Cross-field sheath physics in multi-ion species plasmas

In low-temperature plasmas, transport processes in sheaths and presheaths can be significantly influenced by kinetic instabilities and can also be modified by the presence of external magnetic fields. Previous work has shown that in unmagnetized multi-ion species plasma sheaths, the ion-ion two-stream instability can enhance ion-ion friction due to wave-particle scattering as well as enhance ion heating as indicated by an increase in the energy exchange rate in the second moment of the kinetic equation. In weakly collisional plasmas, these mechanisms may have an important role in cross-field transport where the magnetic field suppresses the electron mobility. In this work, 1D3V particle-in-cell simulations are used to model cross-field multispecies sheaths, and a modified kinetic Bohm criterion is developed to account for the presence of the magnetic field. Using linear response theory, the dielectric response function is modified to account for magnetization and instability-enhanced phenomena are investigated.