New hybrid magnet at Grenoble laboratory will reach 40 Tesla, making it the second strongest continuous field magnet system in the world
The Grenoble High Magnetic Field Laboratory (GHMFL) has taken the first steps to achieving 40 Tesla magnetic field strengths thanks to the delivery of an 8 Tesla class, 1.1m bore, superconducting outsert magnet from Oxford Instruments Superconductivity.
When integrated with a 32T resistive magnet insert that was fully developed at the GHMFL, the system will be capable of reaching up to 40T.
This will make it the second strongest continuous field magnet system in the world and marks another important milestone in Oxford Instruments superconducting magnet history.
The magnet will allow scientists using the GHMFL facility to study new phenomena in the behaviours of organic and inorganic materials and to investigate the fundamental laws of nature.
Using a superconducting magnet in combination with a resistive magnet allows users to boost the total magnetic field with relatively minimal power requirements and much less magnet solenoid winding than with a resistive magnet alone.
The technical challenges involved in building a superconducting magnet for this purpose, however, are considerable.
The Grenoble superconducting magnet not only needed a massive 1.1 metre cold-bore to accommodate the resistive magnet, but also needed to be capable of withstanding mechanical forces in excess of 700 tonnes if the resistive magnet developed a fault.
Martin Wilson, magnet consultant, an internationally renowned scientist in the field of superconductivity, acted as an advisor to the Oxford Instruments magnet design team.
He comments, "The combination of large size, high field and transient external fields serve to make the Grenoble Hybrid a very difficult magnet to construct, perhaps the most difficult attempted so far by Oxford Instruments. "Nevertheless, a very thorough design effort has been put into this project and the superconducting magnet has already been successfully tested on its own without experiencing any training quenches".
The team that developed the hybrid magnet system has involved more than 50 people during the course of the project, including scientists, design engineers and technicians from at least seven different countries.
Project manager for Oxford Instruments Superconductivity, Alessandro Bonito-Oliva, explains some of the ground-breaking technology that was developed to enable the superconducting magnet to work safely and effectively alongside the resistive insert magnet: "A reinforced, low-loss Rutherford cable superconductor was used to diminish the effects of magnetic field transients resulting from resistive magnet faults.
"If the resistive magnet develops a fault and 'trips', a steel-copper quench shield is in place to screen the superconducting magnet from the resulting magnetic flux that could cause it irreversible damage.
"In addition, our team has designed a quench detection system and a magnet active protection system to protect the superconducting magnet in the event of an insert trip or quench".
Other groups working in the field have also acknowledged the technological development behind the new hybrid magnet.
According to Dr H J Scheneider-Muntau, deputy laboratory director of the National High Magnetic Field Laboratory (NHMFL, Tallahassee, USA) the hybrid magnet developed by Oxford Instruments Superconductivity works "by introducing a new concept - it combines the advantages of overall high current density that can be achieved with Rutherford cable conductors with a robust, fully impregnated coil construction".
A joint team from Oxford Instruments Superconductivity and GHMFL will start work shortly on installing and integrating the superconducting outsert magnet with its resistive insert.
Test phases are due to be completed in the next few months.
GHMFL Lab deputy director Walter Joss comments, "This is an important step in realising our dream of providing some of the highest magnetic field capabilities in the world.
"The system will put the GHMFL at the top of the European Magnetic Field league and we expect physics researchers from around the world to make intense use of this capability. "We eagerly await completion of the final project phase next year".
Reference: Scheneider-Muntau, H J, and Nakagawa, Y, Steady State Resistive and Hybrid Magnets, in Physics of High Magnetic Fields and Their Applications, Herlach, F Miura, N (eds), to be published in print, World Scientific (2003).
