Instability-enhanced friction in multi-ion species plasmas

Kinetic instabilities fulfill an important role in transport processes in low-temperature plasmas. In the case of multi-ion species plasmas, linear dielectric response theory predicts how

ion-streaming instabilities could occur and thus increase the friction between ion species through wave-particle scattering. The stability of the plasma has been found to depend on the ion concentrations, electron-ion temperature ratios, flow difference, and mass ratios. This was studied under the context of sheaths, whereby the flow difference between ion species is created through the presheath’s electric field. The instability-enhanced friction causes individual sound speeds to merge toward a system sound speed and dictates the plasma flux to the boundaries. The friction force can be calculated by taking the momentum moment of an instability-enhanced collision operator and then comparing it with PIC simulations. Moving forward, the presence of a magnetic field will be integrated into a PIC model to investigate how the instabilities and transport are affected and whether the dielectric function should be modified to account for such effects.