In slot antenna (SLAN) type plasma sources the microwave power is coupled from an annual waveguide (ring cavity) through equidistantly positioned resonant coupling slots into the plasma chamber made of quartz. The symmetrical power distribution and the surface wave at the plasma-quartz interface allows large-area plasma generation. Three plasma sources with 4, 16 and 66 cm quartz tube diameter (ring cavities with 4, 10 and 30 coupling slots respectively) are compared. The ECR versions of them are also considered. The ignition performance and operation pressure range are presented. Plasma parameters (ion concentration, electron temperature) and their radial and axial distributions are shown. The computation tools used for the design of sources with different dimensions are described. The scaling rules and limitations of up-scaling are discussed. These are plasma inhomogeneity due to diffusion and recombination processes, thermal load of the microwave components, and thermal and mechanical load of the plasma chamber and substrates. The up-scaled discharge architecture for remote processing, suppressing the direct microwave heating and ion bombardment is proposed.
A new large-volume microwave plasma source of interest for technological applications has been developed. An annular waveguide resonator with axial slots on its inner side acts as a field applicator to sustain a plasma at 2.45 GHz in a fused silica cylinder of 16 cm in diameter and 49 cm in length. The distance between slots is equal to a waveguide wave length. The slot antenna (SUN) extends axially for about 9 cm. The plasma fills the tube axially as a result of surface wave propagation at the plasma-fused silica interface. The geometrical properties of the S U U , ~O W O , t : U ~L I I I I I L ~U " ~ use "I a I I " I I I C : , I M I ~u U C : a l l " W l l l ~~a l ~" l a U U I I U1 c.IcullGaal!umagnetic fields inside the slot antenna. The calculated field patterns fit perfectly to those collected by use of a small loop antenna inside the SLAN without a plasma A long time stable operation of the plasma source for pressure range from 0.01 to 1 mbar and Dower ranae from 50 to 1200 W was achieved. Argon Dlasma was
A novel atmospheric pressure plasma jet with a cylindrical symmetry i.e. a tubular dielectric barrier and two tubular electrodes was developed at Microstructure Research Center – fmt, Wuppertal, Germany. The jet was investigated by means of ultra fast (down to tens of nanoseconds exposition time) ICCD photography and regular CCD photography. Some spectacular results were achieved and their partial explanation was presented. The jet acts as a “plasma gun” throwing small “plasma bullets” out of its orifice. The most important findings are: (i) the bullet velocity is approximately 3 orders of magnitude larger than the gas flow velocity, and (ii) the jet dynamics is mainly electrical field controlled. A simple model - formation of a jet in air - based on a Helium metastables core can explain qualitatively reasonably well most of our experimental observations. Some variations of the original cylindrical jet geometry were presented and discussed: microjet and fmt Plasma-Pen, single tube multijet, tube-in-tube single and multijet systems (so-called “Wuppertal-Approach”).
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