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- Path: senator-bedfellow.mit.edu!faqserv
- From: Robert F. Heeter <rfheeter@princeton.edu>
- Newsgroups: sci.physics.fusion,sci.answers,news.answers
- Subject: Conventional Fusion FAQ Glossary Part 20/26 (T)
- Supersedes: <fusion-faq/glossary/t_934543711@rtfm.mit.edu>
- Followup-To: sci.physics.fusion
- Date: 11 Nov 1999 12:26:23 GMT
- Organization: Princeton University
- Lines: 386
- Approved: news-answers-request@MIT.EDU
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- Expires: 23 Feb 2000 12:24:17 GMT
- Message-ID: <fusion-faq/glossary/t_942323057@rtfm.mit.edu>
- References: <fusion-faq/glossary/intro_942323057@rtfm.mit.edu>
- Reply-To: rfheeter@pppl.gov
- NNTP-Posting-Host: penguin-lust.mit.edu
- Summary: Fusion energy represents a promising alternative to
- fossil fuels and nuclear fission for world energy
- production. This Glossary is a compendium of Frequently Used
- Terms in Plasma Physics and Fusion Energy Research. Refer
- to the FAQ on Conventional Fusion for more detailed info
- about topics in fusion research. This Glossary does NOT
- discuss unconventional forms of fusion (like Cold Fusion).
- X-Last-Updated: 1995/02/26
- Originator: faqserv@penguin-lust.MIT.EDU
- Xref: senator-bedfellow.mit.edu sci.physics.fusion:44268 sci.answers:10865 news.answers:170851
-
- Archive-name: fusion-faq/glossary/t
- Last-modified: 25-Feb-1995
- Posting-frequency: More-or-less-quarterly
- Disclaimer: While this section is still evolving, it should
- be useful to many people, and I encourage you to distribute
- it to anyone who might be interested (and willing to help!!!).
-
- ===============================================================
- Glossary Part 20: Terms beginning with "T"
-
- FREQUENTLY USED TERMS IN CONVENTIONAL FUSION RESEARCH
- AND PLASMA PHYSICS
-
- Edited by Robert F. Heeter, rfheeter@pppl.gov
-
- Guide to Categories:
-
- * = plasma/fusion/energy vocabulary
- & = basic physics vocabulary
- > = device type or machine name
- # = name of a constant or variable
- ! = scientists
- @ = acronym
- % = labs & political organizations
- $ = unit of measurement
-
- The list of Acknowledgements is in Part 0 (intro).
- ==================================================================
-
- TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
-
- # t: variable generally used to represent time
-
- # tau: label generally used to represent confinement time
-
- # T: variable generally used to represent temperature
-
- # T: nuclear/chemical symbol for tritium/triton; see entry
-
- $ T: abbreviation for Tesla, SI unit of magnetic field; see entry
-
- > TARA: See entry under TARA below.
-
- @ TCI: Two-Color Interferometry
-
- @ TCV: Variable Configuration Tokamak - from French; see Section 5.
-
- @ TCX: Tangential Charge Exchange
-
- # Te: (subscript e) Electron Temperature
-
- $ Tera: Metric prefix indicating one trillion (10^12) times base unit.
-
- $ Terawatt: One trillion (10^12) watts.
-
- @ TEXT-U: TEXas Tokamak-Upgrade; see entry under TEXT below.
-
- @ TEXTOR: Tokamak EXperiment for Technology Oriented Research; see
- entry for TEXTOR below.
-
- @ TF: Toroidal Field (or Toroidal Field Coil)
-
- @ TFR: FRench Tokamak, see entry under TFR below
-
- @ TFTR: Tokamak Fusion Test Reactor; see entry
-
- # Ti: Chemical Symbol for Titanium; if subscript i, Ion Temperature
-
- @ TMX: Tandem Mirror eXperiment; see entry.
-
- @ TMX-U: Tandem Mirror eXperiment-Upgrade; see entry.
-
- @ TORMAC: TORoidal MAgnetic Cusps; see entry
-
- @ TPX: Tokamak Physics Experiment; see entry
-
- @ TRANSP: Princeton's TRANSPort Simulation Code (Tokamak)
-
- @ TW: terawatt; 10^12 watts; see watt.
