Plasma (physics)

Article By:

Hershkowitz, Noah Department of Nuclear Engineering, University of Wisconsin, Madison, Wisconsin.

Borovsky, Joseph E. Los Alamos National Laboratory, Los Alamos, New Mexico.

Last reviewed:August 2020

DOI:https://doi.org/10.1036/1097-8542.525900

A gas of charged and neutral particles which exhibits collective behavior. All gases become ionized at sufficiently high temperatures, creating what has been called a fourth state of matter, together with solids, liquids, and gases. It has been estimated that more than 99% of the universe is in the plasma state. On the Earth, plasmas are much less common. Lightning is a familiar natural manifestation, and fluorescent lights are a practical application. Plasma applications and studies make use of an enormous range of plasma temperatures, densities, and neutral pressures (Fig. 1). They extend from plasma processing applications at relatively low temperatures (such as plasma etching of semiconductor chips at low pressure, or plasma cutting torches at atmospheric pressure) to studies of controlled fusion at very high temperatures. See also: Fluorescent lamp

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