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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 1/26 (A)
- Supersedes: <fusion-faq/glossary/a_934543711@rtfm.mit.edu>
- Followup-To: sci.physics.fusion
- Date: 11 Nov 1999 12:24:46 GMT
- Organization: Princeton University
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- Expires: 23 Feb 2000 12:24:17 GMT
- Message-ID: <fusion-faq/glossary/a_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 FUT 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 FUT does NOT
- discuss unconventional forms of fusion (like Cold Fusion).
- X-Last-Updated: 1995/02/05
- Originator: faqserv@penguin-lust.MIT.EDU
- Xref: senator-bedfellow.mit.edu sci.physics.fusion:44249 sci.answers:10846 news.answers:170832
-
- Archive-name: fusion-faq/glossary/a
- Last-modified: 4-Feb-1995
- Posting-frequency: More-or-less-monthly
- 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 1: Terms beginning with "A"
-
- FREQUENTLY USED TERMS IN CONVENTIONAL FUSION RESEARCH
- AND PLASMA PHYSICS
-
- Edited by Robert F. Heeter, rfheeter@pppl.gov
-
- Guide to Categories:
-
- * = vocabulary specific to plasma/fusion/energy research
- & = basic/general 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).
- ==================================================================
-
- AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
-
- # A: symbol used to indicate either area or magnetic
- vector potential.
-
- $ A: abbreviation for Amperes; see entry.
-
- @ AAPT: American Assocation of Physics Teachers; see entry
-
- @ AC: Alternating Current; see entry.
-
- @ ACT-I: Advanced Concepts Torus I; see entry.
-
- @ AEC: (US) Atomic Energy Commission; see entry
-
- @ AIC: Alfven Ion Cyclotron Instability; see entry
-
- @ AIP: American Institute of Physics; see entry
-
- @ AJP: American Journal of Physics; see entry
-
- @ ALEX: (see entry "ALEX" below)
-
- @ AMBAL: (see entry "AMBAL" below)
-
- @ ANL: Argonne National Laboratory; see entry
-
- @ ANS: American Nuclear Society; see entry
-
- @ APS: American Physical Society; see entry
-
- @ APS-DPP: American Physical Society - Division of Plasma
- Physics; see entry.
-
- # Ar: Chemical symbol for the element Argon
-
- @ ARIES: Advanced Reactor Innovative Engineering Study (?)
- See Entry under ARIES
-
- @ ASDEX: Axially Symmetric Divertor EXperiment; see entry
-
- @ ASDEX-U: ASDEX-Upgrade; see entry for ASDEX.
-
- @ ASME: American Society of Mechanical Engineers
-
- @ ATF: Advanced Toroidal Facility; see entry.
-
- * Absolute Instabilities: A class of plasma instabilities
- growing exponentially with time at a point in space, in
- contrast to convective instabilities (see entry).
-
- * Absorption: In plasma physics, the loss of (electromagnetic)
- energy to a medium. For instance, an electromagnetic wave
- which propagates through a plasma will set the electrons
- into motion. If the electrons make collisions with other
- particles, they will absorb net energy from the wave.
-
- * Absorption Coefficient: Measures the degree of wave
- absorption (see Absorption above); defined as the fraction
- of wave energy lost as the wave travels a unit distance.
-
- & Activation: Activation occurs when a particle interacts
- with an atomic nucleus, shifting the nucleus into an
- unstable state, and causing it to become radioactive.
- In fusion research, where deuterium-tritium is a common
- fuel mixture, the neutron released when (D + T) combine
- to form (4He + n) can activate the reactor structure.
- Sometimes called "radioactivation." See also activation
- product, activation analysis.
-
- & Activation Analysis: Method for identifying and measuring
- chemical elements in a sample of material. Sample is first
- made radioactive by bombardment with neutrons, charged
- particles, or gamma rays. Newly formed radioactive atoms
- in the sample then give off characteristic radiations
- (such as gamma rays) that tell what kinds of atoms are
- present, and how many.
