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Encyclopedia > Stellarator
 Stellarator magnetic field and magnets
Stellarator magnetic field and magnets

A stellarator is a device used to confine a hot plasma with magnetic fields in order to sustain a controlled nuclear fusion reaction. The magnetic field necessary to confine the plasma is completely generated by external coils. It was invented by Lyman Spitzer and the first devices were built at the Princeton Plasma Physics Laboratory in 1951. The name was given to this early fusion concept because of the possibility of harnessing the power source of the sun (which is a stellar object: a star). Image File history File links Magnetspulen_und_Plasma_des_Stellarators_Wendelstein_7-X.gif Source: ipp. ... Image File history File links Magnetspulen_und_Plasma_des_Stellarators_Wendelstein_7-X.gif Source: ipp. ... A plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Current (I) flowing through a wire produces a magnetic field () around the wire. ... Lyman Spitzer Lyman Spitzer, Jr. ... Princeton Plasma Physics Laboratory (PPPL) is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science. ... 1951 (MCMLI) was a common year starting on Monday; see its calendar. ... This article is about the astronomical object. ...

Some important stellarator experiments are Wendelstein, in Germany, and the Large Helical Device, in Japan. A new stellarator, NCSX, is currently being built at the Princeton Plasma Physics Laboratory. Wendelstein is the name of a mountain in the Chiemgau (see Rosenheim (district)) two experimental stellarators (nuclear fusion reactors) of the Max-Planck-Institut für Plasmaphysik: The Wendelstein 7-AS is located in Garching near Munich, Germany Its successor, the Wendelstein 7-X is currently being built in Greifswald... Categories: Stub | Nuclear technology ... The National Compact Stellarator Experiment (NCSX) is a plasma confinement experiment being conducted at the Princeton Plasma Physics Laboratory. ... Princeton Plasma Physics Laboratory (PPPL) is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science. ...



Wendelstein 7-X Stellarator structural component

Although it would seem at first glance that a magnetic torus could contain plasma, if one examines the windings of an electromagnet's wiring around a torus it becomes clear the windings are less dense on the outside of the loop than on the inside. Plasma particles (ions) on the inner portion of the tube would thus see a greater magnetic force than those at the outside, and only particles near the middle would see the "right amount". Since magnetic forces are generally at right angles to motion, non-centered plasma moving around the toroid would thus be forced up or down until it hit the edges of the tube. Image File history File links Stellarator_Wendelstein_7-X_Plasmagefäß.jpg Beschreibung Source: ipp. ... Image File history File links Stellarator_Wendelstein_7-X_Plasmagefäß.jpg Beschreibung Source: ipp. ...

The stellarator avoids this with a simple "trick": the toroid is bent into a figure-eight shape. Now when a particle orbits the tube, it spends half the time on the inside of the tube and half on the outside. This equalizes the forces, at least to some degree, and the particle experiences a much smaller overall drifting force.

The earliest stellarators were literally figure-eights, consisting of two sides of a torus connected together with crossed straight tubes. In order to allow the tubes to cross without hitting, the torus sections on either end were rotated slightly. This arrangement was less than perfect, however, as a particle on the "inner portion" at one end would not end up at the "outer portion" at the other, but at some other point rotated from the perfect location due to the tilt of the two ends.

Various different geometries were tried to address these problems, starting with simple changes to allow the ends to lie flat at different levels and placing symmetrical bends in the arms instead. A later version solved the problem more convincingly by introducing a "peanut" shaped tube instead of a figure-eight, the in-bent sides offsetting the out-bend toroidal sections on either end.

But the real solution turned out to be magnetic instead of mechanical: by rotating the magnetic windings themselves as they were wrapped around the chamber, the plasma would be rotated around a simple torus, slowly moving from inside to outside.

Configurations of stellarator

Torsatron: A stellarator configuration with continuous helical coils. It is also to have the continuous coils to be replaced by a number of discrete coils producing a similar field.

Heliotron: A stellarator configuration in which a helical coil is used to confine the plasma, together with a pair of PF coils to provide a vertical field. TF coils can also be used to control the magnetic surface characteristics.

Helias: A stellarator configuration in which the coils resemble distorted, non-planar TF coils so that the continuous helical coils or tokamak-like PF coils are present. The Helias (HELIcal Advanced Stellarator) has been proposed to be the most promising stellarator concept for a power plant, with a modular engineering design and optimised plasma, MHD and magnetic field properties. The Wendelstein VII-X device is based on a five field-period Helias configuration.

Comparison to tokamaks

Tokamak magnet field and current

The tokamak provides the required twist to the magnetic field lines not by manipulating the field with external currents, but by driving a current through the plasma itself. The field lines around the plasma current combine with the toroidal field to produce helical field lines, which wrap around the torus in both directions. Image File history File links Tokamak_fields_lg. ... Image File history File links Tokamak_fields_lg. ... A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ...

