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What is a Tokamak and How Does it Work?


Power plants convert mechanical energy, such as the spinning of a turbine, to create electricity. Burning coal, for example, heats water into steam that then drives turbine generators to produce electrical power. Today’s power plants use either fossil fuels, nuclear fission or renewable energy sources such as wind or hydro power.

A tokamak is an experimental machine that uses the energy produced by fusion reactions, with the energy produced by the fusion of atoms being absorbed into the walls of the vessel. A fusion power plant takes this heat energy to produce steam, which drives turbines to generate electricity as with a conventional power plant.

The first tokamak, called T-1, went into operation in Russia in 1958. Subsequent advances in the technology led to the construction of the Tokamak Fusion Test Reactor at the Princeton Plasma Physics Laboratory and the Joint European Torus in England. Both of these tokamaks achieved record fusion power in the 1990s, leading to a growth in fusion research and development as 35 nations came together to create the superconducting ITER tokamak, which is exploring the physics of burning plasmas.

The United States’ Department of Energy Office of Science is also investigating tokamaks through the fusion energy sciences programme and the advanced scientific computer research (ASCR) programme. The tokamak is now being seen as the most promising magnetic fusion machine in the world.


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How Does A Tokamak Work?

The name ‘tokamak’ comes from a Russian acronym for "toroidal chamber with magnetic coils" (тороидальная камера с магнитными катушками).

A tokamak is based around a doughnut-shaped vacuum chamber called a torus, within which gaseous hydrogen fuel is subjected to extreme heat and pressure until it becomes plasma, an electrically charged, hot gas. Plasma is also found in the core of stars and is the environment that allows light elements to fuse and release energy.

The hot plasma is kept away from the walls of the torus by magnetic coils that line the vessel. One set of coils generate an intense toroidal field while a central solenoid (a magnet carrying electric current) creates a poloidal field, confining the plasma particles. A third set of magnetic coils creates an outer poloidal field to shape and position the plasma within the torus. 

The fusion process begins with the evacuation of air and any impurities from the vacuum chamber, before the magnetic systems are charged up and the gaseous fuel (typically hydrogen) is introduced.

An electric current is passed through the vessel, breaking down and ionising the gas so that the electrons are stripped away from the nuclei, forming a plasma. The energised plasma particles collide and heat up, while auxiliary heating systems increase the temperature to the required levels for fusion (150-300 million °C). Under these conditions, the highly energised particles are able to overcome their natural electromagnetic repulsion as they collide, allowing them to fuse and releasing huge amounts of energy.

Tokamak Facts

  1. A tokamak can sustain plasma currents with electric currents equal to the most powerful bolts of lightning, known as the mega-ampere level
  2. The JET tokamak in England managed a world record fusion power output of 16 megawatts in 1997
  3. The central solenoid used for the ITER tokamak will be the largest superconducting magnet ever built, producing a field of 13 tesla, which is equivalent to 280,000 times the magnetic field of the Earth.


Is the Tokamak Safe?

The fusion process is deemed inherently safe and a range of additional safety measures are built into fusion power plant designs. Even a cataclysmic breach in a tokamak would only create very low levels of radioactivity outside of the plant enclosure.

How hot is a Tokamak?

The temperatures within a tokamak must reach 150 million °C to turn the gas into plasma and for the fusion reaction to take place. These high temperatures are ten times greater than the temperature found in the core of the Sun.

Can a Tokamak Explode?

The chamber in a modern tokamak, such as the ITER tokamak, typically contains less than one tenth of a gram of hydrogen fuel at any given moment. Should a disruption occur during a pulse the reaction immediately cools down and ends, meaning that a nuclear explosion at a tokamak like ITER is not possible.

What is the ITER Tokamak?

The ITER tokamak is an experimental machine with ten times the plasma chamber volume of the largest machine currently in operation. Twice the size of the largest machine currently in operation, it will be the world’s largest tokamak, with a plasma radius of 6.2m and a plasma volume of 840 m³.

Who Invented Tokamak?

The tokamak concept was first developed in the 1950s by two Soviet physicists, Igor Tamm and Andrei Sakharov, who had been inspired by a letter from Oleg Lavrentiev. The first working tokamak, the T-1, was created by Natan Yavlinsky, in 1958.

Where did Tokamak Originate?

The first tokamak, the T-1, began operation in Russia in 1958. This led to further advances and the subsequent construction of the Tokamak Fusion Test Reactor at Princeton Plasma Physics Laboratory and the Joint European Torus in England, which both achieved record fusion power in the 1990s.

Where is Tokamak used?

Tokamaks are not currently in use for energy production, as scientists still have to overcome the threshold of being able to create more energy than is used to start and maintain the fusion process. It is hoped that the ITER tokamak, which is being constructed in France, will be able to achieve this. When finished, it will be the world’s largest experimental tokamak nuclear fusion reactor.

What does Tokamak stand for?

The name ‘tokamak’ is an acronym of the Russian, ‘тороидальная камера с магнитными катушками,’ which means toroidal chamber with magnetic coils.

Why we need Tokamak

The development of the tokamak is all about potential, as fusion could provide energy for our towns, cities and industry. The fuels used for fusion are nearly inexhaustible (hydrogen is the most abundant element in the universe) and they produce no high activity, long-lived nuclear waste. Tokamak could be part of the solution to our future green energy needs.


A tokamak is an experimental device that creates a nuclear fusion reaction, which in turn produces energy to heat water and produce steam that drives turbines to generate electricity.

Nuclear fusion has the potential to provide clean and near-limitless energy if the challenges of production can be overcome. These challenges include being able to create more energy than it takes to create the fusion reaction itself.

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