The federal Lawrence Livermore National Laboratory in California, which uses a process called inertial confinement fusion that involves bombarding a tiny pellet of hydrogen plasma with the world’s biggest laser, had achieved net energy gain in a fusion experiment in the past two weeks, the people said.

Although many scientists believe fusion power stations are still decades away, the technology’s potential is hard to ignore. Fusion reactions emit no carbon, produce no long-lived radioactive waste and a small cup of the hydrogen fuel could theoretically power a house for hundreds of years.

The US breakthrough comes as the world wrestles with high energy prices and the need to rapidly move away from burning fossil fuels to stop average global temperatures reaching dangerous levels. Through the Inflation Reduction Act, the Biden administration is ploughing almost $370bn into new subsidies for low-carbon energy in an effort to slash emissions and win a global race for next-generation clean tech.

The fusion reaction at the US government facility produced about 2.5 megajoules of energy, which was about 120 per cent of the 2.1 megajoules of energy in the lasers, the people with knowledge of the results said, adding that the data was still being analysed.

Eoin Treacy's view

To the extent people are familiar with fusion experiments, most think of the tokamak experiments that look like big globes. They basically use magnetic confinement to control and heat plasma with the aim of achieving fusion.

This is the model the ITER project is building in southern France. It also forms the basis for many of the startups which sprung up when MIT cut funding to its tokamak experiment about a decade ago.

The Lawrence Livermore Lab uses directed lasers to heat and compress a packet of fuel until fusion occurs. There are several other laser-based experiments around the world. Now that positive net energy has been achieved it is reasonable to expect a great deal most investment will flow into tackling the remaining issues with developing a targeted laser fusion power plant. This is a massive step for big science experiments and will likely be the foundation of a significant bull market in the 2030s.

This article from the Royal Society may also be of interest.