-
- @ TWyr: terawatt-year; Unit of energy equal to
- 3.15 x10^19 joules or 30 Quads (see entries)
-
- > T-3: A Soviet tokamak located at the Kurchatov Institute
- in Moscow which first proved concept viability, by producing
- a plasma temperature of 10 million degrees centigrage/Kelvin.
- (Result was disbelieved in the West until a British team
- confirmed the results using Thomson scattering.)
-
- > T-10: A later, larger Soviet tokamak, located at the
- Kurchatov Institute (Moscow). (PLT was largely a copy of
- T-10, only PLT had neutral beams, whereas T-10 was (I believe)
- purely ohmic-heated.
-
- > T-11: Another Soviet tokamak (rather small) located at
- the Kurchatov Institute (Moscow); studied neutral-beam heating.
-
- > T-15: (formerly T-10M) Another, much larger Soviet tokamak
- (somewhat smaller than TFTR, but similar size) with superconducting
- magnets, currently (?) under construction. (Was it completed?
- Is it operational?)
-
- > T-20: A huge Soviet tokamak that was designed to operate under
- reactor conditions (net energy production) but which was abandoned
- for budgetary reasons.
-
- > Tandem Mirror Experiment: (TMX) Located at LLNL, this was one of
- the first devices to experiment with placing magnetic mirror
- devices at either end of a (relatively) long cylindrical
- central region. In TMX the plasma was supplied by neutral beams.
-
- > Tandem Mirror Experiment-Upgrade: (TMX-U) Upgrade of TMX
- which was brought on line in 1983. Incorporated rf heating
- systems and improved neutral beam systems. Predecessor to
- MFTF-B (see entry) as a flagship magnetic mirror in the U.S.
-
- > TARA: Medium scale tandem mirror device commissioned at MIT
- in 1984 to develop greater understanding of basic tandem mirror
- physics, with emphasis on microstability properties, thermal
- barrier formation, and RF heating.
-
- * Target Plasma: Plasma used to trap a neutral atom beam. A
- background plasma of sufficiently high density and temperature
- can ionize neutral atoms more effectively than the Lorentz
- process (where v cross B creates effective electric field?).
-
- * Tau: See # tau above.
-
- ! Taylor, J.B.: Renowned plasma physicist; noted for helicity work??
-
- * Taylor State: (John Cobb?)
-
- * Tearing Mode, Tearing Instability: A resistive MHD instability
- which is spatially localized near a rational surface and which
- grows at a rate slower than the MHD Alfven rate, but faster than
- the resistive skin diffusion rate. The instability "tears"
- magnetic field lines and reconnects them into a new state of
- lower magnetic energy. (see other entries for more information
- about the terms used above.)
-
- & Temperature, Kinetic: See Temperature, Plasma, and Kinetic
- Temperature.
-
- * Temperature, Plasma: A measure of the random (thermal) kinetic
- energy of the ions or electrons in the plasma. The temperature
- of each component of a plasma depends on the mean kinetic energy
- of that component. An example of this is the fluorescent light bulb,
- which is an example of a weakly-ionized plasma where the electrons
- are at temperatures of tens of thousands of degrees, whereas the
- ions and neutrals are much cooler (so that you can touch the bulb
- without being burned). See atomic temperature, electron
- temperature, and ion temperature.
-
- $ Tesla - SI unit of magnetic field strength; 1 tesla = 10,000 gauss.
-
- > TEXT-U Device: A medium-size research tokamak at the University
- of Texas, Austin; upgraded version of the TEXT device, with divertor.
-
- > TEXTOR: (Tokamak EXperiment for Technology Oriented Research.
- Medium-sized European tokamak located in Julich, Germany. Research
- objectives involve things like developing plasma-facing components
- and studying effects of plasma-wall interactions.
-
- > TFR: An iron-cored French Tokamak, now retired (I believe).
- Pioneered a number of important tokamak ideas and innovations.
