Compact toroid
Encyclopedia
Compact toroids are a class of toroidal
plasma
configurations that are self-stable, and whose configuration does not require magnet coils running through the center of the toroid. They are studied primarily in the field of fusion energy, where the lack of complex magnets and a simple geometry may allow the construction of dramatically simpler and less expensive fusion reactors. The two best studied compact toroids are the spheromak
and field-reversed configuration
(FRC). A third configuration, the particle ring, does not appear to have attractive performance.
The spheromak configuration is similar in arrangement to a smoke ring
. The FRC is also toroidal, but extended into the general shape of a hot dog
, or more accurately, a corn dog
where the stick has been removed. 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 the need for magnets in the center of the plasma (unlike a tokamak
).
Of the two, the FRC naturally has a higher betas
, 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
, and many spherical tokamak machines were converted from earlier spheromak reactors.
Toroidal
Toroidal describes something which resembles or relates to a torus or toroid:*Torus*Toroid, a doughnut-shaped object which resembles a torus*Toroidal inductors and transformers, a type of electrical device...
plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
configurations that are self-stable, and whose configuration does not require magnet coils running through the center of the toroid. They are studied primarily in the field of fusion energy, where the lack of complex magnets and a simple geometry may allow the construction of dramatically simpler and less expensive fusion reactors. The two best studied compact toroids are the spheromak
Spheromak
A spheromak is an arrangement of plasma formed into a toroidal shape similar to a smoke ring. The spheromak contains large internal electrical currents and their associated magnetic fields arranged so the magnetohydrodynamic forces within the spheromak are nearly balanced, resulting in long-lived ...
and field-reversed configuration
Field-Reversed Configuration
A Field-Reversed Configuration is a device developed for magnetic fusion energy research that confines a plasma on closed magnetic field lines without a central penetration....
(FRC). A third configuration, the particle ring, does not appear to have attractive performance.
The spheromak configuration is similar in arrangement to a smoke ring
Smoke ring
A smoke ring is a visible vortex ring formed by sudden release of smoke. It can be created by blowing smoke from the mouth, quickly lighting a cigarette lighter and putting it out or holding a burning incense stick or a cigarette vertically, pushing it with the burning side up and suddenly pulling...
. The FRC is also toroidal, but extended into the general shape of a hot dog
Hot dog
A hot dog is a sausage served in a sliced bun. It is very often garnished with mustard, ketchup, onions, mayonnaise, relish and/or sauerkraut.-History:...
, or more accurately, a corn dog
Corn dog
A corn dog is a hot dog sausage coated in a thick layer of cornmeal batter and deep fried in oil, although some are baked. Almost all corn dogs are served on wooden sticks, though some early versions had no stick.-History:...
where the stick has been removed. 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 the need for magnets in the center of the plasma (unlike a tokamak
Tokamak
A tokamak is a device using a magnetic field to confine a plasma in the shape of a torus . Achieving a stable plasma equilibrium requires magnetic field lines that move around the torus in a helical shape...
).
Of the two, the FRC naturally has a higher betas
Beta (plasma physics)
The beta of a plasma, symbolized by β, is the ratio of the plasma pressure to the magnetic pressure...
, 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
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 a donut, complete with a large hole in the middle...
, and many spherical tokamak machines were converted from earlier spheromak reactors.