Tokamak

Postage stamp USSR , 1987 .

The proposal on the use of controlled thermonuclear fusion for industrial purposes and a specific scheme using thermal insulation of high-temperature plasma by an electric field were first formulated by the Soviet physicist O. A. Lavrentiev in the mid-1950s. This work served as a catalyst for Soviet research on the problem of controlled thermonuclear fusion. ^[1] A.D. Sakharov and I.E. Tamm in 1951 proposed modifying the scheme by proposing a theoretical basis for a thermonuclear reactor where the plasma would have a torus shape and be held by a magnetic field. At the same time, the same idea was proposed by American scientists, but "forgotten" until the 1970s ^[2] ..

The term “tokamak” was coined in 1957 ^{[3] by} Igor Nikolayevich Golovin , a student of academician Kurchatov . Initially, it sounded like a “tokamag” - an abbreviation of the words “ it ’s a roidal chamber magnetic”, but N. A. Yavlinsky , the author of the first toroidal system, proposed replacing “-mag” with “-mag” for harmony ^[4] . This name was later borrowed by many languages.

The first tokamak was built in 1954 ^[5] , and for a long time tokamaks existed only in the USSR. Only after 1968 , when the T-3 tokamak, built at the Institute of Atomic Energy named after I. V. Kurchatov, under the guidance of Academician L. A. Artsimovich , the electron temperature of the plasma was reached 1 keV (which corresponds to ^[6] 11.6 million ° C ) ^{[7] [8]} , and English scientists from the (Nicol Peacock et al.) Arrived with their equipment in the USSR ^[9] , made measurements on the T-3 and confirmed this fact ^{[10] [11]} , which they initially refused to believe in, a real tokamak boom began in the world. Since 1973, Boris Borisovich Kadomtsev led the research program for plasma physics in tokamaks.

Currently, tokamak is considered the most promising device for the implementation of controlled thermonuclear fusion ^[12] .

A tokamak is a toroidal vacuum chamber on which coils are wound to create a toroidal magnetic field . First, air is pumped out of the vacuum chamber, and then it is filled with a mixture of deuterium and tritium . Then using an inductor in the chamber create a vortex electric field . The inductor is the primary winding of a large transformer , in which the tokamak chamber is the secondary winding. An electric field causes a current to flow and ignition in the plasma chamber.

The current flowing through the plasma performs two tasks:

• heats the plasma in the same way as any other conductor would heat ( ohmic heating );
• creates a magnetic field around itself. This magnetic field is called poloidal (that is, directed along the lines passing through the poles of the spherical coordinate system).

A magnetic field compresses the current flowing through the plasma. The result is a configuration in which helical magnetic lines of force “encircle” the plasma cord. Moreover, the step during rotation in the toroidal direction does not coincide with the step in the poloidal direction. Magnetic lines turn out to be open, they spin endlessly around the torus many times, forming the so-called "magnetic surfaces" of a toroidal shape.

The presence of a poloidal field is necessary for stable plasma confinement in such a system. Since it is created by increasing the current in the inductor, and it cannot be infinite, the stable plasma existence time in the classical tokamak is so far limited to several seconds. To overcome this limitation, additional current maintenance methods have been developed. For this, injection of accelerated neutral deuterium or tritium atoms into the plasma or microwave radiation can be used.

In addition to toroidal coils, additional coils of the poloidal field are needed to control the plasma cord. They are circular turns around the vertical axis of the tokamak chamber.

Heating alone due to the flow of current is not enough to heat the plasma to the temperature necessary for the implementation of the thermonuclear reaction. For additional heating, microwave radiation is used at the so-called resonant frequencies (for example, coinciding with the cyclotron frequency of either electrons or ions ) or injection of fast neutral atoms.

In total, about 300 tokamaks were built in the world. The largest ones are listed below.

USSR and Russia

• T-3 is the first functional unit.
• T-4 - an enlarged version of the T-3
• T-7 is a unique installation in which for the first time in the world in 1979 a relatively large magnetic system with a superconducting solenoid with conductors made of an alloy ( intermetallic ) of niobium - tin , cooled by liquid helium, was realized . The main task of the T-7 was completed: a perspective was prepared for the next generation of superconducting thermonuclear power solenoids.
• T-10 and PLT are the next step in world thermonuclear research, they are almost the same size, equal power, with the same retention factor. And the results are identical: the temperature of thermonuclear fusion is achieved at both reactors, and the lag by the Lawson criterion is 200 times.
• T-15 - a reactor with a superconducting solenoid, giving a field induction of 3.6 T. It was launched in 1988, in 1995 the experiments were suspended, since 2012 it has been undergoing modernization, which is planned to be completed in 2019.
• Globus-M ^[13] is a spherical tokamak, the newest tokamak in Russia, created in 1999.
• T-11M - located in TRINITY (Troitsk, Moscow); installation parameters: plasma current 0.1 MA , plasma temperature 400 ,, 600 eV

Kazakhstan

• Kazakhstan Tokamak Materials Science (KTM) is an experimental thermonuclear installation for research and testing of materials under energy load conditions close to ITER and future energy thermonuclear reactors. The construction site of KTM is Kurchatov .

China

• EAST - Located in Hefei , Anhui Province. On the tokamak, the Lawson criterion for ignition level was exceeded , the profitability coefficient was 1.25 ^[14] .

Europe

• TM1-MH (since 1977 - Castor, since 2007 - Golem). From the beginning of the 1960s until 1976 he acted at the Kurchatov Institute , then was transferred to the Institute of Plasma Physics of the Czechoslovak Academy of Sciences.
• JET ( Joint European Torus ) - created by Euratom in the UK . It used combined heating: 20 MW - neutral injection, 32 MW - ion-cyclotron resonance. The Lawson criterion is 4-5 times lower than the ignition level.
• Tore Supra is a tokamak with superconducting coils. Located in the research center of Cadarache ( France ).
• FTU (Frascati Tokamak Upgrade) - a metal mid-sized tokamak with a strong magnetic field. Located in the research center of Frascati, Italy. Belongs to the European Nuclear Energy Agency (ENEA). The installation parameters are as follows: BT <8T, R = 0.935 m, a = 0.3 m, Ip <1.5 MA.

USA

• TFTR (Test Fusion Tokamak Reactor) is the largest tokamak in the USA ( Princeton University ) with additional heating by fast neutral particles. Lawson's test is 5.5 times lower than the ignition threshold. Closed in 1997.
• NSTX (National Spherical Torus Experiment) is a spheromak (spherical current poppy ), currently working at Princeton University. The first plasma in the reactor was obtained in 1999, two years after the closure of TFTR.
  NSTX-U is built on the basis of NSTX, the upgrade cost $ 94 million. Currently, the installation is the world's most powerful spherical tokamak with magnetic induction of 1 Tesla and a thermal power of 10-12 megawatts. ^[15]
• Alcator C-Mod - characterized by the highest magnetic field and plasma pressure in the world. It has been working since 1993.
• DIII-D - created and works at General Atomic in San Diego .

Japan

• JT-60 - works at the Institute for Nuclear Research since 1985.

• ITER - International Experimental Thermonuclear Reactor
• Stellarator

• An article about tokamaki in the magazine "Around the World"
• Thor that will bring energy
• New plasma retention record - 28.6 seconds
• Physicists from the Celestial Empire say that they will be the first to realize the thermonuclear dream in reality
• Spherical Tokamak Globus-M
• Globe-M Tokamak discharge video recording
• Tokamak in the USSR