What is a Tokamak?
Tokamak is a ring container that uses magnetic constraints to achieve controlled nuclear fusion. Its name Tokamak comes from toroids, vacuum chambers, magnets, and coils. It was originally invented in the 1950s by Azimovici and others at the Kurchatov Institute in Moscow, Soviet Union. Tokamak's center is a ring-shaped vacuum chamber with coils wrapped around it. When energized, a large spiral magnetic field is generated inside the tokamak, and the plasma in it is heated to a high temperature to achieve the purpose of nuclear fusion.
- Chinese name
- Tokamak
- Foreign name
- Tokamak
- Technology category
- Controllable nuclear fusion device
- Constraint type
- Magnetic constraint
- Similar technology products
- Stellar
- Competitive technology
- Inertial confinement controlled nuclear fusion
- Tokamak is a ring container that uses magnetic constraints to achieve controlled nuclear fusion. Its name Tokamak comes from toroids, vacuum chambers, magnets, and coils. It was originally invented in the 1950s by Azimovici and others at the Kurchatov Institute in Moscow, Soviet Union. Tokamak's center is a ring-shaped vacuum chamber with coils wrapped around it. When energized, a large spiral magnetic field is generated inside the tokamak, which heats the plasma to a very high temperature to achieve the purpose of nuclear fusion.
Main components and subsystems of the Tokamak plant
- Tokamak is a ring-shaped device. By constraining the drive of electromagnetic waves, it creates a deuterium and tritium fusion environment and ultra-high temperature, and realizes human's control of fusion reaction. Its name Tokamak comes from toroidal, vacuum chamber (kamera), magnet (magnet), and coil (kotushka). It was originally invented in the 1950s by Azimovici and others at the Kurchatov Institute in Moscow, Soviet Union.
- Controlled thermonuclear fusion has been achieved on conventional tokamaks. However, conventional tokamak devices are bulky, low in efficiency, and difficult to break through. At the end of the last century, scientists applied emerging superconducting technology to the tokamak device, which greatly improved basic theoretical research and system operating parameters. Scientists estimate that a demonstration fusion reactor with controlled thermonuclear fusion will be realized by 2025, and a commercial fusion reactor will be completed by 2040. Prior to the completion of the commercial reactor, Chinese scientists also designed the superconducting tokamak device as a neutron source for environmental protection, scientific research and other approaches. This idea has been highly evaluated by domestic and foreign experts.
- Including magnets (ring field magnets and polar field magnets), vacuum chambers and their extraction systems, power supply systems, control systems (device control and plasma control), heating and current drive systems (neutral beam and microwave), air jets And projectile injection systems, deflectors and apertures, diagnostic and data acquisition and processing systems, cladding systems, radon systems, radiation protection systems, remote operation and maintenance systems, and other components (subsystems). Although the strong magnetic field can improve the restraint performance, due to the limitation of engineering technology and materials, the toroidal magnetic field is generally 2 ~ 8T; in order to obtain stable nuclear fusion energy output, the tokamak fusion reactor will eventually use superconducting magnets (stable state operation requirements ). To this end, Dewar, cold screen and low temperature refrigeration systems should be added. In order to heat the plasma to the required temperature, the total heating power of the large-scale equipment is tens of megawatts, and the heating power of the International Thermonuclear Experimental Reactor equipment is 73 ~ 130MW.
Introduction to Tokamak Fusion
- Nuclear fusion, also known as nuclear fusion, fusion reaction, or fusion reaction [1] Nucleus refers to a low-mass atom, mainly deuterium or tritium, under certain conditions (such as ultra-high temperature and high pressure), only in Only at extremely high temperature and pressure can the extranuclear electrons get rid of the nucleus of the atomic nucleus, so that two atomic nuclei can attract each other and collide with each other, and the nucleus aggregates with each other to generate new heavier nuclei (such as helium), neutron Although the mass is relatively large, because the neutron is not charged, it can also escape from the bondage of the nucleus during this collision and be released. The release of a large number of electrons and neutrons shows a huge energy release. This is a form of nuclear reaction. There is huge energy in the nucleus, and the change of the nucleus (from one kind of nucleus to another kind of nucleus) is often accompanied by the release of energy. Nuclear fusion is the opposite form of nuclear reaction to nuclear fission. Scientists are working on controlled nuclear fusion, which may become a future energy source.
