Coupling parameter for low-temperature plasma with condensed phase

Abstract

The detection of plasma crystals in the dusty plasma [1,2], and the ordered structures of the condensed grains in the plasma of combustion products (smoky plasma) [3,4] stimulated the research of mechanisms of the charged grains interaction in the low-temperature plasma and definition of the criteria parameters of phase transition. Thus it has been found out that the formation of the ordered structures of dust grains occurs in strongly coupled (nonideal) plasma. It has been suggested to use a Coulomb coupling parameter Γ, defined as the ratio of the potential energy of Coulomb interaction between neighboring particles and their kinetic temperature, in order to distinguish the weakly coupled plasma and the strongly coupled plasma [5–11]. The application of such a form of coupling parameter for the description of the condensed grains interactions in the smoky plasma is not always comprehensible, which is caused by a number of its specific properties. The principal distinction of the smoky plasma from discharge dusty plasma is its thermal collision nature. The displacement of ionization equilibrium in the plasma gas phase, caused by the presence of a noncompensate volume charge, is formed in plasma due to the interphase interaction [12]. The condensed grains are formed by homogeneous and heterogeneous condensation in the smoky plasma at burning. Therefore, the condensed phase contains a multimode distribution function for sizes of grains of submicron fraction. This enables us to consider the dusty and smoky plasma as two different kinds of plasma with a condensed disperse phase. Thus, multimode distribution functions for the mentioned grain sizes and the displacement of ionization equilibrium do not make it possible to use the coupling parameter, obtained both for the dusty and smoky plasmas. The present paper is devoted to the development of a coupling parameter applicable to the description of polydisperse systems such as the smoky plasma.