Maglab recently delivered two 2.6 m, three-axis, four-square-segment-per-axis Merritt coil systems. One system was supplied to the Czech Metrology Institute for magnetometer calibration purposes, and the other to the Institute of Geology of the Czech Academy of Sciences for thermal demagnetization of rock samples.
In the case of the Institute of Geology, the complete system consisted of coils with dual windings in the North–South and vertical directions, and a single winding in the East–West direction. The purpose of the coils is to cancel the Earth’s magnetic field while maintaining the highest possible field homogeneity within the central volume, where rock samples are demagnetized in a non-magnetic high-temperature furnace. The additional windings in the North–South and vertical directions are used for coarse field compensation, allowing the precision, feedback-controlled current source to address only the small residual magnetic fields, both static and dynamic. Maglab also designed and delivered a dedicated calibration instrument incorporating a rotating fluxgate sensor, which is used to calibrate the zero offset of the fluxgate sensor employed in the feedback current controller.
The second system, delivered to the Czech Metrology Institute, will most likely be operated in a configuration with the magnetic field sensor placed outside the coils. As with the first system, a rotating fluxgate sensor will be used for the initial zero calibration (in this case with continuous rotation). All three axes are equipped with a double winding, which allows the Earth’s magnetic field and its variation with the first triplet to be completely canceled and arbitrary field with a strength of +-100uT to be generated.
