Presentation Information
[AP3-02]Development of Faro Shuffle Method for Multi-Tape Joints in Large-Current HTS Conductors Using Atmospheric-Pressure Plasma Surface Treatment
*Yuta Onodera1, Yoshiro Narushima1,2, Tomosumi Baba1, Shinji Hamaguchi1,2, Nagato Yanagi1,2, Hirotaka Chikaraishi1,2, Junichi Miyazawa3, Hiroki Chikuma3, Hitoshi Tamura3, Takuya Goto3 (1. National Institute for Fusion Science (Japan), 2. SOKENDAI (Japan), 3. Helical Fusion Co., Ltd. (Japan))
Keywords:
REBCO,Fusion,Joint resistance
In the development of large-current conductors for fusion reactor magnets, reliable low-resistance joints between high-temperature superconducting (HTS) tapes are essential to minimize Joule heating and improve overall magnet performance. Conventional joint fabrication methods often rely on wet chemical processes, such as flux treatment, particularly for making mechanical bonding using indium foils inserted into the contact area. While such methods can provide good electrical contact for large-scale joints, they require careful handling and post-processing, especially due to their corrosive nature in the long term.
To address these limitations, we investigated a novel dry process for joint fabrication that removes the surface oxide layer from the copper surfaces of REBCO tapes by irradiating them with atmospheric-pressure plasma. This plasma treatment effectively cleans the HTS tape surfaces without introducing chemical contaminants, enabling immediate subsequent jointing. For multi-tape joints, we developed the “Faro Shuffle” method, in which numerous HTS tapes are interleaved in a lap configuration. This method is particularly advantageous for fabricating large-current conductors, as it enables the simultaneous preparation of multiple tapes before assembly.
We first applied the method to a simple joint of two HTS tapes and measured the joint resistance with and without plasma irradiation. The results showed that plasma irradiation reduced the joint resistance by more than half, demonstrating an improvement in electrical contact quality. Subsequently, the process was scaled up and applied to a 160-tape stacked large-current conductor. Coil-shaped samples were fabricated to evaluate the method under more realistic operating conditions, and the performance of the joints was confirmed. This study has been carried out as part of a collaborative research program with Helical Fusion Co., Ltd. Details of the Faro Shuffle method and the experimental results from both small-scale and coil-scale tests will be discussed.
To address these limitations, we investigated a novel dry process for joint fabrication that removes the surface oxide layer from the copper surfaces of REBCO tapes by irradiating them with atmospheric-pressure plasma. This plasma treatment effectively cleans the HTS tape surfaces without introducing chemical contaminants, enabling immediate subsequent jointing. For multi-tape joints, we developed the “Faro Shuffle” method, in which numerous HTS tapes are interleaved in a lap configuration. This method is particularly advantageous for fabricating large-current conductors, as it enables the simultaneous preparation of multiple tapes before assembly.
We first applied the method to a simple joint of two HTS tapes and measured the joint resistance with and without plasma irradiation. The results showed that plasma irradiation reduced the joint resistance by more than half, demonstrating an improvement in electrical contact quality. Subsequently, the process was scaled up and applied to a 160-tape stacked large-current conductor. Coil-shaped samples were fabricated to evaluate the method under more realistic operating conditions, and the performance of the joints was confirmed. This study has been carried out as part of a collaborative research program with Helical Fusion Co., Ltd. Details of the Faro Shuffle method and the experimental results from both small-scale and coil-scale tests will be discussed.