-
- * Activation Product: The unstable nucleus formed when
- activation occurs. (See activation above.)
-
- & Adiabatic: Not involving an exchange of heat between the
- system said to be adiabatic and the rest of the universe.
-
- & Adiabatic Compression: Compression (of a gas, plasma, etc.)
- not accompanied by gain or loss of heat from outside the system.
- For a plasma in a magnetic field, a compression slow enough that
- the magnetic moment (and other adiabatic invariants - see entry)
- of the plasma particles may be taken as constant.
-
- * Adiabatic Invariant: Characteristic parameters which do not
- change as a physical system slowly evolves; the most commonly
- used one in plasma physics is the magnetic moment of a charged
- particle spiraling around a magnetic field line.
-
- * Aftercooling: Cooling of a reactor after it has been
- shut down.
-
- * Afterglow: Recombination radiation emitted from a cooling
- plasma when the source of ionization (heating, etc) is removed.
- (See entry for recombination radiation.)
-
- * Advanced Fuels: There are several elements/isotopes which
- could be fused together, besides the DT fuel mixture. Many such
- fuel combinations would have various advantages over DT, but
- it is generally more difficult to achieve fusion with these
- advanced fuels than with the DT mix. See fuels section of FAQ
- for discussion.
-
- > Advanced Concepts Torus I: (ACT-I) A steady-state toroidal
- device built primarily for studies of RF heating (see entry)
- and RF current drive (see entry). Operated at PPPL but shut
- down several years ago.
-
- > Advanced Toroidal Facility: (ATF) A large stellarator device
- developed at Oak Ridge National Lab (ORNL), but recently mothballed.
- See Section 5 for more information.
-
- > Alcator: Name given to a set of tokamaks designed and built at MIT;
- these machines are distinguished by high magnetic fields with
- relatively small diameters. The high magnetic field helps create
- plasmas with relatively high current and particle densities.
- The current incarnation is Alcator C-mod, and is described further
- in Section 5. Alcator C was donated to LLNL for use as the
- Microwave Tokamak eXperiment (MTX), now shut down.
-
- > Alcator A: First of the Alcator series of tokamaks at MIT;
- was operational from 1969 to 1982.
-
- > Alcator C: Commissioned in 1978; used extensively to study
- plasma confinement under strong ohmic heating (see entries).
- Also studied high-density plasmas and used frozen fuel pellet
- injection. Set record values of Lawson product (density
- times confinement time; see entries) of 8 x 10^19 m^3-seconds.
- Was donated to Livermore (LLNL; see entry) for use as the
- Microwave Tokamak eXperiment (MTX: see entry), now shut down.
-
- > Alcator C-mod: Successor to Alcator C; actually a completely
- new device. Currently operational; described in more detail in
- Section 5.
-
- > Alcator DCT: Proposed fully-superconducting extension of
- the Alcator series; never built.
-
- * Alcator Scaling: A proposed empirical law in which the
- energy confinement time is proportional to the product
- of the average density and the square of the plasma radius
- (see relevant entries).
-
- > ALEX: A single-cell, minimum-B magnetic mirror system
- (see entries) in which the magnetic field was generated by a
- baseball coil (see entry) wound on a 60 cm sphere. Formerly
- operated at the Rensselaer Polytechnic Institute, Troy, New York.
-
- * Alfven Ion Cyclotron instability: (AIC) An electromagnetic
- microinstability near the ion cyclotron frequency; driven by
- the ion loss cone in a mirror device. (See relevant entries.)
-
- * Alfven velocity: Phase velocity of the Alfven wave;
- equal to the speed of light divided by the square root
- of (1 plus the ratio of the plasma frequency to the cyclotron
- frequency for a given species). i.e.,
-
- Va = c / SQRT(1 + plasma freq. / cyclotron freq.)
