Radial Distribution of Plasma Concentration in a Positive Glow Discharge Column with Dust Particles
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PLASMA PHYSICS RADIAL DISTRIBUTION OF PLASMA CONCENTRATION IN A POSITIVE GLOW DISCHARGE COLUMN WITH DUST PARTICLES A. A. Pikalev, A. V. Sysun, and O. V. Oleschuk
UDC 533.9
The work considers the influence of dust structures on the positive column of a glow discharge. A formula describing the radial distribution of ions in the case of an extended structure in the uniform positive column is proposed. To determine the flows of ions on a particle and the potential of its surface, approximation of simulation results by the method of molecular dynamics is proposed. Examples of calculations for specific conditions of experiments are presented. Keywords: dust plasma, positive column of a glow discharge, radial distribution of the plasma concentration.
INTRODUCTION Dusty plasma contains suspended macroparticles. The particles in the plasma acquire a charge and can form ordered structures due to interactions among themselves. We investigated dust structures in a positive column of a glow discharge. Under these conditions, particles acquire the negative charge, because the energy of electrons is much greater than of ions, their mass is much less, and heating and emission of electrons are small. The parameters of the dust structure (the charge and the potential of particles and the distance between them) are determined by particle sizes, the pressure, and the nature of the gas as well as by the plasma parameters. However, in the study of the dust structures, the plasma parameters were measured only in some works. The typical parameters of the positive column of the glow discharge with dust structures [1–4] are: – Concentration and temperature of electrons and ions: ne = (3–10)108 cm−3, Te 3–6 eV, and Ti = 300 K, – Pressure p = 30–100 Pa (Ne or Ar) for free ion path lengths i = 50–200 m, – Dust particle diameters 2a = 4–50 m, – Interparticle distance l = 250–500 m for dust particle concentration nd = (0.8–20)104 cm−3, – Radius of discharge tubes rtube = 1–2 cm. High-frequency discharges have analogous plasma parameters and dust structures [5–7]. The Debye electron radius for both discharge types is De
0 kTe e 2 ne
500 1000 m. In this case, the following relationships are valid:
a / De 0.002 0.02 , i / De 0.05 0.3 , l / De 0.25 0.6 , and a / i 0.02 0.15 Let us consider theoretical works. These are works devoted to a study of ionic flows on a dust particle that determines its potential and charge, on particle interactions and establishment of steady-state interparticle distance, and
Petrozavodsk State University, Petrozavodsk, Russia, e-mail: [email protected]; [email protected]; [email protected]. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 162–170, July, 2020. Original article submitted February 15, 2020. 1282
1064-8887/20/6307-1282 2020 Springer Science+Business Media, LLC
on the positive discharge column containing dust particles as a whole. The ionic current density of the dust particle with a floating potential was considered in a numb
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