Although they also have a toroidal magnetic field topology, stellarators are distinct from tokamaks in that they are not azimuthally symmetric. They have instead a discrete rotational symmetry, often five-fold, like a regular pentagon. A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ...

It is generally argued that the development of stellarators is less advanced than tokamaks although the intrinsic stability they provide has been sufficient to pursue an active development of this concept. Stellarators, unlike tokamaks, do not require a toroidal current, so that the expense and complexity of current drive and/or the loss of availability and periodic stresses of pulsed operation can be avoided. In addition, there is no risk of current disruptions.

On the downside, the three-dimensional nature of the field, the plasma, and the vessel make it much more difficult to do either theory or experimental diagnostics with stellarators. On the other hand, it might be possible to use the additional degrees of freedom to optimize a stellarator in ways that are not possible with tokamaks. It is much harder to design a divertor (the section of the wall that receives the exhaust power from the plasma) in a stellarator, the out-of-plane magnetic coils (common in many modern stellarators and possibly all future ones) are much harder to manufacture than the simple, planar coils which suffice for a tokamak, and the utilization of the magnetic field volume and strength is generally poorer than in tokamaks.

External links

  • Stellarator News from ORNL
  • Spherical stellerator
  • Low-cost stellarator

Fusion power
v  d  e
Atomic nucleus | Nuclear fusion | Nuclear power | Nuclear reactor | Timeline of nuclear fusion
Plasma physics | Magnetohydrodynamics | Neutron flux | Fusion energy gain factor | Lawson criterion
Methods of fusing nuclei

Magnetic confinement: Tokamak - Spheromak - Stellarator - Reversed field pinch - Field-Reversed Configuration - Levitated Dipole
Inertial confinement: Laser driven - Z-pinch - Bubble fusion (acoustic confinement) - Fusor (electrostatic confinement)
Other forms of fusion: Muon-catalyzed fusion - Pyroelectric fusion - Migma The Sun is a natural fusion reactor. ... A semi-accurate depiction of the helium atom. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... A nuclear power station. ... Core of a small nuclear reactor used for research. ... Timeline of significant events in the study and use of nuclear fusion: 1929 - Atkinson and Houtermans used the measured masses of light elements and applied Einsteins discovery that E=mc² to predict that large amounts of energy could be released by fusing small nuclei together. ... A Plasma lamp In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. ... Magnetohydrodynamics (MHD) (magnetofluiddynamics or hydromagnetics) is the academic discipline which studies the dynamics of electrically conducting fluids. ... neutron flux n : the rate of flow of neutrons; the number of neutrons passing through a unit area in unit time via dictionary. ... The fusion energy gain factor, usually expressed with the symbol Q, is the ratio of fusion power produced in a nuclear fusion reactor to the power required to maintain the plasma in steady state. ... This article or section does not cite its references or sources. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Magnetic Fusion Energy (MFE) is a sustained nuclear fusion reaction in a plasma that is contained by magnetic fields. ... A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Reversed-Field Pinch is a toroidal magnetic confinement scheme. ... A Field-Reversed Configuration (FRC) is a device developed for magnetic fusion energy research that confines a plasma on closed magnetic field lines without a central penetration. ... A Levitated Dipole is a unique form of fusion reactor technology using a solid superconducting torus, magnetically levitated in the reactor chamber. ... Inertial confinement fusion using lasers rapidly progressed in the late 1970s and early 1980s from being able to deliver only a few joules of laser energy (per pulse) to a fusion target to being able to deliver tens of kilojoules to a target. ... In inertial confinement fusion (ICF), nuclear fusion reactions are initiated by heating and compressing a target – a pellet that most often contains deuterium and tritium – by the use of intense laser or ion beams. ... The Z machine at Sandia National Laboratories in Albuquerque, New Mexico. ... Bubble fusion or sonofusion is the common name for a nuclear fusion reaction hypothesized to occur during sonoluminescence, an extreme form of acoustic cavitation; officially, this reaction is termed acoustic inertial confinement fusion (AICF) since the inertia of the collapsing bubble wall confines the energy causing a rise in temperature. ... U.S. Patent 3,386,883 - fusor — June 4, 1968 The Farnsworth–Hirsch Fusor, or simply fusor, is an apparatus designed by Philo T. Farnsworth to create nuclear fusion. ... Inertial electrostatic confinement (often abbreviated as IEC) of a plasma can be achieved with electrostatic fields which accelerate charged particles (either ions or electrons) directly, in a confined space. ... Muon-catalyzed fusion is a process allowing nuclear fusion to take place at room temperature. ... Pyroelectric fusion is a technique for achieving nuclear fusion by using an electric field generated by pyroelectric crystals to accelerate ions of deuterium (tritium might also be used someday) into a metal hydride target also containing detuerium (or tritium) with sufficient kinetic energy to cause these ions to fuse together. ... Migma was a proposed inertial electrostatic confinement fusion reactor designed by Bogdan Maglich around 1973. ...

