Plasma sources generate plasmas.
Excitation of a plasma requires partial ionization of neutral atoms and/or molecules of a medium. There are several ways to cause ionization: collisions of energetic particles, strong electric fields acting on bond electrons, or ionizing radiation. The kinetic energy for ionizing collisions may come from the heat of chemical or nuclear reactions of the medium, as in flames, for instance. Alternatively, already released charged particles may be accelerated by electric fields, generated electromagnetically or by radiation fields. If at least as many charge carriers are created per time unit as recombine, the plasma can be sustained.
Plasma excitation by electromagnetic fields can be classified according to:
Plasma sources have numerous technical applications, for instance in light generation and plasma processing of materials. They can be used for extracting an ion beam, in which case they are also called ion sources. An innovative and emerging field is the application of non-thermal atmospheric pressure plasma sources in plasma medicine.