Tokamak

From Academic Kids

Missing image
Inside_JET_tokamak.jpg
A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot.
Missing image
TokamakNovillo.jpg
The "Novillo" tokamak, the smallest in the world

A tokamak is a toroidal (doughnut-shaped) magnetic plasma confinement device, the leading candidate for producing magnetic fusion energy. The term tokamak comes from the Russian words: "toroidalnaya kamera s magnitnoi katushkoi" (toroidal chamber with magnetic coil). It was invented in the 1950s by Igor Yevgenyevich Tamm and Andrei Sakharov.

The tokamak is characterized by the use of the plasma current to generate the helical component of the magnetic field necessary for stable equilibria. This can be compared to another toroidal magnetic confinement device, the stellarator, in which all of the confining magnetic fields are produced by external coils and there is a negligible current flowing through the plasma.

Why doughnut shaped?

The distinctive shape of the fusion reactor is necessary because of a particular property of a doughnut that a sphere (for example) does not have. Essentially the problem is the hairy ball theorem: if a sphere has hair growing out of it then it is impossible to comb it so that no hair sticks up. However a hairy doughnut can be so combed.

This is important because a fusion reactor is a hairy doughnut with the hair being the magnetic field lines. A strand of hair that is standing on end would be an instability in the reactor.

See also

External link

  • Plasma Science (http://www-fusion-magnetique.cea.fr/gb/fusion/physique/sommaire.htm) - excellent site on tokamaks.de:Tokamak

es:Tokamak fr:Tokamak ja:トカマク型 nl:Tokamak pl:Tokamak zh:托卡马克

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