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Conventional Fusion FAQ Glossary Part 15/26 (O)

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Archive-name: fusion-faq/glossary/o
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!!!).

See reader questions & answers on this topic! - Help others by sharing your knowledge
Glossary Part 15:  Terms beginning with "O"


Edited by Robert F. Heeter,

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).


@ OFE: Office of Fusion Energy; see entry

@ OH: Ohmic Heating; see entry

@ OH1, OH2L, OH2U:  Ohmic Heating Coils (1,2, upper, lower)
     on Alcator C-Mod

@ OPEC: Organization of Petroleum Exporting Countries; see entry

@ ORNL: Oak Ridge National Laboratory; see entry

% Oak Ridge National Laboratory:  Located in Oak Ridge, TN.  
Home of a series of various fusion devices.  Recent machines
have included the Elmo Bumpy Torus and the Advanced Toroidal
Facility (stellarator).  (Could use more info!)

% Office of Fusion Energy:  This is the office (within the 
Office of Energy Research in the U.S. Department of Energy) 
which administers the fusion energy research program.  
Web users can visit for more info.

! Ohm, Georg Simon (1789-1854): Physicist who discovered the
relationship between electric current, potential and resistance.
(Yes, it is Georg.  Swedish, I believe.)

$ Ohm:  Unit of electrical resistance.

& Ohmic heating:  Heating that results from the flow of current
through a medium with electrical resistance.  In plasmas 
subjected to ohmic heating, ions are heated almost entirely by 
transfer of energy from the hotter, more mobile electrons.

* Ohmic heating coil:  On a tokamak, this is the coil (generally
a set of coils; part of the poloidal field system) used to 
induce an electric field in the plasma via a transformer 
effect.  The electric field generates of a toroidal plasma 
current, with resultant ohmic heating.

* Ohmic heating solenoid:  See ohmic heating coil, solenoid.

& Ohm's Law:  The relationship between the net current and
the electric field in a conducting medium.  For simple 
resistors, the voltage equals current times resistance,
V = I*R.  In plasmas the "generalized Ohm's Law" is a
more complex tensor relationship involving the vector 
current density, the vector for the electric field, and 
a generalized resistance tensor that relates the two.

> OMEGA:  Inertial confinement fusion facility at the Laboratory
for Laser Energetics, University of Rochester (NY).  OMEGA
uses a 24-beam Nd:glass laser at wavelengths of 
1.054 or .351 microns.

# Omega:  Variable frequently used to denote frequencies.

* O-Point:  Place where the poloidal magnetic field vanishes in such 
a way that the nearby flux surfaces are elliptical, e.g. on the 
magnetic axis (see entry) or at the center of a magnetic island (see 
entry). (See also X-Point.) 

& Optical Axis:  The line passing through both the centers of
curvature of the optical surfaces of a lens; the optical 
centerline for all the centers of a lens system.

& Optical Interferometer:  This is an interferometer (see entry)
which uses the interference of optical-frequency light waves.  
These are useful in measuring distances precisely, and can
be used to test optical system elements (lenses, mirrors, etc.)
during manufacture.

* Optical Pumping:  In laser physics, this denotes the process
in which absorbed light is stored in the laser medium.  If the
absorption & storage process creates a population inversion, 
laser action can occur (and extract the energy stored by optical
pumping in the form of laser emission).

* Oscillator:  In laser physics, this refers to a device to
generate coherent optical energy.  (i.e., it's another term 
for the laser-light creating device itself, minus the source
of power which pumps the oscillator.)  The oscillator generally 
consists of a laser medium placed within an optical resonant
cavity (pair of mirrors).  Optical energy will be trapped between
the mirrors and the optical (laser) oscillations will grow
so long as the gain of the laser medium exceeds the losses at
the mirrors.

* Outboard Side:  portion of a tokamak / toroidal device on
the outer side, opposite the central axis.

* Overturning Moment:  Torque ("moment") on a toroidal field
coil in a tokamak, about the device's radial direction, 
that results from out-of-plane forces on the coil due to
the interactions between the coil current and the poloidal
(vertical) magnetic field.  This torque tends to "overturn"
the vertical toroidal field coil, and must be engineered

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