Helical Fusion further develops its high-temperature superconductor cable

1 March 2024

Japan’s Helical Fusion, based in Chuo-ku, Tokyo, has conducted a critical test involving a 19kA current in its proprietary High-Temperature Superconductor (HTS) cable. Helical says this experiment “positions the company at the forefront of achieving a steady-state fusion reactor, establishing a new standard in the fusion energy domain”.

Helical Fusion in October 2023 was selected by the Japanese Ministry of Education, Culture, Sports, Science & Technology (MEXT) for its total JPY 6.5bn ($43m) Small Business Innovation Research (SBIR) programme to develop cutting-edge fusion technologies. Helical Fusion was one of four companies to be selected to receive JPY2bn.

Helical Fusion, together with Japan’s National Institute for Fusion Science (NIFS), has developed a new HTS conductor, Wind & Impregnated Stacked Elastic (WISE) tapes that can be scaled and engineered into high-performance magnets. The funding will accelerate commercialisation of the WISE conductor by increasing its Technology Readiness Level from Level 5 to Level 7 (an index created by NASA used to evaluate the proficiency level of a particular technology and determine its maturity level).

The company's state-of-the-art HTS cable, developed and manufactured in-house, has showcased superior superconductivity at cryogenic temperatures of -253°C (20 Kelvin) within a high magnetic field environment of 8 Tesla. The experiment was conducted at NIFS.

The HTS cable, crafted with 30 layers of REBCO (a top-tier HTS wire), constituted a durable conductor with a cross-section of approximately 3 cm and a length exceeding 4 metres. This configuration underwent testing nearly at the maximum capacity of the facility, 20 kA. Helical Fusion aims to significantly enhance this current capacity by integrating additional HTS wires, targeting a current density of over 100 amperes per square millimetre. Such high current density is vital for the development of fusion reactors to be both compact and efficient. The experiment also introduced an innovative HTS wire joint technique, facilitating the scalable production of these advanced conductors.

The innovative conductor design, spearheaded by Dr Junichi Miyazawa, Head of R&D at Helical Fusion, leverages NIFS's extensive research in superconductor technology. Helical says this conductor characterised by its high current density and narrow-wind-ability, holds promise for broad applications beyond fusion reactors.

Image: Installation of the High-Temperature Superconductor cable into the testing apparatus (courtesy of Helical)

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