Strongest magnet proves highly attractive

The Hahn-Meitner Institute in Berlin has signed a contract with the National High Magnetic Field Laboratory and Florida State University to build an $8.7m hybrid magnet for neutron scattering experiments.

When finished in 2011, the new, high-field magnet, which is based on the magnet lab’s Series-Connected Hybrid concept, will be housed at the Berlin Neutron Scattering Centre. The magnet will produce a magnetic field between 25 tesla and 30 tesla – more than half a million times stronger than the Earth’s magnetic field. It will be the world’s strongest magnet for neutron experiments, eclipsing the 15-tesla system presently at the Hahn-Meitner Institute (HMI).

The magnet lab’s Magnet Science & Technology division has been working with Hahn-Meitner since the summer of 2005, recently completing a design study. The results of that study were strong enough to convince the review committee of the German Helmholtz Association and the Federal Ministry of Education and Research that the investment in the new technology was worth the cost.

The lab’s Series-Connected Hybrid combines copper-coil resistive magnet technology in the magnet’s interior with a superconducting magnet, cooled with liquid helium, on the exterior. An electrical current powers the copper-coil insert, while the superconducting outsert conducts electricity without resistance as long as it is kept colder than -268oC. By combining the power supplies of these two technologies, engineers can produce extremely high magnetic fields using just one-third of the power required by traditional magnets.

The version that magnet lab engineers will build for HMI is different in that its bore, or experimental space, will be conical to allow neutrons to be scattered through large angles. It also will be horizontal, as opposed to the traditional vertical bore of most high-field magnets. These modifications make the magnet ideal for neutron scattering experiments, which are among the best methods for probing atoms to better understand the structure of materials.

With this new magnet, scientists will be able to carry out experiments that are not currently possible. One of the greatest challenges in condensed matter physics is to develop a comprehensive theory describing high-temperature superconductors. The combination of neutrons and high magnetic fields will allow scientists to study the normal state of high-temperature superconductors in the low-temperature limit. In addition, it will be possible to probe hydrogen structure in both biological and hydrogen-storage materials.