I want know about 'tokamak'?

Answer 1

Ions and electrons in a fusion plasma are at very high temperatures, and correspondingly have very significant velocities. In order to produce continuous fusion reactions, a fusion device must somehow ensure that the hot plasma does not lose its particles (and therefore its heat) at a too rapid rate, a goal known as confinement. Magnetic confinement fusion devices exploit the fact that charged particles in a magnetic field feel a Lorentz force and fall into helical paths along the field lines.

In the early days of fusion research, the devices used were variations on the Z-pinch, which aimed to use a poloidal field to contain the plasma. (See figure; the center graphic shows the poloidal field.) Researchers discovered that such plasmas are prone to many instabilities and quickly lose confinement. The tokamak introduces a toroidal field (see figure, top) that effectively "stiffens" the plasma against instability. (In practice, however, numerous instabilities occur, some of which are not yet fully understood.)

An aside: the doughnut has a particular topological property that a sphere (for example) does not have, a property explicated by the hairy ball theorem. Imagine a sphere with hair growing out of it. The hair is analogous to the magnetic field lines needed in a fusion reactor. It turns out that it is impossible to comb hair on a sphere so that no hair sticks up. A strand of hair that is standing on end would be equivalent to an instability in the reactor. However, a hairy doughnut can be so combed and thus adjustments to the magnetic field can be made to correct the irregularities. This allows the magnetic field to better confine the plasma.A tokamak is a machine producing a toroidal (doughnut-shaped) magnetic field for confining a plasma. It is one of several types of magnetic confinement devices and the leading candidate for producing fusion energy. The term tokamak is a transliteration of the Russian word Токамак which itself comes from the Russian words: "тороидальная камера в магнитных катушках" (toroidal'naya kamera v magnitnykh katushkakh — toroidal chamber in magnetic coils). It was invented in the 1950s by Igor Yevgenyevich Tamm and Andrei Sakharov (who were in turn inspired by an original idea of O.A. Lavrent'ev).The tokamak is characterized by azimuthal (rotational) symmetry and the use of the plasma current to generate the helical component of the magnetic field necessary for stable equilibrium. This can be contrasted to another toroidal magnetic confinement device, the stellarator, which has a discrete (e.g. five-fold) rotational symmetry and in which all of the confining magnetic fields are produced by external coils with a negligible current flowing through the plasma

Answer 2

A tokamak is a machine producing a toroidal (doughnut-shaped) magnetic field for confining a plasma. It is one of several types of magnetic confinement devices and the leading candidate for producing fusion energy. The term tokamak is a transliteration of the Russian word Токамак which itself comes from the Russian words: "тороидальная камера в магнитных катушках" (toroidal'naya kamera v magnitnykh katushkakh — toroidal chamber in magnetic coils). It was invented in the 1950s by Igor Yevgenyevich Tamm and Andrei Sakharov (who were in turn inspired by an original idea of O.A. Lavrent'ev).

The tokamak is characterized by azimuthal (rotational) symmetry and the use of the plasma current to generate the helical component of the magnetic field necessary for stable equilibrium. This can be contrasted to another toroidal magnetic confinement device, the stellarator, which has a discrete (e.g. five-fold) rotational symmetry and in which all of the confining magnetic fields are produced by external coils with a negligible current flowing through the plasma.

Answer 3

A tokamak is a machine producing a toroidal (doughnut-shaped) magnetic field for confining a plasma. It is one of several types of magnetic confinement devices and the leading candidate for producing fusion energy. The term tokamak is a transliteration of the Russian word Токамак which itself comes from the Russian words: "тороидальная камера в магнитных катушках" (toroidal'naya kamera v magnitnykh katushkakh — toroidal chamber in magnetic coils). It was invented in the 1950s by Igor Yevgenyevich Tamm and Andrei Sakharov (who were in turn inspired by an original idea of O.A. Lavrent'ev).