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Simulations
(Click
the title to view the movie)
3D Fully Kinetic (Monte-Carlo/PIC) simulations of
a sustain discharge in a PDP Cell (2004).
This is the first (and the
only) 3D kinetic
simulation of a pdp cell. In this movie we show the most
interesting and important (energy-wise) part of the sustain discharge, when one can observe the striations above the anode and the
spread of the discharge over the cathode (the cathode wave). This part of the
discharge can't be reproduced using fluid methods. The arc-shape of
the front of the cathode wave, and the shape of the striations with maximum
density at the ends of arcs have been observed experimentally. Simulations were
made for a 7%Xe-93%Ne mixture, commonly used in the PDP panels. The number of
particles in the last frame of this movie exceeds 3,000,000.
Dynamics of
the breakdown of the discharge gap at high overvoltage (2004).
Here we studied the dynamics of the
breakdown of the discharge in a gap between two plane electrodes at high
over-voltage (3D MC/PIC). In these simulations, the macroparticles represent
exactly their physical counterparts (one
ion/electron is represented by just ONE macroparticle!). Total of up to
250 million of ions and electrons are tracked on a
up to 64 processors. The breakdown is initiated by a single seed electron, and
then an ionization region formed at the anode spreads toward the cathode. Such
realistic simulations allow the elucidation of the role of fluctuations in
microdischarges, when the gap width is small and the number of particles is
relatively low. When the charge produced by an avalanche originated by just a
single electron emitted from the cathode is comparable with the charge at the
tip of the ionizing wave, its front moves erratically (see 800um gap case).
3D
Fluid simulation of a sustain discharge in a PDP Cell (1998). This is the first 3D simulation of the
discharge in a pdp-cell. We
used 7%Xe-93%Ne mixture for the simulations, and the local field
approximation for the kinetic coefficients and rates. Although these
simulations feature good general similarity with a real discharge, ( fast comet-like
development of the initial part of the discharge; influence of the dimensions of certain elements
and dielectrics on the discharge; cross-talk between cells, etc.) they
give a wrong shape and the speed of the cathode wave, as well as they don't
show any striations. As any fluid simulations, they also can't provide
reliable information on the efficiency of the discharge.
3D Fluid simulation of
the cathode wave (2000). Here we tried to analyze the properties
of the cathode wave (speed, shape) using hydrodynamic simulations.
Unfortunately the numerical diffusion in the very front of the cathode wave
is too strong, so the shape of it is clearly triangular (top view), rather
than arc-like. Even high-resolution simulations had this triangular shape,
though the tip was much better. The problem was resolved only in the
Monte-Carlo simulations (above). General characteristic of the discharge -
currents through electrodes, etc. are in good agreement with experiment.
Monte-Carlo simulations of the avalanche sliding along the surface
(2004).
When doing fluid simulations related to PDPs we came
across a strange effect - the discharge sustained or even grew, long
after it was expected to die. For example, we can place a small amount
of electrons in a long narrow channel, with electric field directed at about
45 degrees to the surface and even if we "turn off" the secondary emission (to
avoid secondary avalanches), the ion/electron density in the gap can stay much
longer than the ion drift time between walls. We used extremely low density of
electrons, so that all nonlinear effects were negligible.
Further investigation
have
shown that this is a real effect caused by electron diffusion, it has nothing
to do with fluid approximation, and can be observed in MC simulations.
In the movie we show the avalanche initiated with just
one electron, sliding along the narrow channel with electric field directed at
a large angle to the surface. To worsen the case, we have chosen the
secondary emission to be zero. Remarkably, the avalanche propagation effect is
present even in the uniform electric field, in the absence of any effects
related to a space or surface charge.
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