Usually plasma sources operated at atmospheric pressure are based on arc discharges and produce thermal plasmas with temperatures well above a few thousand K. We generated an Atmospheric Pressure Plasma Jet in a capacitive radio-frequency (RF) plasma source, that results in a stable glow-like discharge with a rather low gas kinetic energy.
This kind of atmospheric pressure plasma sources provides a large area of appliances in surfaces technology, like etching, coating, disinfection, sterilisation and decontamination. Primary we focus our work on the research of stability conditions and discharge modes of the atmospheric plasma for various gas mixtures and different geometrical and electrical performances.
The discharge used for the studies is generated between two planar electrodes. One RF-powered, and the other grounded. Both electrodes are water cooled to input an electrical power up to 500W and the discharge is operated at a frequency of 13.56 MHz using an impedance matching network. In our setup the powered RF electrode is surrounded by grounded electrodes and separated from them by insulators. This construction allows a variation of the gap spacing between 0.5 and 2.5mm. Gas is injected through both side walls close to the back side where the gap between RF and grounded electrode is much larger. After flowing through the narrow gap spacing, where the discharge is maintained, gas is exhausted into ambient air.

Up to now we run the plasma jet with Argon and Helium and various insulator materials. Other gases and mixtures will be tested in near future. The discharge gap was observed with optical instruments to investigate the discharge pattern between the electrodes. The voltage across the discharge and the current are measured simultaneously as well. Our new test setup will allow us to investigate the discharge pattern between the electrodes with optical spectrometer and cameras much more precisely.