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Archive-name: fusion-faq/glossary/c
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!!!). See reader questions & answers on this topic! - Help others by sharing your knowledge
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Glossary Part 3: Terms beginning with "C"
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).
==================================================================
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
# c: Speed of light; 3.0x10E+8 meters/second or 3.0x10E+10 cm/sec
@ CAMAC: Computer Automated Measurement and Control
@ CANDU: CAnadian Deuterium-Uranium class of fission reactor;
see entry
> CASCADE: See entry (not an acronym as far as I know).
@ CCD: Charge Coupled Device
@ CGS: Centimeters, Grams, Seconds; see CGS Units
@ CGS Units: see entry below; see also CGS above.
@ CFFTP: Canadian Fusion Fuels Technology Project; see entry.
@ CIT: Compact Ignition Tokamak; see entry
@ COE: Cost of Electricity
@ CT: Compact Torus; see entry
@ CTX Facility: Compact Toroid Experimental facility; see entry.
@ cw: Continuous Wave (distinct from pulsed).
@ CY: Calendar Year (as opposed to Fiscal Year, FY)
$ cm: centimeters; unit of distance. See also centi-
* C-Coil: C-shaped magnet coil
* Calorimeter: In conventional fusion research, this name
refers to any device used to measure power or energy in
a laser or particle beam. (e.g., for ICF or neutral beam
heating or a magnetically-confined plasma.)
* Canadian Deuterium-Uranium Fission Reactor: Nuclear fission
reactor type developed in, and prominent in, Canada; characterized
by use of heavy water (deuterium instead of hydrogen, D2O) as
moderator and coolant. Neutrons absorbed by the deuterium create
a source of marketable tritium.
* Canadian Fusion Fuels Technology Project: Fusion power
development project, jointly funded by the National Research
Council of Canada, the Province of Ontario, and Ontario
Hydro (energy company and project manager), to develop
and internationally apply technologies related to management
of fusion fuels. (Any current info, anyone?)
& Carbon: (C) Sixth element (Z=5) in the periodic table; has
6 protons; often described as the basis of life on earth because
of its chemical properties; has potential for use with silicon
as a low-activation structural material for fusion reactors,
in the form silicon carbide. (See relevant parts of FAQ
section 2.) Also useful as a neutron moderator. See also
low-activation materials.
& Carnot Efficiency: maximum possible efficiency for conversion
of thermal energy to useful work (such as electrical energy),
as determined by the laws of thermodynamics. The Carnot efficiency
(eta) for conversion of thermal to electric energy (e.g., the upper
limit on efficiency of a steam turbine) is given by
(eta) = [ (T-hot) - (T-cold) ] / (T-hot). That is, one gets the
efficiency from the values of the input and output temperatures
(measured in Kelvin).
& Capacitor: device used to store electrical energy by accumulating
charges on nearby conductors. Energy may be stored and withdrawn
at varying rates. Used in short-pulse plasma devices where only
a moderate amount of energy is needed.
* Capacity Factor: Index (typically in percent) indicating the
average power supplied by an energy plant, relative to its
maximum rated capacity.
* Capital: Economic term for wealth of a permanent nature, rather
than that which is consumed; includes money and other financial
goods, plant & equipment, etc. (I'm not an economist - anyone
know any better?)
> CASCADE: An inertial-fusion energy conversion concept where
a flowing, replenished layer of ceramic granules (in a rotating
chamber) protects the chamber wall from the fusion environment
while absorbing neutrons, breeding tritium fuel, and serving as
the high-temperature heat exchange fluid.
& Celsius: Temperature scale where zero degrees corresponds to the
freezing point of water (32 Fahrenheit) and 100 degrees corresponds
to the boiling point (212 Fahrenheit). Zero celsius = 273.16 Kelvin.
* Centering Force: Term for the mutual attraction
between the parallel currents in the inboard leg of the toroidal
field coils in a toroidal magnetic fusion system (e.g., a tokamak).
The portion of the coil running "through the doughnut hole" is
attracted towards the center of the hole.
& Centi-: metric prefix indicating 1/100th of a given unit.
e.g., one centimeter is 1/100th of a meter.
& Centigrade: see Celsius
& CGS Units: System of measurement where the fundamental units
are centimeters, grams, and seconds.
& Chain Reaction: (from Herman) A self-sustaining series of
chemical or nuclear reactions in which the products of the
reaction contribute directly to the propagation of the process.
* Channel Transport: In inertial fusion research using light
ion drivers, describes the use of current-carrying plasma
channels (which are magnetically confined to the channel) to
transport electron or ion beams between the ion diode and the
fusion target. This allows the ion source to stand back from
the target.
& Charge Density: See density, and apply to electrical charge.
& Charge, Electrical:
As a noun: A fundamental physical attribute of a
particle, which characterizes the particle's electromagnetic
interaction with other particles and with electric and magnetic
fields. (See also particle, field)
As a verb: Storing energy in a battery or electric capacitor by
running a current through it; opposite of discharge. (It is possible
to charge most capacitors in either direction, but batteries charge
one way, and discharge the other.)
