Atomic vector gradiometer system using cesium vapor cells for magnetocardiography: Perspective on practical application

We developed an optical pumping magnetometer system for magnetocardiography (MCG). The basic system requirements for measuring MCG are as follows: a 5-mu T weak bias field in a magnetically shielded room, a 20-mm cell for spatial resolution, and a 30-Hz bandwidth for heart signals. In order to reduce the environmental magnetic noise, a double-cell gradiometer configuration has been adopted. The measured noise level was similar to 10 pT/root Hz. By switching current flows through a symmetrical three-axis rectangular Helmholtz coil set, the system is designed to measure three vector components of the magnetic field gradient. We show that this configuration reduces the error in current dipole localization with respect to the usual normal component detection by computer simulation of confidence-region estimation. Based on the simulation, we suggest that the system is applicable for diagnosing myocardial infarction on the anterior wall of a human heart in coronary artery disease.