Because the tokamak is the most common research machine for magnetic confinement fusion today, we provide several descriptions from various sources. One of several types of toroidal discharge chamber in which a longitudinal magnetic field is used to confine a plasma. The tokamak is distinguished by a plasma current running around the torus, which generates a stabilising poloidal magnetic field. An externally-applied vertical magnetic field is also used to achieve plasma equilibrium.
An axisymmetric toroidal confinement device characterised by a strong toroidal magnetic field (1-10 Tesla) and a toroidal plasma current (several mega-Amps) that leads to a modest poloidal magnetic field. The plasma current is usually induced by ramping a current in a large solonoid along the symmetry axis of the tokamak. This is an inherently pulsed mode of operation, and other mechanisms of current drive are under investigation.
A three component magnetoplasma toroidal construct in which the poloidal magnetic component is provided by a toroidal plasma current. The other two components are coil driven, namely, the vertical field (which opposes the major radial expansion) and the toroidal field (which acts to provide a stiff guide field for the plasma to gain more magnetohydrodynamic stability. Note: It is better to think that the toroidal or longitudinal field stiffens the plasma as against flopping or kinking, while the plasma current driven poloidal (locally azimuthal) field provides confinement pressure. Actually, the toroidal field interacting with plasma diamagnetism may also contribute to a magnetic bouyancy, which is a sort of UN-confinement (it actually gives the plasma a tendency to expand radially outward in the equatorial plane).
Based on an original Soviet design, a device for containing plasma inside a torus chamber by using the combination of two magnetic fields - one created by electric coils around the torus, the other created by intense electric current in the plasma itself, which also servers to heat the plasma [partially].
(09 Oct 1997)
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