Plasma is cool, but can it be cold?

Materials have different temperatures for phase transitions (boiling, melting, ...). Do these also differ when it comes to plasma? If yes, is there such a thing as a "cold plasma", which would be a material that is in a plasma state at more or less 300K or are they all way much hotter?


It depends what you mean.

Plasma necessarily require ionisation. If one has a gas in thermal equilibrium then you don't get ionisation at room temperature.

However, it is possible to produce non-thermal plasmas, for example by thermionic emission into a cold gas, which have high energy electrons but "cold" ions. It is unclear what "the temperature" really means in this case.

The most obvious, everyday example is the plasma inside a fluorescent lights, which have operating temperatures of maybe 320-340 K. Thermionic emission accelerates electrons into the tube, which collide and ionise atoms of (e.g. Argon) to make a conductive plasma.


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