Formation of Non-Monotonic Potential Structure in the Detached Plasma

Plasma detachment has been investigated by means of PIC simulation which includes plasma-neutral collision and Coulomb collision. In our previous study, we have shown that a strong gradient in temperature appears in front of the target plate in the case that high density and low temperature neutral gas is introduced.\footnote{T. Pianpanit et al. Plasma and Fusion Res. \textbf{11}, 2403040 (2016).} It is observed that a potential hill is created in the neutral gas region where ions lose energy due to the elastic and charge exchange collision and, as a result, the ion density increases. This potential structure traps the low energy electrons and may play a role in the development of plasma detachment state.