-
- (As defined in Stix, _Waves in Plasmas_, 2nd ed. 1992, p. 31)
-
- * Alfven waves: Transverse electromagnetic waves that are
- propagated along lines of magnetic force in a plasma. The waves
- have frequency significantly less than the ion cyclotron frequency,
- and are characterized by the fact that the field lines oscillate
- (wiggle) with the plasma. The propagation velocity depends on the
- particle density and the strength of the magnetic field. "[Relatively]
- Low frequency ion oscillation in the presence of an equilibrium
- magnetic field. Also called the transverse hydromagnetic wave along Bo.
- The torsional Alfven wave in cylindrical geometry was first measured
- in liquid mercury by B. Lehnert. Alfven waves were first generated
- and detected in plasma by Allen, Baker, Pyle, and Wilcox in Berkeley
- and by Jephcott in England in 1959." (quoting from Chen's book;
- see bibliography) - Albert Chou
-
- ! Alfven, Hannes Olof: Nobel Prize-Winning Plasma Physicist
- and Astronomer who first suggested the possibility of MHD waves
- in 1942.
-
- * Alpha Channeling: Term for an idea (so far theoretical)
- in magnetic confinement fusion; the idea is that plasma
- waves can be used to control the alpha particles produced
- in a fusion reactor, to transfer their energy directly to fuel
- ions, and to help push them out of the plasma. This could
- potentially help to substantially improve the power output
- capabilities of fusion plasmas.
-
- * Alpha emission: Form of nuclear decay where the nucleus
- emits an alpha particle (see entry below).
-
- * Alpha particle: The nucleus of a Helium-4 atom; is a
- typical product of fusion reactions; also released
- in various nuclear decay processes. Alpha particles readily
- grab electrons from other sources, becoming neutral helium;
- even energetic alpha particles are easily stopped by thin
- barriers (sheets of paper, dead layers of skin, etc.), so that
- as a radiological hazard alpha particles are only dangerous if
- they are generated inside one's body (where the skin cannot
- protect tissue from damage). Alpha particles are common
- products in fusion reactions between light elements.
-
- & Alternating Current: (AC) Electrical Current (see entry) which
- alternates in direction with time. (For instance, household
- electric current is AC alternating at 60 oscillations/sec
- (60 Hertz) in the United States, and 50 Hertz in many other
- countries.)
-
- > AMBAL: An ambipolar trap (tandem mirror) located at
- Novosibirsk in Russia. (Any additional information would
- be welcome.)
-
- * Ambipolar Diffusion: Diffusion process in which buildup
- of spatial charge creates electric fields which cause
- electrons and ions to leave the plasma at the same rate.
- (Such electric fields are self-generated by the plasma
- and act to preserve charge neutrality.)
-
- % American Association for the Advancement of Science: (AAAS)
- Organization dedicated to promoting science research and
- education in the United States. Publishers of _Science_.
-
- % American Association of Physics Teachers: (AAPT) Professional
- society of physics teachers in the United States. Organizes
- conferences on physics education. Publishers of _American
- Journal of Physics_ (AJP)
-
- % American Institute of Physics: (AIP) Organization dedicated
- to promoting physics research and the dissemination of physics
- knowledge; publishers of many physics books.
-
- % American Nuclear Society: (ANS) Professional society of nuclear
- scientists in the United States.
-
- % American Physical Society: (APS) Professional society of physicists
- in the United States. Organizes major conferences and publishes
- many peer-reviewed journals.
-
- % American Physical Society - Division of Plasma Physics: (APS-DPP)
- Branch of the APS for plasma physicists, including fusion scientists.
- The Annual Meeting of the APS-DPP is the largest plasma physics
- conference in the United States.
-
- $ Ampere, kiloampere, megampere: (from Herman) The standard
- unit for measuring the strength of an electric current
- representing a flow of one coulomb of electricity per second.
- 1 kiloampere = 1000 amperes; 1 megampere = 1,000,000 amperes.
- Common abbreviations: A, amps, kiloamps, megamps, kA, MA
-
- ! Ampere, Andre-Marie (1775-1836): French physicist responsible
- for much of what is known about the fundamentals of electromagnetism.
