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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 5/26 (E)
- Supersedes: <fusion-faq/glossary/e_934543711@rtfm.mit.edu>
- Followup-To: sci.physics.fusion
- Date: 11 Nov 1999 12:25:04 GMT
- Organization: Princeton University
- Lines: 429
- Approved: news-answers-request@MIT.EDU
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- Expires: 23 Feb 2000 12:24:17 GMT
- Message-ID: <fusion-faq/glossary/e_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:44253 sci.answers:10850 news.answers:170836
-
- Archive-name: fusion-faq/glossary/e
- Last-modified: 4-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 5: Terms beginning with "E"
-
- 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).
- ==================================================================
-
- EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
-
- # e: symbol for the electron, for the unit electric
- charge (e = 1.6x10^-19 coulombs), and for a Euler's fundamental
- mathematical constant e = 2.71828...
-
- # E: Variable typically used for Energy or Electric Field
- (usually in vector notation in the latter case; which is meant
- is usually clear from context; when both are used in the same place
- the energy is usually represented as U instead of E.)
-
- @ EBT: Elmo Bumpy Torus; see entry
-
- @ EC: European Community; see entry
-
- @ ECDC: Electron Cyclotron Discharge Cleaning; see entry
-
- @ ECE: Electron Cyclotron Emission; see entry
-
- @ ECH: Electron Cyclotron Heating; see entry
-
- @ ECRH: Electron Cyclotron Resonance Heating - same as ECH.
-
- @ EF: Equilibrium (vertical) Field Electromagnet Coil; see vertical field
-
- $ ECU: European Currency Unit
-
- @ ELM: Edge-Localized Mode; see entry
-
- @ EM: Electromagnetic
-
- @ EM Wave: Electromagnetic Wave; see entry
-
- @ EPA: Environmental Protection Agency (U.S.); see entry
-
- @ ERDA: Energy Research and Development Agency; see entry
-
- @ ESECOM: Reactor design study done in the mid 1980s to
- evaluate the Environmental, Safety, and ECOnoMic potential
- of different types of fusion and advanced fission reactors.
-
- @ ESNET: Energy Sciences NETwork; no entry yet
-
- @ ETF: Engineering Test Facility
-
- @ EU: European Union; see entry
-
- @ eV: Electron-volt; see entry
-
- $ Exa: metric prefix for 10^18 or 1,000,000,000,000,000,000
-
- $ Exajoule: unit of energy, 10^18 joules; often used as unit
- of measure for world annual energy use. Comparable in size to
- a Quad (1 EJ = 0.948 Quads); see entry for Quad.
-
- * E-Coil: The plasma current driving (Ohmic Heating) coil
- in a Doublet device (see entry for doublet). Ideally the
- E-coil makes no magnetic field in the confinement system. (?)
-
- * E-Layer: Cylinder of relativistic electrons gyrating in
- a magnetic field, which produce a self-field strong enough
- to dominate the externally applied field and produce a
- field-reversal (where the B field changes sign) in the
- system. See Field-Reversed Configuration, Field-Reversed Pinch.
-
- * Echoes: Wave packets (pulses) which have been reflected
- or otherwise returned to the detector, which are sufficiently
- delayed and retain sufficient magnitude so that they are
- perceived as a signal distinct from the one transmitted
- directly. (In other words, just like sound echoes, only
- for analogous phenomena with other waves.)
-
- * Eddy Current: Electric current induced inside a conductor
- when the conductor (a) moves through a nonuniform magnetic
- field, or (b) experiences a change in the magnetic flux
- through its surface.
-
- * Eddy-Current Loss: Energy loss due to eddy currents
- circulating in a resistive material.
-
- * Edge Localized Mode: (ELM) Mode found often in H-mode plasmas.
- This is a temporary relaxation of the very high edge gradients
- found in H-modes. It may be a relaxation back to the L-mode.
- (Borrowed from a posting by Paul Stek)
-
- * Edge Plasma: Cooler, less dense plasma away from the center
- of a reactor; affected by limiter or divertor, includes
- scrape-off layer. Distinguished from core plasma. See entries
- for relevant terms used.
-
- * Edge-Localized Mode: (info from Paul Stek) Found often in
- H-mode plasmas, this is a temporary relaxation of the very high
- edge gradients found in H-modes. It may be a relaxation back
- to the L-mode.
