Scientists achieve self-sustaining nuclear fusion… But now they can’t do it again: ScienceAlert

Scientists achieve self-sustaining nuclear fusion... But now they can't do it again: ScienceAlert
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Last year, scientists confirmed that they had achieved a self-sustaining (instead of extinguishing) fusion reaction in the lab for the first time, bringing us closer to replicating the chemical reaction that powers the Sun.

However, they are not quite sure how to recreate the experiment.

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

This is a process that occurs frequently in nature, but is very difficult to replicate in the laboratory because a high-energy environment is required for the reaction to proceed.

Sun you create energy using nuclear fusion – hitting hydrogen atoms together to create helium.

Supernovae – exploding suns – also use nuclear fusion due to space fireworks displays. The strength of these reactions is what creates heavier molecules like iron.

In artificial conditions on Earth, heat and energy tend to escape through cooling mechanisms such as X-rays and thermal conduction.

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

Once ignition is achieved, the fusion reaction starts itself.

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

The ignition of nuclear reactions usually occurs in extremely dense 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 now confirmed A landmark experiment on August 8, 2021 actually led to the first successful ignition of a nuclear fusion reaction.

In the final analysis, the 2021 experiment was evaluated according to nine different versions of the Lawson criterion.

“This is the first time we’ve passed the Lawson criterion in the lab,” said Annie Kritcher, 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-coated depleted uranium chamber and fired 192 high-energy lasers at it to create a bath of intense X-rays.

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

Under these conditions, the hydrogen atoms combined released 1.3 megajoules of energy per 100 trillionth of a second, which is equivalent to 10 quadrillion watts of power.

Over the past year, researchers have tried to replicate the result four similar experimentshowever, it was only able to produce half the energy yield produced in the record-breaking original experiment.

Kritcher explains that ignition is very sensitive to subtle changes in the structure of each capsule and differences in the intensity of the lasers.

“If you start from a microscopically worse starting point, this is reflected in a larger difference in final energy yield” he says Jeremy Chittenden, a plasma physicist at Imperial College London. “The August 8 experience was the best case scenario.”

The team now wants to determine exactly what is required to achieve ignition and make the experiment more robust to small errors. Without this knowledge, it is impossible to scale up the process to create fusion reactors that can power cities, which is the main goal of this kind of research.

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

This article has been published Physical review letters.

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