It is a week of breakthroughs and exciting announcements about nuclear fusion. Following the exciting updates from the American’s Inertial Fusion, scientists in the United Kingdom have announced the highest energy output ever achieved with nuclear fusion.

A test in the Joint European Torus (JET) was able to create high-fusion power for five seconds, releasing 69.26 megajoules of energy from just 0.21 milligrams of fuel. This is equivalent to the energy you can get out of 2 kilograms (4.4 pounds) of coal. The fuel in question is a mixture of two types of heavy hydrogen called deuterium and tritium, which will be employed in the nuclear fusion power stations of the future.

Despite the record, JET is not designed to reach the energy expected for those stations. It is a pathfinder for full-scale prototypes like ITER and DEMO.  ITER will come on next year and should generate 10 times as much energy as put in. Its successor, DEMO, will generate electricity and 25 times the energy put in. Still, the JET results show the potential of this technology.

“Our successful demonstration of operational scenarios for future fusion machines like ITER and DEMO, validated by the new energy record, instil greater confidence in the development of fusion energy. Beyond setting a new record, we achieved things we’ve never done before and deepened our understanding of fusion physics,” Professor Ambrogio Fasoli, Programme Manager (CEO) at EUROfusion, said in a statement.   

“We can reliably create fusion plasmas using the same fuel mixture to be used by commercial fusion energy powerplants, showcasing the advanced expertise developed over time,” added Dr Fernanda Rimini, JET Senior Exploitation Manager.

JET, ITER, and DEMO are a nuclear fusion design known as a tokamak. The fusing plasma is contained in a donut-shaped chamber by powerful magnets. Fusion is the process that powers the Sun and all the stars, but on Earth, we don’t naturally have the pressures and temperatures present at the core of these objects. So we need to get creative, and usually, this means heating plasma to over 100 million degrees.

At such temperatures, the plasma releases a lot of energy (that is the goal) but there can be bursts that damage the confinement walls. The fusion of deuterium and tritium creates helium and this byproduct needs to be discarded without destroying the exhaust system. JET has demonstrated that both these challenges can be solved.

“Not only did we demonstrate how to soften the intense heat flowing from the plasma to the exhaust, we also showed in JET how we can get the plasma edge into a stable state thus preventing bursts of energy reaching the wall. Both techniques are intended to protect the integrity of the walls of future machines. This is the first time that we’ve ever been able to test those scenarios in a deuterium-tritium environment,” Dr Emmanuel Joffrin, EUROfusion Tokamak Exploitation Task Force Leader from CEA, added.

To create those high temperatures, it is necessary to input a lot of energy. In nuclear fusion, the goal is to reach a Q factor higher than one, with one being you get out as much energy as you put in. The only experiment that has reached that so far was the Inertial Fusion system in the US, which got a Q of 1.5. The best that JET has done is 0.69 but the energy output of JET was 20 times higher than what the Inertial Fusion has achieved.

Commercial fusion power stations are still a couple of decades away but these recent breakthroughs show that there are multiple paths to that goal and only by further experimentation can we continue to refine and improve.