An ac/dc magnetometer for space missions: Improvement of a Hall sensor by the magnetic flux concentration of the magnetic core of a searchcoil

Theoretically, the sensitivity of Hall sensors can be improved by at least three orders of magnitude by implementing them into an especially tailored magnetic concentrator [P. Leroy, C. Coillot, A. Roux, G. Chanteur, High magnetic field amplification for improving the sensitivity of hall sensors, IEEE Sens. J. 6 (3) (2006) 707–713]. Noise-equivalent magnetic induction (NEMI) down to 10 pT/Hz could be reached by using a good conditioning electronics. These conclusions have been drawn from numerical simulation and physical modelling.In the laboratory, we have been able to plot the variation of the magnetic gain, in case of a Hall sensor implemented between two ferromagnetic concentrators as a function of the distance between two cores (typically from 100 μm to 1 mm). We have used an especially designed low-noise Hall effect sensor using a GaAs-based quantum well heterostructure, whose thickness was machined down to 70 μm. The measured values of the magnetic gain (up to 400 typically) merely fit well with the values provided by the numerical simulations that we have carried out.As we have confirmed our numerical predictions on the magnetic amplification with our experimental assembly, we have built an ac/dc magnetometer, including a Hall sensor whose sensitivity is improved by the ferromagnetic core of a searchoil used as a magnetic concentrator. This triaxial magnetometer will be onboard a NASA experimental rocket flight to be launched in 2007.