Steady-state ion pumping of a potential dip near an electron collecting anode

A negative potential well is found in front of a positively biased electron collecting plate in a low temperature laboratory plasma. The well parameters are governed by the Child–Langmuir condition and a necessary condition for the existence of such potential wells is the presence of an ion pumping mechanism which removes trapped ions from the wells. Here ion pumping was provided by the presence of negative electrically floating ceramic on the back of the plate.