Electron distribution function in the anode region of inert gas discharges at low pressures and currents

The formation of the electron distribution function (EDF) in the anode region of an inert gas discharge at low pressures and currents is analysed on the basis of non-local electron kinetics in spatially inhomogeneous fields. The deformations of the distribution function occurring in the axially extended, non-uniform quasi-neutral plasma disturbed by the anode and in the thin collisional sheath of space charge are studied. The EDF is modelled for the two field configuration observed in experiment. One is a constant electric field in the positive column ascending to a strong field due to space charge. The second configuration consists of weak field region between the positive column and the strong field in the anode sheath. The specific deformation of the electron distribution is demonstrated, in particular, its population with high-energy electrons in a strong field of space charge. Interesting kinetic phenomena, such as deformations of the EDF in the weak field region near the anode are found. Particular calculations are carried out for discharges in neon.