41 research outputs found
Capacitively-coupled rf discharge with a large amount of microparticles: spatiotemporal emission pattern and microparticle arrangement
The effect of micron-sized particles on a low-pressure capacitively-coupled
rf discharge is studied both experimentally and using numerical simulations. In
the laboratory experiments, microparticle clouds occupying a considerable
fraction of the discharge volume are supported against gravity with the help of
the thermophoretic force. The spatiotemporally resolved optical emission
measurements are performed with different arrangements of microparticles. The
numerical simulations are carried out on the basis of a one-dimensional hybrid
(fluid-kinetic) discharge model describing the interaction between plasma and
microparticles in a self-consistent way. The study is focused on the role of
microparticle arrangement in interpreting the spatiotemporal emission
measurements. We show that it is not possible to reproduce simultaneously the
observed microparticle arrangement and emission pattern in the framework of the
considered one-dimensional model. This disagreement is discussed and attributed
to two-dimensional effects, e.g., radial diffusion of the plasma components
Dust density waves in a dc flowing complex plasma with discharge polarity reversal
We report on the observation of the self-excited dust density waves in the dc
discharge complex plasma. The experiments were performed under microgravity
conditions in the Plasmakristall-4 facility on board the International Space
Station. In the experiment, the microparticle cloud was first trapped in an
inductively coupled plasma, then released to drift for some seconds in a dc
discharge with constant current. After that the discharge polarity was
reversed. DC plasma containing a drifting microparticle cloud was found to be
strongly non-uniform in terms of microparticle drift velocity and plasma
emission in accord with [Zobnin et.al., Phys. Plasmas 25, 033702 (2018)]. In
addition to that, non-uniformity in the self-excited wave pattern was observed:
In the front edge of the microparticle cloud (defined as head), the waves had
larger phase velocity than in the rear edge (defined as tail). Also, after the
polarity reversal, the wave pattern exhibited several bifurcations: Between
each of the two old wave crests, a new wave crest has formed. These
bifurcations, however, occurred only in the head of the microparticle cloud. We
show that spatial variations of electric field inside the drifting cloud play
an important role in the formation of the wave pattern. Comparison of the
theoretical estimations and measurements demonstrate the significant impact of
the electric field on the phase velocity of the wave. The same theoretical
approach applied to the instability growth rate, showed agreement between
estimated and measured values.Comment: 7 pages, 4 figure
Physics and applications of dusty plasmas: The Perspectives 2023
Dusty plasmas are electrically quasi-neutral media that, along with electrons, ions, neutral gas, radiation, and electric and/or magnetic fields, also contain solid or liquid particles with sizes ranging from a few nanometers to a few micrometers. These media can be found in many natural environments as well as in various laboratory setups and industrial applications. As a separate branch of plasma physics, the field of dusty plasma physics was born in the beginning of 1990s at the intersection of the interests of the communities investigating astrophysical and technological plasmas. An additional boost to the development of the field was given by the discovery of plasma crystals leading to a series of microgravity experiments of which the purpose was to investigate generic phenomena in condensed matter physics using strongly coupled complex (dusty) plasmas as model systems. Finally, the field has gained an increasing amount of attention due to its inevitable connection to the development of novel applications ranging from the synthesis of functional nanoparticles to nuclear fusion and from particle sensing and diagnostics to nano-contamination control. The purpose of the present perspectives paper is to identify promising new developments and research directions for the field. As such, dusty plasmas are considered in their entire variety: from classical low-pressure noble-gas dusty discharges to atmospheric pressure plasmas with aerosols and from rarefied astrophysical plasmas to dense plasmas in nuclear fusion devices. Both fundamental and application aspects are covered
A way of estimating the convergence rate of the Fourier method for PDE of hyperbolic type
summary:The Fourier expansion in eigenfunctions of a positive operator is studied with the help of abstract functions of this operator. The rate of convergence is estimated in terms of its eigenvalues, especially for uniform and absolute convergence. Some particular results are obtained for elliptic operators and hyperbolic equations