[Zurück]

H. Störi, Q. ul Ain, J. Laimer, E. Wemlinger:
"Glow-like discharges in RF operated non-equilibrium atmospheric pressure plasma jets";
Poster: XXth European Conference on the Atomic and Molecular Physics of Ionized Gases (20th ESCAMPIC), Novi Sad/Serbia; 13.07.2010 - 17.07.2010; in: "Proc. of XXth European Conference on the Atomic and Molecular Physics of Ionized Gases (20th ESCAMPIC), Eds. . Z.L. Petrovic, G. Malovic and D. Maric", European Physical Society, 34B (2010), ISBN: 2-914771-63-0; Paper-Nr. P3.42, Topic number: 10, 2 S.

Meanwhile it is well established that non-equilibrium plasmas can be produced at
atmospheric pressure by a variety of techniques; one of them makes use of atmospheric pressure
glow discharges (APGDs) operated with radio-frequency (RF) [1]. Even in the absence of
dielectric barriers uniform discharges can be sustained [2-10]. One application with great potential
is the so-called atmospheric pressure plasma jet (APPJ) [1-2,4-5,8-10]. Usually the APPJ is
operated with a gap spacing of 1 mm or even more. Hence, most investigations have been
performed in this regime. Only recently narrow gaps have attracted some attention. However, a
detailed investigation is still missing.
In the present study RF discharges were investigated in gap spacings ranging from 1 mm
down to 0,1 mm in 0,1 mm steps. Two APPJs with different size were studied; the electrode area
of device APPJ3 has half the electrode surface of device APPJ2. However, both exhibit a
sandwich structure as shown in Fig. 1. Electrodes were made of stainless steel. The experiments
were performed using pure helium as process gas at ambient conditions. An excitation frequency
of 13,56 MHz was used for the RF power. The electrical properties of the discharges were
determined using a digital oscilloscope, a high voltage and a current probe, all with high
bandwidth. The discharge pattern between the electrodes was investigated using a conventional
digital camera. The time evolution of the discharge pattern was studied using a synchronized
image-intensified CCD camera with nanosecond time resolution.