-
- * Thermal Barrier: In magnetic mirror devices, this is a
- depression of electrostatic potential formed by enhancing ion
- loss in the region between the central cell and the positive
- potential plug. The thermal barrier significantly reduces the
- density requirements in the plug and lowers the overall power
- required to sustain the solenoidal plugging by thermally decoupling
- central cell electrons from the end plugs.
-
- & Thermal Conductivity: degree to which a substance transmits heat.
- (basic definition, I believe, is:
- (heat flow) = (thermal conductivity) * (temperature gradient) )
-
- & Thermal Conversion Cycle: Process of generating electrical power
- with a fusion reactor by means of a steam / other gas turbine. This
- is distinct from "direct conversion" cycles.
-
- & Thermal Efficiency: Ratio of the electric power produced by
- a power plant to the original amount of heat produced. This measures
- the efficiency with which the thermal energy is converted to
- electricity.
-
- * Thermal (Slow) Neutron: A neutron in thermal equilibrium with
- its surrounding environment. Thermal neutrons are those that
- have been slowed down by a moderator to speeds characteristic
- of the local temperature. (Compare with fast neutron.)
-
- & Thermodynamic Equilibrium: There is a very general result from
- statistical mechanics which states that, if a system is in
- thermodynamic equilibrium with another (or several other) system(s),
- all processes by which the systems can exchange energy must be
- exactly balanced by their reverse processes, so that there is no
- net exchange of energy. For plasma systems in thermodynamic
- equilibrium, ionization must be balanced by recombination,
- Bremsstrahlung by absorption, and so on. When thermodynamic
- equilibrium exists, the distribution function of particle energies
- and excited energy levels of the atoms can be obtained from the
- Maxwell-Boltzmann distribution (which is a function only of
- the temperature). The Saha equation is a special application of this.
-
- * Thermonuclear Conditions: Achievement of an adequately confined
- plasma, having temperature and density sufficiently high to
- yield significant release of energy from fusion reactions.
-
- * Thermonuclear Fusion: fusion achieved by heating
- up the fuel into the plasma state to the point where
- ions have sufficient energy to fuse.
-
- > Theta Pinch: A fast-pulsed pinch device in which the external
- current imposed goes in the azimuthal/circumferential direction
- (generally in a solenoid) around a cylindrical plasma. Use
- of a fast-rising solenoidal current causes a rapidly increasing
- axial magnetic field, which compresses and heats the plasma.
-
- * Thomson Scattering: Scattering of photons by electrons, in
- the classical (low photon energy) limit. Laser light passed
- through a plasma will experience Thomson scattering; the
- spread of the scattered light in energy provides a very good
- measurement of the electron temperature of the plasma.
-
- > Tokamak: (Acronym created from the Russian words,
- "TOroidalnaya KAmera MAgnitnaya," or "Toroidal Chamber-Magnetic".)
-
- Because the tokamak is the primary 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 stabilizing
- poloidal magnetic field. An externally-applied vertical
- magnetic field is also used to achieve plasma equilibrium.
-
- -> (Contributed by James Crotinger, jac@gandalf.llnl.gov)
- An axisymmetric toroidal confinement device characterized 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.
-
- -> TOKAMAK (tokomak) (contributed by Paul M. Koloc)
- "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 MHD 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)."
-
- -> (from Herman:) "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]. TFTR and JET are tokamaks."
-
- > Tokamak Fusion Test Reactor: Large tokamak at Princeton,
- first machine to use 50-50 mix of D-T fuel, current world's
- record holder in fusion energy production. Largest tokamak
- in the United States.
-
- > Tokamak Physics Experiment: Smaller successor to TFTR at
- Princeton. Engineering design underway; construction
- scheduled to begin in FY 1995.
-
- > Tore Supra: Large tokamak in Cadarache (southern France).
- The second largest tokamak in Europe; largest tokamak using
- superconducting toroidal field magnets. Tore Supra has a
- circular cross-section (like TFTR), which limits the achievable
- confinement time and experimental flexibility. In addition to
- developing superconducting technology, it concentrates on the
- physics of long pulses and ergodic magnetic limiters.
- See also: ergodic; magnetic limiter; superconductor; tokamak.
