The pressure was greater than the centre of Jupiter. The temperature was approaching that found deep inside the Sun. The projectile was travelling at 6.5 kilometres per second. And for the smallest fraction of a second, these conditions came together to release 50 neutrons, a barely-perceptible amount of energy. But in doing so, a company in Oxfordshire has demonstrated a new way of making nuclear fusion.
For the first time, First Light Fusion, one of a growing number of nuclear fusion start-up companies, has provided proof of concept that its unusual approach to the technology, which involves firing a projectile at a pellet of fuel, is feasible.
If, and it remains a big if, it can be scaled up, then there is a chance it might offer a means of making almost limitless carbon-free electricity.
“This is a completely new idea of fusion,” said Dr Nick Hawker, the company’s founder. “If we can get the core physics to work, which I think we can, it potentially has a much faster trajectory to a power plant. The engineering is much simpler. The physics is simpler.”
Nuclear fusion is the process that powers the Sun. It involves forcing together hydrogen atoms under intense heat and pressure to make helium, and in doing so release energy in the form of neutrons. The difficulty is that it requires replicating Sun-like conditions on Earth.
Down the road from Hawker’s company in Culham, lies Jet, the international experiment that represents the conventional approach to achieving viable fusion.
Inside a doughnut-shaped container, scientists use extremely powerful magnets to contain a superheated plasma, so hot it cannot be allowed to touch the sides. Earlier this year this experiment broke the world record for fusion, but is still far from a viable power plant.
First Light Fusion is planning a different, riskier, route. Rather than attempting to continuously recreate Sun-like conditions, as Jet does, it tries to instantaneously recreate them by shooting a super high-velocity slug at a carefully shaped fuel pellet. When the projectile hits, the pellet implodes, increasing the pressure still further and effectively magnifying the 6.5km per second impact tenfold.
Now the company has been able to do this in such a way that fusion occurred. However, it has a long way to go. Its reaction made only 50 neutrons.
The Culham experiment made many billions of times as many and is itself still a prototype. “We’re not daft,” said Hawker. “We know that 50 neutrons is not very much.” The point is though, he said, it matches their calculations and validates the approach. “The important thing is that the measured amount of fusion agrees very closely to the predicted amount from a simulation,” he said. Now Hawker said they are looking to speed up the projectile. With more pressure, yield should increase greatly.
Dr Richard Kembleton, from Eurofusion, the European consortium of fusion researchers, said that what is key now is to see how those experiments progress.
“This is good news for First Light, as it proves their approach can produce implosions as their models predict,” he said. “It’s scaling this up to the complex and precise geometries they show in their simulations, which is the really tricky bit.”
