Tokamak Energy’s HTS magnets achieve fusion-grade magnetic fields, advancing commercial fusion power

Tokamak Energy has successfully replicated the magnetic fields required for a fusion power plant using its advanced high temperature superconducting magnets. The company’s Demo4 system, consisting of a complete set of HTS magnets arranged in a tokamak configuration, recently produced magnetic fields of 11.8 Tesla at temperatures of -243 degrees Celsius during tests at their headquarters near Oxford.

The Demo4 achievement represents more than incremental progress. While previous tests focused on individual superconducting magnets, Demo4 operates an entire magnet system simultaneously, running 14 toroidal field magnets and two poloidal field magnets together. This system-level validation matters because each REBCO superconducting tape within the magnet coils must function reliably amid the intertwined magnetic forces generated by neighbouring coils, influencing current-carrying capability and mechanical integrity in ways that single-magnet tests cannot capture.

The HTS magnets operate with electrical currents delivering seven million ampere turns through their centre column, achieving current densities approximately 200 times greater than copper conductors. The precision-wound magnets use multi-layered metal conductors coated internally with rare earth barium copper oxide, enabling high magnetic fields with minimal electrical resistance. This produces magnets that are smaller and lighter than conventional low-temperature superconductors while operating at higher temperatures, dramatically reducing cooling costs.

During testing, the magnets endured compressive forces exceeding 30 tons within compact coils just 10 centimeters in outer diameter. The system was subjected to over 100 field ramp-ups, including deliberate quenches from peak field conditions, with no degradation observed.

According to Warrick Matthews, CEO of Tokamak Energy, Demo4 validates HTS magnets as a disruptive technology for clean fusion energy. Graham Dunbar, Demo4’s chief engineer, explains that the project builds the confidence and expertise necessary to scale this technology for energy-producing systems.

The success also unlocks possibilities beyond fusion. Potential applications include power distribution in data centres, zero-emission electric flight propulsion, and magnetic levitation transport. The company is already working with General Atomics to design HTS magnets for magnetohydrodynamic propulsion systems for silent marine propulsion.

Tokamak Energy continues pushing Demo4’s capabilities with ongoing tests aiming for higher magnetic fields. Results are expected in early 2026.

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