Helical Fusion’s laboratory magnet carries 40 kA without quenching

Inside a specialized cryogenic chamber, a double-pancake coil built with Helical Fusion’s UROCOIC conductor carried 40 kA without quenching or leaving its superconducting state. The laboratory test ran at temperatures up to 30 K (-405°F).

The coil was tested by researchers from Helical Fusion and Japan’s National Institute for Fusion Science. External coils supplied a background field of 7 Tesla, producing a maximum field of 8.9 Tesla on the test magnet. The coil also withstood electromagnetic forces of 356 kilonewtons per meter, data that the researchers say directly tests conditions expected inside a fusion device.

The conductor’s architecture is designed for stellarators, whose superconducting coils must follow complex three-dimensional shapes while handling large currents and mechanical loads. UROCOIC — Unitized Reinforcing Outer Cover On Internal Components — adds an external metal jacket that absorbs physical stress and protects the superconducting tapes inside.

The test used another unusual choice: no conventional electrical insulation between the coil’s layers. In a standard superconducting magnet, insulation can trap heat when a small section warms up, triggering a quench, the sudden loss of superconductivity. An uninsulated winding lets heat and excess current bypass hot spots, and the team observed stable behavior during sudden changes in the external magnetic field.

The practical consequence is a clearer route to Helical Fusion’s next experiment, Helix HARUKA, where the company plans to integrate the magnet technology. If those tests succeed, Helical Fusion aims to scale the conductor for Helix KANATA, a full-scale commercial fusion plant planned for the 2030s. For now, the evidence comes from one laboratory test magnet, not a working power plant.