Spatial and field resolution of wire-wound fluxgates in magnetic dipole fields

We have enhanced the field and the spatial resolution of fluxgate magnetometers to measure magnetic dipole fields. With finite element simulations, we studied the flux distribution in the racetrack shaped core of a reference fluxgate magnetometer that was optimized for low noise performance in homogeneous fields. The influence of core length and thickness on the spatial and the field resolution was analyzed. The simulation was used to optimize the size and the location of the detection coil. The performance of new fabricated fluxgates was measured in homogeneous fields and compared with their measurement capabilities in dipole fields. Parameters of interest were the sideband detection signal, the signal-to-noise ratio, the detection limit and the spatial resolution by means of the point spread function. Despite higher noise levels in homogeneous fields, it was found that the field and the spatial resolution in dipole fields can be improved by optimizing the geometry of the core and the detection coil, but both parameters cannot be optimized independently.