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November 13-14, 2017 Paris, France
5
th
International Conference on
PLASMA CHEMISTRY AND
PLASMA PROCESSING
Journal of Biotechnology and Phytochemistry
Volume 1, Issue 2
Plasma Chemistry 2017
Self-organization of current structures on
electrodes of glow and arc micro-discharges at
atmospheric pressure
A I Saifutdinov
Kazan Federal University, Russia
Saint Petersburg State University, Russia
F
or gas discharges of direct current at high pressures, including
atmospheric pressure, a violation of spatial homogeneity is
characteristic. This is due to the fact that a uniform distribution
of the current density over the cross section is unstable and
current structures are formed. In addition, at high pressures, in
cases of sufficient heating of the electrodes, the glow discharge
passes into an arc. In this transition was simulated and various
scenarios of current-voltage characteristics (CVC) were shown.
However, without due attention, the study of the formation
of various current structures in the entire range of currents
corresponding to the independent discharge remained. In the
work presented, numerical studies of the formation of current
spots on the cathode and anode in micro discharges of direct
current in an argon atmosphere were carried out. A hybrid
discharge model based on the continuity equations for charged
and excited particles, heat balance equations for the electronic
and heavy plasma components, Poisson's equation for describing
the electric field, and the heat balance equations for describing
the thermal fields in the cathode and anode was considered.
On the solid-plasma boundaries, self-conjugate effect, taking
into account the heating of the electrodes, were considered.
As a result, the onset of thermionic emission was taken into
account at the cathode. Transport coefficients, as well as inelastic
processes involving electrons, were determined from the local
boltzmann kinetic equation. The formulated model described
the main parameters of a gas discharge (glow and arc discharges)
in a wide range of discharge currents and to obtain its classical
current-voltage characteristic. In this case, violation of the radial
uniformity of the plasma parameters of the discharge, which are
noticeable near the surface of the electrodes, appeared across all
sections of the CVC through a characteristic time. Perturbations
occurred randomly both on the axis of the computational
domain, forming a classical current spot, and at an arbitrary
distance from the axis, forming a ring. It is worth noting that
the ring current structures appeared on the CVC section
corresponding to a normal glow discharge. In certain cases, the
ring formed was unstable, its radius decreased and the formation
of a stationary spot occurred, as in the first case. At high values
of the discharge current characteristic of the arc discharge, the
dynamics of the formation of a contracted current spot was
obtained. The study was carried out with the financial support of
the Russian Foundation for Basic Research in the framework of
the scientific project No. 16-38-60187 Mol_a_dk.
Biography
A I Saifutdinov is postdoctoral fellow from Sain Petersburg State University, SPbGU.
as.uav@bk.ruA I Saifutdinov, J Biot Phyt 2017