-
- * Effective Collision Cross-section: (See collision cross section)
-
- * Effective Collision Radius: Effective size of a particle
- equal to the square root of (cross section/pi). Determines the
- effective range of interaction of the particle.
-
- * Effective Half-Life: Time required for a radioactive substance
- contained in a biological system (such as a person or an animal)
- to reduce its radioactivity by half, as a combination result
- of radioactive decay and biological elimination from the system.
-
- & Eigenfrequency: One of the characteristic frequencies at
- which an oscillatory system can vibrate.
-
- & Eigenfunction: Function describing an eigenstate of a
- system.
-
- & Eigenstate: One of the characteristic states of an
- oscillatory system, such that the system does not leave the
- state unless disturbed. (?)
-
- & Eigenvector: Same thing as an eigenfunction, only from the
- perspective that the eigenfunction is a "vector" in an
- appropriate mathematical vectorspace.
-
- * Eikonal Equation: An equation for propagation of electromagnetic
- or acoustic waves in an inhomogenous medium; valid only when the
- scale length for variation in the properties of the medium is
- small compared to a wavelength. (Similar in character to WKB?)
-
- & Elastic: Term used to describe a process in which kinetic energy
- is conserved; usually refers to (elastic) collisions or (elastic)
- scattering.
-
- & Electric Charge: See charge, electrical.
-
- & Electric Field: A property of a patch of space which causes
- the acceleration of electric charges located at that patch of
- space. The acceleration is given by a = qE/m, where q is the
- charge, E the electric field vector, and m the mass of the
- particle.
-
- % Electric Power Research Institute: (EPRI) Research organization
- funded by the electric power utilities to study, well, electric
- power.
-
- * Electric Probe: See Langmuir Probe.
-
- & Electrical Conductivity: Degree to which a substance conducts
- electric current. Can be defined by:
- (current density) = (conductivity) * (applied electric field)
- Electrons and ions both contribute to current in proportion to
- their mobility in the system. In a plasma with a magnetic field,
- there is no longer a one-to-one correspondence between current
- and electric field. Instead, the current in each direction can
- be due to combinations of the electric fields in all the other
- directions. In this case, the current density and the
- electric field are vectors, and the conductivity becomes a
- tensor (matrix) which relates them.
-
- * Electromagnetic Coupling: A means of extracting energy from a
- magnetically confined plasma, where the plasma expands and pushes
- on the confining magnetic field, causing electrical energy to
- be generated in the external field-generating circuits.
-
- & Electromagnetic Force:
-
- * Electromagnetic Radiation: Radiation (such as radio waves,
- microwaves, infrared, visible light, ultraviolet, x-rays, and
- gamma rays) which consists of associated, interacting electric
- and magnetic field waves which travel at the speed of light
- (because electromagnetic radiation *is* light, except for the
- variation in frequencies!). All forms of electromagnetic
- radiation can be transmitted through vacuum. Electromagnetic
- waves in plasmas are generally more complex in their behavior,
- depending on their frequency.
-
- & Electromagnetic Wave: Wave characterized by combined oscillations
- of both electric and magnetic fields. The particle equivalent
- is the photon. There is a whole spectrum of electromagnetic
- waves where the classes are distinguished by energy (or,
- equivalently, wavelength or frequency); the spectrum of
- electromagnetic waves includes radio waves, microwaves,
- infrared light, visible light, ultraviolet light, x-rays, and
- gamma rays.
-
- & Electron: Elementary particle with a negative electric
- charge. Electrons orbit around the positively charged nucleus
- in an atom. The charge on an electron is -1.6x10^-19 coulombs;
- the electron has a mass of 9.11 x 10^-31 kg (about 1/1837
- times that of a proton.) The configuration of electrons around
- an atom determines its chemical properties. The positron
- is the antiparticle to the electron, and is identical except
- for having a positive charge.
-
- > Electron Beam Fusion Accelerator: See PBFA (Particle Beam
- Fusion Accelerator)
-
- * Electron Capture: Nuclear decay process whereby a proton in
- the nucleus absorbs an orbiting electron and converts to a
- neutron.
