Ion confinement efficiency and ionization balance in a complex DC discharge plasma

Abstract

We consider the efficiency of an ion confinement inside a cloud of charged microparticles in a low-pressure DC discharge. To describe the ion confinement efficiency in such complex plasma, we propose the indicators calculated taking into account the processes responsible for the generation, the losses, and the accumulation of ions in a cloud of charged microparticles in a plasma using a fluid model. The efficiency of ion accumulation by a microparticle cloud shows the ratio of the average ion densities in discharge with microparticles and without them. The efficiency of ion accumulation by a microparticle shows the difference of average ion densities in a discharge with microparticles and without them, related to microparticle number density. The specific power costs of the existence of one ion in a microparticle cloud determines the linear power costs of the discharge in a cloud related to the linear number of ions in it. The power efficiency of ion accumulation by a microparticle cloud is defined as a ratio of specific power costs in a discharge without microparticles, to specific power costs of ion existence in a cloud. A strong dependence of indicators on the microparticle number density has been revealed. Inefficient conditions of ion confinement inside a cloud are found. Experimental data on dynamic instabilities of a discharge with microparticles was analyzed. It is found that efficiency of ion confinement is connected with dynamic processes in complex plasma. The limiting microparticle number density is shown to serve as the criterion of the occurrence of plasma instability. Exceeding the limiting microparticle number density results, generally, in the development of dynamic instability of complex plasma, and, in inefficient states, in quenching of the discharge.