Series Connected Hybrid, HZB

MagLab engineer Lee Marks prepares  the 7.2 ton “cold-mass” of the series connected hybrid magnet for its journey from Tallahassee to Berlin. MagLab engineer Lee Marks prepares the 7.2 ton “cold-mass” of the series connected hybrid magnet for its journey from Tallahassee to Berlin.

In 2014, MagLab completed the world's strongest magnet for neutron scattering for the Helmholtz Centre Berlin (HZB).

Begun in 2007, the magnet project was based on the Magnet Lab’s Series-Connected Hybrid concept, is housed at the Berlin Neutron Scattering Center. At 25 tesla, it is the strongest magnet of its kind in the world; it constitutes a 47% increase in field coupled with a 100% increase in solid-angle over magnets available for neutron scattering. The magnet system will be part of the Extreme Environment Diffractometer to study the structure and dynamics of materials, primarily high temperature superconductors

Project Specs
Strength 25 tesla
Type Series connected hybrid magnet
Warm bore size

50 mm

Year completed 2014
Cost $11.7 million
Total scattering angle

30°

Operating current

20kA

Superconductor

Nb3Sn/CICC coil

Customer

Helmholz Zentrum Berlin

The lab’s own 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. The copper-coil insert is powered by an electrical current, while the superconducting outsert conducts electricity without resistance as long as it is kept colder than 450° below zero Fahrenheit. 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 have built for HZB is different in that its bore, or experimental space, will be conical to allow neutrons to be scattered through large angles. A patent (US 7,825,760) was awarded for the design of this unique magnet. 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.

Neutrons are remarkable probes of phenomena within solids. With this new magnet, scientists from around the world will be able to carry out experiments that aren’t currently possible. Presently, 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.

The hybrid magnet consists of a 13-T superconducting Nb3Sn/CICC coil and a set of 12-T resistive, water cooled coils at 4.4 MW. Much of the cryostat and cold mass functional requirements were dictated by the electromagnetic interactions between the superconducting and resistive coils. This includes the radial decentering and axial aligning forces from normal operations and a 1.1 MN fault load. The system assembly was an international achievement; the cold mass was completed at the MagLab, cryostat to cold mass interfaces made at Criotec Impianti in Italy, and final assembly at the HZB in Germany.

The field contributed by the resistive coils has the potential to be increased to 24 T with an upgrade in the power supply and chilled water systems. The resistive coils are the first to have a conically conforming inner diameter to take advantage of the available space in the conical bore, which is shaped as such to allow for reflection of neutrons upstream and downstream of the beamline toward detectors. The superconducting coil is a 13-T, 600-mm bore coil consisting of Nb3Sn/CICC and weighs 5 ton (6.5 ton full cold mass).

The project is funded primarily through the German Federal Ministry for Education and Research. In addition to the $11.6-million magnet, the Germans are putting $14.4 million into infrastructure, such as cooling and current supplies, needed to run a high-field magnet. The agreement will be administered by Florida State University Magnet Research and Development, Inc., a not-for-profit direct support organization of the magnet lab.

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Staff Contact

Project manager Iain Dixon.

Last modified on 21 August 2014