-
- * Electron Cyclotron Discharge Cleaning: (ECDC) Using relatively
- low power microwaves (at the electron cyclotron frequency) to
- create a weakly ionized, essentially unconfined hydrogen plasma
- in the vacuum chamber. The ions react with impurities on the
- walls of the tokamak and help remove them from the chamber. For
- instance, Alcator C-mod typically applies ECDC for a few days
- prior to beginning a campaign, and a few hours before each day's run.
-
- * Electron Cyclotron Emission: (ECE) As electrons gyrate around in
- a magnetic field (see also larmor radius or cyclotron radius),
- they radiate radio-frequency electromagnetic waves. This is
- known as electron cyclotron emission, and can be measured to
- help diagnose a plasma.
-
- * Electron Cyclotron Heating: (ECH or ECRH) Radiofrequency
- (RF) heating scheme that works by injecting electromagnetic (EM)
- wave energy at the electron cyclotron gyration frequency.
- The electric field of the EM wave at this frequency looks to
- a gyrating electron like a static electric field, and it
- causes acceleration of the electron. The accelerated
- electron gains energy, which is then shared with other particles
- through collisions, resulting in heating.
-
- * Electron Cyclotron Wave: Radiofrequency waves at the
- electron cyclotron frequency. See also Whistler.
-
- * Electron Density: Number of electrons in a unit volume.
- See density for more info.
-
- * Electron Temperature: The temperature corresponding to
- the mean kinetic energy of the free electrons in a
- plasma.
-
- $ Electron-volt: 1 eV = 1.6 x 10^-12 erg, or 1.6 x 10^-19 Joules.
- This is a unit of kinetic energy equal to that of an electron
- having a velocity of 5.93 x 10^5 m/sec. This is the energy
- an electron (or other particle of charge=1 such as a proton),
- gains as it is accelerated through a potential difference
- of 1 volt. In plasma physics the eV is used as a unit of
- temperature; when the mean particle energy is 1eV, the
- temperature of the plasma is roughly 11,700 Kelvin.
-
- * Electrostatic Analyzer: A device which filters an
- electrn beam (band-pass), permitting only electrons within
- a narrow energy (velocity) range to pass.
-
- > Electrostatic Confinement: An approach to fusion based on
- confining charged particles by means of electric fields, rather
- than the magnetic fields used in magnetic confinement. See
- discussion in Section 4 for more information.
-
- * Electrostatic Waves: Longitudinal oscillations appearing in a
- plasma due to a perturbation of electric neutrality. For a cold
- unmagnetized plasma, or at large wavelengths, the frequency of
- these waves is by definition the plasma frequency.
-
- & Element: One of the fundamental chemical substances which
- cannot be divided into simpler substances by chemical means.
- Atoms with the same atomic number (# of protons) all belong
- to the same element. (e.g., hydrogen, helium, oxygen, lead)
- (list and perhaps periodic table in
- appendix? isotope table with half-lives and decay modes
- might also be useful.)
-
- & Elementary Particles worth knowing about:
- (at the nuclear-energy level)
- electron & positron - seem to be stable
- proton - thought to be stable, life > 10^30 sec
- neutron - decays in ?10 min unless it's in a nucleus, which often
- extends its life.
- other particles important for nuclear energy:
- muon, neutrino (m,e,tau),
- photon
- muonic atoms
- pi-meson
- antiparticles
- this part is new - maybe separate entries with listing
- here??
-
- > Elmo Bumpy Torus: Bumpy Torus at ORNL; no longer operating.
- See Bumpy Torus, ORNL.
-
- * Elongation: parameter indicating the degree to which the cross
- section of a toroidal plasma is non-circular. kappa=b/a, where "b"
- and "a" are the vertical and horizontal minor radii. As kappa is
- increased, the confinement in relation to the total current improves,
- but the plasma also becomes more and more unstable to vertical
- displacements. A circular plasma has kappa of 1, a common value for
- elongated plasmas is 1.7, and the absolute limit is probably
- around 2.
-
- & Energy: Typically defined as "the ability to do work". Power
- is the rate at which work is done, or the rate at which energy
- is changed. "Work" characterizes the degree to which the properties
- of a substance are transformed. Energy exists in many forms,
- which can be converted from one to another in various ways.
- Examples include: gravitational energy, electrical energy,
- magnetic and electric field energy, atomic binding energy (a form
- of electrical energy really), nuclear binding energy, chemical
- energy (another form of electrical energy), kinetic energy (energy
- due to motion), thermal energy ("heat"; a form of kinetic energy
- where the motion is due to thermal vibrations/motions), and so on.
