MadSci Network: Physics
Query:

Re: Effects of low-temperature plasmas on biological matter

Date: Fri Apr 30 18:17:11 2004
Posted By: Aaron J. Redd, Post-doc/Fellow, Plasma Physics and Controlled Nuclear Fusion, University of Washington
Area of science: Physics
ID: 1078262670.Ph
Message:

The main obstacle to answering your question is that the conditions which
are good for the human body (temperature and pressure) are not so good for
a plasma, and vice versa.

A plasma is a superheated gas, superheated to the point where the very
atoms and molecules of the gas have been broken down into free electrons
and ions.  Creating and sustaining such a gas generally involves either:
ionizing and heating the gas with large electrical currents; or,
maintaining the ionization in a diffuse gas using high voltages or
significant amounts of high-energy light (UV light, for example).  Either
way, a human exposed to these conditions will have far more urgent concerns
than how the plasma will affect his/her complexion.

If a plasma were to be exposed to the temperatures and pressures necessary
for human life, the result would be the rapid "snuffing-out" of the plasma,
as the free ions and electrons collide with the relatively slow molecules
of the air (or the wall or the human), and give up their thermal energy. 
The main point to consider here is the rather low heat capacity of any
plasma -- it is, after all, a gas, meaning that there isn't much mass in
which to store thermal energy.  The total thermal energy in the plasmas of
most university fusion experiments, for example, is (at most!!) measured in
hundreds of Joules, less than the heat energy in a hot cup of coffee.

So, your question is an interesting one, but it seems that any human-plasma
interaction involves either a soon-to-be-ex-human or a
soon-to-be-ex-plasma.  Or both.

I hope that you find this helpful.

Aaron




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