Numerical study of presheath evolution in multicomponent dusty plasmas

The transition of bulk plasmas to the walls involves a variety of complex phenomena that are of considerable interest from both physical and technical perspectives. This study numerically examines the evolution of the presheath in a multicomponent dusty plasma containing an electron beam emitted from a cathode. Our results indicate that the characteristics and polarity of the presheath are profoundly influenced by the properties of the electron beam. Particularly, we observe that at a specific current density of the electron beam, the formation of the presheath becomes impossible, resulting in a singularity in the evolution of presheath, where the presheath potential approaches infinity. The numerical analysis further demonstrates that the polarity of the presheath is altered upon traversing the singularity. The obtained data prove that the dynamics of ions play a crucial role in the evolution of presheath. For cold ions, in the low e-beam density regime, an increase in e-beam current density leads to a rise in presheath potential. Conversely, in high electron beam density conditions, the absolute value of the presheath potential diminishes as the electron beam current density increases. Our research further reveals that in plasmas consisting of thermalized ions, increasing the beam current density and the cathode potential leads to nonlinear reductions in presheath potential for both polarities of dust grains. Numerical assessments of the modified Bohm criterion indicate that an increase in ion temperature results in an increase in presheath potential. This behavior is affected by the characteristics of the electron beam as well as the polarity of the dust grains.