List of fusion experiments

Magnetic confinement devices
ITER (International) | JET (European) | JT-60 (Japan) | Large Helical Device (Japan) | KSTAR (Korea) | EAST (China) | T-15 (Russia) | DIII-D (USA) | Tore Supra (France) | ASDEX Upgrade (Germany) | TFTR (USA) | NSTX (USA) | NCSX (USA) | UCLA ET (USA) | Alcator C-Mod (USA) | LDX (USA) | H-1NF (Australia) | MAST (UK) | START (UK) | Wendelstein 7-X (Germany) | TCV (Switzerland) | DEMO (Commercial) Experiments directed toward developing fusion power are invariably done with dedicated machines which can be classified according to the principles they use to confine the plasma fuel and keep it hot. ... Cutaway of the ITER Tokamak Torus in casing. ... Split image of JET with right side showing hot plasma during a shot. ... JT-60 (JT stands for Japan Torus) is the flagship of Japans magnetic fusion program, run by the Japan Atomic Energy Research Institute (JAERI), and the Naka Fusion Research Establishment in Ibaraki Prefecture, Japan. ... Categories: Stub | Nuclear technology ... The KSTAR, or Korean Superconducting Tokamak Advanced Reactor is a magnetic fusion device being built at the Korea Basic Science Institute in Daejon, South Korea. ... The Experimental Advanced Superconducting Tokamak (EAST, internally called HT-7U) is a project being undertaken to construct an experimental superconducting tokamak magnetic fusion energy reactor in Hefei, the capital city of Anhui Province, in eastern China. ... The T-15 is a Russian nuclear fusion research reactor, based on the (Russian-invented) tokamak design. ... DIII-D or D3-D is the name of a tokamak machine developed in the 1980s by General Atomics in San Diego, USA, as part of the ongoing effort to achieve magnetically confined fusion. ... Tore Supra is a tokamak français en activité après larrêt du TFR (Tokamak de Fontenay-aux-Roses) et de Petula (à Grenoble). ... The ASDEX Upgrade divertor tokamak (Axially Symmetric Divertor EXperiment) went into operation at the Max-Planck-Institut für Plasmaphysik, Garching in 1991. ... The Tokamak Fusion Test Reactor (TFTR) was an experimental fusion test reactor built at Princeton Plasma Physics Laboratory (in Princeton, New Jersey) circa 1980. ... The National Spherical Torus Experiment (NSTX) is an innovative magnetic fusion device that was constructed by the Princeton Plasma Physics Laboratory (PPPL) in collaboration with the Oak Ridge National Laboratory, Columbia University, and the University of Washington at Seattle. ... The National Compact Stellarator Experiment (NCSX) is a plasma confinement experiment being conducted at the Princeton Plasma Physics Laboratory. ... The UCLA Electric Tokamak is a low field (0. ... Alcator C-Mod is a tokamak, a magnetically confined nuclear fusion device, at the MIT Plasma Science and Fusion Center. ... The Levitated Dipole Experiment (LDX) is a project devoted to researching a type of nuclear fusion which utilizes a floating superconducting torus to provide an axisymmetric magnetic field which is used to contain plasma. ... The H-1 flexible Heliac is a three field-period helical axis stellarator located in the Research School of Physical Sciences and Engineering at the Australian National University. ... The Mega Ampere Spherical Tokamak, or MAST experiment is a nuclear fusion experiment in operation at Culham since December 1999. ... The Small Tight Aspect Ratio Tokamak, or START was a nuclear fusion experiment that used magnetic confinement to hold plasma. ... Magnetic coils and plasma of the Wendelstin 7-X stellarator Plasma vessel of Wendelstein 7-X Wendelstein 7-X is an experimental stellarator (nuclear fusion reactor) currently being built in Greifswald, Germany by the Max-Planck-Institut für Plasmaphysik (IPP), which will be completed by 2012. ... Tokamak à Configuration Variable (TCV): inner view, with the graphite-claded torus. ... Look up demo in Wiktionary, the free dictionary. ...

