Gas Dishcharge Sustained By Surface Wave Propagating Along The Hybrid System
N.A. Azarenkov, A.V. Gapon
Karazin Kharkiv National University, 31 Kurchatov Ave., Kharkov
Keywords: surface wave, gas discharge, plasma technology
Study of long-length gas discharges sustained by surface waves of 10 MHz-10 GHz frequency range continues from
the middle of 80-th. Interest to this subject is based on the set of applications such as efficient plasma sources, ion and
excited atoms sources and sources of optical radiation for the purposes of spectral analysis.
Plasma column sustained by surface wave in the cylindrical dielectric tube is a classical example of this type
discharges . The plasma stability and density gradient along the column are determined by dispersion characteristics
of the surface wave. In one’s turn wave propagation conditions are entirely determined by the state of the plasma. So,
the discharge sustained by azimuthally nonsymmetrical waves exists when the product of generator frequency and
tube radius is more than constant value, which equals approximately to 2 GHz cm . It was shown  this limit
appears due to the inevitable generator frequency fluctuations. In  the condition for the sustaining wave dispersion
is derived on the base of energy conservation law.
One of the typical characteristics of the surface wave discharge in the long dielectric tube is plasma density profile
linearly decreased out of the wave launcher. Such inhomogeneity may be not desirable feature in plasma technological
processes of material etching and deposition. Some solutions for to get more homogeneous density profiles were
proposed in early works, for example, applying tapered tubes or setting up two launchers on the opposite tube ends
one toward another.
In our report it is shown that such problem appears due to mixing of two things: plasma column is the main
component of waveguide structure and simultaneously is the electromagnetic power absorber.We present theoretically
calculated structure consisted of dielectric plate, separating working gas and open waveguide. Coupling between open
waveguide and plasma can be readily controlled by changing of waveguide parameters along the wave propagation
direction. Then, two aims are achieved: wave is an eigenmode of the structure and power absorption is made to be
uniform along the structure.
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