Irving Langmuir first introduced the term plasma in 1929 [6] to describe the behavior of ionized
gases in high current vacuum tubes. Plasma is often referred to as the "Fourth State of Matter",
the other three being solid, liquid and gas. Plasma is a distinct state of matter containing a
significant number of electrically charged particles, a number sufficient to affect its electrical
properties and behavior. In an ordinary gas each atom contains an equal number of positive and
negative charges where the positive charges in the nucleus are surrounded by the of negatively
charged electrons, so that each atom is electrically "neutral". A gas becomes plasma when the
addition of heat or other energy causes a significant number of atoms to release some of their
electrons. The remaining parts of those atoms are left with a positive charge, and the detached
negative electrons are free to move about. When enough atoms are ionized to significantly
affect the electrical characteristics of the gas, it is a plasma. The transformation between gas and
plasma is depending on the material and gas pressure, but a typical characteristic of a plasma is
the ability to screen out an internal electric field. Commonly used examples of well-known
plasmas are the aurora borealis (or the northern light), neon signs, fluorescing lights and the
solar corona.
Plasma science underlies numerous important technological applications and devices as well as