencephalography (MEG) signals. One of the virtues of the atomic magnetometers is their ability to operate as a multi-channel detector while using many common elements. Here we study two configurations of such a multi-channel atomic magnetometer optimized for MEG detection. We describe measurements of auditory evoked fields (AEF) from a human brain as well as localization of dipolar phantoms and auditory evoked fields. A clear N100m peak in AEF was observed with a signal-to-noise ratio of higher than 10 after averaging of 250 stimuli. Currently the intrinsic magnetic noise level is 4fTHz−1/2 at 10Hz. We compare the performance of the two systems in regards to current source localization and discuss future development of atomic MEG systems. [Copyright &y& Elsevier]

Graphical abstract Highlights • The first in-situ Overhauser-enhanced nuclear magnetic resonance experiment using an atomic magnetometer at ultra-low field. • Signal-to-noise ratio was 32 after sixteen averages. • On the Larmor precession of 1 H spins, a decaying oscillation was superimposed. • We attribute it to a transient 87 Rb spin precession in response to a non-adiabatic field variation. • Atomic magnetometry technique shows a new capability of zero and ultralow-field NMR. Abstract The development of atomic magnetometers has led to nuclear magnetic resonance (NMR) in zero and ultralow magnetic fields without using cryogenic sensors. However, in-situ detection, meaning that a sample locates in the detection space beside a vapor cell, has been conducted only with parahydrogen-induced polarization. Other hyperpolarization techniques remain unexplored yet. In this work, we demonstrate that Overhauser dynamic nuclear polarization allows in-situ NMR detection with an atomic magnetometer at less than 1 μ T. The 1 H NMR signal of a nitroxide radical solution was observed at 13.83 Hz, which corresponds to 325 nT. Signal-to-noise ratio was 32 after sixteen averages. On the Larmor precession of 1 H spins, a decaying oscillation was superimposed. We attribute it to a transient 87 Rb spin precession in response to a non-adiabatic field variation. This work shows a new capability of zero- and ultralow-field NMR. [ABSTRACT FROM AUTHOR]