Researchers in the US have overcome a key barrier to making nuclear fusion reactors a reality. In results published in Nature, scientists have shown that they can now produce more energy than the fuel put into an experiment. The use of fusion as a source of energy remains a long way off, but the latest development is an important step toward that goal.
Nuclear fusion is the process that powers the Sun and billions of other stars in the universe. If mastered, it could provide an unlimited source of clean energy because the raw materials are plentiful and the operation produces no carbon emissions.
During the fusion process, smaller atoms fuse into larger ones releasing huge amounts of energy. To achieve this on Earth, scientists have to create conditions similar to those at the center of the Sun. This involves creating very high pressures and temperatures.
There are two ways to achieve this: one uses lasers and is called inertial confinement fusion (ICF), another deploys magnets and is called magnetic confinement fusion (MCF). Omar Hurricane and colleagues at the Lawrence Livermore National Laboratory opted for ICF, with the help of 192 high-energy lasers at the National Ignition Facility in the US, which was designed specifically to boost fusion research.
A typical fusion reaction at the facility takes weeks of preparation. But the fusion reaction is completed in an instant (150 picoseconds, to be precise, which is less than a billionth of a second). In that moment, at the core of the reaction, the pressure is 150 billion times atmospheric pressure. The density and temperature of the plasma created is nearly three times that at the center of the Sun.
The most critical part of the reaction, and one that had been a real concern for Hurricane 19s team, is the shape of the fuel capsule. The capsule is made from a polymer and is about 2mm in diameter (about the size of a pinhead). On the inside it is coated with deuterium and tritium 14isotopes of hydrogen 14that are frozen to be in a solid state.
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