2006 Fiscal Year Final Research Report Summary
Development of advanced magnetically-levitated high-temperature superconducting coils with YBCO coated conductors
| Project/Area Number |
17560735
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Nuclear fusion studies
|
|---|
| Research Institution | National Institute for Fusion Science |
|---|
Principal Investigator |
NAGATO Yanagi National Institute for Fusion Science, 大型ヘリカル研究部, Associate Professor (70230258)
|
|---|
| Project Period (FY) |
2005 – 2006
|
| Keywords | High-temperature superconductor / Magnetic levitation / Mini-RT / Persistent current / YBCO / Coated conductor / Self-stabilized levitation / Magnetic shielding current |
|---|
| Research Abstract |
Magnetic levitations of high-temperature superconducting coils were examined using state-of-the-art YBCO coated conductors. Three coils (diameter: 90-140 mm) were fabricated and tested by inducing persistent currents using liquid nitrogen under external magnetic field (field-cooling method). These coils, despite their small sizes, have become the world first magnetically-levitated YBCO coils. The decay time constant of persistent currents were found to be long enough (2-7 hours) owing to the application of sophisticated joint structures between pancakes of the coils. When the external magnetic field was applied in a special way, it was found that the persistent current even increased after the initial excitation. This phenomenon can be explained by the magnetic coupling between the locally induced shielding currents in the superconducting layers and the transport current through the coil windings. By using stable persistent currents, magnetic levitation experiments were carried out with and without feedback controls. Self-stabilized magnetic levitations were observed with specified conditions, which could be explained by conservation of magnetic flux in the superconducting floating coils. These results are supposed to be valuable for designing the upgraded high-field version of the present Mini-RT device for internal plasma confinement. Furthermore, feasibility studies for applying YBCO high-temperature superconductors for fusion machines have been carried out. It is shown that field correction coils used for helical machines, such as the Large Helical Device, can be provided by high-temperature superconducting coils. They are supposed to be much more efficient than the present copper coils and will soon be available with the near future technology.
|