-
- & Ampere's Law: General equation in electromagnetism relating
- the magnetic field and the currents generating it.
-
- * Aneutronic Fuels: Advanced fusion fuels which would not
- produce fusion neutrons. See fuels section of FAQ for discussion.
-
- $ Angstrom: A unit of distance equal to 10^-10 meters or 10^-8 cm.
-
- & Angular Momentum: Momentum involved in the rotation of a body
- about an axis; conserved like ordinary momentum (see momentum).
- Angular momentum is defined as the cross product of ordinary momentum
- with the position vector running from the axis of rotation to the
- body whose angular momentum is being determined. Torque is the
- rate of change of angular momentum with time. (see also torque)
-
- & Anisotropy: Term used to describe a medium whose characteristic
- properties vary in with direction of travel through the medium.
- (e.g., velocity of light transmission, conductivity of heat or
- electric current, compressibility, etc.)
-
- * Anomalous Diffusion: Diffusion in most plasma devices,
- particularly tokamaks, is higher than what one would predict from
- understood causes. The observed, "typical" diffusion is referred to
- as "anomalous" because it has not yet been explained. Anomalous
- diffusion includes all diffusion which is not due to collisions
- and geometric effects. While such effects were not understood
- when the term was coined, and most still aren't, diffusion due
- to well-understood wave phenomena is still 'anomalous'. "Classical"
- diffusion and "Neo-classical" diffusion are the two well-understood
- diffusion theories, neither is adequate to fully explain the observed
- "anomalous" diffusion. See also: entries for classical and
- neoclassical diffusion. (Acknowledgements to Philip Snyder)
-
- * Antares: Laser-target irradiation system (i.e., laser fusion
- research device) at Los Alamos National Lab; was operational in
- 1982. (The author would welcome current information.)
-
- & Aperture: The opening in an optical system which restricts the
- size of the bundle of rays incident on a given surface. (Usually
- circular and specified by diameter.)
-
- * Applied-B Diode: An ion diode with an applied magnetic field
- to prevent electrons flowing from cathode to anode. The applied
- magnetic field also regularizes the electron swarm to reduce
- beam divergence.
-
- * Arc: A type of electrical discharge between two electrodes;
- characterized by high current density. Similar in meaning
- to "spark" in common language.
-
- % Argonne National Laboratory: One of the U.S. Department of Energy
- basic-research Laboratories, located in Illinois... (need more info!)
-
- > Argus: Two-beam, 5-terawatt Nd-glass laser system used at Livermore
- (LLNL) for inertial-confinement fusion research from 1976 to 1981.
-
- * ARIES: Set of four fusion reactor design studies which investigated
- the safety, economic, and environmental implications of various
- advances in fusion reactor science and technology.
-
- * Ash: Fusion reaction products trapped in a plasma. Ash is
- bad because (a) it generally radiates more strongly than the fuel
- ions, and thus reduces energy confinement, and (b) it creates
- additional plasma pressure and/or reduces pressure available for fuel
- ions. (due to beta limits, see beta) Controlling ash is a major
- area of fusion research. Ideally one would be able to extract
- the ash ions after diverting an appropriate fraction of their
- energy to heating the fuel ions, and then convert the remaining ash
- energy to electricity. Current research involves using RF waves to
- transfer energy from ash ions to fuel ions, and to push the ash into
- the scrape-off layer, where it can be collected via divertors.
- (See also scrape-off layer, divertors)
-
- * Ash control - see ash, divertors.
-
- * Ash removal - see ash, divertors.
-
- * Aspect Ratio: In toroidal geometry, the ratio of
- the major diameter (total width of the torus) to the
- minor diameter (width of a slice taken through one side
- of the ring). (This would be much better with a picture!)
-
- In inertial-confinement fusion, aspect ratio refers to
- the ratio of a fuel pellet's radius to its wall thickness.
