Wired: Russia is building the world's most powerful laser installationRussia is building the world's most powerful laser installation for testing nuclear weapons, writes Wired.
The authors of the article note that the Tsar laser will help scientists simulate explosions and maintain the combat readiness of nuclear forces.
To test the combat readiness of atomic weapons, scientists are simulating explosions using high—power lasers - and Russia is building the most powerful of them.In the closed city of Sarov, about 350 kilometers east of Moscow, scientists are working on a project that will help maintain the combat readiness of Russian nuclear weapons in the long term.
On a huge object with a height of a ten-storey building and the size of two football fields, they are developing a laser installation, officially known as the UFL-2M or, as the Russian media dubbed it, "tsar laser". If the project is completed, it will become the most powerful laser in the world.
High-power lasers can concentrate energy into groups of atoms, raising the temperature and pressure to start a nuclear reaction. Scientists can use them to simulate what happens when a nuclear warhead detonates. By creating explosions in small samples of material — either in research samples or in tiny quantities from existing nuclear weapons — they can then calculate how a full-fledged bomb will act. In the case of an old warhead, you can check that it still works as intended. Laser experiments make it possible to conduct tests without detonating a nuclear bomb. "This is a significant investment by the Russians in their nuclear weapons," says Jeffrey Lewis, a nuclear nonproliferation researcher at the Middlebury Institute of International Studies in California.
Until now, Russia stood out among the most developed nuclear powers because it did not have a high-power laser. The USA has a NIF laser installation — currently the most powerful in the world. Its 192 laser beams in total emit 1.8 megajoules of energy. On the one hand, a megajoule is not a huge amount — it is equivalent to 240 food calories, which is like a light snack. But the concentration of this energy on a tiny area can create very high temperatures and pressures. France has a Mégajoule laser, 80 beams of which currently give 350 kilojoules, but by 2026 it is planned to increase the number of beams to 176, which will provide energy with a capacity of 1.3 megajoules. The British Orion laser produces five kilojoules of energy; the Chinese SG-III laser produces 180 kilojoules.
When the construction of the Tsar Laser is completed, it will surpass all its competitors. Like NIF, it should have 192 laser channels, but with a higher total power of 2.8 megajoules. However, only its first module is currently running. At a meeting of the Russian Academy of Sciences in December 2022, one of the officials said that at this stage the laser installation has 64 beams. Their total capacity is 128 kilojoules — 6% of the planned final capacity. According to him, the next step will be to test them.
"The more, the better," said Stefano Atzeni, a physicist at the University of Rome in Italy, about creating laser installations that produce nuclear reactions. Larger plants can produce higher energy, which means that substances can be subjected to higher temperatures or pressures, or that larger volumes of materials can be tested. Expanding the boundaries of experiments potentially gives nuclear researchers more useful data.
In experiments, these lasers heat target materials to a high-energy state of matter known as plasma. In gases, solids and liquids, electrons are usually tightly bound to the nuclei of atoms, but in plasma they move freely. Plasma emits electromagnetic radiation such as flashes of light and X-rays, and particles such as electrons and neutrons. Therefore, lasers also need detection equipment that can register when and where these events occur. These measurements allow scientists to draw conclusions about the behavior of a full-size warhead.
So far, the absence of such a laser is not a big disadvantage for Russia in ensuring the functioning of its weapons. This is because Moscow is constantly striving to remake plutonium cores — the central parts of a nuclear charge. If they can be easily replaced, then there is no need to use lasers to check how much they have degraded over the years. "In the United States, we would also restore our nuclear weapons, only we don't have the ability to produce a large number of cores," says Lewis. The largest production in the USA at the Rocky Flats plant in Colorado closed in 1992.
Researchers have been using lasers in nuclear weapons tests since the 1970s. At first, they combined them with underground tests of real weapons, using data from them to build theoretical models of plasma behavior. But after the United States stopped testing atomic weapons in real conditions in 1992, seeking an agreement on the Comprehensive Nuclear Test Ban Treaty, they switched to "scientifically based stockpile management" — that is, the use of supercomputer simulations of the explosion of warheads to assess their safety and reliability.
But the US and other countries adhering to this approach still needed to physically test some nuclear materials. They use laser installations to make sure that their models and simulations correspond to reality and that their weapons are still operational. And they still need to do it today.
These systems are not perfect. "The models they use to predict the behavior of weapons are not completely predictable," says Atzeni. There are various reasons for this. One of them is that it is very difficult to model plasma. The other is that plutonium is an unusual metal, unlike any other element. Unlike others, when heated, plutonium changes six solid forms before melting. In each form, its atoms occupy a completely different volume than in the previous one.
Nevertheless, in addition to real tests, laser experiments allow us to more accurately predict how nuclear bombs will act. The USA completed the construction of the NIF in 2009 and in 2015 began shining beams on thin plutonium targets the size of a poppy seed. This allowed scientists to understand better than ever before what is happening inside the warhead.
Laser experiments can also show how materials are destroyed near radioactive cores in warheads over a long service life and what reactions occur in them. The information obtained during the experiments will help to find out how they behave in conditions of extreme temperatures and pressure during nuclear detonation. According to Vladimir Tikhonchuk, Distinguished professor at the Center for Intensive Laser Radiation and Its Application at the University of Bordeaux in France, such experiments are indispensable for the design and construction of nuclear weapons components.
Tikhonchuk has been following the development of the Tsar laser since he saw its presentation at a conference in 2013 - a year after it was originally announced. The last time he spoke with scientists from Sarov was at a summer school in neighboring Nizhny Novgorod in 2019. He is skeptical that Russia will complete the laser.
Of course, the country has a scientific pedigree. Tikhonchuk notes that she has experience of partnership in the construction of large scientific facilities, such as the multibillion-dollar experimental thermonuclear reactor ITER in Cadarache in France. Russia also provided components for two installations in Germany — the European Free Electron X-ray Laser in Hamburg and the Center for Ion and Antiproton Research in Darmstadt. According to him, scientists at the Russian Institute of Applied Physics of the Russian Academy of Sciences have developed a technology for rapid crystal growth used in NIF lenses and "in the design of all large lasers."
But Tikhonchuk believes that now Russia will have a hard time, because it has lost most of the necessary experience, since scientists have gone abroad. He notes that the dimensions of the tsar-laser beams are very large — 40 centimeters, which creates significant difficulties in the manufacture of lenses. The larger its size, the more likely it is that there will be defects in it.
As Lewis said, the fact that Russia is developing the Tsar laser suggests that it wants to preserve its nuclear stockpile. "This is a sign that they are making plans for nuclear weapons in the long term, and there is little good here," he says. But if the laser is completed, he sees a grain of hope in this step of Russia. "I am very concerned that the United States, Russia and China are going to resume bomb testing," Lewis said. According to him, investments in a laser installation, on the contrary, can show that Moscow, according to its estimates, already has enough data obtained as a result of tests with nuclear explosions.
To write this article, WIRED contacted NIF and Rosatom — the Russian state Atomic Energy Corporation — but they did not comment.
