Pioneering commercial
fusion technology
Pioneering commercial
fusion technology
The spherical tokamak
Tokamaks are the most researched and best understood path to fusion energy.
Tokamaks use magnetic fields to confine and control plasma. Decades of development have established them as the leading approach to commercial fusion. Tokamak Energy is the only private company with over a decade’s experience developing and operating tokamaks.
In the 1980s, our founder Alan Sykes demonstrated that the low aspect ratio tokamak, with its more spherical shape, offered benefits in efficiency, plasma stability, and cost-effectiveness. Today, this approach 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.
In 2022, we achieved a record plasma ion temperature of 100 million degrees Celsius—the threshold for fusion energy. We 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.
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. In 2026, it will undergo a $52 million upgrade programme in collaboration with the US Department of Energy and the UK Department of Energy Security and Net Zero, advancing critical technologies such as lithium plasma-facing components and radio-frequency (RF) heating.
HTS magnets for fusion
Tokamaks use strong magnetic fields to control the shape and position of the plasma, trapping it long enough for fusion to occur.
High temperature superconducting (HTS) magnets generate these fields at higher temperatures than conventional superconductors, making them more than five times as energy-efficient. Combining the increased efficiency of the spherical tokamak with the improved magnetic confinement made possible by high-field HTS magnets offers the most viable and cost-effective route to fusion energy.
Tokamak Energy is a world leader in HTS technology. Our fusion magnet coils are wound from HTS tapes, which are multi-layered conductors typically 12mm wide and less than 0.1 mm thick made mostly of strong and conductive metals, but with a crucial thin internal coating of ‘rare earth barium copper oxide’ (REBCO) superconducting material. Our advanced winding, testing and production techniques are the key to creating robust and reliable HTS magnets.

HTS is a transformative technology for getting clean, limitless fusion energy on the grid faster.
Demo4
The world’s first HTS fusion magnet system to achieve fusion power plant 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 establish a blueprint for scaling up 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 a vacuum at 20 Kelvin (-250°C), Demo4 has enabled us to develop the design, manufacturing, and operational expertise required to deliver large-scale HTS magnet systems.































