Multi-channel MEG measurements inside a glass cell using hybrid optically pumped magnetometers

Abstract

Recently, optically pumped magnetometers (OPMs) have attracted much attention as magnetic sensors for magnetoencephalography (MEG). In general, MEG requires multi-channel simultaneous measurements to estimate the signal sources. In this study, a hybrid OPM using a 5 cm glass cell containing two kinds of alkali metal atoms, K and Rb, was used to simultaneously measure MEGs at ten locations inside the cell.In the event-related desynchronization (ERD) measurements, the subjects were opened and closed their eyes 100 times every 4 seconds, whereas in the auditory evoked field (AEF) measurements, the sound stimuli were presented to the left ear 200 times.We could observe ERD in most of channels, but could not detect AEF signals using the hybrid OPM. This is because the distance between the sensing locations and the scalp was about 3 cm, so that we will reduce the distance by redesigning heaters and change the insulation method as well.