Scientists confirmed last year, for the first time in the lab, that they had achieved a fusion reaction that self-sustains (rather than fizzles out) – bringing us closer to replicating the chemical reactions that power our Sun.
However, they are not sure how to recreate the experiment.
Central addition Occurs when two atoms combine to form a heavy atom, releasing a huge energy explosion in the process.
This is a process often found in nature, but it is very difficult to replicate in the lab because it requires a high-energy environment to drive the reaction.
the sun generate power Using nuclear fusion – hydrogen atoms are broken together to form helium.
Supernova – exploding sun – also Nuclear fusion leverage for their cosmic fireworks display. It is the energy of these reactions that creates heavy molecules like iron.
In artificial settings here on Earth, however, heat and energy escape through cooling processes such as X-ray radiation and thermal conduction.
To make nuclear fusion a viable energy source for humans, scientists must first achieve something called ‘ignition’, where self-heating processes overcome all energy losses.
Once ignition is achieved, the fusion reaction powers itself.
In 1955, physicist John Lawson developed a set of criteria, now known as ‘Lawson-like ignition criteria’, to help identify when this ignition had occurred.
Ignition of nuclear reactions usually occurs in extremely intense environments, such as supernovae or nuclear weapons.
Researchers at the National Ignition Facility at Lawrence Livermore National Laboratory in California spent more than a decade perfecting their technique and sure now That landmark test conducted on 8 August 2021 produced, in fact, the first successful ignition of a nuclear fusion reaction.
In a recent analysis, the 2021 test was judged against nine different versions of Lawson’s criteria.
“This is the first time we’ve exceeded Lawson’s criteria in the lab,” said Annie Kreacher, a nuclear physicist at the National Ignition Facility. new scientist.
To achieve this effect, the team placed a capsule of tritium and deuterium fuel in the center of a gold-lined depleted uranium chamber and fired 192 high-power lasers at it for an intense X-ray bath.
The intense environment generated by the internally directed shock wave creates a self-sustaining fusion reaction.
Under these conditions, hydrogen atoms undergo fusion, releasing 1.3 megajoules of energy for 100 trillionths of a second, which is 10 quadrillion watts of power.
Over the past year, researchers have been trying to replicate the results Four similar experimentsBut it managed to produce only half the energy yield produced in the record-breaking initial tests.
Ignition is highly sensitive to small changes that are barely perceptible, such as differences in the structure of each capsule and the intensity of the laser, Kreacher explains.
“If you start from a microscopically bad starting point, it reflects a much larger difference in final power output,” said Jeremy Chittenden is a plasma physicist at Imperial College London. “The August 8 test was the best-case scenario.”
The team now wants to determine exactly what is needed to achieve ignition and how to make the experiment more resilient to small errors. Without that knowledge, the process cannot be scaled up to build fusion reactors that can power cities, which is the ultimate goal of this type of research.
“You don’t want to be in a position where you have to get absolutely everything right to get the ignition,” Chittenden says.
This article was published Physical review letter.