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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 8/26 (H)
- Supersedes: <fusion-faq/glossary/h_934543711@rtfm.mit.edu>
- Followup-To: sci.physics.fusion
- Date: 11 Nov 1999 12:25:28 GMT
- Organization: Princeton University
- Lines: 223
- Approved: news-answers-request@MIT.EDU
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- Expires: 23 Feb 2000 12:24:17 GMT
- Message-ID: <fusion-faq/glossary/h_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:44256 sci.answers:10853 news.answers:170839
-
- Archive-name: fusion-faq/glossary/h
- 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 8: Terms beginning with "H"
-
- 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).
- ==================================================================
-
- HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
-
- # H: chemical symbol for the element hydrogen; see entry
-
- # He: chemical symbol for the element helium; see entry.
-
- @ HIREX: High-REsolution X-ray spectroscopy
-
- @ H-mode: see high-mode
-
- @ HTO: (Hydrogen-Tritium-Oxygen) Water with a tritium atom
- replacing a hydrogen. See entry for tritium.
-
- * Half-life: For a given quantity of a radioactive isotope,
- there is a time period in which half the nuclei will decay to
- a different state; this period is called the half-life. Measured
- half-lives range from less than millionths of a second (for very
- short-lived isotopes) to billions of years (for isotopes which
- are almost stable, but not quite). The time in which half the
- atoms of a particular radioactive isotope disintegrate
- to another nuclear form. By analogy, "half-life" can also be
- used to describe similar time-periods for other sorts of
- exponential decay phenomena.
-
- * Hall Effect: Transverse electric field which develops in a
- conductor (as a result of the Lorentz Force acting on the charge
- carriers) when current is driven across a magnetic field.
-
- * Halo: The cold, dense plasma formed outside the last closed flux
- surface during a vertical displacement event. The large currents
- which flow through this plasma stop the displacement and transfer the
- force to the vacuum vessel. If care is not taken in design, the halo
- currents can be large enough to threaten the structural integrity of
- the vacuum vessel or in-vessel components. Whereas the center of a
- tokamak plasma is too hot for material probes to survive, probes
- (such as magnetic-field coils) can sometimes be placed in the
- halo, and can measure things such as the halo current (see below).
- See also entry for vertical instability.
-
- * Halo Current: Currents in the halo region of a plasma discharge.
- See entry for halo above.
-
- * Hamada coordinates: A particular magnetic-flux coordinate
- system useful for MHD calculations. In this system the current
- density and magnetic field lines are straight and the Jacobian
- of the coordinate transformation equals one.
-
- & Hamiltonian Function: Function arising from the Hamiltonian
- approach to mechanics which characterizes the total energy of
- a system as a function of generalized coordinates and momenta
- and can be used to obtain the dynamical equations of motion
- of the system. (Consult an intermediate or advanced mechanics
- text for more info.)
-
- > Hard-core pinch device: plasma pinch-discharge device using a
- solid central conductor ("hard-core"). The discharge then occurs
- in an annular region about the central conductor.
-
- & Hartree-Fock approximation: a refinement of the Hartree method
- (see entry) in which one uses determinants of single-particle
- wave functions rather than products, thereby introducing exchange
- terms into the Hamiltonian.
-
- & Hartree method: An iterative, variational method of finding an
- approximate quantum-mechanical wavefunction for a system of many
- electrons, in which one attempts to find a product of
- single-particle wave functions, each of which is a solution of
- the Schrodinger equation with the field deduced from the charge
- density distribution due to all the other electrons; also known
- as the self-consistent field method.
-
- & Heat exchanger: device that transfers heat from one fluid
- (liquid or gas) to another (or to an external environment).
-
- * Heavy Hydrogen: somewhat informal alternative name for deuterium.
- (see entry for deuterium).
-
- * Heavy Water: (D2O) Water with enriched content of deuterium
- relative to hydrogen (greater than the natural abundance of 1 D
- per 6500 H). Heavy water is used as a moderator in some fission
- reactors (see CANDU entry) because it slows down neutrons effectively
- but also has a low collision cross-section for absorption of neutrons.
-
- > Heliac: A confinement configuration which superimposes an l=1
- stellarator-type field upon a tokamak-like poloidal field. The
- resulting plasma configuration is a helix bent around into a loop.
