CHARTER, WHAT IS A PLASMA? March 2006
John W. McKelliget
This posting is intended to introduce you to the
newsgroup, and to plasmas in general.
CONTENTS:
1. sci.physics.plasma Archive
2. Role of Moderator
3. Current Moderator
4. Previous Moderator
5. Problems
6. Charter
7. What is a Plasma?
8. Plasma Related Links
1. SCI.PHYSICS.PLASMA ARCHIVE:
Previous postings to the newsgroup, can be found in the sci.physics.plasma archive at http://sci-phys-plasma.caeds.eng.uml.edu
The archive website has been completely redesigned. It should be operational. Please let me know of any problems, broken links, or corrupt files.
2. ROLE OF MODERATOR:
sci.physics.plasma is a moderated newsgroup.
All postings are sent to the moderator who checks to see that the
posting conforms to the newsgroup's charter. The moderator is not an
editor or censor and should not be considered at fault for any incorrect
information appearing in the newsgroup.
3. CURRENT MODERATOR: (since July 1996)
John W. McKelliget
Dept. of Mechanical Engineering
University of Massachusetts
Lowell, MA 01854
mailto:John_Mc...@uml.edu
4. PREVIOUS MODERATOR AND NEWSGROUP INITIATOR:
sci.physics.plasma was initiated by Tim Eastman in
July 1994
5. PROBLEMS:
If you are experiencing problems posting to sci.physics.plasma or in
using the archive please contact the current moderator at his email
address. If your newsreader does not allow you to post to newsgroups
you can email your post to sci-physi...@uunet.uu.net
6. CHARTER: NEWSGROUP for Plasma Science and Technology
Plasmas are as rich as any other state of matter in terms of distinct
processes and they encompass distinguishable scales ranging from the
atomic to the galactic. Opportunities in plasma science and technology
reflect this breadth in phenomena and scales; one recent list contains
close to 200 subject areas and more than 90 applications areas including
thin-film diamond deposition, toxic waste disposal, plasma arcs for
steel processing, laser self-focusing, fusion for energy production, gas
and arc lamps, cutting and welding, and semiconductor production.
The Plasma Science and Technology research community seeks an increased
dialogue among its multifarious constituencies. The NEWSGROUP for Plasma
Science and Technology is intended as a community forum for sharing new
developments and bringing researchers together for potential new
collaborations. The newsgroup also provides a forum for public outreach
and education. Postings from students and the general public are
welcome as we all help one another in learning more about the "fourth
state of matter" and its enormous range
of applications.
7. WHAT IS A PLASMA?:
The loosest definition of a plasma is that it is an electrically
conducting gas. At normal temperatures and pressures gases are usually
very good electrical insulators. This is because the electrons in the
gas are tightly bound inside gas atoms and are not free to move in
response to externally applied electric or magnetic fields.
Under certain conditions, however, some or all of the electrons can be
removed from their parent atoms, a process called ionization. The gas
then consists of a mixture of negatively charged electrons, positively
charged atoms, called ions, and un-ionized neutrally charged atoms. Now
the electrons and ions are free to move under the action of applied
electromagnetic fields and the gas can conduct electricity. Due to
their much smaller mass the electrons respond to the applied fields much
more readily than the ions and, consequently, carry most of the
current. Since electrons and ions are produced in pairs and have
opposite charges most of the plasma remains electrically neutral.
There are three principal methods for ionizing a gas. The first, called
field ionization, involves applying an extremely high electrical field
that acts on the electrons in a neutral atom and essentially disrupts
the atom. The second, called thermal ionization, involves raising the
temperature of the gas until collisions knock electrons out of the
atoms. Thus, a plasma does not have to be "hot", although some are
extremely so. The third method involves bombarding the gas with
high energy radiation or other sub-atomic particles.
Because the properties of a plasma are so very diferent from those of a
neutral gas the plasma state is sometimes called " the fourth state of
matter ".
In practice the plasma state covers an extremely large range of
temperature and pressure, from the gas in the fluorescent lamps in your
house to the fusion reactions in the center of the sun. Although you
may have to search for a plasma in your daily life, most of the visible
matter in the universe is in the plasma state.
Technological applications of plasmas include: fluorescent lights,
welding arcs, steelmaking furnaces, experimental fusion reactors,
semiconductor processing, flat panel displays,
photovoltaics, solar coatings, architectural coatings,
and hazardous waste processing.
- J. McKelliget 1998
8. PLASMA RELATED LINKS:
"The Pervasive Plasma State" an essay commisioned by the American Physical Society
Division of Plasma Physics
http://w3fusion.ph.utexas.edu/aps/plasmaState/PPSPage1.html
Plasma science & technology homepage
http://www.plasmas.org/
Extensive additional plasma material can be found at
http://plasma-gate.weizmann.ac.il/PlasmaI.html
Listings of upcoming plasma conferences can be found at the following
site
http://plasma-gate.weizmann.ac.il/CoAPP.html
Chris
I have got a fluorescent tube to light in the inductor coil of a Hartley
oscillator at 2.645MHz.
Do I have plasma?
Chris remove .nospam. from the reply address to e-mail me.
Jim Logajan
"Chris" <chris...@chriss.nospam.pages.co.uk> wrote:
> I have got a fluorescent tube to light in the inductor coil of a Hartley
> oscillator at 2.645MHz.
>
> Do I have plasma?
Yes - a little. I believe that the Saha equation can be used to determine
the extent of the ionization:
http://en.wikipedia.org/wiki/Saha_equation
The information given on that page may be a bit difficult to figure out, so
here is a different version (taken from "Introduction to Plasma Physics and
Controlled Fusion" by Francis F. Chen):
ni/nn ~= 2.4E21 * T**(3/2.) * e**(-Ui/(K*T))/ni
ni: number of ionized atoms per m**3
nn: number of neutral atoms per m**3
T: gas temperature in degrees Kelvin
K: Boltzmann's constant
Ui: Ionization energy of the gas in ergs
e: Euler's number
2.4E21: Fairly standard programming notation for large real numbers.
**: Fairly standard programming notation for powers.
Need to take a guess at the gas density in the tube (typical values might
be on the net somewhere). Ionization energy can be looked up once the
nature of the gas is determined. As to temperature ... hmmm.
Chris
Thank you.
I next put a Pyrex tube of hydrogen at a pressure of 3 Tor in an 850 watt
microwave oven.
The tube got very hot then after 40 seconds it glowed with a bright blue
light.
What is happening here? Do I have plasma.
--
Chris.
London,
UK.
To reply remove ns_ from e-mail address
..
"Jim Logajan" <Jam...@lugoj.com> wrote in message
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