Thermophoresis in Plasma with Structures of Charged Dust Particles
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USTION, EXPLOSION, AND SHOCK WAVES
Thermophoresis in Plasma with Structures of Charged Dust Particles V. V. Shumovaa, b, *, D. N. Polyakova, and L. M. Vasilyaka aJoint
b
Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received January 15, 2020; revised January 15, 2020; accepted February 20, 2020
Abstract—The phenomenon of thermophoresis in a gas discharge in neon is studied in the presence of structures of charged dust particles. This system can simulate gas with combustion products in the form of a condensed dispersed phase. The relationship of the thermophoresis force acting on charged dust particles in a plasma with their concentration and gas pressure is analyzed. It is shown that with decreasing gas pressure the dependence of the thermophoresis force on the concentration of dust particles increases due to the mutual screening of the dust particles. Keywords: dusty plasma, thermophoresis, charged microparticles, dust structure, dust void, hollow dust structure, glow discharge DOI: 10.1134/S1990793120040223
INTRODUCTION The condensed dispersed phase (CDP) particles formed during the combustion of fuels or introduced as catalysts participate in transport processes in the gas and can affect the operation of engines and chemical reactors [1, 2]. When an electric field is applied or in the plasma of a gas discharge, these particles are charged and can form dust structures. Gas discharge plasma with CDP microparticles (dusty plasma) is a unique model system for research in plasma physics, elementary processes, and transport processes in gas; and it is also used to modify the surface and deposit oriented coatings on micron and submicron particles [3, 4] together with other technologies [5, 6]. The number and concentration of microparticles confined in the discharge, as well as the shape and position of the dust structures, are self-consistently determined by the parameters of the potential specified by the superposition of the forces acting on the microparticles. The study of the effect of the discharge current on the shape of dust structures makes it possible to obtain data on the magnitude of the forces acting on microparticles in the plasma, which are necessary for the development of dusty plasma models [7–19]. The discharge current is the main parameter that determines the heat release of the discharge. Its value determines the shape of the dust structure, which was observed in the plasma with various sizes of dust particles and at different gas temperatures [8, 10–12, 17, 20–25]. The increase in the current at room temperature is usually accompanied by the formation of a cavity—a dust void—in a dust cloud. For the first time, a transition to dust structures with void (ring dust struc-
tures) in long discharge tubes with increasing current in a direct current discharge was detected in helium, argon, nitrogen, air, and their mixtures in [20].
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