A scalar magnetometer developed by Graz University of Technology (TU Graz) and the Space Research Institute of the Austrian Academy of Sciences has been improved to not only measure the strength of magnetic fields but also the direction. The dual capability, according to the researchers, is a feat that has not yet been achieved with optical magnetometers. “Until now, there have only been theoretical considerations on how the direction of a magnetic field can be determined with a scalar magnetometer,” said Roland Lammegger of TU Graz. “With our device, we now have a kind of compass for measuring the magnetic field, which shows us the strength and direction. This further development could replace several measuring devices in the future. This would have several advantages for missions in space: less required space, lower weight, and less energy consumption.” Computer model of the test sensor for measuring the magnetic field. Courtesy of TU Graz. The experimental magnetometer consists of rubidium atoms and their response to a magnetic field. When rubidium atoms are stimulated by laser light, the laser's frequency shifts. These shifts enable conclusions to be drawn about the magnetic field strength. To obtain vector information, it was necessary to analyze the resonance amplitudes of the atoms in detail. The resonance amplitude measures how strongly the rubidium atoms respond to the transmitted laser light. Several such resonances exist, with amplitudes related in specific ratios, providing angular information. Through their experimental setup of two laser light beams angled towards each other, the researchers measured two resonances: one that is mainly parallel to each light beam and a second that has a maximum at right angles to it. By comparing the strength of these resonances, the angle of the magnetic field could be determined to the nearest angular minute. The team carried out tests at GeoSphere Austria’s Conrad Observatory in Lower Austria, where it was not only possible to measure the Earth’s magnetic field, but also to generate test magnetic fields to analyze the magnetometer’s blind spots. The device ran for over a month to test its functionality and stability. “If we ran the magnetometer with four laser beams instead of two, we could achieve even more accurate results,” said Christoph Amtmann from the Space Research Institute. “However, this would greatly increase the mechanical and optical complexity and would be unsuitable for use in satellites at the current state of technology. Nevertheless, our development shows that this magnetometer is also promising for planetary probes with two laser beams — provided the magnetic field is not too weak.”
