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J. Laimer, S. Haslinger, H. Störi:
"Characterization of an atmospheric pressure radio-frequency capacitive plasma jet";
Poster: 10th Intern. Conf. on Plasma Surface Engineering (PSE), Garmisch-Partenkirchen/D; 10.09.2006 - 15.09.2006; in: "Book of Abstracts, 10th Intern. Conf. on Plasma Surface Engineering (PSE)", (2006).

Today, non-equilibrium atmospheric pressure plasmas attract more and more attention. They can be realized by a variety of techniques, one of them is the atmospheric pressure plasma jet (APPJ). The APPJ operates in a capacitively coupled configuration using radio-frequency (rf) power and produces a stable glow-like discharge without dielectric material between the electrodes.
We developed an APPJ with planar electrodes featuring a rectangular cross section of the effluent. The exit of the APPJ has a width of approximately 50 mm and a gap spacing, which can be adjusted between 0.5 mm and 2.5 mm in steps of 0.5 mm. The APPJ was operated with pure helium, pure argon, mixtures of helium and argon and with admixtures of nitrogen and oxygen.
The electric properties of the APPJ were studied by measuring voltage and current simultaneously by using a high voltage probe a current probe and a digital oscilloscope. Additionally, pictures showing the front view of the discharge were taken with a digital camera. Alternatively, an optical spectrometer was used to study the emitted light across the gap with spatial resolution.
Two very distinct discharge modes were observed. The first one is a rather uniform glow-like mode, which was identified as the A-mode of an rf discharge. This mode is only stable up to a certain power limit, where a transition to another discharge mode occurred. Depending on the conditions used this mode was identified as either a pure Gamma-mode of an rf-discharge or a coexisting Alpha- and Gamma-mode. The Gamma-mode (high current density mode) covered the electrodes only partially.