* Charge Exchange: Phenomenon in which an ion colliding with
a molecule (or an atom) neutralizes itself by capturing an electron
from the molecule/atom, and transforming the molecule/atom into a
positive radical/ion.
* Charge Transfer: see charge exchange
* Charged Particle: a particle which carries a positive or
negative electrical charge. In plasma physics, this typically
means an ionized atom or molecule, or an electron.
* China Syndrome: American jargon/slang for a nuclear fission
meltdown accident (see meltdown) in which the molten nuclear core
heats and melts the ground beneath it, thus sinking into the
earth, and heading towards China (which is roughly on the opposite
side of the globe).
* Classical Confinement: Plasma confinement in which energy transfer is
via classical diffusion; best possible case for magnetically
confined plasmas. See entry for classical diffusion below.
* Classical Diffusion: In plasma physics, diffusion due solely
to scattering (collisions) of charged particles (with unlike
charges) via electrical ("Coulomb") interactions. (See also diffusion.)
* Coherent Radiation: Any form of radiation in which the phase
relationship between sections of the wave at different locations is
not random (or incoherent!). Typical example is a laser beam, in
which the phase is more or less uniform across the beam, and changes
along the beam in accordance with the wavelength. Radiation in
which the photons tend to "agree" with one another, rather than
being randomly distributed.
* Cold Plasma Model: Model of a plasma in which the temperature is
neglected with respect to the effects of interest.
* Collision: Refers to the close approach of two or more
particles, photons, atoms, nuclei, etc, during which such quantities
as energy, momentum, and charge may be altered. More-or-less
synonymous with "scattering," except in scattering one generally
thinks of one of the particles as being at rest, and the other
colliding particles "scatter" from their initial direction of
motion due to the collision.
& Collision Cross-Section: Effective surface area of a particle
when it collides with another; describes probability of collisions
between the two particles.
* Collisionless Plasma Model: Model of a plasma in which the density
is so low, or the temperature so high, that close binary (two-body)
collisions have practically no significance (on certain timescales)
because the time scales of interest are smaller than the
collision time. Yields valid physical results for timescales
much shorter than the average collision time in a real plasma.
& Collision Time: Typical time which passes between the time
a particle collides, and when it collides again. Inverse of the
collision frequency; equal to the mean free path divided by the
particle's velocity. The collision time decreases with increasing
density, and increases with increasing temperature.
> Compact Ignition Tokamak (CIT): Proposed U.S. successor to TFTR;
never funded. See also, BPX, TPX.
> Compact Torus: Any of a series of axially symmetric fusion
configurations having closed flux surfaces (like a tokamak, not
like a mirror machine), but having no material objects piercing
the core (as do the toroidal field coils of a tokamak). These
devices have an inherently low aspect ratio, approximately unity.
The most successful variants are the spheromak and the Field
Reversed Configuration. See also: low aspect ratio, spheromak,
field-reversed configuration. (Arthur Carlson,
awc@ipp-garching.mpg.de)
> CTX Facility (Compact Toroid Experimental facility):
Los Alamos facility to investigate plasma physics of compact
toroids. (No longer in operation?)
* Compression Waves: Also known as density waves (I think!);
waves where the quantity which oscillates is the density of the
medium, that is the medium at a given point alternately
compresses and expands. Low-amplitude compression waves in
air or water are commonly known as sound waves; shock waves
are a high-amplitude form. See also waves.
& Conductivity: Degree to which a substance transmits (conducts)
a given physical property, such as heat or electricity.
See electrical conductivity, thermal conductivity.
* Confinement, Classical: See classical confinement.
* Confinement, Electrostatic: See electrostatic confinement.
* Confinement, Inertial: See inertial confinement.
* Confinement, Magnetic: See magnetic confinement.
* Confinement Time: There are several types. The general
definition is that tau = [total]/[loss per unit time];
hence Tau_E = [total energy]/[energy loss per unit time].
Tau_[E, N, ...] is the amount of time the plasma is contained
by magnetic fields before its [energy (E), particles (N or P)]
leak / dissipate away. The different types are, in general,
similar but not equal.
(Note note note: Tau_E is NOT electron confinement time!)
> Constance: Small mirror devices; formerly operated at MIT.
* Containment Vessel: Gas-tight shell or other enclosure
around a fusion (or fission) reactor, to prevent accidental
leakage of radioactive contents.
* Controlled Thermonuclear Fusion: The process in which
light nuclei, heated to a high temperature in a confined
region, undergo fusion reactions under controlled conditions,
with associated release of energy which may be harnessed
for useful purposes.
* Coolant: Substance circulated through a device (including
fusion reactors, fusion reactor magnets, etc.) to remove or
transfer heat. Common types include water, helium, and
liquid-metals such as sodium (Na).
* Cooperative Phenomena: The motion of interacting particles
acting collectively, rather than individually. Includes
plasma oscillations, turbulence, and instabilities. (Plasmas
are distinguished from collections of individual particles
in that they exhibit cooperative phenomena, whereby the plasma
particles "cooperate" with one another. Early fusion researchers
who devised fusion schemes based upon theories where plasmas
acted as merely a collection of individual particles (and
therefore sought to confine only individual particles) often
found themselves frustrated at the ability of plasma
cooperative phenomena (such as MHD instabilities) to thwart
their efforts.