-
- * Helicity: (from John Cobb) A measurement of the topological
- "tangledness" of magnetic field lines. It is formally defined as the
- scalar product of the magnetic vector potential with the magnetic
- field, K = A dot B. If the plasma is perfectly conducting, then
- helicity is a conserved quantity. (Without resistance, field lines
- cannot reconnect, and magnetic topology is conserved, so helicity is
- conserved). (See frozen-in flow). If the plasma has a small amount
- of resistivity, then Helicity is not exactly conserved. However, the
- total helicity inside of a given flux surface is often conserved to a
- good approximation. In that case, the dynamics of a plasma can be
- analyzed as an evolution toward a minimum energy state subject to the
- constraint of a conserved total helicity (See Taylor State, J.B.
- Taylor). This is often used in analyzing the equilibrium and
- relaxation of RFP's and other toroidal devices.
-
- > Helios Facility: Los Alamos laser inertial fusion facility.
-
- & Helium: Element whose nuclei all contain two protons.
- Stable isotopes are 3He and 4He. 3He is rare on earth (only 1.3
- ppm of naturally-occuring He), can be generated from decaying
- tritium (half life of about 12 years), and is relatively abundant
- in the crust of the moon. Helium is the second most abundant element
- in the universe and in the sun, and occurs at about (I believe)
- 1 part per million in earth's atmosphere. Helium is also found
- in significant quantities in natural gas deposits. The nucleus
- of the He atom is also known as an alpha particle. Helium is
- chemically inert, behaves nearly as an ideal gas under a wide
- range of pressures and temperatures, and can only be liquefied
- at 4 Kelvin (at atmospheric pressures). One mole of He weighs
- 4 grams.
-
- ! Hertz, Heinrich: 19th-century German physicist; first (?)
- observed low-frequency electromagnetic waves.
-
- $ Hertz: Unit of frequency equal to one complete oscillation (cycle)
- per second. Common abbreviation is Hz.
-
- * High-beta plasma: A plasma in which the beta value (see entry)
- is typically 0.1 to 1.
-
- * High-mode or H-mode: A regime of operation most easily
- attained during auxiliary heating of diverted tokamak
- plasmas when the injected power is sufficiently high.
- A sudden improvement in particle confinement time leads to
- increased density and temperature, distinguishing this mode
- from the normal "low mode." However, H-mode has been achieved
- without divertors, auxiliary heating, or a tokamak. (H-modes
- have been observed in stellarators.)
-
- & Holography: A technique for recording and later reconstructing
- the amplitude and phase distribution of a wave disturbance.
-
- & Homopolar generator: A direct-current generator in which the
- poles presented to the armature are all of the same polarity,
- so that the voltage generated in the active conductors has the
- same polarity at all times. A pure direct current is thus
- produced without commutation.
-
- * Hot cells: Heavily radiation-shielded enclosure in which
- radioactive materials can be handled by persons using remote
- manipulators and viewing the materials through shielded windows
- or periscopes.
-
- * Hybrid diode: An ion diode that uses a field coil in series
- with the ion diode's accelerating gap to generate sufficient
- magnetic flux in the diode for electron control. The diode is
- a combination of the Applied-B diode's ion source and the
- Ampfion diode's field coil.
-
- * Hybrid reactor: see fusion-fission hybrid.
-
- * Hybrid resonance: A resonance in a magnetized plasma which
- involves aspects of both bunching of lighter species parallel
- to the magnetic field, characterized by the plasma frequency;
- and perpendicular particle motions (heavier species) characterized
- by the cyclotron frequency.
-
- & Hydrogen: (H) Element whose nuclei all contain only one proton.
- Isotopes are protium (p, no neutrons) deuterium (D or d,
- one neutron), and tritium (T or t, two neutrons). Hydrogen is
- the lightest and the single most abundant element in the
- universe, and in the sun. Hydrogen is a major element in
- organic compounds, water (H2O), and many other substances.
- Hydrogen is ordinarily a gas, but can be liquefied at low
- temperatures, and even solidified at low temperature and
- high pressure. Hydrogen gas can burn explosively
- in the presence of oxygen.
-
- * Hydrogen bomb or H-bomb: (from Herman) An extremely
- powerful type of atomic bomb based on nuclear fusion.
- The atoms of heavy isotopes of hydrogen (deuterium and
- tritium) undergo fusion when subjected to the immense
- heat and pressure generated by the explosion of a nuclear
- fission unit in the bomb.
-
- * Hydrogen embrittlement: A decrease in the fracture
- strength of metals (embrittlement) due to the incorporation
- of hydrogen within the metal lattice.
-
- * Hydromagnetic Instability: See MHD Instability
-
- * Hydromagnetics: see magnetohydrodynamics (MHD)
-
-
-
-
-
-