Researchers in California confirmed a breakthrough in nuclear fusion, where they recorded the first case of ignition on August 8, 2021, which has now been published.
On August 8, 2021, 192 laser beams pumped far more energy than the entire US electrical grid into a tiny golden 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 explored in detail in three new papers, one published in Physical Review Letters and two papers published in Physical Review E, which argue that the researchers achieved “ignition,” a crucial step showing that controlled nuclear fusion is feasible. But definitions of what constitutes “ignition” vary, and regardless of how it is defined, the 2021 results are still a long way from a reactor. practical fusion, despite producing a large amount of energy.
Nuclear fusion involves the fusion of two elements, typically isotopes of hydrogen, into helium, a heavier element. It releases huge amounts of energy in the process, which is the process that powers stars like the Sun.
Nuclear fusion reactions are also self-sustaining, as once the atoms collide and achieve ‘ignition’, they produce enough energy to keep the temperature high without external input. At its core, the Sun fuses 620 million metric tons of hydrogen and produces 616 million metric tons of helium every second.
The team at the National Ignition Facility and the authors of one of the three new papers, the one published in the journal Physical Review Letters, argue that “ignition is a state in which the fusion plasma can begin to ‘burn propagation ‘ into the surrounding cold fuel, allowing for the possibility of high energy gain.” That is, fusion began 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 instigate a fusion reaction in a small frozen pellet of hydrogen isotopes, an inertial confinement fusion reaction design, and released 1, 3 megajoules of energy, or about 70%. of the energy put into the experiment. The output, in other words, was more than a quadrillion watts of power, even if released for just a tiny fraction of a second.
“The record firing was a major scientific breakthrough in fusion research, establishing that laboratory ignition of fusion is possible at the NIF,” Omar Hurricane, chief scientist for the inertial confinement fusion program, said in a statement. of the Lawrence Livermore National Laboratory. “Achieving the conditions necessary for ignition has been a long-standing goal for all inertial confinement fusion research and opens access to a new experimental regime in which alpha particle self-heating outperforms all cooling mechanisms in the fusion plasma.
In experiments conducted to achieve this ignition result, researchers heat and compress a central “hot spot” of deuterium-tritium fuel (hydrogen atoms with one and two neutrons, respectively) using a surrounding dense piston also made of deuterium-tritium. tritium, creating a super hot, super pressurized Hydrogen Plasma.
“Ignition occurs when heating from the absorption of α particles [two protons and two tightly bound neutrons] created in the fusion process overcomes the loss mechanisms in the system for a period of time,” the authors said in a paper that publishes the results in the journal Physical Review E.
The new studies suggest that researchers are keen to continue exploring what the National Ignition Facility is capable of, especially since, unlike other fusion researchers, researchers at the facility are not primarily focused on developing fusion power plants. , but to better understand thermonuclear weapons.
“It is extremely exciting to have a ‘proof of existence’ ignition in the lab,” Hurricane said in a statement. “We’re operating in a regime that no researcher has accessed since the end of nuclear testing, and it’s an incredible opportunity to expand our knowledge as we continue to make progress.”
How Nuclear Fusion Reactors Work
Nuclear fusion is a general term that covers any reaction in which the nuclei of two different atoms literally fuse together. It’s that easy. That’s the opposite of nuclear fission, where one nucleus splits into two. Nuclear fusion generally takes place on lighter elements that have lower atomic numbers (the number of protons in the nucleus), while nuclear fission takes place on heavier elements with much higher atomic numbers.
In both fission and fusion, it is important to choose the right elements. In fusion, that’s because elements of a certain atomic size can still fuse together, but they won’t produce the abundant energy we associate with the promises of the nuclear fusion industry.
In fact, most fusion projects focus on the absolute lightest elements: hydrogen and helium. ITER, the huge proof-of-concept nuclear fusion reactor to be built over the next ten years in the south of France, uses the hydrogen isotopes deuterium and tritium. The names mean exactly what you may be thinking: deuterium has an atomic mass of two, while tritium is three.
That’s where TAE Technologies comes in. Its fusion reactor uses a different fuel mix, and the reactor itself has a totally different form factor than tokamaks or stellarators. (A tokamak uses a current to control solar-heated plasma in a reactor, while a stellarator does not.) The TAE machine is a completely non-radioactive linear reactor because it uses hydrogen and boron: two naturally abundant elements that react to produce only helium. ITER, by comparison, will produce helium and also free neutrons that will literally radiate out into surrounding materials. Because of this, the TAE approach is known as aneutronic fusion.
TAE uses “a proprietary combination of plasma physics and accelerator physics in a linear fashion,” CEO Binderbauer tells Popular Mechanics by email. And the footprint size is dramatically different. “Our current fifth-generation device, Norman, is 24 meters long with a vacuum vessel that is about 4 meters long and less than 2 meters in diameter. Our next machine, Copernicus, will be about 50 percent larger than Norman and take up 2 acres of space. In contrast, the ITER site measures over 100 acres with ITER’s tokamak vacuum vessel nearly 20 meters in diameter and 11.5 meters tall.”
Naturally, there is a catch. “One of the biggest challenges with hydrogen-boron is the temperature required for fusion to occur, which is on the order of a billion degrees [Celsius],” says Binderbauer. (ITER requires “only” a temperature of 150 million degrees Celsius, by comparison.) “However, CERN’s Large Hadron Collider has reached more than five trillion degrees [Celsius] for non-fusion applications, so these conditions are within reach.” For context, the hottest part of the sun is its core, which can reach 15 million degrees Celsius, according to NASA.
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