Newsgroups: sci.physics.plasma
From news@ipp-garching.mpg.de Fri Jul 26 02:40:09 1996
From: carlson@ipp-garching.mpg.de (Arthur Carlson TOK )
Organization: Max-Planck-Institut fuer Plasmaphysik
Subject: Re: A "cold" dense plasma?

In article <4t86pm$1vi@mojo.eng.umd.edu> dmr@aix1.uottawa.ca (Daniel Racicot) writes:

> My question is: what kind of density would be possible at low
> plasma temperatures in a simple mirror or Tokomak at say 5 Tesla?
> Back of the envelope calculation assuming near ideal gas behaviour
> would suggest a 3000 K plasma at 5 Tesla would result in
> 10 times atmospheric density. Does this somewhat surprising
> result make sense or are there other factors that would come into
> play? What kind of difference in ion and electron temperatures
> would one expect? At these "cool" temperatures would the field be
> effective at keeping a reactive plasma away from the walls? Would
> this setup be equally valid for atoms of low or high atomic weight?
> Although admitedly prohibitively expensive, would this be
> technologically feasible?

Due to various instabilities, the plasma pressure in a tokamak cannot
be more than about 5-10% of the magnetic field pressure, so you lose
another order of magnitude on the back of your envelope. At 3000 K,
the plasma will not be fully ionized, so you might want to go up a
factor of 3 to 10, at least, in the temperature, which brings your
density down again. A more serious problem is that a plasma at such
low temperatures will radiate like mad, hydrogen less than other
elements, but still. The electrical resistance will also be very high,
so you will have to work hard to keep your current flowing. I don't
know what you want to do with this plasma (no good for fusion, e.g.),
but I don't see any fundamental reason you cannot create a tokamak
plasma with a substantial fraction of atmospheric density.

--
To study, to finish, to publish. -- Benjamin Franklin

Dr. Arthur Carlson
Max Planck Institute for Plasma Physics
Garching, Germany
carlson@ipp-garching.mpg.de
http://www.rzg.mpg.de/~awc/home.html