Contrib. Plasma Phys. 53, No. 4-5, 432 – 435 (2013) / DOI 10.1002/ctpp.201200072 Glow Discharge Positive Column with Dust Particles in Neon L. M. Vasilyak ∗ , D. N. Polyakov, and V. V. Shumova Joint Institute for High Temperatures, Izhorskaya str., 13 Bd.2, 125412 Moscow, Russia Received 09 October 2012, revised 11 Febrary 2013, accepted 24 February 2013 Published online 13 May 2013 Key words Dusty pasma, diffusion/drift approximation, step-wise ionization, current-voltage characteristic. Experimental and numerical study of positive column of glow discharge in neon with dust particles is presented. The influence of dust structures on integral parameters was measured and simulated. Spatial distributions of electrons and electric field configuration in presence of dust cloud are represented. The reverse radial electric field direction is shown to appear within the dust cloud at high dust particle concentration. The current-voltage characteristics of discharge in neon with and without dust particles are represented. c  2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Plasma with condensed disperse particles serves as a working medium for different types of technical arrange- ments widely used for plasma surface modification and plasma coating [1–3]. Frequently dust particles present or appear in plasma in the course of technological process and produce the significant change of both local pa- rameters of their ambient and the overall properties of a discharge. These questions were considered in recent studies [4–6]. The present study was motivated by the need to measure and simulate the influence of micron size particles on the integral characteristics of the positive column of glow discharge in neon. Experiments were carried out in a cylindrical discharge tube of 20 cm length and 16.5 mm i.d. with two ring electrodes, glued into the tube walls in front of the region of formation of dust structure for measuring the voltage drop in the positive column with and without dust particles. Dust structures were formed from melamine formaldehyde particles of 2.55 μm in diameter. The dust cloud size and dust particle concentration were determined using the microscope equipped with high resolution camcorder and diagnostic laser. For more details see [6]. The positive column was stratified and one to three strata were usually situated between the ring electrodes. The increment of the longitudinal electric field strength caused by the presence of dust structures was calculated as the difference between the voltage drop in the discharge with and without dust particles divided by the total length of the dust structure situated between the rings. As a model we consider neon plasma consisting of neutrals, electrons, ions and metastable neon atoms of 1s configuration (in Paschen’s notation) with the energy of 16.62 eV. The ionization by single electron collision with neon atom in the ground state, and the step-wise ionization through the metastable state is considered. The later process is important for the adequate simulation of the plasma ionization degree at low energies of electrons. Molecular ions and negative ions were neglected. Under our experimental conditions the collisional regime of gas discharge was realized, permitting to describe the plasma in frames of diffusion/drift approximation. We consider the positive column with uniform gas density and apply Schottky theory, basing on the idea of ambipolar diffusion of ions and electrons towards the tube walls in quasi-neutral plasma. The electric field of discharge is represented as a combination of invariable longitudinal component E l , and self-consistent radial component E r determined by radial gradient of the field potential. The radial flow densities of ions, electrons and metastables J e , J i and J m result from the superposition of drift and diffusion constituents. In the regime of ambipolar plasma J e and J i are equal. For metastables the drift term is zero. The radial flows J i,m,e submit to the equation of continuity with the corresponding source terms q i,m,e of species: divJ i,m,e = q i,m,e . (1) q i,e = k i n a n e + k im n m n e + k mm n 2 m - n d J d i,e (2) q m = k exc n a n e - k im n m n e - 2k mm n 2 m - k qa n m n a - k qe n m n e - n d J d m . (3) ∗ Corresponding author. E-mail: vasilyak@ihed.ras.ru, Phone: +07 495 484 26 10, Fax: +07 495 485 79 90 c  2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim