A 2021 fusion energy breakthrough is being celebrated in three new studies, but controversy remains over replicating the findings.

On August 8, 2021, 192 laser beams pumped far more power than the entire U.S. electrical grid into a tiny gold capsule and ignited, for a split second, the same thermonuclear fire that powers the sun.

The experiment in fusion energy, conducted by the National Ignition Facility at Lawrence Livermore National Laboratory in California, is examined in detail in three new papers — one published in Physical Assessment Lettersand two papers published in Physical Assessment E — who claim the researchers have achieved “ignition,” a critical step showing that controlled nuclear fusion is feasible. But definitions of what “ignition” is vary, and how defined, the 2021 results are still very far from a practical fusion reactor, despite producing a very large amount of energy.

Nuclear fusion involves the fusion of two elements, usually isotopes of hydrogen, into the heavier element helium. This releases enormous amounts of energy, the process that powers stars like the sun.

A fusion power plant would produce abundant energy using only hydrogen from water as fuel and helium as waste, without the risk of meltdowns or radiation. This is in contrast to nuclear fission, the type of reaction in today’s nuclear power plants, where the nuclei of heavy elements such as uranium are split to produce energy.

While fusion reactions take place in the sun, and uncontrolled fusion takes place in thermonuclear weapon explosions, controlling a sustained fusion reaction to generate energy has eluded nuclear engineers for decades. Experiments of varied design have succeeded in producing fusion reactions for very short periods of time, but have never reached “ignition”, the point where the energy released in a fusion reaction exceeds the amount of energy required to start that reaction. awaken and maintain.

The National Ignition Facility team and authors of one of three new articles published in the journal Physical Assessment Letters, argue that “ignition is a state in which the fusion plasma can begin to ‘burn’ in the surrounding cold fuel, allowing for the possibility of high energy gain.” That is, fusion started in cold hydrogen fuel and the reaction expanded to generate much more energy than in previous experiments.

The August 8, 2021 experiment required 1.9 megajoules of energy in the form of ultraviolet lasers to initiate a fusion reaction in a small, frozen grain of hydrogen isotopes — an inertial confinement fusion reaction design — and 1.3 megajoules of energy was released, or about 70% of the energy put into the experiment. The output, in other words, was more than a quadrillion watts of power, even when released for only a tiny fraction of a second.

“The record recording was an important scientific advance in fusion research, showing that laboratory fusion ignition is possible at NIF,” Omar Hurricane, chief scientist for Lawrence Livermore National Laboratory’s inertial confinement fusion program, said in a statement. “Achieving the conditions necessary for ignition is a long-standing goal for all inertial confinement research and opens the door to a new experimental regime in which the self-heating of alpha particles outperforms all cooling mechanisms in the fusion plasma.”

Subsequent attempts to replicate the experiment have produced much less output energy, most in the 400 to 700 kilojoule range, leading some researchers to suggest that the National Ignition Facility’s experimental design is a technical dead end, according to news outlet coverage in the United States. journal Nature.

“I think they should call it a success and stop,” physicist and former US Naval Research Laboratory laser fusion researcher Stephen Bodner told me. Nature.

The National Ignition Facility cost $3.5 billion, more than $2 billion more than expected, and is behind schedule, with researchers initially having a 2012 deadline to prove ignition was possible using the design.

The new studies suggest that researchers are willing to continue exploring what the National Ignition Facility is capable of, especially since the facility’s researchers, unlike other fusion researchers, are not primarily focused on developing fusion power plants, but on better understanding of thermonuclear weapons.

“We operate in a regime that no researchers have had access to since the end of nuclear tests,” said Dr Hurricane. “It’s an incredible opportunity to expand our knowledge as we continue to make progress.”

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