A non-Maxwellian kinetic approach for charging of dust particles in discharge plasmas

Abstract

Effect of large-angle scattering, ion flow speed and ion-neutral collisions on dust transport under microgravity conditions V Land and W J Goedheer Abstract. Nanoparticle charging in a capacitively coupled radio frequency discharge in argon is studied using a particle in cell Monte Carlo collisions method. The plasma parameters and dust potential were calculated selfconsistently for different unmovable dust profiles. A new method for definition of the dust floating potential is proposed, based on the information about electron and ion energy distribution functions, obtained during the kinetic simulations. This approach provides an accurate balance of the electron and ion currents on the dust particle surface and allows us to precisely calculate the dust floating potential. A comparison of the obtained floating potentials with the results of the traditional orbital motion limit (OML) theory shows that in the presence of the ion resonant charge exchange collisions, even when the OML approximation is valid, its results are correct only in the region of a weak electric field, where the ion drift velocity is much smaller than the thermal one. With increasing ion drift velocity, the absolute value of the calculated dust potential becomes significantly smaller than the theory predicts. This is explained by a non-Maxwellian shape of the ion energy distribution function for the case of fast ion drift.

One-dimensional vertical dust strings in a glass box

“…The energy balance for electrons is also solved using a similar drift-diffusion approximation while the ion energy is assumed to be locally dissipated through frequent collisions with neutral atoms. A complete explanation of the fluid model can be found in [23,24]. The resulting profiles for the electron density, ion density, electron temperature, and ion velocity were used in the current balance equation to obtain the dust potential as a function of height above the lower electrode, z, with the results shown in Fig 6(a).…”

Modeling the interaction between two dimensional strongly coupled confined dust clusters

“…This is true if the electrons and ions relaxation time are smaller than the characteristic time of the physical phenomenon under consideration. Recently, Alexandrov et al 20 used a hybrid numerical model based on the Monte Carlo method and particle-in-cell simulation to show that the ͑OML͒ approach can be valid for a weak electric field. The ion drift velocity must be less than the thermal velocity, such as in the central region when the plasma is produced by a capacitively coupled radio frequency discharge.…”

Manipulation of the plasma-dust layer in high-frequency discharge with an additional alternative phase

“…The simplest Monte Carlo simulation approach is based on (I) moving the particle in accordance with the equation of motion for time t  (updating the position and velocity vectors) and (II) verifying the occurrence of the collision using equation (3). In practice, it is necessary to choose t  sufficiently small to realize the exact integration of the equation of motion and to withstand the probability of more than one collision, the motion of the particle will occur during a time step with a negligibly small value.…”

“…Complex (dusty) plasma is actively studied all over the world, both for a fundamental understanding of the dynamics of strongly coupled open systems [1][2][3][4] and for practical purposes [5][6][7]. In the laboratory, dust plasma is investigated in various types of gas discharge [8].…”