Energetic ion bombardment of the grounded anode in pulsed DC-glow discharges

Abstract

We present measurements of ion-energy distributions of the ions impinging on the grounded anode of a pulsed argon DC-glow discharge (cathode voltages of –300 to –450 V, and a gas pressure of 0.5 mbar) with on and off pulse times of 100–900 μs. During the on pulses of the discharge, as expected, low energy ions (<10 eV) were observed, originating from the potential difference between the plasma (i.e. the plasma potential) and the grounded anode. However, during the initial tens of microseconds of the off pulse, ions were detected with energies of the order of the cathode potential (i.e. several hundred eV). Furthermore, voltage measurements of a floating anode show that the plasma potential has a high positive voltage peak during the onset of the off pulse. The explanation of the observed phenomena must be sought in the sudden change in the boundary conditions of the discharge and the subsequent redistribution of charged particles, leading ultimately to the collapse of the discharge. This has been confirmed by Monte-Carlo simulations of the discharge.