Volt-Ampere Characteristics of Water Vapour Discharges

We report on experimental studies of Volt-Ampere characteristics of low-pressure DC discharges in water vapour. Electrical measurements are supported by recordings of axial discharge structure by ICCD camera. Our studies are focused on conditions in the range close to the minimum of the Paschen curve and to the left of it. We analyzed discharge properties for four different electrode gaps (d = 0.55 cm, 1.1 cm, 2.1 cm and 3.1 cm) and for two pressure x electrode gaps (pd = 0.6 Torrcm and 0.3 Torrcm). By comparing results obtained for several electrode gaps we tested the validity of scaling laws for fixed pd value. We also manage to identify dominant processes at different discharge regimes