Enlarge image
The so-called target chamber in the National Ignition Facility: 192 lasers on tiny capsules with deuterium and tritium
Photo: Philip Saltonstall / Lawrence Livermore National Laboratory
Our sun is a gigantic power plant.
Under the pressure of gravity, it draws its energy at around 15 million degrees Celsius from the fusion of hydrogen to form helium.
The star does not shine indefinitely - according to forecasts, the fuel will be used up in a few billion years.
But the energy that our sun will produce by then is enormous.
If it were possible to imitate the stellar power plant on earth, this technology could generate almost emission-free electricity. Such a form of energy generation sounds tempting, especially in the fight against climate change. Researchers have been pursuing this goal in experimental fusion reactors for a long time. However, the progress made in such experiments has so far remained within a manageable range - especially in relation to the costs that such systems produce.
Researchers at the Lawrence Livermore National Laboratory near San Francisco have come closer than ever to the goal of igniting the fusion process. At the National Ignition Facility (NIF), the scientists concentrate primarily on setting the so-called inertial fusion in motion. The principle is used on a larger scale with the hydrogen bomb, but it could also release energy in a controlled manner. At the NIF, the researchers work with the world's most powerful laser, distributed over 192 beam lines that are aimed at a tiny capsule containing deuterium and tritium.
Both substances are isotopes of the element hydrogen.
The energy of the laser should create plasma and push the fusion process. At 100 million degrees Celsius, the hydrogen atoms fuse to form helium, which in turn should release the energy hoped for.
Once the process has started and the ignition threshold has been reached, the fusion reactions themselves should provide the heat for further fusions.
That is why the ignition is so important.
Ignition is achieved when the energy released during the fusion is greater than the 1.9 megajoules introduced by the laser.
In an experiment on August 8, the researchers now achieved a released energy of 1.35 megajoules.
This corresponds to around 70 percent of the laser energy that is fed into the fuel capsule.
So the researchers are still a long way from their goal, energetically it is still a loss-making business.
In spite of this, they speak in a message that they are now on the threshold of the ignition.
The results would correspond to a 25-fold increase in efficiency compared to the 2018 yield and an eight-fold increase in an experiment from this spring.
The NIF announced that it would publish the data in a scientific journal, where they can be subjected to an appropriate assessment by independent colleagues.
In addition, the researchers want to successfully repeat the experiment again in order to collect more data.
We will then work on a further improvement in the coming year.
But scientists are already saying positive things about the work at the NIF. The plasma physicist Stephen Bodner, who was actually considered a critic of the experiment, congratulated the researchers in an article in the New York Times and was surprised. The team has come close enough to its goal of ignition and breakeven to be called a success, they say. Siegfried Glenzer from Stanford University, who once carried out fusion experiments himself at the Livermore laboratory, also spoke of promising results in order to achieve an energy source on the planet that does not emit CO₂.
Construction of the NIF began in 1997 and was completed in 2009.
The size of the laser is roughly equivalent to three soccer fields.
The facility cost $ 3.5 billion.
The Iter fusion reactor in southern France, which will cost more than 20 billion euros and should go into service in 2025, will be even more expensive.
However, this is a different type of reactor than the one in the USA.
joe