![]() But getting to the burning-plasma point has been a slow process, full of technical hurdles and setbacks. Researchers demonstrated the feasibility of starting fusion this way back in the 1970s. ![]() In the NIF method, the laser beams do not directly spark detonation but instead strike the hohlraum’s inner surface, unleashing a furious bath of capsule-compressing x-rays within the tiny chamber. The laser energy heats and vaporizes the capsule’s outer layer, blowing it away and creating a recoil that compresses and heats the fuel in the center. The NIF team used 192 high-power lasers, all focused into a chamber called a hohlraum that is about the size and shape of a pencil’s eraser and contains the fuel capsule of deuterium and tritium. “Fusion energy schemes based on inertial confinement involve repeating the pulsed process over and over again, much like the pistons in an internal combustion engine, firing several times per second to give nearly continuous power,” says Omar Hurricane of LLNL, chief scientist for the NIF’s Inertial Confinement Fusion program, who was a team leader for the latest experiments.Īlthough inertial-confinement fusion does not have to solve the problem of maintaining a hot, wobbly plasma inside a tokamak, it does require tremendous inputs of energy to trigger the fusion process. That creates a very brief outburst of energy-a tiny thermonuclear explosion-before the burning fuel expands and dissipates its heat. Inertial fusion does not try to trap the plasma but instead relies on inertia alone to hold it together for a brief instant after fusion is triggered by an ultrafast compression of the fuel. for which a global collaboration is building a massive experimental reactor in France that is slated to achieve sustained fusion no earlier than 2035. This is the method of choice for many fusion projects, including the International Thermonuclear Experimental Reactor (ITER). One approach is to confine it with magnetic fields into a doughnut shape inside a chamber called a tokamak. Handling such a seething plasma is, to put it mildly, immensely challenging. And in contrast to fission, fusion does not involve a chain reaction, which makes it inherently safer: any changes to the working conditions of a fusion reactor will cause it to automatically shut down in an instant.įission’s advantage is that it typically occurs in reactors at temperatures of a little more than 1,000 kelvins, whereas deuterium-tritium (D-T) fusion starts at temperatures of around 100 million kelvins-hotter than the heart of the sun. Unlike nuclear fission-the process used in all nuclear power plants today-fusion does not use or generate large quantities of long-lived radioactive materials. The energy this releases can be harnessed for electricity generation-for example, by using the heat to drive conventional power turbines. The usual fuel for producing controlled fusion in reactors consists of a mix of the heavy hydrogen isotopes deuterium and tritium, which may unite to make helium. Nuclear fusion, the process that fuels stars and that is triggered explosively in hydrogen bombs, requires extreme heat and pressure to give atoms enough energy to overcome the electrostatic repulsion between their positively charged nuclei so that they can fuse and release energy. “This is an incredible achievement, which is a culmination of a decade of careful, incremental research,” she says. “They show that the pursuit of an inertial fusion reactor is a realistic possibility for the future and not built upon difficult and insurmountable physics.” Plasma physicist Kate Lancaster of the University of York in England, who was also not involved in the research, agrees. “The NIF results are a really big deal,” says fusion physicist Peter Norreys of the University of Oxford, who was not part of the studies. “The data clearly show that they have reached that condition,” says fusion physicist George Tynan of the University of California, San Diego, who was not involved in the work. The researchers’ findings appear in Nature, with companion papers published in Nature Physics and on the preprint repository. An important milestone toward that goal has now been passed: a fusion reaction that derives most of its heat from its nuclear reactions themselves rather than the energy pumped into the fuel from outside.Ī team at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in California has reported this so-called burning plasma condition using an approach called inertial-confinement fusion, where the ferociously high temperatures and pressures needed to initiate fusion in a fuel of hydrogen isotopes are produced by intense pulses of laser light. But it has remained frustratingly elusive as a practical technology for decades. Nuclear fusion could potentially provide abundant, safe energy without the significant production of greenhouse gas emissions or nuclear waste.
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