VIPER cable is a high-current, high-temperature superconducting cable developed by the 📝MIT Plasma Science and Fusion Center and 📝Commonwealth Fusion Systems for winding large-scale fusion magnets.
The name is an acronym for the cable's manufacturing recipe — Vacuum Pressure Impregnated, Insulated, Partially transposed, Extruded, and Roll-formed. Stacks of thin 📝REBCO superconducting tape are set into channels in an extruded copper former, twisted, and sealed inside a steel jacket with coolant passages, producing a rugged conductor that carries tens of kiloamperes. The design answered a gap the tape itself could not fill: 📝HTS tape is a ribbon a few millimeters wide, and a fusion magnet needs a compact, mechanically robust, jointable conductor rated for enormous currents and forces. The near-neighbor distinction is with the 📝no-insulation coil winding approach — VIPER is a cable, a conductor from which coils are wound, not a winding technique.
Test campaigns at the SULTAN facility in Switzerland showed the cable retained performance through thousands of mechanical load cycles and repeated cryogenic cycling, and the design was published in Superconductor Science and Technology in October 2020 as an industrially scalable conductor for 📝High-Temperature Superconducting (HTS) Magnets. That qualification paper is covered in 📝VIPER: An Industrially Scalable HTS Cable; a 2024 successor, PIT VIPER, adapted the design for the fast-ramping magnets a tokamak also needs.
We co-developed VIPER with MIT because delivering fusion on a meaningful timescale meant inventing the conductor first — the same engineering line that carried us to the 20-tesla magnet demonstration and into 📝SPARC's magnets.