Pioneering commercial
fusion technology

The spherical tokamak

Tokamaks are the most researched and best understood route to fusion energy.

Tokamaks use powerful magnetic fields to confine and control plasma, and decades of development have established them as one of the leading approaches to commercial fusion. Tokamak Energy is the only private company with more than a decade of experience designing, building and operating tokamaks.

In the 1980s, our founder Alan Sykes demonstrated that a low‑aspect‑ratio, more spherical tokamak could offer significant benefits in efficiency, plasma stability and cost‑effectiveness. This approach now underpins fusion programmes worldwide, including the UK Government’s Spherical Tokamak for Energy Production (STEP) project.

ST40

Designed, built, and operated by Tokamak Energy, ST40 is the world’s highest-field spherical tokamak.

As one of the most advanced fusion devices in the world, ST40 is the perfect testbed for developing the technologies and expertise needed to deliver commercial fusion energy. It is currently undergoing a $52 million upgrade in collaboration with the US Department of Energy and the UK Department of Energy Security and Net Zero, advancing critical fusion technologies such as lithium plasma-facing components and radio-frequency (RF) heating.

In 2022, ST40 achieved a record plasma ion temperature of 100 million degrees Celsius; the threshold for fusion energy. It also achieved the highest triple product of any private fusion company, a key measure of plasma performance combining temperature, density, and energy confinement. Our achievement was documented in a peer-reviewed scientific paper published by the Institute of Physics.

HTS magnet systems for fusion

Magnetic‑confinement fusion relies on strong, precisely controlled magnetic fields to shape and hold the plasma.

High‑temperature superconducting (HTS) magnets can generate these fields with far greater efficiency than conventional superconductors because they operate at higher temperatures that can be achieved without liquid helium. They also maintain superconductivity in much higher background fields, making them far better suited to the high‑field conditions needed in fusion devices.

HTS magnets are now used across several fusion approaches, including tokamaks, stellarators and other magnetic-confinement concepts.

Tokamak Energy has more than a decade of experience in the design, build and operation of HTS magnet systems for fusion. Our magnets are wound from REBCO HTS tape, a multilayer conductor around 12 mm wide and less than 0.1 mm thick, with a thin superconducting layer of rare‑earth barium copper oxide. Our design, modelling, testing and production methods are focussed on delivering robust and reliable high-field HTS systems for fusion and other demanding applications.

HTS is a transformative technology for getting clean, limitless fusion energy on the grid faster.

Demo4: HTS fusion magnet system

Demo4 is the world’s first HTS fusion magnet system to reach fusion‑relevant magnetic fields.

Demo4 is a vital step toward delivering fusion power. Engineered in a full tokamak configuration, it operates under real‑world stresses to validate a complete HTS magnet system and provide a blueprint for scaling to energy‑producing fusion devices.

The system integrates 44 high‑temperature superconducting coils into 14 toroidal‑field limbs and two poloidal‑field coils, forming a cage‑like structure. Operating in vacuum at 20 K (‑250 °C) and achieving fields up to 11.8 T in tests, Demo4 has enabled us to build the design, manufacturing and operational capability required for large‑scale HTS magnet systems.