Theory of holow cathode arc discharges. I. Energy transfer in cascade from electrons to neutral particles. Application to argon

The formation of a plasma column inside a hollow cathode in the normal arc regime is due to the injection of fast electrons, with a few tens of electron-volts, which transfer a large amount of their initial energy to neutrals by inelastic collisions in cascade. A model describing this energy degradation problem in the electron velocity space has been studied which gives the number of ionizations and excitations per primary electron injected in the plasma as a function of their initial energy. Numerical results obtained in argon are given. The role played by the excited states in stepwise ionization is also discussed and demonstrated