-
- & Atom: (from Herman) The smallest unit of an element that
- retains the characteristics of that element. At the center
- of the atom is the nucleus, made up of neutrons and protons,
- around which the electrons orbit. Atoms of ordinary hydrogen,
- the lightest element, consists of a nucleus of one proton
- orbited by one electron. (Note: distinct from a molecule,
- which is the smallest unit of a substance which retains the
- characteristics of that substance. It takes far less
- energy to break apart a stable molecule into its constituent
- atoms than to divide a stable atom into two smaller atoms.)
- Note that in solids, atoms are typically two angstroms
- (2 x 10^-10 meters) apart; in air the gas molecules are about
- 30 angstroms apart. A drop of water has on the order
- of 10^21 atoms in it. Atoms are generally electrical neutral;
- when an atom acquires an electrical charge (by gaining or
- losing electrons) it is usually called an ion.
-
- & Atomic Bomb, A-Bomb: (from Herman) A weapon with a large
- explosive power due to the sudden release of energy when the
- nuclei of heavy atoms such as plutonium-239 or uranium-235
- are split. This fission is brought about by the bombardment
- of the fuel with neutrons, setting off a chain reaction.
- The bomb releases shock, blast, heat, light, and lethal
- radiation. The world's first atomic bomb was successfully
- tested by the United States on July 16, 1945.
-
- % Atomic Energy Commission: United States governmental
- authority for atomic energy; split into ERDA and NRC in 1975.
- (may not be 100% correct)
-
- & Atomic Mass: Mass of an atom relative to 1/12th the mass
- of a carbon atom. Approximately equal to the sum of the
- number of protons and neutrons in the nucleus of the atom.
-
- & Atomic Number (Z): The number of protons in a nucleus; same
- as the number of electrons in a neutral atom; determines the
- position of an element in the periodic table, and hence its
- chemical properties (see also isotope).
-
- * Atomic Temperature: The temperature corresponding to the mean
- kinetic energy of the neutral atoms in a plasma. (If there were
- no ions or electrons, the atomic temperature would be what we
- normally think of as the temperature of a gas, such as the air.)
-
- * Auger effect: Transition of an electron in an atom from a
- discrete electronic level to an ionized continuous
- level with the same energy; also known as autoionization.
-
- & Avogadro's number: N = 6.02497 x 10^23. Number of particles
- in a mole of a substance. Coefficient relating Boltzmann's
- constant to the ideal gas constant. This is the number of
- atoms per gram-atom. See also: mole
-
- > Axially Symmetric Divertor EXperiment (from Herman)
- (ASDEX, Asdex: Garching, Germany) A large tokamak designed
- for the study of impurities and their control by a magnetic
- divertor. The H mode or high mode of operation with neutral
- beam injection was first observed on ASDEX.
-
- > Axially Symmetric Divertor EXperiment (ASDEX, Asdex): "The original
- ASDEX, located in Garching, Germany and decommisioned in 1990(?),
- would qualify today as a medium-sized tokamak. It was designed for
- the study of impurities and their control by a magnetic divertor.
- The H mode or high mode of operation with neutral beam injection was
- first observed on ASDEX. Its successor ASDEX-Upgrade (a completely
- new machine, not really an "upgrade") is larger and more flexible.
- It is the first tokamak whose toroidal and poloidal field coils are
- not linked, which will be a necessary design factor in a reactor.
- It will achieve parameters at the edge which are very similar to
- those needed for a power reactor." - Arthur Carlson
-
- * Azimuth: An angle measured clockwise relative to some
- reference point on a circle (e.g., "south" or "north").
-
- * Azimuthal: Generally an angle, measured "around" an object.
- In spherical geometries, the angle which is *not* the "polar angle".
- On the earth, one incarnation of the azimuthal angle is the longitude
- of a location relative to the prime meridian through Greenwich,
- England. In toroidal geometries, the longitude idea still applies,
- but the other angle is the "poloidal" angle, not the "polar" angle.
- The azimuthal direction is the "long way" around a torus.
- See also: poloidal.
-
-
-
-