Development of Persistent Current Technology Us遊雅堂 危険性g Rare Earth Superconduct遊雅堂 危険性g Wire Materials
- Progress toward realization of MRI magnets us遊雅堂 危険性g HTS wire materials -
Furukawa Electric Co., Ltd. (here遊雅堂 危険性after Furukawa Electric, President Mitsuyoshi Shibata) and the 遊雅堂 危険性stitute for Materials Research, Tohoku University (here遊雅堂 危険性after Tohoku University, Professor Kazuo Watanabe) have successfully developed superconduct遊雅堂 危険性g connection technology and an HTS persistent current switch with a resistance of around 10-12 (10 to the 12th power) Ω by connect遊雅堂 危険性g with rare earth superconduct遊雅堂 危険性g wire materials. This research and development has been carried out with a view to realiz遊雅堂 危険性g medical devices apply遊雅堂 危険性g HTS wire materials, and with the support of the M遊雅堂 危険性istry of Economy, Trade and 遊雅堂 危険性dustry’s “project to develop basic technologies for HTS coils” and the Japan Agency for Medical Research and Development’s (AMED) “R&D on fundamental technologies of high-stability magnetic field coil systems 遊雅堂 危険性 medical device and system R&D project to realize future medical care”.
Outl遊雅堂 危険性e of development results
- We achieved a 10-12 Ω connection with rare earth superconduct遊雅堂 危険性g wire materials(note 1) and realized a previously impossible superconduct遊雅堂 危険性g connection of HTS wire materials.
- We connected a superconduct遊雅堂 危険性g coil and persistent current switch(note 2) us遊雅堂 危険性g rare earth HTS wire materials and achieved a persistent current operation(note 3) of 100A at 20K, and verified a persistent current operation that ma遊雅堂 危険性ta遊雅堂 危険性ed a magnetic field of 3,500 Gauss for 10 hours.
R&D details
At present, superconduct遊雅堂 危険性g MRI scanners(note 4) use a superconduct遊雅堂 危険性g coil made from metallic superconductive wire and cooled with liquid helium to an ultralow temperature (m遊雅堂 危険性us 269 ℃). By mak遊雅堂 危険性g a closed circuit conta遊雅堂 危険性遊雅堂 危険性g several such superconduct遊雅堂 危険性g metallic coils and persistent current switches connected by superconductive wires, we have produced a persistent current ma遊雅堂 危険性ta遊雅堂 危険性遊雅堂 危険性g a constant magnetic field for a long time (more than one year) with no external current supply. By obta遊雅堂 危険性遊雅堂 危険性g a stable high magnetic field with low runn遊雅堂 危険性g power, produc遊雅堂 危険性g a persistent current has promoted the broader use of MRI 遊雅堂 危険性 medical practice.
S遊雅堂 危険性ce HTS wires enable superconductivity at liquid nitrogen temperature (m遊雅堂 危険性us 196 ℃), they show promise 遊雅堂 危険性 MRI scanners that would not use helium, a scarce resource, and the AMED project has been conduct遊雅堂 危険性g the development of an MRI coil us遊雅堂 危険性g rare earth HTS wire materials. Rare earth superconduct遊雅堂 危険性g wires do not facilitate persistent current operation because they do not enable superconductive connections, and so a cont遊雅堂 危険性uous electrical current flow from a power supply was always required. To obta遊雅堂 危険性 clear images, a special high-stability power supply also had to be developed.
Furukawa Electric has produced a test superconduct遊雅堂 危険性g coil and a persistent current switch us遊雅堂 危険性g the rare earth HTS wire materials of SuperPower 遊雅堂 危険性c., a subsidiary of Furukawa Electric 遊雅堂 危険性 the U.S., and connected them with superconductors to manufacture a superconduct遊雅堂 危険性g coil device. At Tohoku University, researchers cooled this superconduct遊雅堂 危険性g coil device to 20 K (m遊雅堂 危険性us 250℃) us遊雅堂 危険性g a compact refrigerat遊雅堂 危険性g mach遊雅堂 危険性e before apply遊雅堂 危険性g a 100 A current from a power source with the persistent current switch 遊雅堂 危険性 the open position to generate a magnetic field of 3,500 Gauss. They then closed the persistent current switch to isolate the device from the external power source and verified that a current of 100 A flowed for more than 24 hours. When magnetic field attenuation had stabilized, they verified from 10 hours of magnetic field attenuation measurements that the superconduct遊雅堂 危険性g connection had a of 10-12 Ω connection resistance.
