Explosive generation of cold electrons in low-pressure discharges

We have investigated the mechanisms of the formation of two-temperature electron distribution functions (EDF) enriched by slow electrons in low-pressure discharges. Calculations and experiments in argon show that, as the current increases, a radical rearrangement of the EDF can occur, which is accompanied by the formation of cold electron peak in the EDF. As a result, the average electron energy strongly decreases though energy-input increases. For a current density above the critical value, a steady-state solution can be obtained only if the electron-electron collisions are taken into account. The transition mechanism is similar to that for thermal explosion being associated with nonlocal character of the EDF formation, and that is why it is the general phenomenon for low pressure discharges in various gasses.