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Conventional Fusion FAQ Glossary Part 14/26 (N)


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Archive-name: fusion-faq/glossary/n
Last-modified: 20-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!!!).

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===============================================================
Glossary Part 14:  Terms beginning with "N"

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).
==================================================================

NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN

# n: variable used for number density of particles.
# n: also used as the symbol for a neutron.
# n: also sometimes used for the index of refraction

@ NAS: National Academy of Sciences; see entry

@ NASA: National Aeronautics and Space Administration

$ nano: metric prefix indicating 10^-9 * the base unit

@ NBETF: Neutral Beam Engineering Test Facility

@ NBI: Neutral Beam Injection; see entry

@ NBS: National Bureau of Standards

@ ND-YAG: Neodymium yttrium Aluminum Garnet

# ne: (n subscript e) - usually electron density

# Ne: chemical symbol for Neon.

@ NERSC: National Energy Research Supercomputer Center; see entry

@ NIF: National Ignition Facility; see entry

@ NIKE: Naval? Inertial Confinement Experiment????; see entry

@ NINJA: Neutral gas INJection Array (on Alcator C-Mod)

@ NIST: National Institute for Science & Technology?

@ NRC: National Research Council *OR* Nuclear Regulatory
Commission; see entries.

@ NRL: Naval Research Laboratory; see entry

@ NSTX: National Spherical Tokamak eXperiment; see entry

% National Academy of Sciences:  Elite, honorary, independent,
self-perpetuating organization of highly-successful scientists;
chartered by the U.S. Congress to provide technical advice
to the federal government upon request. 

% National Energy Research Supercomputer Center (NERSC):
Formerly the National Magnetic Fusion Energy Computer Center,
or NMFECC, NERSC is a supercomputer facility located at
Livermore, CA.  Originally developed to provide high-performance
computing facilities for the needs of the magnetic fusion
energy program, the facility now benefits all energy research
programs.  NERSC is a part of the Energy Sciences Network, ESNET,
run by the Department of Energy, which links several of the
national laboratories.

> National Ignition Facility (NIF):  Inertial-Confinement 
Fusion Facility proposed to be built at Livermore and 
operational around the year 2000.  See Section 9 on Future 
Plans for more information.

% National Research Council:  Research arm of the National
Academy of Sciences.

> National Spherical Tokamak eXperiment (NSTX):  Mid-sized 
low aspect-ratio tokamak / spheromak experiment proposal; 
still in design phase / not funded.  See Section 9 on Future 
Plans for more information.

% Naval Research Laboratory:  Basic-science research laboratory
operated by the U.S. Navy.    

* Neoclassical Diffusion:  In a magnetized plasma, _classical_ 
diffusion refers to transport of particles due to Coulomb collisions, 
taking the spiral orbits in the magnetic field into account.  In a 
toroidal magnetic field, the actual rate of diffusive transport is 
much higher due to slow changes in the positions of the centers of the 
spirals, known as banana orbits (see entry).  This faster transport 
is called _neo-classical_.  With very few exceptions the transport 
in toroidal devices is observed to be 10-100 times larger still, 
presumably due to small-scale turbulence.  The observed transport is 
called _anomalous_ (although it actually is the "normal" state).

* Neoclassical transport:  See neo-classical diffusion.

> Neutral Beam Engineering Test Facility:  Facility located at
LBL which tested neutral beam injection systems that were 
designed for use in magnetic fusion reactors.

* Neutral Beam Injection: This is one of the fundamental plasma
heating methods.  A particle accelerator is used to create
fast ion beams (the particle energies are on the order of 100 keV);
the ion beam is then passed through a neutral gas region, where
the ions neutralize via charge-exchange reactions with the neutral
gas.  The neutralized beam is then injected into a magnetically 
confined plasma.  The neutral atoms are unaffected (not confined)
by the magnetic field, but ionize as they penetrate into the
plasma.  The high-energy ions then transfer some of their energy 
to the plasma particles in repeated collisions, and heat the 
plasma.  

* Neutral Injection Concept:  See Neutral Beam Injection, above.

* Neutralized Plasma:  Plasma with no net electrical charge.

& Neutron:  [Symbol: n]  Fundamental atomic particle with 
zero electrical charge (therefore not confined by a magnetic 
field) and a mass roughly equal to a proton's mass.  Neutrons
are found in all nuclei except for ordinary hydrogen; they are
also products of many nuclear reactions.  Neutrons will react
with nuclei, and can induce radioactivity or fission.  Free 
neutrons which do not collide and react with a nucleus decay into 
an electron, a proton, and an neutrino, with a half life of 
about 13 minutes. 

* Neutron Wall Loading:  Energy flux carried by fusion neutrons into
the first physical boundary that surrounds the plasma (the first 
wall).  (see also First Wall, Flux, Neutrons)

> NIKE:  Medium-scale(?) inertial-confinement fusion facility at
the Naval Research Lab; see discussion in Section 5.

* Non-Inductive Current Drive:  Current drives schemes that do not 
rely upon the "transformer" effect in tokamaks.  The attainment of 
non-inductive current drive is crucial to the success of tokamaks 
as truly steady-state devices.  See also inductive current drive.

> Nova:  The United States' largest laser (ICF) fusion
facility, and the world's most powerful laser; located at LLNL.  
This is a 10-beam, 100 terawatt, Nd-glass laser system, which can
operate at the infrared/visible wavelengths of 1.05, 0.53, or 
0.35 microns.  It was completed in 1984 and is the successor to 
the Shiva system.  (The next flagship laser-fusion facility 
currently planned in the U.S. is the National Ignition Facility.)

* Nuclear Binding Energy:  The difference between the total
energy ( = mc^2) of the bound nucleus, and the energies of
the individual constituent particles ( = sum of masses * c^2).
The nuclear binding energy *per nucleon* is a maximum for iron.
Fusion releases energy because light nuclei are less tightly
bound than medium-weight nuclei, and thus energy is liberated
when they become more tightly bound after fusing.  Fission
releases energy for the same reason - heavy nuclei are also 
less tightly bound than medium-weight nuclei, and energy is
liberated when heavy nuclei split into lighter nuclei.

& Nuclear Force:  See Weak (Nuclear) Force, Strong (Nuclear) Force.

% Nuclear Regulatory Commission:  U.S. organization in charge
of overseeing safety of nuclear facilities, including fission
(and presumably fusion) reactors.  

* Nucleon:  Generic term for a component particle of a nucleus,
i.e., either a proton or a neutron.

& Nucleus:  The tiny core of an atom, positively charged,
containing protons and neutrons (except for simple hydrogen, 
which has only a single proton).  In an atom, electrons "orbit" 
the nucleus, forming a cloud around it.





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