- The process of nuclear fusion is the opposite of nuclear fission. It is a process in which several atomic nuclei are aggregated into one atomic nuclei. Only lighter nuclei can undergo nuclear fusion, such as hydrogen isotopes deuterium (do), tritium (chun), and so on. Nuclear fusion also emits huge amounts of energy, and it emits more energy than nuclear fission. The process of hydrogen fusion to helium continues in the sun, and its light and heat are generated by nuclear fusion.
- Compared with nuclear fission, nuclear fusion can hardly cause environmental problems such as radioactive pollution, and its raw materials can be directly taken from deuterium in seawater. The sources are almost inexhaustible, which is an ideal energy source. Humans can already achieve uncontrolled nuclear fusion, such as the explosion of a hydrogen bomb. However, if energy can be effectively used by human beings, the speed and scale of nuclear fusion must be able to be reasonably controlled to achieve continuous and stable energy output. Scientists are working hard on how to control nuclear fusion.
Tokamak structural principle
- In the Tokamak device, the change in the current of the ohmic coil provides the number of volt-seconds required to generate, establish, and maintain the plasma current (transformer principle); the polar magnetic field generated by the polar field coil controls the plasma cross-sectional shape and position balance; The toroidal magnetic field generated by the toroidal field coil guarantees the macroscopic overall stability of the plasma; the toroidal magnetic field and the polar magnetic field generated by the plasma current together form a magnetic field line rotation transformation and a magnetic field structure nested magnetic field configuration to constrain the plasma. . At the same time, the plasma current also ohmically heats itself. The cross-sectional shape of the plasma can be circular or it can be separated from the filter (located in the edge area of the vacuum chamber. The confinement area is isolated from the edge area by generating a magnetic interface. It has the functions of heat removal, impurity control, and helium ash removal. Functional special parts) configuration combined into a D-shape. On the Tokamak device, the plasma can reach and exceed the temperature (> 10K) required for effective combustion of deuterium and tritium by high-power neutral beam injection heating and microwave heating, up to 4.4 × 10K. Increasing the size of the device will increase the restraint time approximately by the square of the size. In addition, it can be improved by increasing the hoop magnetic field, optimizing the constraint configuration and the operating mode.
- Energy constraint time. Experimental results show that the Tokamak device has basically met the requirements for establishing a nuclear fusion reactor.
Tokamak countries profile
- Compared to other types of controlled nuclear fusion, Tokamak has many advantages. At the Third International Conference on Plasma Physics and Controlled Nuclear Fusion Research, held in Nov. Siberia, Soviet Union in August 1968, Acemoviz announced that the electron temperature 1keV and proton temperature were achieved on the Soviet T-3 Tokamak. 0.5 keV, n = 10 to the power of 18 m-3.s. This is a major breakthrough in controlled nuclear fusion research. It has set off an upsurge of tokamak in the world. Countries have successively built or rebuilt a large number of
- 1 meter high and 0.785 meter radius [1]
- On September 28, 2006, China s new-generation thermonuclear fusion device EAST, which took 8 years and cost 200 million yuan to independently design and build, successfully completed the discharge experiment for the first time, and obtained a current of 200 kA and a time close to 3 seconds. High temperature plasma discharge. EAST became the first fully superconducting non-circular cross-section nuclear fusion experimental device built and actually running in the world.
Tokamak historical development
- At the end of World War II, the former Soviet Union, the United States, and the British countries had military considerations.
- Tokamak interior
- In 1954, the first Tokamak plant was completed at the former Soviet Kurchatov Atomic Energy Institute. After people put forward the concept of magnetic confinement, the research on magnetic confinement fusion progressed smoothly in some aspects, and the hydrogen bomb was quickly tested successfully. This once made nuclear scientists in many countries overly optimistic about controlled nuclear fusion. . But people soon discovered that the magnetic field that constrained the plasma, although not afraid of high temperatures, was very unstable. In addition, the plasma also loses energy during heating.
- In 1985, President Reagan of the United States and President Gorbachev of the former Soviet Union at a summit initiated an international cooperation program for nuclear fusion research, which called for "the widest practical international cooperation in nuclear fusion energy." Later, Gorbachev, Reagan, and French President Mitterrand held several high-level meetings to support the conceptual design of the International Thermonuclear Experimental Reactor (ITER) and auxiliary research and development under the auspices of the International Atomic Energy Agency (IAEA). Cooperation. This was the most important international scientific and technical cooperation project for nuclear fusion research at the time. In the spring of 1987, the Director General of the IAEA invited representatives of the European Union, Japan, the United States and Canada, and the former Soviet Union to meet in Vienna to discuss the issue of strengthening international cooperation in nuclear fusion research and reached an agreement. The Quartet cooperated in the design and construction of the International Thermonuclear Experimental Reactor.
