Three new studies celebrate a 2021 breakthrough in fusion power generation, but controversy remains around replicating the findings.

On August 8, 2021, 192 laser beams injected far more energy than the entire U.S. electrical grid into a small gold capsule, igniting the same thermonuclear flames that power the sun in a flash.

Fusion energy experiments conducted at the National Ignition Facility at Lawrence Livermore National Laboratory in California are explored in detail in three new papers – one of which is published in Physical Review Lettersand two papers published in Physical Review E – Think the researchers achieved “fire-off,” a key step in proving that controlled nuclear fusion is achievable. But definitions of what constitutes an “ignition” vary, and whatever the definition, the 2021 results are still far from an actual fusion reactor, despite the enormous amount of energy it produces.

Nuclear fusion involves fusing two elements (usually isotopes of hydrogen) into the heavier element helium. It releases enormous amounts of energy in the process, which powers stars like the sun.

The fusion power plant will generate abundant energy using only hydrogen from water as fuel and produce helium as waste, with no risk of melting or radiation. This is in contrast to nuclear fission, the type of reaction in contemporary nuclear power plants that splits the nuclei of heavy elements such as uranium to produce energy.

While fusion reactions occur in the sun, and uncontrolled fusion occurs in thermonuclear explosions, nuclear engineers have been unable to control ongoing fusion reactions to generate electricity for decades. Experiments of various designs have managed to generate fusion reactions in very short periods of time, but have never achieved “fire-off”, that is, the energy released by the fusion reaction is greater than the energy required to generate and sustain the reaction.

Team at the National Ignition Facility and author of one of three new papers, one of which is published in the journal Physical Review Lettersarguing that “ignition is a state in which fusion plasma can begin to ‘burn and propagate’ into the surrounding cold fuel, enabling the possibility of high energy gain.” That is, fusion begins in cold hydrogen fuel and the reaction expands to produce More energy than previous experiments.

The Aug. 8, 2021 experiment required 1.9 megajoules of energy in the form of an ultraviolet laser to initiate a fusion reaction in a small particle of frozen hydrogen isotope — inertial confinement fusion reactions designed — and release 1.3 megajoules of energy, Or about 70% of the energy put into the experiment. In other words, even if only a fraction of a second is released, the output exceeds a petawatt of power.

“The record-breaking footage is a major scientific advance in fusion research that identifies fusion ignition in the laboratory,” Hurricane Omar, chief scientist of the Inertial Confinement Fusion Program at Lawrence Livermore National Laboratory, said in a statement. It is possible at NIF.” “Achieving the conditions required for ignition has been a long-standing goal of all inertial confinement fusion research, and opens up a new experimental mechanism in which alpha particle self-heating exceeds all cooling mechanisms in fusion plasmas. “

Subsequent attempts to replicate the experiment produced much less output energy, mostly in the 400 to 700 kilojoule range, leading some researchers to believe that the experimental design of the National Ignition Facility was a technical dead end, according to the news service. magazine nature.

“I think they should call it success and stop,” physicist and former U.S. Naval Research Laboratory laser fusion researcher Stephen Bodner told nature.

The National Ignition Facility cost $3.5 billion, $2 billion more than expected, and is behind schedule, with the researchers initially targeting 2012 as the deadline to prove that the design could fire.

The new study shows that researchers are willing to continue to explore the capabilities of the National Ignition Facility, especially because, unlike other fusion researchers, the researchers at this facility are not primarily focused on developing fusion power plants, but rather on better understanding thermonuclear weapons.

“We are operating in a system that no researcher has been in since the end of the nuclear test,” said Dr. Hurricane. “This is a great opportunity to expand our knowledge as we continue to make progress.”

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