High-sensitivity multi-channel probe beam detector towards MEG measurements of small animals with an optically pumped K-Rb hybrid magnetometer.

Multi-channel measurements with fine spatial resolution will make magnetoencephalograms (MEGs) possible with small animals using optically pumped magnetometers (OPMs). Therefore, we fabricated a 20-channel probe-beam detector that uses a K-Rb hybrid OPM to increase the spatial resolution. First, we investigated the sensitivity of the detector using the multi-channel measurements and demonstrated that the detector had a fine sensitivity (10-20 fT/Hz1/2 at 10 Hz). Subsequently, we measured magnetic field distribution generated from a loop coil and compared those measurements with analytically calculated distributions. The measurements were in good agreement with the theoretical predictions. The experimental results indicate that our newly developed multi-channel OPM detector has sufficient performance specifications for MEG measurements.