https://www.wsj.com/articles/how-fusion-works-and-why-its-a-breakthrough-national-ignition-facility-laser-beam-laboratory-science-nuclear-weapon-11671052081?mod=opinion_lead_pos6
The Energy Department has announced the first gain in energy from fusion in a laboratory—the first time fusion reactions produced more energy than it took to induce them. Last week 192 laser beams at the Lawrence Livermore Laboratory’s National Ignition Facility heated and compressed a capsule of hydrogen to previously unattainable temperatures and pressures, igniting fusion reactions that produced 50% more energy than the laser beams had delivered.
Nuclear reactions can release the energy that binds together protons and neutrons in an atom’s nucleus. Nuclear power plants use fission, not fusion. Fission releases energy when a large uranium nucleus splits into two radioactive fragments, which carry the energy as they fly apart.
Fusion, by contrast, relies on the universe’s smallest atom, hydrogen. Energy is released when two hydrogen nuclei combine to produce a helium nucleus and a neutron. Unlike fission, fusion produces no radioactive fragments. Fusion is much harder to induce than fission, since the hydrogen nuclei must be heated to nearly 100 million degrees Celsius to overcome the electrical repulsion that hinders their reaction. Stars run on fusion energy, but on Earth it has previously been released only in thermonuclear explosions. This stunning new result in laboratory fusion opens doors for unprecedented studies in basic and applied science.
The concept of laser fusion had been pursued without success since the 1960s and it became a central part of a 1990s program to ensure continued confidence in the nuclear-weapons stockpile without underground testing. Although scientists knew that high-powered laser beams could probe the properties of matter relevant to the early stages of detonating a nuclear weapon, the goal of laser fusion would allow for studies in the later stages. It would also challenge and demonstrate the ability to understand and predict the dynamics of hot, dense matter more generally.
Construction of the ignition facility at the Livermore lab began in 1997, and experiments attempting ignition began soon after construction was completed in 2009. The design and construction of the world’s most powerful laser was an engineering triumph, but three years of failed attempts to achieve fusion ignition brought the program close to cancellation in 2012. But the program continued with a more deliberate approach that included outside peer review.