- In 1990, the Plasma Institute of the Chinese Academy of Sciences built a large superconducting tokamak device, which received strong support from Russia, the United States, the European Union and other institutions and experts. In particular, Russian scientist Professor Kadomtsev, the most authoritative Russian National Research Center for fusion research in the world, has become a "regular technical guide" for device construction.
- The HT-7 was completed in 1993, and China became the fourth country in the world to have similar large-scale installations after Russia, France, and Japan (Tore-Supra in France, T-15 in Russia, and JT-60U in Japan). China's research on device-related superconductivity, low-temperature refrigeration, and strong magnetic fields has reached a new level.
- On December 9th and 10th, 1993, the United States used a 50% mixture of deuterium and tritium on a TFTR device to bring the temperature to 300 to 400 million degrees Celsius. The fusion energy released by the two experiments was 0.3 kilowatts and 0.56, respectively. 10 kilowatts, about 2 and 4 times the output power of JET, and the energy gain factor Q is 0.28. Compared with JET, the Q value has been greatly improved.
- On September 22, 1997, the joint European ring JET created a world record with an output power of 12,900 kilowatts, an energy gain factor Q value of 0.60, and a duration of 2 seconds. After only 39 days, the output power increased to 161,000 kilowatts, and the Q value reached 0.65.
- In December 1997, the Japanese side announced that the deuterium-deuterium reaction experiment was successfully carried out on JT-60. When converted to the deuterium-tritium reaction, the Q value can reach 1.00. Later, the Q value exceeded 1.25. On the JT-60U, a higher equivalent energy gain factor is also achieved, which is greater than 1.3, which is also calculated by extrapolating the results obtained from the deuterium-deuterium experiment.
- In 2000, the HT-7 experimental discharge time exceeded 10 seconds, marking China's entry into the world's forefront in this major field of basic theoretical research.
- On January 28, 2002, research on controlled thermonuclear fusion based on the superconducting tokamak device HT-7 was obtained at the Southwest Institute of Physics of the Nuclear Industry in Chengdu, China, and the Institute of Ex vivo Physics, Chinese Academy of Sciences in the western suburb of Hefei. The breakthrough achieved a high-constrained steady-state operation with a discharge pulse length greater than 100 times the energy confinement time and an electronic temperature of 20 million degrees Celsius. The center density was greater than 1.2 × 1019 per cubic meter, and the operating parameters ranked the top two in the world. This round of experiments involved 18 foreign experts from 14 research institutions including the United States and Japan.
- In 2006, China's new-generation "artificial sun" experimental device (EAST) achieved the first "ignition"-excited plasma states and nuclear fusion. Soon, it achieved a maximum continuous operation of 1000 seconds, which was an unprecedented achievement at the time.
- EAST
- On April 22, 2012, China's next-generation "artificial sun" experimental device (EAST) neutral beam injection system (NBI) completed a high-energy ion beam extraction experiment with a hydrogen ion beam power of 3 MW and a pulse width of 500 milliseconds. The beam energy and power obtained in this round of experiments set a domestic record in China, and basically reached the design goals of the EAST project. This indicates that China's self-developed neutral beam injection system with international advanced level has basically overcome all major technical difficulties.
Tokamak status quo and prospects
- Only when the three conditions of density (> 10cm), temperature (> 10K) and energy constraint time (> 1s) (or fusion triple product> 10cm·K·s) can be achieved, can the deuterium-thorium self-sustaining nuclear fusion reaction be achieved. These three conditions have been met or exceeded respectively on different devices, but have not been met or exceeded simultaneously on one device. The JET (see picture) and JT-60U devices have basically reached the equivalent energy gains and losses (Q1). JET's deuterium-plutonium test also obtained 17MW fusion power output.
- European Union Ring JET Device Structure
- Experimental research also found a variety of models to improve the constraints. According to these models, the economic performance of the Tokamak-type fusion reactor can be further improved. Based on more than 50 years of significant progress in plasma theory, physics experiment research, and engineering technology, the ITER project, a very large international cooperation project jointly participated by the seven parties, has entered the engineering construction stage.