A vector rubidium magnetometer

A version of the rubidium magnetometer has been developed which provides complete vector information of field variations without the use of artificially applied fields. Two perpendicular light beams are passed through a single vapour cell and the relative phases of the Larmor frequency modulations on the two beams determines the direction of the field, the magnitude being provided by the Larmor frequency itself. The device has a resolution of about 0.1 gamma in 1 s for the field direction, and 0.01 gamma in 1 s for field magnitude. It is compact and easily set up, so may find application as an Observatory variometer and as a field instrument for geomagnetic studies.