Dec 19, 2023 07:00:00

Lawrence Livermore National Laboratory, which successfully ``ignited'' a laser fusion experiment, achieved 4 out of 6 ignitions.

One year ago, on December 5, 2022, Lawrence Livermore National Laboratory in the United States

succeeded in ``nuclear fusion ignition'' in a laser fusion experiment that produced an output that exceeded the amount of energy input. Subsequent trials have shown that this did not happen by chance, with four successful ignitions out of six attempts so far.

US nuclear-fusion lab enters new era: achieving 'ignition' over and over
https://www.nature.com/articles/d41586-023-04045-8

'Nuclear fusion' is expected to be the energy of the future because it can safely obtain higher output than 'nuclear fission,' which has the possibility of runaway, but it requires a huge amount of energy to cause the essential reaction, and it has been used for a long time. Since the output energy was lower than the input energy, it was thought that it was far from practical use.

However, on December 5, 2022, success in

``fusion ignition'' was confirmed in an ``inertial confinement laser fusion'' experiment conducted by Lawrence Livermore National Laboratory.

The Department of Energy officially announces that a nuclear fusion experiment has achieved an output that exceeds the energy input and confirmed ``ignition'' - GIGAZINE

The National Ignition Facility (NIF) in the United States, which conducted the experiment, is an experimental facility that has been in operation since 2009. Frozen pellets of deuterium and tritium are suspended in a diamond capsule inside a gold cylinder, and when 192 lasers are directed at them, an implosion occurs, releasing helium and a large amount of energy. The mechanism is that it is generated.

When the first 'fusion ignition' was successful, an output of approximately 3.15 MJ was obtained, which was a 54% increase compared to the 2.05 MJ (megajoule) laser irradiation.

NIF continued testing after that. In June and September 2023, slightly more energy was generated than the input energy, but ignition could not be confirmed, but on July 30, 2023, irradiation was 3.88MJ, an 88% increase compared to the irradiation of 2.05MJ. occurs and ignition is confirmed. Furthermore, ignition was confirmed twice in October 2023.

Although these results have raised expectations for the realization of nuclear fusion power generation, Nature points out that the practical application of energy obtained from fusion reactions is still a long way off.

First of all, NIF's laser system is very inefficient, with more than 99% of the energy invested in a single ignition attempt being lost before reaching the target. For this reason, developing more efficient laser systems is one of the goals of the Department of Energy's new inertial fusion energy research program.

In the sixth experiment, which was already conducted on October 30, 2023, the amount of energy irradiated by the laser has increased by 7%. In this experiment, 3.4MJ was obtained with 2.2MJ laser irradiation. In theory, even greater yields are expected.

Annie Critcher, NIF's lead designer, said the team is focusing on changes to the laser pulse that could produce more symmetrical implosion, with a target of 4 in 2024. It seems that several experiments are planned.