New type of three-axix hall sensor designed for high-accuracy magnetic field measurements

Hall sensors (1D and 3D) are routinely used in magnetic field measurements of beamline magnets, insertion devices, and detector magnets at research institutes and accelerator facilities. These measurements are a high-end application of Hall sensors, demanding high accuracies up to 10-4 (at 1 T level) or even beyond. While this is consistently achieved with uniaxial (1D) Hall sensors in a single-component magnetic field volume, the measurement of all three components of a magnetic field, simultaneously to high accuracy with Hall sensors, remains a challenge. None of the commercially available three-axis (3D) Hall sensors proclaims similar measurement accuracy to 1D Hall sensors. Currently, 3D Hallsensors suffer from either, or a combination, of the following: large spatial distribution between sensors’ active areas; high signal noise; cross-sensitivity among measurement axes due to angular errors or due the planar Hall effect (PHE); the inability to measure at a single point in space and time. A new type of three-axis Hall sensor is proposed, consisting of three pairs of uniaxial Hall sensors in a very small active volume. Due to its unique configuration, the new sensor can address current three-axis Hall sensor limitations — it provides: a high spatial resolution of 30 μm × 30 μm × 1 μm for each field component; the full field vector measurements practically at a single point in space and time; and compensation of the planar Hall effect as well as loop-induced voltages by the pairs of 1D Hall sensors. The feasibility of the proposed sensor has been proven in a prototype with an active volume as small as 200 μm × 200 μm × 200 μm and outer dimensions of 4 mm × 4 mm × 4 mm. Its design, fabrication, 3D characterization and calibration is reported on.