Magnesium diboride (MgB2) is a known material whose superconducting properties were discovered in 2001. It has a critical temperature of 39 K which ranks in the intermediate temperature superconductors between the low critical temperature superconductors, such as niobium titanium (NbTi) and niobium tin (Nb3Sn), and the high critical temperature superconductors such as cuprates. Its discovery has aroused great interest because its components are cheap and its manufacturing process is similar to that of conventional superconductors. It could therefore eventually replace the conventional NbTi. Only two manufacturers in the world offer this material as tape or wire: Columbus in Italy and Hypertech in the United States.
Its present superconducting properties suggest that a MgB2 magnet could operate at a temperature of the order of 10 K in a magnetic field range up to 4 T. It is then possible to design cryogenics without helium, using only cryocoolers as cold source.
This perspective has led the Department to start a R&D program for developing design and technical tools for building such magnets. Two lines of research are studied: cryogenics specific to this type of application (current leads, electrical insulating thermal contact, etc.), the electromagnet design (characterization of the wire in a magnetic field at different temperatures, protection in case of quench, winding technique, etc.).
This work has begun in late 2011 as part of a thesis in partnership with SigmaPhi. A characterization test facility, without helium, to measure up to 600 A and 3 T the critical current of a MgB2 tape over a length of one meter on a cylinder of 300 mm diameter at temperatures between 10 K to 40 K has been performed. The first results in self field were obtained in early 2013.
Future goals of SACM are now to wind a test double pancake coil and a solenoid for generating a 1 T in a background field of 3 T. These prototypes will allow to define the operating margins necessary for this type of magnet and to study their protection.
Test facility without helium for measuring the critical current of a MgB2 tape.
Critical current measurement on a MgB2 tape from Columbus; n is the index of transition.
• superconducting magnet physics and technology › Instrumentation and development for R&D magnets