-
- * Toroidal: in the shape of a torus, or doughnut.
- Or: Coordinate indicating which part of the torus a particle is in.
- (Azimuthal coordinate)
- Or: General term referring to toruses as opposed to other geometries.
- (e.g., tokamaks and stellarators are examples of toroidal devices.)
-
- * Toroidal Field Coils: Coils in a toroidal system, typically
- wound around the torus in a solenoid-like arrangement, used to
- generate the toroidal magnetic field. Each turn completely
- surrounds the plasma.
-
- > TORMAC: (TORoidal MAgnetic Cusps) Hybrid confinement scheme
- operating at high beta. A region of closed toroidal magnetic
- flux with high-beta plasma is separated by a narrow sheath from
- the surrounding field, which contains externally produced
- poloidal components arranged in a toroidal line-cusp configuration.
- Plasma migrating to the outer sheath is temporarily
- mirror-confined before being removed in a divertor system.
-
- > Toroidal Pinch:
-
- & Torque:
-
- > Torsatron: A modification of the stellarator concept, the
- torsatron has a toroidal non-axisymmetric configuration, and
- rotational transform is provided by external coils. Unlike
- a stellarator, however, both toroidal and poloidal fields are
- generated by helical fields alone, with half the number of
- helical conductors required for a stellarator.
-
- & Transformer, Transformer Effect: See entry for Induction.
-
- & Transmittance: Ratio of the radiant power transmitted
- by an object to the incident radiant power. See also reflectivity.
-
- & Transmutation: Transformation of atoms of one element into
- atoms of another element via nuclear reactions. (e.g., the
- transmutation of uranium-238 into plutonium-239 via the absorption
- of a neutron and subsequent beta emission.)
-
- * Transport: Refers to processes which cause heat energy, or
- particles, or something else, to flow out of the plasma and cease
- being confined. Diffusion partly determines the rate of transport.
- See also: diffusion, classical diffusion, neoclassical diffusion,
- anomalous diffusion.
-
- * Transverse Waves: Waves in which the direction of the
- oscillation is perpendicular ("transverse") to the direction
- of the wave propagation. Examples include plucked strings and
- electromagnetic waves in free space/air.
-
- * Trapped-Particle Instability: Slowly-growing class of
- instabilities driven by particles which cannot circulate
- freely in a toroidal system. See also banana orbit.
-
- * Trapped-Particle Modes: See trapped-particle instability
-
- * Triangularity: Geometric factor measuring an aspect of
- the shape (how "triangular" it is) of the cross-section of
- a non-circular plasma in a toroidal device. See also elongation.
-
- & Tritium: A radioactive isotope of hydrogen with one proton and
- two neutrons in its nucleus and one orbiting electron. A more
- efficient fuel than ordinary hydrogen (protium) because of the
- extra neutrons. Tritium decays to helium-3 by emission of an
- electron ("beta emission") with a half-life of 12.3
- years. Tritium can be synthesized from deuterium via neutron
- bombardment, or by fissioning lithium (see lithium).
-
- * Tritium-Breeding Ratio: The amount of tritium generated by
- the breeding blanket of a D-T fusion reactor, divided by the
- amount of tritium burned in the reactor. A tritium breeding
- ration greater than unity is necessary for self-sufficient fueling.
-
- * Triton: nucleus of a tritium atom; tritium ion.
-
- * Troyon Limit: see beta limit
-
- * Turbulence: "Violent macroscopic fluctuations which can develop
- under certain conditions in fluids and plasmas and which usually
- result in the rapid transfer of energy through the medium."
- (PPPL & OSTI Glossaries have same entry)
-
- * Turbulent Heating: Technique of using turbulence induced by
- large electric fields to rapidly heat a plasma.
-
- * Two-Stream Instability: Instability which can develop when a
- stream of particles of one type has a velocity distribution with
- its peak well separated from that of another type of particle
- through which it is flowing. A stream of energetic electrons
- passing through a cold plasma can, for example, excite ion waves
- which will grow rapidly in magnitude at the expense of the kinetic
- energy of the electrons.
-
-
-
-