The construction of the Compact Fusion Energy Experiment (BEST) project located in Hefei, Anhui Province, China, has recently achieved a key breakthrough and attracted widespread attention. The successful development and precise installation of the "Duwa base" marks a new stage in the construction of the main project, and also means that we are one step closer to the dream of "artificial sun". Fusion is the principle of nuclear reaction in which the sun emits light and generates heat, and the "artificial sun" is a fusion device that simulates this process. Scientists believe that fusion power generation is the ultimate energy pursued by humans due to its clean and infinite characteristics. Currently, multiple international research projects are tackling related technologies. So, what are the leading aspects of China's BEST project? What benefits does it have for achieving an 'artificial sun'? How will the development of fusion energy reshape the energy future of the Earth? The Duwa base structure mentioned in this news has a diameter of about 18 meters, a height of about 5 meters, and weighs more than 400 tons. It is the heaviest component in the main system of the compact fusion energy experimental device and the largest vacuum component in the domestic fusion field. The Duwa base is equivalent to the "foundation" of the device, and in the future, it will bear the weight and insulation function of more than 6000 tons of equipment for the entire host. After its installation is completed, the core components of the host will also be gradually installed on site. So, what exactly is fusion that scientists are concerned about? Unlike common chemical reactions, fusion is a nuclear level reaction where two lighter nuclei combine to form a heavier nucleus. Chemical reactions only involve the outer electrons of atoms and cannot touch the nucleus, while fusion reactions change the nucleus itself. Taking the sun as an example, its center is undergoing a reaction of hydrogen fusion into helium nuclei, with hydrogen gradually decreasing and helium continuously increasing. From a chemical perspective, this reaction equation is unbalanced. When it comes to nuclear reactions, people's first impression is often overwhelming energy. This energy comes from the binding energy of nucleons (including protons and neutrons) within the atomic nucleus, driven by the strong interaction among the four fundamental interactions (strong interaction, electromagnetic interaction, weak interaction, gravitational interaction), which is much stronger than the electromagnetic interaction involved in chemical reactions. How strong is this energy? At a distance of 1 flying meter (trillionth of a meter) at the atomic nucleus scale, the nuclear force that attracts two protons (the residual force of strong interaction outside the nucleus) is about 100 times stronger than the electromagnetic force that repels them. Therefore, if you want to break a helium nucleus into four nucleons, you need to apply tremendous energy far beyond chemical reactions to achieve it. Conversely, if four nucleons merge into a helium nucleus, they will release an equally enormous amount of energy. After converting this energy using Einstein's famous mass energy equation E=mc2 (energy=mass multiplied by the square of the speed of light), it is sufficient to detect mass loss. For example, if 1000 grams of hydrogen were completely fused, only about 993 grams of helium would be obtained, and the lost 7 grams would actually be released in the form of 630 trillion joules of energy. If this energy is used for the daily electricity consumption of urban and rural residents in the entire Beijing area, it can basically support two days. There is another type of nuclear reaction that is opposite in direction to fusion, which involves the splitting of a heavier nucleus into several lighter nuclei, physically known as fission. If two or more particles in the fission products can collide with other atomic nuclei, causing more new fission, the nuclear reaction will also increase exponentially, triggering a "chain reaction". Typical examples of fission are atomic bombs and nuclear power plants. Whether it's fusion or fission, examples can be found: in the universe, every star, including the sun, is a massive natural fusion reactor; On Earth, scientists have discovered a natural fission reactor in the Oklo uranium mine in Gabon, Africa, which naturally deposited 1.7 billion years ago and operated intermittently for hundreds of thousands of years with an average power of 100 kilowatts. What makes artificial fusion difficult? People's understanding of fusion began in 1920 with British scientist Arthur Stanley Eddington's conjecture about the principle of solar radiation and heat generation. At that time, the scientific community had not yet fully understood the structure of atomic nuclei, and had not even discovered neutrons. Compared to fusion, although scientists did not discover the phenomenon of fission until 1938, the application of fission has developed much faster. The reason behind this is that the difficulty of artificial fusion is too high. Where is the difficulty? The difficulty lies in the fact that all atomic nuclei carry positive charges. To merge two atomic nuclei together, one must overcome the electromagnetic repulsion between them. People may ask: Isn't it said earlier that the nuclear force of mutual attraction is much stronger than the electromagnetic force of mutual repulsion? Yes, but nuclear force has a fatal weakness, which is that it rapidly decays with increasing distance. At a distance of 1 flying meter, the nuclear force between protons is about 100 times stronger than the electromagnetic force, but at 1.7 flying meters, the electromagnetic force begins to dominate. That is to say, two atomic nuclei moving in opposite directions have already been pushed away by electromagnetic repulsion before they reach the "territory" of nuclear force. What should I do? On the one hand, we need to increase the temperature to make the atomic nuclei move faster. Only by running fast enough can they break through the barrier of electromagnetic repulsion, rush into the range of nuclear force, and merge with other atomic nuclei. For example, the fusion stage of a hydrogen bomb is initiated by the high temperature of tens of millions of degrees Celsius produced by detonating an atomic bomb; The core of the Sun has a temperature of 15 million degrees Celsius, barely capable of igniting very inefficient fusion reactions that can burn for billions of years. On the other hand, to choose atomic nuclei that are more prone to fusion, in jargon, is to look for nuclei with "larger reaction cross-sections" and lower temperature requirements. The currently known best raw materials are the two isotopes of hydrogen: deuterium and tritium (both have 1 proton, deuterium has 1 neutron, and tritium has 2 neutrons). The two can undergo massive fusion at temperatures