The Lawrence Livermore National Laboratory has successfully conducted a record-breaking nuclear fusion experiment, achieving unprecedented energy output through hydrogen plasma within its fuel chamber.
Last year, scientists at the Lawrence Livermore National Laboratory in Northern California announced a record release of 1.3 megajoules of energy in 0.0000000001 seconds at the National Ignition Facility (NIF). In two newly published studies in the journals Nature Physics and Nature, the NIF research team reported that they achieved this milestone thanks to the precise design of a tiny chamber and fuel chamber at the center of the world’s most powerful laser system, where the fusion reaction takes place.
The nuclear fusion reaction at NIF occurs at the center of the world’s most powerful laser system, consuming about 400 megajoules of energy per ignition. (Photo: Damien Jemison)
Although the fuel chamber is only about one millimeter wide and the fusion reaction lasts for just a moment, the system’s output is equivalent to 10% of the total energy from sunlight reaching Earth. This significant energy release occurs because the reaction heats the remaining fuel into plasma at a temperature high enough to facilitate further fusion reactions, according to Annie Kritcher, a physicist at the Lawrence Livermore National Laboratory (LLNL). Kritcher is the lead author of a study published on January 26 in Nature Physics describing how NIF was optimized to create hot plasma. He is also a co-author of another study published in Nature on the same day, detailing the first experiments with hot plasma at NIF conducted in 2020 and early 2021.
Nuclear fusion is the process that powers stars like the Sun. This reaction differs from the fission process commonly used in power plants on Earth, which generates energy by splitting heavy atomic nuclei such as plutonium into smaller nuclei. Fusion reactions release enormous energy when atomic nuclei combine to form larger nuclei. The simplest fusion reaction uses hydrogen fuel. Researchers hope that in the future, fusion could develop into a relatively “clean” energy source by utilizing the abundant hydrogen found in Earth’s oceans.
Due to the immense gravitational forces in very large stars, fusion reactions occur at extremely high pressures. However, such pressures cannot be achieved on Earth. Instead, fusion must occur at extremely high temperatures. Researchers have experimented with various methods to sustain fusion reactions at high temperatures, with NIF focusing on an approach known as “inertial confinement.” This method generates high temperatures by firing 192 powerful lasers at a hydrogen pellet at the center. These lasers consume a massive amount of energy and can only be fired once a day.
The inertial confinement method requires extensive development before it can become a viable energy source, as it needs to vaporize several fuel pellets per second to produce enough energy for electricity generation. However, NIF has recently demonstrated success by achieving ultra-high energy output in a short time. An experiment last August generated energy from a fuel pellet nearly equal to the energy consumed. Researchers are hopeful that future experiments will yield even greater results.
The two new studies describe plasma-burning experiments conducted over several months, resulting in the production of 10 million trillion watts of electricity. Previous experiments generated 170 kilojoules of energy from a hydrogen pellet weighing just 200 micrograms. The research team reached this milestone through careful shaping of the fuel chamber (a spherical polycarbonate diamond shell surrounding the fuel pellet) and the containment vessel (a small cylindrical structure made of depleted uranium coated in gold, known as a hohlraum).
The new design allows NIF’s lasers to heat the fuel pellet more efficiently within the hohlraum. As a result, hydrogen fuses at such high temperatures that other parts of the pellet…
