Oxford scientists leap ahead in race to harness nuclear fusion

Otto Asunta smiles as he traces the patches of light and dark displayed on the screen in front of him, revealing the outlines of the plasma he and his team have bent the earth’s natural forces to create. 

“Where you have light you have a cold plasma,” says the senior physicist at Tokamak Energy. “You don’t see anything there because it’s so hot that it doesn’t emit any visible light.”

This ethereal matter has been created not millions of miles away on another planet, but inside a vacuum chamber just downstairs from Asunta’s computer screens on this Oxfordshire industrial estate. 

The Finnish scientist is among the new torch-bearers of a quest that has lured scientists since at least the 1920s: replicating the process that powers the sun, to help power the earth. 

The potential for abundant, clean energy from this nuclear fusion process means it has long been considered something of a holy grail, with efforts to replicate and commercialise the process now given added impetus by the push to replace fossil fuels and cut global warming. 

“We have to, right?” says Asunta, a graduate of Finland’s Aalto University who has devoted his career so far to Tokamak Energy’s efforts to crack the problem.  

That will not be easy. Nuclear fusion happens naturally in the sun because the temperature is so high that hydrogen atoms are pushed together, unleashing helium and masses of energy in the process. Achieving those sorts of temperatures on earth and controlling the result is staggeringly complex and energy-intensive, however. 

Tokamak Energy, spun out of Oxford's Culham fusion research laboratory, builds on an approach dating back to the 1940s, using powerful magnetic fields and 250,000-amp electric currents in a 'tokamak' device, protected by a bio-shield inside its base. 

For all the challenges, however, a flurry of progress in recent months has spurred hopes that the industry may be lurching forwards after decades of spluttering pace, with significant advancements in the UK. 

In February, scientists at the JET European project near Oxford managed to use fusion to generate 59 megajoules of energy - an inconsequential amount able to boil about sixty kettles, but a leap forward in the long march towards commercial nuclear fusion. 

"If we can maintain fusion for five seconds, we can do it for five minutes and then five hours,” Tony Donne, programme manager for the Eurofusion group responsible for the JET research said at the time. 

After achieving temperatures of 15m degrees celsius in 2018, Tokamak Energy then broke through the 100m celsius fusion threshold in March. Meanwhile last month, Oxford-based First Light Fusion managed to achieve fusion by going down a non-magnetic route.

Instead, First Light Fusion have triggered the reaction by using a 22-metre gas gun to fire a 100g projectile at 6.5km a second - about 20 times the speed of sound - at a pellet containing tritium and deuterium. 

Both private companies are at the stage of measuring their reactions in terms of neutrons produced rather than energy harnessed, with Tokamak claiming far greater progress on that score compared to First Light.

They say progress is getting faster and cheaper, with Tokamak reaching 100m degrees celsius over five years at a cost of £50m.  

The companies are enjoying growing investor interest in the sector, with First Light Fusion recently raising $45m (£36m) from backers including Chinese giant Tencent. Tokamak’s backers include the investment giant Legal & General and the Capri-Sun juice magnate Hans-Peter Wild. 

Whether fusion will eventually branch out from the realms of experimental physics and into the cold, hard realities of commercial power production is still very much an open question, however. 

No fusion project has yet managed to produce more energy from the reaction than is required to trigger the reaction in the first place: the so-called Q ratio. To just break-even, Q needs to equal one. 

The best that has been achieved so far is Q of 0.7. To get to commercial fusion, the Q ratio probably needs to be in the teens or low 20s, says Chris Kelsall, Tokamak’s chief executive, who is in charge of steering it towards its goal of a pilot power plant in the 2030s. 

Hired as finance chief in 2020 after a varied career including stints in oil exploration, mining and hydrogen fuel cells, he took the top role after Jonathan Carling stepped down last year for personal reasons.  

“As a generalist, part of my role is to help ensure that our specialists are optimally integrated and there’s no constraints on their effectiveness,” says Kelsall. 

“I've got to unlock that efficiency, but also plot the medium and longer term. There are a range of metrics in terms of temperature, density of the plasma and other behavioural characteristics that need to be optimised over long periods of time. 

“We've got to strike a very careful balance around overly focusing our technology roadmap on one milestone, to the detriment of neglecting all the others.”

Having reached the 100m degree Celsius time-frame, Tokamak is pushing ahead with work on improving the design of its tokamak, which is already smaller than others and uses a spherical design that bosses say is more efficient and lower cost. The next will build on advances in superconductors over the last decade.  

“It [the advances] have been a game changer for fusion because you're now able to get far stronger currents through far stronger magnets,” says Kelsall. Tokamak will be seeking fresh, international investment this year as it pushes ahead with its plans. 

Asunta pushes back against sceptics of the technology's potential. “I have no doubts that it will [succeed],” he says. “I really believe that it is the way forward and something we have to pursue,” he says. 

The all-important Q ratio is not necessarily a problem, he adds. “We need bigger devices, we need more powerful devices, and we need more experience. But we are on the path. It’s in our nature that we are always looking at the world thinking, what’s the next problem we can solve.”