Combining spherical tokamaks and high temperature superconductors

The world needs a clean and reliable source of base-load energy. That’s what we’re striving to achieve at Tokamak Energy.

Our route to fusion power is unique. We are taking established science and building on it by pioneering the use of spherical tokamaks in conjunction with high temperature superconductors (HTS).

Fusion – the energy source that powers the sun – is globally accepted as the best way to generate plentiful, safe, secure and clean energy. The tokamak is the most heavily researched and best understood of all the different paths to fusion.

It is now acknowledged that the spherical tokamak design offers the smallest and most cost-effective solution. This is our solution. Yet there are many complex engineering challenges that need to be overcome for demonstration and commercialisation of this technology.

Our team of world-class fusion scientists and magnet engineers is tackling these challenges to develop efficient and affordable fusion power. Our unique approach is centred on rapid innovation using the latest materials and technology – but building on decades of scientific research and experience. This strategy gives us – and the world – a faster way to fusion.

Once fusion electricity is achieved, our scalable technology could be rolled out across the world as a solution to one of humanity’s greatest challenges: clean and sustainable energy for all.



Spherical tokamaks

Scientists first realised the potential of tokamaks to achieve fusion conditions back in the 1960s when the Russian tokamak T3 reached much higher plasma temperatures than any other fusion machine at the time.

But it was later found that the shape of the early tokamak – a wide, ring-doughnut shape – is far from an ideal design.

In the 1980s, one of our founders, Alan Sykes, who was working at the Culham Centre for Fusion Energy, did a theoretical study that revealed modifying the shape of the tokamak would have an impact on performance.

By moving from a doughnut-shaped plasma ring to an apple-shaped plasma ring, the plasma is contained more efficiently. Alan found that it is possible to achieve a much higher plasma pressure for a given magnetic field. Experimental studies in the 1980s by teams led by Alan and Mikhail Gryaznevich on first START (shown) and then MAST tokamaks verified this result.

The problem with the more compact spherical design was the lack of space in the centre of the machine for magnets and their protective shielding. This meant that achieving high enough magnetic fields for fusion power production would be tricky. That was until new superconductor technology came along…

By combining the increased efficiency of the spherical tokamak with the improved magnetic confinement made possible by high temperature superconductors (HTS), we can see a viable route to cost-effective, commercial fusion power in smaller machines. This is central to our faster fusion approach.

High temperature superconductors

The key to our compact spherical tokamak device route to fusion power is the use of high temperature superconductors (HTS), made from Rare earth Barium Copper Oxide (REBCO).

Magnetic fields are a vital component of tokamaks as they trap the electrically-charged plasma particles and keep the fusion fuels contained and hot.

For power stations that require continuous tokamak operation, the magnets will have to be made of superconductor materials to prevent them heating up and needing down-time to cool. Conventional superconductors have been around commercially since the 1960’s but the newer ‘high temperature’ superconducting materials offer some important advantages for tokamak development:

  1. High temperature superconductors are manufactured in narrow tapes that are less than 0.1mm thick. When wound into coils, they can create much higher magnetic fields while taking up less space than conventional superconductor magnets.
  2. The ‘high’ temperatures at which HTS materials operate is still pretty cold (between -250 and -200 degrees Celsius) but there are still a considerable energy – and cost – savings to be had over cooling to -269 degrees Celsius.

HTS technology is a perfect complement to the efficient compact spherical tokamak design that is able to achieve the high current density and strong magnetic fields that are needed for economical fusion power.