Tensor gradiometry with a diamond magnetometer

Vector magnetometry provides more information than scalar measurements for magnetic surveys utilized in space, defense, medical, geological, and industrial applications. These areas would benefit from a mobile vector magnetometer. Here we present a scanning fiber-coupled nitrogen-vacancy (N-V) center vector magnetometer. Feedback control of the microwave excitation frequency is used to improve dynamic range and maintain sensitivity during movement of the sensor head. Tracking of the excitation frequency shifts for all four orientations of the N-V center allows us to image the vector magnetic field of a damaged steel plate. We calculate the magnetic tensor gradiometry images in real time, and they allow us to detect smaller damage than is possible with vector or scalar imaging. Published by the American Physical Society 2024