We’ve Got Ignition: A Remarkable Breakthrough in Nuclear Fusion Represents a New Physical Milestone

For the first time, scientists have confirmed a major breakthrough in nuclear fusion involving the first instance of successful ignition, the point at which a nuclear fusion reaction becomes self-sustaining.

The performance, the results of which have been published in three peer-reviewed papers, took place at the National Ignition Facility at Lawrence Livermore National Laboratory (LLNL) on August 8, 2021.

Nuclear fusion involves a reaction in which two or more atomic nuclei with a low atomic number fuse, forming heavier atomic nuclei. During such a reaction, the differences between the masses of the reactants and the products result from the difference in energy that binds the atomic nuclei before and after the reaction. This difference will cause either the absorption or the release of energy.

Nuclear fusion is the same process seen in nature that powers stars like our Sun, as hydrogen atoms fuse under powerful conditions that fuse them into helium, producing vast amounts of energy in the process. Under such conditions, hydrogen plasmas are excited to the point of igniting, becoming capable of producing enough energy to become self-sufficient.

In the laboratory, ignition during a fusion reaction would allow a self-contained power source with a variety of applications, which includes a potential source for electrical power generation. Physicists have long believed that such a nuclear-generated source of electricity would be incredibly efficient and environmentally friendly. It would also rely on readily available resources, as it would only need hydrogen as a fuel source, and its only resulting by-product would be helium.

Now, after decades of research into how this process can be performed in the laboratory, LLNL’s National Ignition Facility (NIF) announced the peer-reviewed results of its findings last August, where an yield of more than 1 .3 megajoules (MJ) is said to have been achieved by the team of scientists in a groundbreaking physical achievement.

In the laboratories of the National Ignition Facility, the world’s largest laser is used to replicate the nuclear fusion that occurs naturally on our Sun by heating and compressing a capsule filled with hydrogen, which is used in a process known as of inertial confinement fusion to fuel nuclear fusion reactions.

Above: A cryogenic target used in the production of burning plasma conditions at Lawrence Livermore National Laboratory (Credit: James Wickboldt/LLNL).

“An inertial fusion implosion on the National Ignition Facility, performed on August 8, 2021 (N210808), recently produced more than one megajoule of fusion yield and met Lawson’s ignition criterion,” the authors wrote in the first of three recent articles.

According to the study, “These results are consistent with self-heating dominating other power balance terms,” indicating a burn rate that “increases by an order of magnitude after maximum compression, and the conditions of hot spot show clear evidence of burn propagation in the dense fuel surrounding the hot spot.

“These new dynamic and thermodynamic properties have never been observed in previous inertial fusion experiments,” the team says.

Alex Zylstra, LLNL physicist, lead author of the first paper published in physical examination E, said the research team first reached the fusion threshold where the burning plasma occurred, which enabled the team’s future success with what they call the record hit.

“Improvements in physical design and target quality all contributed to the success of the August shot,” Zylstra said in a statement, “which is discussed in the Physical examination E papers.”

Articles include over 1,000 authors in recognition of the decades-long work that led to this achievement.

Omar Hurricane, chief scientist of LLNL’s inertial confinement fusion program, said “the record was a major scientific breakthrough in fusion research, which establishes that laboratory fusion ignition is possible at NIF.” .

“Achieving the conditions necessary for ignition is a long-standing goal for all inertial confinement fusion research,” Hurricane said in a statement, “and opens up access to a new experimental regime where self- alpha particle heating exceeds all cooling mechanisms in the fusion plasma.

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Artist’s concept of the array of lasers used to facilitate plasma combustion (National Ignition Facility).

Achieving the ignition under laboratory conditions involved the use of an array of more than 190 lasers which, from one use to another, do not always behave in exactly the same way, which is only one of the many challenges the research team faced.

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“These experiments provided an opportunity to test and understand the variability inherent in this sensitive new experimental regimen,” said the lead designer and first author of the design. Physical examination E article Annie Kritcher, LLNL physicist.

Currently, the team’s attempts to reproduce the results of nuclear fusion ignition observed last August have been unsuccessful, although each of the capsules shown has a gain greater than unity with efficiencies on the order of 430 at 700 kJ, indicating yields well above 170 kJ, which had been the previous record set in February 2021.

Armed with this data, the research team believes they will be able to refine their experimental setup to allow ignition to be achieved reliably in the future. The adjustments the research team hopes to institute include improvements to the system that facilitates the delivery of energy to the central heat zone, or “hot spot”, as well as increasing the pressure there to optimize regulating the fuel used in the nuclear fusion process.

For Omar Hurricane, physicists finally getting proof that inflammation can occur in a laboratory environment is “extremely exciting”.

“We are operating in a regime that no researcher has had access to since nuclear testing ended,” Hurricane said recently.

The research (articles one and two) has been published in Physical examination letters and physical examination E, marking the first anniversary of this historic achievement.

“[I]It’s an incredible opportunity to expand our knowledge as we continue to progress,” says Hurricane.

Micah Hanks is editor and co-founder of The Debrief. Follow his work on micahhanks.com and on Twitter: @MicahHanks.

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