ranging from 50 million to 200 million degrees Celsius, generating one helium nucleus, one neutron, and 17.6 megaelectronvolts of energy. When we raise the temperature to billions of degrees Celsius, not only will matter completely vaporize, but electrons and atomic nuclei will also "separate" and enter a plasma state. At this point, it is necessary to confine this plasma to a higher density, otherwise even if the temperature rises, fusion will not occur if the atomic nuclei cannot meet each other. At the same time, there must be sufficient energy confinement time, otherwise the heat dissipation will be too fast and fusion will still not occur or continue. In the field of fusion energy development, n (density), T (temperature), and τ (energy confinement time) are the three most critical parameters, and the product of the three determines whether the fusion reaction can sustain itself or, in other words, whether it can be "profitable" by allowing the energy output of the fusion reaction to exceed the energy input required to manufacture the fusion. When it comes to energy constraints, there are currently three known methods for constraining high-temperature plasmas: gravity constraints, inertia constraints, and magnetic constraints. The sun uses gravity confinement, its immense gravity tightly seals fusion fuel within its body, with a central density of over seven times that of gold. Inertial confinement is the use of multiple intense lasers to simultaneously irradiate a deuterium tritium mixture target, instantly generating high temperatures, while atoms cannot escape due to inertia and have to undergo fusion on site. Magnetic confinement utilizes the principle that charged particles will deflect when crossing a magnetic field (Lorentz force) to confine the plasma in a "cage" created by a strong magnetic field. Among these three methods, gravity constraint cannot be achieved on a small Earth, inertia constraint can only hit targets one by one, making it difficult to achieve continuous production. Currently, magnetic constraint has more development prospects. The magnetic confinement equipment mainly includes tokamak, star simulator, magnetic mirror, and confinement device, among which tokamak is the most mature. The compact fusion energy experimental device in China that has attracted attention this time is a tokamak. Why is the large-scale fully superconducting tokamak the preferred choice? TOKAMARK is regarded by scientists as one of the experimental devices for artificial sun, carrying the dream of human energy freedom. The world's first tokamak was born in the 1950s in the Soviet Union. So, "Tokamak" is actually a transliteration of the Russian abbreviation, which includes the four most crucial elements: toroidal, kamera, magnet, and kotushka. It can also be translated as "ring-shaped magnetic confinement fusion device" in Chinese. The function of tokamak can be understood from these four elements. Circles achieve the purpose of confinement by allowing finite matter to flow continuously in a limited space; Vacuum is used to provide an environment for plasma flow and fusion reactions, while avoiding direct contact of high-temperature substances with the chamber walls; Magnetism is a means of guiding plasma flow; A coil is a device that uses electric current to generate a magnetic field. Overall, the core goal of tokamak is to generate a magnetic field through electric current and confine a circle of flowing high-temperature plasma in the center of the annular vacuum chamber. The concrete understanding is that the core part of a tokamak is like a swimming circle lying flat on the ground, with high-temperature plasma flowing along the center of the cavity of the "swimming circle". In order to achieve stable constraints, the motion path of the plasma is not a monotonic circle, but rather a spiral wristband that twists while moving forward, constantly winding from the inner circle to the outer circle, and then back to the inner circle, forming a spiral twisted "magnetic surface". Creating such a magnetic field environment requires three sets of electromagnetic coils: one is several longitudinal field coils surrounding the cross-section of the "swimming ring", which generate a strong circumferential magnetic field along the cavity direction, which is the main magnetic field component that constrains high-temperature plasma; The second is the central spiral tube located in the center of the "swimming circle", which is used to induce and maintain plasma current; The third is the polar field coil enclosed outside the "swimming circle", used for plasma balance control. The tokamak compact fusion energy experimental device constructed in our country is extremely large, with the Dewar base alone weighing over 400 tons. The main reasons for making such a large device are as follows: firstly, the large equipment can establish stronger magnetic field constraints and allow for higher plasma currents to be accommodated, thereby increasing the probability of nuclear collisions and total power output in fusion reactions; Secondly, it can better suppress unstable disturbances and significantly extend the constraint time; Thirdly, it can reduce the surface area to volume ratio of high-temperature plasma, allowing energy to remain inside the plasma as much as possible and prolonging the energy confinement time; Fourthly, it is more conducive to integrating high-power peripheral systems and maintenance equipment, and also closer to practical fusion energy output, laying the foundation for future engineering. The role of the Dewar base installed this time in the entire compact fusion energy experimental device is to provide insulation function, isolating the high-temperature plasma and room temperature operating zone of billions of degrees Celsius from the superconducting coil operating in an environment of -269 ℃. The use of superconducting coils is because Tokamaks require the establishment of a strong magnetic field. The coils made of conventional conductors have resistance and generate intense heat when subjected to high currents, making them unable to operate continuously for a long time. The magnetic field strength they can generate is also quite limited, making it difficult to meet the confinement requirements of high-temperature plasmas. To avoid coil burnout, early Tokamaks only dared to run for a few seconds and required the use of pulsed current. Superconducting materials have zero resistance at extremely low temperatures and do not generate heat even when subjected to high currents of millions of amperes for a long time. They can also generate extremely strong magnetic fields, greatly improving their confinement performance. The HT-7 superconducting tokamak, which was used as a concept validation in China, set a record of 400 seconds in operation in 2008, and the subsequent "Eastern Super Ring" (EAST, where S is the abbreviation for "superconductivity") was even more successful