Magnetometer calibration setup controlled by nuclear magnetic resonance

For the calibration of magnetometer sensors in the field range from 1 mT to 200 mT, a measuring setup has been developed consisting of a water-cooled multilayer solenoid and a nuclear magnetic resonance (NMR)-magnetometer of the marginal oscillator type. With a coil constant of about 20 mT/A, the field coil provides a field profile with two flat regions, where the field maxima are equal within 10^-5 and with a distance of more than 40 mn so that the magnetometer readings can be compared simultaneously. The NMR-magnetometer operates with water samples having an absorption linewidth of 2 μT by adding paramagnetic CuSO₄-ions. The volume of the samples amounts to 0.8 cm³ to 1.5 cm³ for fields below 20 mT and 0.08 cm³ to 0.5 cm³ for higher fields. The uncertainty of detecting the center of the absorption line amounts to less than 0.1 μT