Ion accumulation by a dust cloud in a dc discharge

摘要

The ion accumulation within the negatively charged dust cloud embedded in a plasma of dc glow discharge has been studied numerically under the conditions corresponding to recent experiments. The characteristics of neon plasma in a positive column of dc discharge with various densities of micron-sized particles have been simulated by a diffusion-drift model with the use of experimental values of parameters of dust clouds. The model considers an additional gas heating associated with the presence of a dust component. It has been shown that the injection of dust particles into a plasma can either reduce the density of ions due to their recombination on dust particles or increase it due to the formation of an ion concentrator. Conditions under which the plasma-dust cloud represents an ion concentrator have been found; the density of ions in this trap can be several times higher than that in a discharge without dust particles. The method of elevating the ion density with dust particles has been shown to be more efficient than increasing the discharge current without dust particles and the value of relative overheating of the discharge with dust particles is many times less. The possibility of obtaining the desired ion density in a dust cloud at different neon pressures and the same discharge current has been demonstrated; it should be emphasized that this is impossible in a discharge without dust particles.