Tokamak Energy has recorded breakthrough results on the path to clean, limitless energy after replicating fusion power plant fields for the first time in its world-leading magnet system.
Demo4 also demonstrates the transformative potential of high temperature superconducting (HTS) technology across a range of spin-out applications, from power distribution for data centres, electric motors for zero emission flight, and fast, efficient magnetic levitation transport systems.
Creating fusion energy requires extremely strong magnetic fields to confine and control hydrogen fuel, which is heated to a plasma several times hotter than the centre of the sun inside a vessel called a tokamak.
Tokamak Energy’s Demo4 – a complete set of HTS magnets built in a tokamak configuration – produced the milestone results at the company’s headquarters outside Oxford, achieving field strengths of 11.8 Tesla at -243 degrees Celsius in recent tests.
The world-first system had an incredible seven million ampere turns of electrical current running through its centre column, demonstrating huge potential for power distribution as HTS can deliver around 200 times the current density of copper.
Warrick Matthews, Tokamak Energy CEO, said: “These results are a major victory for the race to deliver fusion and HTS as a disruptive new commercial technology. Demo4 represents over a decade of HTS innovation at Tokamak Energy. Born from our fusion mission, it validates one of the technical solutions for getting clean, limitless, safe and secure fusion energy on the grid.
“Demo4 is also best in class at showcasing and demonstrating the transformative potential for superconductors, including power distribution for high-demand environments like data centres and applications across science, power systems, propulsion, and beyond.”
Strong magnetic fields are generated by passing large electrical currents through arrays of electromagnetic coils assembled in a cage-like formation. The magnets are wound with precision from HTS tapes using multi-layered metal conductors with a crucial internal coating of ‘rare earth barium copper oxide’ (REBCO) superconducting material.
While recognising the achievement of demonstrating a single high-field HTS magnet, Tokamak Energy has focused on the next essential step: validating a complete HTS magnet system. In a fusion power plant, each REBCO superconducting tape must operate within the complex, combined magnetic environment created by neighbouring coils – conditions that significantly influence its effective critical current and structural performance.
These system-level interactions cannot be captured through individual magnet tests. Demo4 is therefore a world-first high field platform to generate and study fusion-relevant forces across a system coil set (14 toroidal field magnets and two poloidal field magnets), providing uniquely valuable engineering insight and data to inform power plant designs of the future.
Graham Dunbar, Demo4 chief engineer at Tokamak Energy, said: “Demo4 is delivering exactly what it was built for. Every test provides us with invaluable data and deepens our understanding. This isn’t just about achieving a number; it’s about gaining the confidence and build expertise to scale our technology for future energy-producing fusion systems.”
Demo4’s results confirm Tokamak Energy’s HTS magnets can generate the high fields essential for a fusion power plant and prove their capacity to support higher current densities with plug-in cooling capability. This means they can be made smaller and lighter than traditional low-temperature superconductors and operate at a fraction of the cooling cost. Further testing to reach higher magnetic fields continues, with next results due in early 2026.
