Recent progress in the understanding of electron kinetics in low-pressure inductive plasmas

The electron kinetics of low-pressure plasmas is often dominated by the so-called “nonlocal” behavior of electrons which becomes evident if the electron energy relaxation length is of the order or larger than typical discharge dimensions. In this paper, a brief review of the various manifestations of “nonlocal electron kinetics” is given. Two effects based on nonlocal electron behavior are discussed in more detail. (1) In a steady-state inductive plasma, a flux pattern in electron energy–configuration space was observed through Langmuir probe measurements which resembles a convection cell. Comparisons between Langmuir probe measurements and numerical solutions of the Boltzmann equation are presented. (2) The temporal evolution of the electron distribution function was studied in the afterglow of a pulsed inductive plasma. An unusually fast decay of the electron mean kinetic energy was observed which is related to “diffusive cooling” of electrons.