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Conventional Fusion FAQ Glossary Part 17/26 (Q)

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Archive-name: fusion-faq/glossary/q
Last-modified: 21-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 17:  Terms beginning with "Q"


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).


# q - Variable used to indicate electric charge; also used for
the "safety factor" (see charge, safety factor).  Usually clear
from context which is meant.

# Q: See Q-factor

* Q-enhancement:  Refers to methods for improving the power
balance in mirror-based magnetic confinement fusion reactors.

* Q-factor:  Ratio of power produced by fusion to power
put into the reactor to heat the plasma and drive the
magnetic fields.  Q = 1 is the definition of scientific
breakeven, where power out = power in.  Economical fusion
will require Q significantly greater than 1.  Fortunately
Q increases dramatically as the plasma parameters 
approach the Lawson criterion for ignition.  Power to drive
the magnetic fields is frequently ignored in discussions of
Q, with the justification that a steady-state, continuous-output
fusion reactor will have superconducting magnet coils.

* Q-machine:  Plasma device studied in the 1960s; noted for
its natural quiescence, which made it attractive for plasma
wave phyics experimentation.

* Q-switch:  Optical switch used to rapidly change the Q of
an optical resonator (see entry for oscillator); utilized
in the optical resonator of a laser to prevent lasing action
until a high level of gain and energy storage are achieved
in the laser medium.  When the switch is triggered and
rapidly increases the Q of the cavity, a stronger laser 
pulse is generated.

$ Quad:  Unit of energy equal to a Quadrillion BTUs (10^15)
or roughly one exajoule (see entry for joule, exajoule, BTU).

* Quasi-linear Theory:  A weakly nonlinear theory of plasma
oscillations which uses perturbation theory and the random
phase approximation to find the time-evolution of the 
plasma state.

* Quasi-neutral plasma: an ionized gas in which positive 
and negative charges are present in approximately 
equal numbers.

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