A compact toroid (CT) is a type of
plasmoid
A plasmoid is a coherent structure of Plasma (physics), plasma and magnetic fields. Plasmoids have been proposed to explain natural phenomena such as ball lightning, magnetic bubbles in the magnetosphere, and objects in cometary tails, in the so ...
, a class of
toroidal plasma configuration that is self-stable, and which does not need magnet coils running through the center of the toroid. They are studied mainly in the field of
fusion power
Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices d ...
, where a lack of complex magnets and a simple geometry may allow building dramatically simpler and less costly fusion reactors.
The two best studied compact toroids are the
spheromak and
field-reversed configuration (FRC). A third configuration, the particle ring, lacks attractive performance to date.
A CT containment system for plasma asymmetrically toroidally shaped by the containment, was first introduced into thought as a concept by Alfvén. The two examplar types; Field-reversed configuration plasma with a null toroid, firstly, is generally produced by prolate-theta-pinches with the necessarily existing field condition where the field magnetic bias is in a reversed situation. The second type has a non-null toroid, known as a spheromak configuration,
is similar in arrangement to a
vortex ring
A vortex ring, also called a toroidal vortex, is a torus-shaped vortex in a fluid; that is, a region where the fluid mostly spins around an imaginary axis line that forms a closed loop. The dominant flow in a vortex ring is said to be toroidal, ...
such as a
smoke ring
A smoke ring is a visible vortex ring formed by smoke in a clear atmosphere.
Smoking, Smokers may blow smoke rings from the mouth, intentionally or accidentally. Smoke rings may also be formed by sudden bursts of fire (such as lighting and i ...
. The FRC is also toroidal, but extended into a tubular shape or hollow cylinder. The main difference between the two is that the spheromak contains poloidal (vertical rings) and toroidal (horizontal) magnetic fields, while the FRC has only the poloidal fields and requires an external magnet for confinement. In both cases the combination of electrical currents and their associated magnetic fields result in a series of closed magnetic lines that maintains the ring shape, without need of magnets in the plasma center, unlike a
tokamak
A tokamak (; ) is a device which uses a powerful magnetic field generated by external magnets to confine plasma (physics), plasma in the shape of an axially symmetrical torus. The tokamak is one of several types of magnetic confinement fusi ...
.
Of the two, the FRC naturally has a higher
beta
Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...
, a measure of fusion economics. However, the spheromak had generated better confinement times and temperatures, and recent work suggests that great advances in performance can be made.
Compact toroids are also similar to the
spherical tokamak
A spherical tokamak is a type of fusion power device based on the tokamak principle. It is notable for its very narrow profile, or ''aspect ratio''. A traditional tokamak has a toroidal confinement area that gives it an overall shape similar to ...
, and many spherical tokamak machines were converted from earlier spheromak reactors.
See also
*
High beta fusion reactor
References
Bibliography
*
"ProtoSphera, General Framework", CR-ENEA Frascati, July 2001
*
Fusion power
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