Energy balance and plasma potential in low-density hot-filament discharges

Electron energy balance is shown to play an important role in determining the plasma potential in low-density hot-filament discharges. The confined electrons that are lost to the walls are those with energy just above the plasma potential, thus the electron energy loss rate is the product of the electron loss rate and the height of the potential barrier. The sources of the electron energy are the energy at creation plus the energy gained from equilibration with energetic, unconfined electrons. An experiment in a soup-pot plasma device demonstrates that the plasma potential has values that satisfy the energy balance equation. The ion loss rate affects the electron loss rate through the quasi-neutrality condition, thus collisions of ions play a role in determining the plasma potential by reducing the particle loss rates