-
- * Energy Balance: Comparison of energy put into a plasma with the
- energy dissipated by the system; related to energy confinement.
-
- * Energy Confinement Time: See energy loss time.
-
- * Energy Loss Time: Characteristic time in which 1/e (or sometimes
- 1/2) of a system's energy is lost to its surroundings. In a plasma
- device, the energy loss time (or the energy confinement time) is
- one of three critical parameters determining whether enough
- fusion will occur. (See Lawson criterion)
-
- * Energy Replacement Time: Time required for a plasma to lose
- (via radiation or other loss mechanisms) an amount of energy
- equal to its average kinetic energy.
-
- % Energy Research and Development Agency (ERDA): US Agency created
- by splitting of the AEC into ERDA and NRC in about 1975, charged
- with managing US energy R&D (???). Merged with ??? to become the
- Department of Energy in about 1977. (???? correct? help??)
-
- * Entropy Trapping: The process of trapping an ordered beam of
- particles in a magnetic field configuration (e.g., cusp geometry)
- by randomizing the ordered motion of the particles, with
- corresponding increase in the entropy of the system.
-
- % Environmental Protection Agency: Agency within the executive
- branch of the U.S. government (under the Department of the Interior?
- Independent?) charged with, well, protection of the environment.
- Activities include research, regulatory, and cleanup functions.
- (Any government people reading this who could help me out?)
-
- * Equations of Motion: Set of equations describing the time
- evolution of the variables which describe the state of a
- physical system.
-
- * Equilibrium: [ acknowledgements to John Cobb ] An equilibrium is
- a state of a system where the critical parameters do not change
- significantly, within a given time frame. In the case when this time
- frame is infinite, It is called a Thermodynamic equilibrium. There
- are many cases where a plasma equilibrium is constant on some fast
- time scale, but changes over some slower time scale. For example, an
- IDEAL MHD equilibrium is constant over fluid time scales
- (microseconds to milliseconds), but it will evolve on the slower
- resistive or viscous time scales (milliseconds to seconds). All
- terrestial plasmas are NOT in thermodynamic equilibrium, but they may
- be constant over very long time periods.
-
- An equilibrium is unstable when a small change in a critical
- parameter leads the state of the system to diverge from the
- equilibrium. An equilibrium is stable when a small change in a
- critical parameter leads to a "restoring force" which tends to
- return the system to equilibrium.
-
-
- * Equilibrium Field: See Vertical Field
-
- $ Erg / ergs: CGS unit for energy. 1E7 ergs = 1 joule.
-
- * Ergodic: A mathematical term meaning "space-filling". If a
- magnetic field is ergodic, any field line will eventually pass
- arbitrarily close to any point in space. Closely related to
- "chaotic".
-
- * Ergodic Regime: In this regime, a given magnetic field
- line will cover every single point on a magnetic surface
- (see magnetic surface or flux surface) if the rotational
- transform (or q) is not rational.
-
- * ESECOM: Reactor design study done in the mid 1980s to
- evaluate the Environmental, Safety, and ECOnoMic potential
- of different types of fusion and advanced fission reactors.
-
- * Eulerian Coordinates: Coordinates which are fixed in
- an inertial reference frame.
-
- % European Community: see European Union
-
- % European Union: (from Herman) Organization of European
- countries (formerly European Community, EC, formerly European
- Economic Community, EEC) established in 1967 to coordinate policies
- on the economy, energy, agriculture, and other matters. The original
- member countries were France, Belgium, West Germany, Italy,
- Luxembourg, and the Netherlands. Joining later were Denmark,
- Ireland, the United Kingdom, Greece, Spain, and Portugal. Other
- countries are in the process of joining now.
-
- % Euratom: European Atomic Energy Community. International
- organization established in 1958 by members of the European
- Economic Community for the purpose of providing joint
- funding and management of the scientific research of the
- member countries - initially Belgium, France, Italy,
- Holland, and West Germany.
-
- * Excitation Radiation: Line radiation (at characteristic
- frequencies / wavelengths) as a result of the excitation
- of excited states, and the subsequent de-excitation of
- these states by radiative transitions.
-
-
-
-