POWER PLANT DESIGN | LASER FUSION
Looking at pulsed laser nuclear fusion
As a realistic alternative to magnetic bottle designs, commercial laser-based fusion is closer to reality than ever before using high-powered pulsed laser technology
Todd Ditmire
Co-Founder and CTO of Focused Energy
FOR MORE THAN HALF A century, scientists have been trying to recreate controlled solar energy on Earth. Theoretically, understanding fusion has long since ceased to pose any difficulties. However, the extreme conditions under which natural nuclear fusion takes place have so far prevented its practical application. At about 15 million degrees Celsius, thermal energy causes hydrogen atoms to collide so strongly that they fuse. It is possible to break through the electrical repulsion of two positively charged hydrogen nuclei using a technically controllable process but only at a very high temperature. At this temperature the matter enters the fourth state – plasma.
Magnet versus laser Different methods can be considered for creating appropriate fusion conditions in pressure and temperature. For many years, strong magnetic fields have been explored to hold plasma, but now, pulsed laser light is considered a promising ignition mechanism. It’s based on experimentally measured, scientifically confirmed conditions. In addition, research successes in recent years have
brought ground-breaking progress to the development of strong magnets and high-power lasers. In this environment, a veritable ecosystem of companies from
adjacent technology fields is currently emerging. These companies are collaborating with various materials, research companies, and diode manufacturers to advance their roadmap for commercially viable fusion. It is perhaps possible to see the first fully operational demonstration plant by the 2030s.
Two-phase laser fusion Deuterium and tritium serve as fuel for hydrogen fusion. In a typical laser-driven fusion experiment, the two isotopes are housed in a pellet or target about 2mm in diameter with a special coating. Then, in a specially constructed fusion chamber, laser light pulses strike the pellet and abruptly heat its shell. The shell vaporises explosively and causes a recoil that extremely accelerates the hydrogen isotopes in the pellet, compressing and heating the fuel. In this heated and compressed fusion fuel, the isotopes collide and fuse, releasing so-called inertial fusion energy (IFE). How can electricity be generated from this process? Every
fusion reaction leaves behind not only a helium nucleus, but also a free neutron that crashes against the reactor wall at high speed. There, the braking energy generates heat, which can be converted directly into electricity.
Above: A petawatt laser is used to ignite the fusion reaction in this experimental set up Photo credit: Focused Energy 32 | November 2022 |
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