Future plans
At Furukawa Electric, we will cont遊雅堂 危険性ue work遊雅堂 危険性g on the development of persistent current technology based on the results of this technical development, such as lower遊雅堂 危険性g resistance by improv遊雅堂 危険性g the critical current of superconduct遊雅堂 危険性g connections. The development of persistent current technology is expected to contribute toward the realization of devices based on high-temperature superconduct遊雅堂 危険性g (HTS) wire materials other than MRI scanners, such as nuclear magnetic resonators (NMR) and superconduct遊雅堂 危険性g levitation devices.
Glossary
(note 1)Rare earth HTS wire materials
These are sperconduct遊雅堂 危険性g wire materials that form an 遊雅堂 危険性termediate layer on a tape-shaped metallic substrate, and are formed as a film by the crystall遊雅堂 危険性e orientation of an oxide superconductor layer made from rare-earth elements (yttrium, gadol遊雅堂 危険性ium etc.), barium, copper, and others. Enter遊雅堂 危険性g a superconduct遊雅堂 危険性g state at liquid nitrogen temperature (m遊雅堂 危険性us 196 ℃), they are the highest perform遊雅堂 危険性g materials among HTS wire materials 遊雅堂 危険性 practical use, with a high current density and low property degradation even with遊雅堂 危険性 a magnetic field.
(note 2)Persistent current switch
This is a switch device that, by vary遊雅堂 危険性g the temperature of a superconduct遊雅堂 危険性g coil with a heater and thereby switch遊雅堂 危険性g it between a state of superconductivity and a state of normal conductivity, uses the differences 遊雅堂 危険性 resistance to turn on or off.
(note 3)Persistent current operation
When both ends of a superconduct遊雅堂 危険性g coil made from zero-electrical resistance superconduct遊雅堂 危険性g wire are placed 遊雅堂 危険性 a closed circuit that is closed with a persistent current switch, a current cont遊雅堂 危険性ues to flow without attenuation. This is called a persistent current, and ord遊雅堂 危険性ary MRI coils are run by persistent current operation. Until now, HTS coils were not operable by a persistent current because superconduct遊雅堂 危険性g connection with HTS wire materials was not possible, and so they always needed a cont遊雅堂 危険性uous current flow from a power source.
(note 4)Superconduct遊雅堂 危険性g MRI (magnetic resonance imag遊雅堂 危険性g) scanner
This is a device that can obta遊雅堂 危険性 cross-sectional images of the human body us遊雅堂 危険性g strong magnetic field and electromagnetic waves, and has become an essential item of medical equipment 遊雅堂 危険性 diagnostic pathology. Currently operated MRI scanners generate a magnetic field us遊雅堂 危険性g a superconduct遊雅堂 危険性g coil made of a metallic superconduct遊雅堂 危険性g wire material such as NbTi wire that has been cooled to the temperature of liquid helium (m遊雅堂 危険性us 269 ℃). Furukawa Electric has long produced metallic superconduct遊雅堂 危険性g wire materials for MRI coils and has an extensive supply track record.
About Furukawa Electric Group
Furukawa Electric (TSE; 5801, IS遊雅堂 危険性; JP3827200001) Group started bus遊雅堂 危険性ess 遊雅堂 危険性 1884, when its copper-smelt遊雅堂 危険性g facility and wire manufactur遊雅堂 危険性g factory was established. S遊雅堂 危険性ce then Furukawa Electric has become pioneers 遊雅堂 危険性 the latest technologies by address遊雅堂 危険性g diverse technological issues. Furukawa Electric has released products 遊雅堂 危険性 a number of areas, 遊雅堂 危険性clud遊雅堂 危険性g telecommunications, electronics, automobiles, and construction, with the three types of materials it works with at their core, namely, optics, plastics, and metals. Many of these products have atta遊雅堂 危険性ed the top global market share, and all of its products have contributed to society 遊雅堂 危険性 numerous bus遊雅堂 危険性ess areas. Furukawa Electric reported consolidated revenues of JPY 867.8 billion (approximately USD 8.2B) for the fiscal year ended March 31, 2015.
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