Fujikura Ltd.

07/11/2019 | Press release | Distributed by Public on 07/11/2019 00:24

Successful development of technology for mass-production of second-generation rare-earth high-temperature superconducting wire -Achieving world's highest performance wire with[...]

July 11, 2019

Fujikura Ltd. (President & CEO: Masahiko Ito) has succeeded in the development and marketing of technology for mass-production of the world's highest performance rare-earth high-temperature superconducting wire with a critical current density in a low-temperature magnetic field exceeding 400A/mm2, more than 1.5 times that of conventional wire (compared to Fujikura's conventional products).

Superconductivity technology is known for its use in equipment such as MRI (Magnetic Resonance Imaging) devices in the medical field and in the pullers for silicon crystal furnaces in the field of semiconductors. While conventional superconducting devices use a metallic low-temperature superconducting wire that uses liquid helium (minus 269°C) for cooling, liquid helium is a rare natural resource, and there are concerns about issues such as rising prices and procurement problems. For this reason, we expect to put the rare-earth high-temperature superconducting wire we are developing into practical use as soon as possible as an important product for realizing next-generation high-temperature superconducting devices that do not use liquid helium.

In the period from fiscal 2016 to 2018, Fujikura was involved in projects under the commision and subsidization by the New Energy and Industrial Technology Development Organization, a national research and development agency, for the 'promotion to the commercialization of high-temperature superconductivity technology, development of high magnetic field magnet system and development of technology for the commercialization of wire for high-temperature superconductivity high-magnetic field coils,' leading to the development of a rare-earth high-temperature superconducting wire for use in MRI devices. The high-temperature superconducting MRI system has already been successfully used for image acquisition using small devices, and, with the achievement of a critical current density in a magnetic field up to 400A/mm2, we have now reached the level where we can realize a compact next-generation MRI system that does not use liquid helium.

The past few years have seen lively development of next-generation devices using rare-earth high-temperature superconducting wire, some of which are already being tested for practical use. In addition, along with increases in the amount of wire supplied, verification devices are growing in size, with several tens to hundred of kilometers of wire used. The new product announced by Fujikura is intended to promote these activities for commercialization and we are already supplying wire in response to increasing numbers of inquiries from customers not only in Japan, but also overseas.

Fujikura intends to expand its high-temperature superconductivity business by providing rare-earth high-temperature superconducting wire and coil products in response to growing demand.

Exterior view of rare-earth high-temperature superconducting wire
(A 4-mm-wire-width product)

Exterior view of rare-earth high-temperature superconducting coil
(A Fujikura product (reference photo))

[Reference: Glossary]

High-temperature superconducting wire Superconductivity is a phenomenon in which the electrical resistance becomes zero when the temperature falls below a certain level. Superconductivity comprises low-temperature superconductivity (metallic superconductivity), which uses liquid helium (Boiling point: -269°C) for cooling, and high-temperature superconductivity (oxide superconductivity), which manifests superconductivity even at high temperatures without using liquid helium.
Since high-temperature superconducting wire exhibits superconductivity at a higher temperature than low-temperature superconducting wire, less equipment is required for cooling, making it possible to realize a compact shape and reduce cooling costs (energy conservation). Rare-earth high-temperature superconducting wire Superconductive wire on which oxide superconductive material made of substances such as rare earth (e.g. Yttrium), barium or copper is deposited through an intermediate layer onto a tape-like metal substrate such as a long metal tape with a crystalline-oriented surface or a chromium-nickel-based alloy while promoting crystal growth using a method such as IBAD (Ion Beam Assisted Deposition). The properties of superconductive wire are low characteristic degradation, even in a magnetic field, high current density, and small AC loss. This material demonstrates the highest performance among of all the high-temperature superconductive wires that have been commercialized. Critical current density The value of the maximum current that a superconductor can carry is called the critical current, and the value obtained by dividing the current value by the wire cross-sectional area is called the critical current density. This is one of the important indices of superconductivity. The value is usually shown as the current value per 1 square millimeter (A/mm2). The 1.5 times critical current density achieved with this product is the value obtained by dividing the critical current density by the cross-sectional area of the entire wire including the non-superconducting portion, and shows the performance at a temperature of 30K (-243°C) and a magnetic field of 7T (70,000 Gauss).