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Re: Plasma



Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


----- >
> > << A plasma nead not be hot,
>
> It does.
>
> > it only must be ionized.
>
> Ionized is another way of saying 'hot'.


Nope... you can ionize a gas without doing it thermally, and without having
the atoms moving fast (which is what temperature is all about, really...)...
Consider the following.  I have a volume of gas.. I blast an intense xray
source at it.. temperature remains the same, but the electrons are stripped
off the atoms, forming an ionized gas.

Consider this... I have a chamber pumped down to, say, 1 torr... I add a
small amount of RF power.. the gas ionizes.. Is it hot?

How about an ion gun? generating ions at, say, 0.01 eV...  at 1 eV=11000K,
that's 110K... (although I'm not sure that the 1eV=11000K doesn't really
refer to a Maxwellian or thermalized distribution..)


I think the upshot is that in air at usual temperatures and pressures...
heat and ionization go together.  But, there are enough situations where
temperature, heat, and ionization might be decoupled, particularly at low
pressures.

>