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I read about non-thermal plasma, but I still have some questions:

  1. The ions and neutral particles are not in thermal equilibrium with the electron, does that mean that the overall temperature is low like in neon signs?

  2. Does the non-thermal plasma have relatively low ionization percentages, like 2 or 3%? Or higher ionizations can be achieved?

  3. Is the super cold plasma the only way to get a non-thermal plasma?

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Non-thermal is a broad catch-all for energy distributions that are not Maxwellian. The reason it is interesting is because if it's not Maxwellian, it's not in thermodynamic equilibrium and some work can be extracted from it while it relaxes or the energy differences between electrons and ions produced an interesting or desirable phenomena.

So to answer your questions:

  1. very hot plasmas can still be non-thermal, one hopeful example is the inertial electrostatic confinement plasma approach known as Polywell, they are hoping to get a very sharp energy distribution of plasma.
  2. 1% actually is a very appreciable ionization percentage. Gases will have plasma-like behaviors with ionization percentages as low as .01%.
  3. sort of referenced in 1.

Hope this was helpful.

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  • $\begingroup$ Doesn't "non-thermal" imply that the temperature of the plasma is meaningless? $\endgroup$ – endolith Aug 2 '13 at 18:30
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    $\begingroup$ As a whole, yes, a non-thermal plasma may not have a single temperature which is relevant, but subspecies could still have well behaved maxwellian temperatures. Such an example would be when the electron temperature is very different from the ion temperature, a surprisingly common occurrence. $\endgroup$ – Wolfram074 Apr 9 '14 at 21:47

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