Initiation and termination of a hydrogen dc-glow discharge plasma sheath

Understanding the formation and structure of sheaths is critical to the understanding of plasma physics. In recent decades researchers have begun to make detailed, time-resolved measurements of plasma sheaths as diagnostic technology has improved. In this work, an investigation of a dc-glow discharge sheath for a hydrogen plasma will be presented. Imaging of the plasma is performed using a gated ICCD camera to capture photographs of the plasma emission during the initiation of the sheath, as well as the termination and afterglow of the plasma, on the order of tens of nanoseconds time resolution. Studies of the plasma sheath dynamics are made for a range of rise- and fall-times of the electrode voltage, as well as a range of electrode voltages. Using an image doubler, images of H-α and H-β emission are captured simultaneously providing spatial maps of the emission intensity and spectral line ratios. To provide more quantitative measurements from the plasma emission, Langmuir probe measurements are made during the plasma steady state to ascertain plasma densities and electron temperatures at various electrode voltages and correlate those measurements to H-α and H-β intensities and spectral-line ratios.