A 4He vector zero-field optically pumped magnetometer operated in the Earth-field.

Low intrinsic noise, high bandwidth, and high accuracy vector magnetometers are key components for many ground or space geophysical applications. Here, we report the design and the test of a 4He vector optically pumped magnetometer specifically dedicated to these needs. It is based on a parametric resonance magnetometer architecture operated in the Earth magnetic field with closed-loop compensation of the three components of the magnetic field. It provides offset-free vector measurements in a ±70 µT range with a DC to 1 kHz bandwidth. We demonstrate a vector sensitivity up to 130 fT/√Hz, which is about ten times better than the best available fluxgate magnetometers currently available for the same targeted applications.