Advanced superconducting wire

We have developed a magnesium diboride (MgB₂) superconducting wire that has a critical temperature (Tc) of -234 degrees Celsius (30 degrees higher than previously). We hope to use this superconducting wire to develop superconducting magnets that do not require liquid helium or other such liquid refrigerant, thus realizing superconducting technology that can contribute to the global society.

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This "MgB₂ multi-filament long superconducting wire" was developed jointly by the Central Japan Railway Company and Hitachi, Ltd. This work was also, in part, conducted as part of joint research with the National Institute for Materials Science.

A1: It makes superconducting magnets that do not use liquid helium or other such liquid refrigerants possible. The Tc of previous superconductor wire made of NbTi or other such material is -263 degrees Celsius. That is a difference of only six degrees from the temperature of liquid helium (-269 degrees Celsius). Accordingly, the only way to configure highly reliable superconducting magnets is to immerse them in liquid helium. MgB₂ has a high Tc that differs from liquid helium temperature by about 30 degrees, which means that superconducting magnets that do not use liquid helium are possible.

A2: The manufacture of a large superconducting coil requires a kilometer-scale superconducting wire. The wire must have high and uniform conductivity over its entire length. Achieving that characteristic is the most difficult point. If there is even just 1 mm of low conductivity in the kilometer of wire, the wire cannot be used.

A3: The largest application is the superconducting coils for magnetic bearings that we have developed jointly with Central Japan Railway Company. Those coils have a diameter of as large as 500 mm. We are also developing persistent current switches that use superconducting magnets. In the laboratory, we have demonstrated the world's first Nb3Al superconducting magnets that operate under conduction cooling (liquid helium free cooling).

A4: I think it's important to maintain a dream. In maintaining a dream, you have to be a person who has 'shin', which is the pronunciation of many different Japanese characters for fitting concepts such as 'core' (fortitude), 'trust' (reliability), 'new' and 'deep' (discovery and quest), 'spirit' and 'forward' (ability to grow), 'truth', 'humility', 'heart' and others. I think that an organization that ties the work of each of us as individuals to a dream is the most important thing.