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Atmospheric-pressure plasma

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Title: Atmospheric-pressure plasma  
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Atmospheric-pressure plasma

Atmospheric-pressure plasma (or AP plasma or normal pressure plasma) is a plasma in which the pressure approximately matches that of the surrounding atmosphere – the so-called normal pressure.

Technical significance

Atmospheric-pressure plasmas have prominent technical significance because in contrast with low-pressure plasma or high-pressure plasma no reaction vessel is needed to ensure the maintenance of a pressure level differing from atmospheric pressure. Accordingly, depending on the principle of generation, these plasmas can be employed directly in the production line. The need for cost-intensive chambers for producing a partial vacuum as used in low-pressure plasma technology is eliminated.[1]

Plasma generation

Various forms of excitation are distinguished:

The only atmospheric-pressure plasmas that have attained any noteworthy industrial significance are those generated by DC excitation (electric arc) and AC excitation (corona discharge, dielectric barrier discharge and plasma jets).

Operating principle of a plasma jet

By means of a high-voltage discharge (5–15 kV, 10–100 kHz) a pulsed electric arc is generated. A process gas, usually oil-free compressed air flowing past this discharge section, is excited and converted to the plasma state. This plasma then passes through a jet head to arrive on the surface of the material to be treated. The jet head is at earth potential and in this way largely holds back potential-carrying parts of the plasma stream. In addition, it determines the geometry of the emergent beam.


The plasma jet is used inter alia in industry for activating and cleaning plastic and metal surfaces prior to adhesive bonding and painting processes. Even sheet materials having treatment widths of several metres can be treated today by aligning a large number of jets in a row. In doing so the modification of the surface achieved by plasma jets is comparable to the effects obtained with low-pressure plasma.[2]

Depending on the power of the jet, the plasma beam can be up to 40 mm long and attain a treatment width of 15 mm. Special rotary systems allow a treatment width per jet tool of up to 13 cm.[3] Depending on the required treatment performance, the plasma source is moved at a spacing of 10–40 mm and at a speed of 5–400 m/min relative to the surface of the material to be treated.

A key advantage of this system lies in its capability of being integrated in-line. This means that it can usually be installed without any difficulty in existing production systems. In addition the activation achievable is distinctly higher than in potential-based pretreatment methods (corona discharge).

It is possible to coat varied surfaces by means of this technique. Thus, anticorrosive layers and adhesion promoter layers can be applied to many metals without the use of solvents and hence in a environmentally friendly manner.

See also


  • Tendero C., Tixier C., Tristant P., Desmaison J., Leprince P.: Atmospheric pressure plasmas: A review; Spectrochimica Acta Part B: Atomic Spectroscopy; Volume 61, Issue 1, January 2006, pp 2–30.
  • Förnsel P.: Vorrichtung zur Oberflächen-Vorbehandlung von Werkstücken (Device for surface pretreatment of workpieces); DE 195 32 412

External links

  • Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung (IFAM): Plasmatechnik und Oberflächen (Plasma technology and surfaces) – PLATO
  • Leibniz Institute for Plasma Science and Technology (INP Greifswald e.V.)
  • Generation of atmospheric plasma and effect on surfaces - Flash animations
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