Inertial confinement devices
Laser driven: NIF (USA) | OMEGA laser (USA) | Nova laser (USA) | Novette laser (USA) | Nike laser (USA) | Shiva laser (USA) | Argus laser (USA) | Cyclops laser (USA) | Janus laser (USA) | Long path laser (USA) | 4 pi laser (USA) | LMJ (France) | Luli2000 (France) | GEKKO XII (Japan) | ISKRA lasers (Russia) | Vulcan laser (UK) | Asterix IV laser (Czech Republic) | HiPER laser (European)
Non-laser driven:
Z machine (USA) | PACER (USA)
A construction worker inside NIFs 10 meter target chamber. ... The Laboratory for Laser Energetics (LLE) is a scientific research facility which is part of the University of Rochesters south campus, located in Rochester, New York. ... The Nova laser was a laser built at the Lawrence Livermore National Laboratory in 1984 and which conducted advanced inertial confinement fusion experiments until its dismantling in 1999. ... The Novette target chamber with two laser chains visible in background. ... Final amplifier of the Nike laser where laser beam energy is increased from 150 J to ~5 Kj by passing through a krypton/fluorine/argon gas mixture excited by irradiation with two opposing 670,000 volt electron beams. ... The Shiva laser was an extremely powerful 20 beam infrared neodymium glass (silica glass) laser built at Lawrence Livermore National Laboratory in 1977 for the study of inertial confinement fusion and long-scale-length laser-plasma interactions. ... Argus laser overhead view. ... The single beam Cyclops laser at LLNL around the time of its completion in 1975. ... The Janus laser as it appeared in 1975. ... The Long Path laser was an early high energy infrared laser at the Lawrence Livermore National Laboratory used to study inertial confinement fusion. ... Physicist Frank Rainer (inset), who was involved in laser research and development at LLNL since 1966, holds the target chamber seen at the center of the larger picture. ... Laser Mégajoule (LMJ) is an experimental inertial confinement fusion (ICF) device being built in France by the French nuclear science directorate, CEA. Laser Mégajoule plans to deliver about 1. ... LULI2000 is a high-power laser system dedicated to scientific research. ... GEKKO XII is a high-power 12-beam neodymium doped glass laser at the Osaka Universitys Institute for Laser Engineering completed in 1983, which is used for high energy density physics and inertial confinement fusion research. ... The ISKRA-4 and ISKRA-5 lasers are lasers which were built by the Russian federation at RFNC-VNIIEF in Arzamas-16() with the ~2Kj output ISKRA-4 laser being completed in 1979 and the ~30Kj output ISKRA-5 laser which was completed in 1989. ... The Vulcan laser is an 8 beam 2. ... The Asterix IV laser in Prague (commonly reffered to by the acronym PALS for Prague Asterix Laser System) is a high power photolytically pumped iodine gas laser which is capable of producing ~300 to 500 picosecond long pulses of light at the fundamental line of 1. ... HiPER is an experimental laser-driven inertial confinement fusion (ICF) device currently undergoing preliminary design for possible construction in the European Union starting around 2010. ... Zork universe Zork games Zork Anthology Zork trilogy Zork I   Zork II   Zork III Beyond Zork   Zork Zero   Planetfall Enchanter trilogy Enchanter   Sorcerer   Spellbreaker Other games Wishbringer   Return to Zork Zork: Nemesis   Zork Grand Inquisitor Zork: The Undiscovered Underground Topics in Zork Encyclopedia Frobozzica Characters   Kings   Creatures Timeline   Magic   Calendar... The PACER project, carried out at Los Alamos National Laboratory in the mid-1970s, explored the possibility of a fusion power system that would involve exploding small hydrogen bombs (fusion bombs)—or, as stated in a later proposal, fission bombs—inside an underground cavity. ...

See also: International Fusion Materials Irradiation Facility The International Fusion Material Irradiation Facility, also known as IFMIF, is an international scientific research program designed to test materials for suitability for use in a fusion reactor. ...

  Results from FactBites:
Stellarator (160 words)
In a stellarator, the screw-like twisting of field lines around the torus centre is generated by external coils.
In contrast to the Tokamak, a stellarator does not need a direct-axis flow component in the plasma.
In a stellarator, the magnetic field cage is formed by a single coil system.
Scientific Visualization of 3-dimensional Optimized Stellarator Configurations (1388 words)
A particularly convenient choice for stellarators (as shown in Figure 1) are the magnetic or Boozer coordinates [2] which allow the particle trajectory equations to be expressed in an accurate Hamiltonian form which depends only on the magnitude of the magnetic field and its derivatives.
In Figure 2 we display an outer magnetic flux surface of a low aspect ratio stellarator with color contours proportional to the strength of the magnetic field (light purple is low field, light blue-green is high field) and the trajectory of a magnetic field line is shown in white.
Stellarator transport optimizations focus directly on the dependence of the magnetic field strength on the two angular coordinates which span each flux surface.
  More results at FactBites »



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