In 1950 he also proposed an idea for a controlled nuclear fusion reactor, the tokamak, which is still the basis for the majority of work in the area.

It is much harder to design a divertor ( the section of the wall that receives the exhaust power from the plasma ) in a stellarator, the out-of-plane magnetic coils ( common in many modern stellarators and possibly all future ones ) are much harder to manufacture than the simple, planar coils which suffice for a tokamak, and the utilization of the magnetic field volume and strength is generally poorer than in tokamaks.

A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus.

In a tokamak, the toroidal field is produced by electromagnets that surround the torus, and the poloidal field is the result of a toroidal electric current that flows inside the plasma.

An alternative to the tokamak is the stellarator.

The word tokamak is a transliteration of the Russian word токамак, an acronym of either " тороидальная камера с магнитными катушками " ( toroidal ' naya kamera s magnitnymi katushkami )— toroidal chamber with magnetic coils, or " тороидальная камера с аксиальным магнитным полем " ( toroidal ' naya kamera s aksial ' nym magnitnym polem )— toroidal chamber with axial magnetic field.

In the ITER tokamak, it is expected that the occurrence of a limited number of major disruptions will definitively damage the chamber with no possibility to restore the device .< ref > Wurden, G., ( 2011 ) International Workshop " MFE Roadmapping in the ITER Era ", Princeton < http :// advprojects. pppl. gov / Roadmapping / presentations / MFE_POSTERS / WURDEN_Disruption_RiskPOSTER. pdf ></ ref >< ref > Baylor, L. R .; Combs, S. K .; Foust, C. R .; Jernigan, T. C.

In current tokamak ( and other ) magnetic fusion experiments, insufficient fusion energy is produced to maintain the plasma temperature.

It appears that the maximum plasma temperature attainable by ohmic heating in a tokamak is 20-30 million degrees Celsius.

In a tokamak system this compression is achieved simply by moving the plasma into a region of higher magnetic field ( i. e., radially inward ).

This is a large advantage of tokamak reactors since these freed neutrons provide a simple way to extract heat from the plasma stream ; this is how the fusion reactor generates usable energy.

The most widely studied configuration for terrestrial fusion is the tokamak, a form of magnetic confinement fusion.

In the advanced tokamak and ST, wall stabilization is critical for operation with a large bootstrap fraction.

The NTM is already an important performance-limiting factor in many tokamak experiments, leading to degraded confinement or disruption.

as demonstrated in tokamak experiments, and rotational shear is also predicted to stabilize resistive

The western scientists visited the experiment and verified the high temperatures and confinement, sparking a wave of optimism for the prospects of the tokamak as well as construction of new experiments, which is still the dominant magnetic confinement device today.

* 2006-China's EAST test reactor is completed, the first tokamak experiment to use superconducting magnets to generate both the toroidal and poloidal fields.

Its main purpose is to open the way to future nuclear fusion experimental tokamak reactors such as ITER and: DEMO.

Because of the extremely high power requirements for the tokamak, and the fact that power draw from the main grid is limited, two large flywheel generators were constructed to provide this necessary power.

As of 1998, a higher Q of 1. 25 is claimed for the JT-60 tokamak ; however, this was not achieved under real D-T conditions but extrapolated from experiments performed with a pure deuterium ( D-D ) plasma.

* T-3 ( tokamak ), one of the first successful tokamaks ever to be constructed

* The Japan Atomic Energy Agency operates a Fusion research facility in the town, which houses the JT-60, one of the premiere tokamak fusion reactors in the world.

Sakharov, in association with Igor Tamm, proposed confining extremely hot ionized plasma by torus shaped magnetic fields for controlling thermonuclear fusion that led to the development of the tokamak device.

The tokamak provides the required twist to the magnetic field lines not by manipulating the field with external currents, but by driving a current through the plasma itself.

In 1981 Furth became the director at PPPL and led the laboratory until 1990 during record setting magnetic fusion energy experiments on the largest tokamak in the country, the Tokamak Fusion Test Reactor ( TFTR ).

" The leading designs for controlled fusion research use magnetic ( tokamak design ) or inertial ( laser ) confinement of a plasma, with heat from the fusion reactions used to operate a steam turbine which in turn drives electrical generators, similar to the process used in fossil fuel and nuclear fission power stations.

In 1951, together with Andrei Sakharov, Tamm proposed a tokamak system of the realization of CTF on the basis of toroidal magnetic thermonuclear reactor and soon after the first such devices were built by the INF, resulting the T-3 Soviet magnetic confinement device from 1968, when the plasma parameters unique for that time were obtained, of showing the temperatures in their machine to be over an order of magnitude higher than what was expected by the rest of the community.

* 1968-Results from the tokamak, a T-3 Soviet magnetic confinement device, which Igor Tamm and Andrei Sakharov had been working on, shows the temperatures in their machine to be over an order of magnitude higher than what was expected by the rest of the fusion community.

Its magnetic geometry is somewhat different from that of the more common tokamak.

* D3D ( fusion ), a tokamak experiment on magnetic confinement fusion

A 500-MW heat generating fusion plant using tokamak magnetic confinement geometry is currently being built in France ( see ITER ).

In 1968 Russian research on the toroidal tokamak was first presented in public, with results that far outstripped existing efforts from any competing design, magnetic or not.

Since then the majority of effort in magnetic confinement has been based on the tokamak principle.

The mainline confinement concepts of tokamak and stellarator do this in a toroidal chamber, which allows a great deal of control over the magnetic configuration, but requires a very complex construction.

Spheromaks have also been used to inject plasma into a bigger magnetic confinement experiment like a tokamak.

The Western scientists visited the experiment and verified the high temperatures and confinement, sparking a wave of optimism for the prospects of the tokamak.

Hundreds of fusion scientists and engineers in each participating " country " took part in a detailed assessment of the then present status of the tokamak confinement concept vis-a-vis the requirements of an EPR, identified the required R & D by early 1980 and produced a conceptual design by mid-1981.

This has advantages relative to the more conventional deuterium-tritium ( D-T ) reaction of other confinement and compression devices such as the tokamak or inertial confinement fusion ( ICF ) devices that amplify and focus multiple high-energy beams of lasers, electrons or ions onto tiny pellets of D-T fuel.

In spite of these early successes, by the late 1980s the tokamak had surpassed the confinement times of the spheromaks by orders of magnitude.

In conventional devices such as the tokamak this increased temperature / pressure increases turbulence that dramatically lowers confinement time.

More recently, in the 1990s, problems with the tokamak concept have led to renewed interest in the stellarator design, and a number of new devices have been built.

Unlike the stabilized pinch devices in the US and UK, the tokamak used considerably more energy in the stabilizing magnets, and much less in the plasma current.

For example, tokamak fusion devices impose very large peak loads, but relatively low average loads, on the electrical grid.