The key to the rapid development of Tokamak Energy’s fusion technology is a series of working prototypes that are being used to validate our novel approach and confirm our predictions about plasma performance.

Tokamak Energy founders, Dr Mikhail Gryaznevich and Alan Sykes, built our first experimental device, ST25, which uses conventional copper magnets to confine the plasma.

The device performed successfully during tests and achieved plasma for three milliseconds in 2012. ST25 demonstrated our expertise in tokamak engineering and allowed us to test, on a smaller scale, systems and techniques that will be critical to our future programme. We continue to use ST25 to support the ST40 programme.

ST25 showed that a small device can be built rapidly and that by testing, where possible, on smaller machines, we can speed up technology development.



Highlighting the potential of high temperature superconductors for fusion

With the success of the ST25 experimental tokamak, attention turned to the next phase of development in our fusion strategy – to determine the suitability of high temperature superconductors (HTS) for tokamak magnets.

Mikhail Gryaznevich made a very crude initial test of HTS tapes, hand wound into a tokamak magnet, on the GOLEM tokamak in Prague in 2011. Following this successful initial test, we upgraded the ST25 to include poloidal field coils made from HTS. During testing in 2013, we created a poloidal field using the HTS magnetic coils and achieved a plasma pulse for five seconds.

This iteration gave us increased confidence in the use of HTS technology for fusion.

Further evolution secures a new fusion world record

Progressing from the HTS tests on the ST25, we built a whole new tokamak of the same size but this time with all its magnets made from HTS material. This new machine was dubbed ST25-HTS.

Being fully HTS, allows the tokamak to run continuously – something that will be vital when using fusion reactions to create energy on a commercial scale.

The ST25-HTS device achieved a world first in July 2015, transmitted live to our stand at the Royal Society Summer Exhibition (a prestigious event held by the world’s oldest scientific academy). ST25-HTS succeeded in sustaining plasma continuously for 29 hours until it was switched off.

Testing on ST25 and ST25-HTS demonstrated the suitability of high temperature superconductors for use on tokamaks, while theoretical studies showed their potential. The combination of high temperature superconductors and spherical tokamaks allows us to design revolutionary compact tokamaks.