Scientists from the US government have for the second consecutive time achieved a net energy gain during a fusion process. This result will fuel optimism about the progress being made in the quest to achieve limitless zero-carbon energy.
Since the 1950s, physicists are trying to harness the fusion reactions that power the sun. But up until December, no group has been able produce more energy than the reaction consumes – a condition known as ignition.
Three people familiar with the preliminary results say that researchers at the federal Lawrence Livermore National Laboratory, in California, who had achieved ignition for the very first time in the past year, repeated this breakthrough on July 30, producing a greater energy output than they did in December.
The lab confirmed that it had achieved energy gains again in its laser facility and added that the analysis of results was under way.
We have performed experiments to continue studying this new exciting scientific regime since demonstrating fusion combustion for the first at the National Ignition Facility on December 20, 2022. “In an experiment performed on July 30th, we repeated ignition at NIF,” the report said. As is our usual practice, we will report those results in upcoming scientific conferences as well as peer-reviewed journals.
The fusion process is accomplished by heating two isotopes of hydrogen — typically deuterium or tritium — at such high temperatures that their atomic nuclei fuse. This releases helium, as well as vast amounts of energy (in the form of neutrons).
The potential of fusion technology is difficult to ignore, even though many scientists think fusion power plants are decades away. Fusion reactions produce no radioactive waste or carbon dioxide and can theoretically power an entire house with a cup of hydrogen.
Magnetic confinement is the most studied method, which uses large magnets to keep the fuel in place as it heats up to temperatures higher than the sun.
The NIF uses an alternative process called inertial containment. It fires the largest laser in the world at a capsule of fuel, triggering implosion. Jennifer Granholm, the US Energy Secretary, described ignition in December as “one the most impressive scientific feats of the 21st Century”. In this experiment, produced approximately 3.15 megajoules. This was around 150 per cent the 2.05MJ from the lasers.
Two people who were familiar with the results of the experiment in July said that the initial data indicated a higher energy output than 3.5MJ. This energy is roughly enough to run a household iron on for an hour.
Since decades, achieving net energy gains has been seen as a key step to proving commercial fusion power plants are possible. There are still a few hurdles to be overcome.
The energy gain is only compared to the laser energy, and not the total energy that was pulled from the grid for the system. This amount of energy is higher. Scientists estimate commercial fusion reactions will need to generate energy between 30 and 100-fold that of the lasers.
A nuclear power plant with internal confinement would need to fire several shots per second, while the NIF only makes one shot a week.
One of those with access to the results said that the NIF’s improved result, which came “only eight” months after the initial breakthrough was another sign of the increasing pace of progress.