* Core plasma: Hot plasma at the center of a fusion reactor;
distinguished from edge plasma. The core plasma does not
directly feel the effects of the divertor or limiter in the
way the edge plasma does. (More info anyone?)
* Corona: The outermost (?) part of a star's atmosphere;
characterized by high temperatures and low densities; home to
many plasma phenomena.
* Corrosion: Chemical interactions between a fluid, (such
as lithium or water coolant) and the containing material
(such as stainless steel), which results in wall material
dissolving into the fluid, and possibly degradation of
the mechanical properties of the containing structure
$ Coulomb: standard unit of electric charge. A single electron or
proton has a charge of (+/-) 1.6022E-19 coulombs. Hence there are
6.2414E+18 electrons in a coulomb of electrons.
* Coulomb Collision: An interparticle collision where Coulomb's Law
(electrical attraction and repulsion) is the governing force.
(See Coulomb's Law) Coulomb collisions have a number of interesting
properties, but these are better described in textbooks. The
interaction of the charged particles with each other's electric
fields results in deflections of the particles away from their
initial paths.
& Coulomb Force: See Coulomb's Law. Also called
"electrostatic force."
* Coulomb Ionization: Ionization produced by Coulomb forces
between a moving particle ("projectile") and another particle
it interacts/collides with ("target").
& Coulomb's Law: Force law governing the electrical interaction
between charged particles. Force is proportional to (charge of
first particle) * (charge of second particle) / (square of separation
between particles). Constant of proportionality depends on system
of units used. (In SI units, it is 1/(4*pi*epsilon-0), where
epsilon-0 is the permittivity of free space = 8.854 x 10^-12 )
& Cross Section: (usually symbolized with a lower-case Greek sigma)
In physics this usually refers to the (apparent) area presented
by a target particle to an oncoming particle (or electromagnetic
wave). This measures the probability of an interaction occuring.
For typical interactions between ions and electrons, or between
two nuclei, these cross sections are generally measured in barns.
(See relevant entries.)
& Cryogenic: Loosely, "very cold". Used to describe systems which
operate at very low temperatures. Superconducting magnetic field
coils currently need to operate at cryogenic temperatures (e.g.,
liquid helium at 4 Kelvin).
* Curie: Unit of radioactivity roughly equal to the rate of
radioactive decay of a gram of radium; named after Marie
Curie (see below). Corresponds to 3.7 x 10^10
disintegrations/second (37 billion). (See Becquerel)
! Curie: Marie and Pierre; husband-wife pair of French scientists.
Pierre's name is attatched to the "Curie point" in magnetism, which
is not discussed here. He and his wife shared with Antoine-Henri
Becquerel the Nobel Prize for physics in 1903. Marie Curie,
a.k.a. Madame Curie, received the Nobel Prize for chemistry
in 1911, becoming the first person to receive more than
one Nobel Prize. She remains the only person to receive Nobel
Prizes in different fields. (I believe - RFH)
& Current Density: Amount of current flowing through a substance,
per unit area perpendicular to the direction of current flow. (See
also density)
* Current Drive: Any of a variety of techniques used to cause
current flow in a plasma. See inductive current drive, RF current
drive, non-inductive current drive. Usually applied to schemes
used to generate current in tokamaks and other toroidal devices
which require internal plasma currents. See also: bootstrap current.
* Cusped Geometry: I can't figure out how to explain this one in
words; suffice it to say that this is a description of a magnetic
field configuration where the magnetic field lines, rather than
closing in on themselves, tend to squirt out and form cusps at
certain points; I recommend you look this up in a plasma physics
text (e.g., Chen - see bibliography entry) to really understand it.
The magnetic field lines are everywhere convex towards the center.
Such a geometry is interesting because it is theoretically stable
against a variety of MHD instabilities.
> Cyclops: Single-chain, 0.6 terawatt Nd-glass laser system at
Lawrence Livermore National Laboratory that was used for laser
studies and inertial-confinement fusion experiments in 1975-1976.
* Cyclotron: Particle accelerator in which a magnetic field causes
particles to orbit in circles, and an oscillating electric field
accelerates the particles.
* Cyclotron Frequency: Number of times per second that a particle
orbits in a magnetic field. (Often, and incorrectly, called the
Larmor frequency. The cyclotron or gyrofrequency is twice the
Larmor frequency of precession.)
* Cyclotron Radius: Radius of orbit of charged particle about
a magnetic field line. Also called gyroradius, Larmor radius.
* Cyclotron Radiation: See synchrotron radiation
* Cyclotron Resonance: Charged particles in a magnetic field
resonate with (and absorb energy from) an electric field
(perpendicular to the magnetic field) which oscillates at
the particles' cyclotron frequency, or at a harmonic
(multiple) of that frequency.
* Cyclotron Resonance Heating: see Electron Cyclotron Resonance
Heating, Ion Cyclotron Resonance Heating.
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