Adapting a commercial integrated circuit 3-axis Hall sensor for measurements at low temperatures: mapping the three components of B in superconducting applications

Mapping the magnitude and the direction of the flux density B at cryogenic temperature is of particular interest in numerous applications involving superconductors. However, it is difficult to find 3-axis Hall probes or magnetometers operating at low temperature and above the mT range. In this work, we report the design and the construction of a device able to perform such a measurement. We show that it is possible to take advantage of a commercially available, inexpensive, room-temperature 3-axis Hall sensor and place it inside a thin cylindrical insert whose inner temperature is carefully controlled to be 25 ± 0.2 ℃, irrespective of the outer cryogenic temperature (typically 77 K). The active area of the Hall sensor is located at 2.2 ± 0.25 mm from the bottom of the insert, so that it can be positioned close to the magnetic structures to be characterized. We built the interfacing electronics that is located sufficiently close (typ. < 300 mm) to the digital Hall sensor and manages the temperature control. The whole system behaves thus as an independent and reliable 3-axis Hall probe able to operate in cryogenic conditions. We tested this device to characterize Bx, By and Bz generated by two magnetized high-Tc superconductors: a bulk polycrystalline tube and a ring magnet made from an eye-shaped coated conductor. We show that the device allows measurements down to ∼ 0.16 mT. Combining the three measured components of B enables mapping the local magnitude and direction of the flux density.