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This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

Image source: 21:00 on April 12, EAST's official website, EAST (Advanced Experimental Superconducting Tokamak Experimental device), the world's first fully superconducting tokamak device, achieved stable plasma operation for 403 seconds in steady-state long-pulse high-constraint mode, setting a new world record for steady-state high-constraint mode operation of the tokamak device. The previous world record of 101 seconds was also set by EAST in 2017. EAST is a new generation of controllable nuclear fusion research device in China, independently developed by Hefei Institute of material Sciences, Chinese Academy of Sciences, and achieved the success of the first round of physical discharge experiments on September 28, 2006.

/ photos by Stuart Clark (Stuart Clark)

Editor | Zhao Jiaming

Maybe some friends will ask, what does this 403 seconds mean? This 403 seconds means that humans are one step closer to using controllable fusion to generate energy, and controllable fusion power generation may soon become a reality.

Why do we need nuclear fusion? To answer this question, we must first understand what nuclear fusion is. Nuclear fusion is the process in which two lighter atoms merge into one and release a large amount of energy at the same time. The sun and other stars emit light and heat through nuclear fusion. If we can "replicate" this process on Earth, it will produce a lot of energy. This is the first reason why we need nuclear fusion.

The sun is the closest natural nuclear fusion reactor to the earth. Inside the sun, it has a temperature of about 15 million ℃, which is unimaginable pressure and density. Under such conditions, the nuclear fusion reaction continues to occur. Climate change and energy security have also prompted people to change their minds and begin to accept nuclear fusion. For climate change, nuclear fusion can provide abundant clean energy. Compared with power generation modes such as thermal power generation, there are almost no greenhouse gas emissions. Nuclear fusion can also be used in conjunction with solar, wind and other renewable energy sources. As for energy security, with the rapid growth of global energy demand, once fossil energy is exhausted, we must rely on nuclear fusion energy.

In fact, it is not recent for us to use nuclear energy. Nuclear power plants operating around the world generate electricity through nuclear fission. However, compared with nuclear fusion, nuclear fission has safety problems, nuclear waste disposal problems, and the selection of nuclear materials. As a result, scientists have shifted their attention to nuclear fusion.

Why is it difficult to achieve controllable nuclear fusion? We now know that nuclear fusion occurs under the conditions of extreme high temperature, high pressure and high density as in the interior of the sun. However, man-made fusion reactors cannot replicate such pressure and density conditions. Inside the JET, for example, the density of the gas is about the same as that of the normal atmosphere outside the reactor. Then, in order to achieve nuclear fusion, the temperature in the reactor must exceed 100 million ℃. At this temperature, the gas will become a plasma. At this point, they can be constrained by a magnetic field.

Because any kind of material will melt when it comes into contact with a plasma with a temperature of more than 100 million ℃, the plasma can only be confined by a magnetic field. At the same time, the magnetic field can also accelerate the flow of plasma, creating conditions for nuclear fusion. It can be seen that the magnetic field is very important in nuclear fusion reactors. The new world record set by EAST is about the magnetic field constraining the plasma to operate stably. This is the key to using controllable nuclear fusion to generate energy.

A schematic diagram of a plasma confined by a magnetic field in a nuclear fusion reactor. (photo source: IAEA) in addition, there is a problem of "input-output ratio" incoordination in nuclear fusion power generation at this stage: although reactors can produce a lot of energy, they need more energy to meet their own operation. To solve this problem, the International Thermonuclear Fusion reactor (ITER) is being built in southern France and is expected to be put into operation in 2025. During the first 10 years of operation, scientists will gradually increase the operating power of the reactor and eventually allow it to operate at full capacity. Scientists estimate that the final output of ITER will be more than 10 times the energy needed to start fusion.

ITER's tokamak reactor is under construction in southern France. (photo Source: The ITER Organisation) in recent years, scientists and private enterprises have made some new attempts to achieve controlled nuclear fusion as soon as possible.

Like a snake, the MASCOT robotic arm winds its way into the tokamak and can perform maintenance and maintenance tasks. (photo Source: Jesse Wild Photography) in a tokamak, the stronger the magnetic field, the stronger the constraint on the plasma, so the reactor can be designed to be smaller. Tokamak Energy, in collaboration with several other laboratories, has developed a device called high-temperature superconducting magnets that produce powerful magnetic fields up to 1 million times the strength of the Earth's magnetic field. Through the magnet, Tokamak Energy uses a small reactor to raise the temperature of the plasma to about 100 million ℃.

There are several different ways to start a fusion reaction. In addition to accelerating the rotation of plasma in a tokamak, there is another method called inertial fusion-nuclear fuel droplets are squeezed so that the temperature and density increase, reaching the conditions of nuclear fusion. First Light Fusion, an American company, achieves squeezing by firing bullets from an ultra-high-speed gun and hitting a target containing nuclear fuel. After hitting the target, the bullet can cause the nuclear fuel to implode at a speed of 70 kilometers per second, triggering nuclear fusion and releasing energy.

Once the fusion reactor is put into operation, humans will not be able to enter the reactor. Because the deuterium-tritium nuclear fusion reaction will release a lot of neutrons and energy, resulting in strong short-term radiation, which is harmful to the human body. Therefore, robots are needed to do some work instead of human beings. To this end, scientists and engineers have developed robotic arms to replace human work. For example, the giant robotic arm MASCOT developed by RACE.

If the artificial intelligence technology is integrated into the robot, the robot will be more agile and automated. With more advanced artificial intelligence technology, the control system of the fusion reactor may be able to adjust at any time to the rapid changes in the state of the plasma, thus keeping the fusion reaction as efficient as possible.

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