He 3 absolute magnetometer at geomagnetic field

The high accuracy of the nuclear spin g factor provides a feasible way to construct absolute magnetometry. However, at geomagnetic field, the sensitivity and accuracy of the nuclear spin magnetometer are limited by the ratio of nuclear-spin polarization and the detection efficiency of low-frequency signal. We propose an absolute magnetometer scheme based on the nuclear spin of He 3 , demonstrating an order-of-magnitude improved sensitivity and onefold improved accuracy compared to a proton magnetometer for the current geomagnetic field standard. We present systematic estimations on the sources of errors within the He 3 magnetometer. Through adopting multipass-probe scheme and radio-frequency power stabilization, it is promising to further improve the accuracy of the He 3 magnetometer to 100 ppb at geomagnetic field, paving the way to the next generation of geomagnetic field standard.