Scientists have achieved self-sustaining nuclear fusion…but now they can’t replicate it: ScienceAlert

Scientists confirmed that last year, for the first time in the lab, they had a fusion reaction that perpetuates itself (rather than dies out) — bringing us closer to repeating the chemical reaction that powers the sun.

However, they are not entirely sure how to recreate the experience.

nuclear fusion It occurs when two atoms combine to form a heavier atom, releasing a massive burst of energy in the process.

This process is often found in nature, but it is very difficult to replicate in a laboratory because it needs a high-energy environment to keep the reaction going.

the sun generates energy Using nuclear fusion – by smashing hydrogen atoms together to form helium.

Supernovae – Exploding Suns – Too Take advantage of nuclear fusion Cosmic fireworks display. It is the strength of these interactions that creates heavier particles such as iron.

However, in artificial places here on Earth, heat and energy tend to escape through cooling mechanisms such as X-ray radiation and thermal conductivity.

To make nuclear fusion a viable energy source for humans, scientists must first achieve something called “ignition,” in which self-heating mechanisms overcome all energy loss.

Once ignition is achieved, the fusion reaction powers itself.

In 1955, physicist John Lawson created the set of criteria, now known as the “Lawson-like ignition criteria,” to help identify when this ignition occurred.

The ignition of nuclear reactions typically occurs within highly dense environments, such as a supernova, or nuclear weapons.

Researchers at Lawrence Livermore National Laboratory’s National Ignition Facility in California have spent more than a decade perfecting their method, Confirmed now That the historical experiment conducted on August 8, 2021 actually led to the first-ever successful ignition of a nuclear fusion reaction.

In a recent analysis, the 2021 trial was judged against nine different versions of the Lawson benchmark.

“This is the first time we’ve exceeded Lawson’s criterion in the lab,” said nuclear physicist Annie Kretcher at the National Ignition Facility. new world.

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-powered lasers at it to create a bath of intense X-rays.

The intense environment created by the internally directed shock waves created a self-sustaining fusion reaction.

Under these conditions, the hydrogen atoms underwent fusion, releasing 1.3 megajoules of energy for one hundred trillionth of a second, which is equivalent to 10 quadrillion watts of energy.

Over the past year, researchers have tried to replicate the finding in Four similar experiencesbut only managed to produce half the energy yield produced in the record-breaking initial experiment.

Critcher explains that the ignition is very sensitive to small, barely perceptible changes, such as differences in the structure of each capsule and laser intensity.

“If you start from a microscopically worse starting point, that is reflected in a much larger difference in the final energy yield,” Says Plasma physicist Jeremy Chittenden at Imperial College London. The August 8 experience 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 in the face of small errors. Without this knowledge, the process cannot be scaled up to create fusion reactors that can power cities, which is the ultimate goal of this type of research.

“You don’t want to be in a situation where you have to get everything just right in order to ignite,” Chittenden says.

This article was published in physical review messages.