NEW RESULTS ON A POINT-TO-PLANE DC PLASMA REACTOR IN LOW-PRESSURE DRIED AIR

Electrical and mass-spectrometric studies of a glow discharge produced by a direct current positive voltage applied to a point-to-plane gap in low-pressure dry air have provided many useful results, which help to clarify the interaction of the underlying physical mechanisms. Syst ematic studies of this discharge show that electrical parameters and g as pressure influence drastically the cold plasma behaviour. A dischar ge state similar to that of Townsend is obtained for a restricted regi on of operation while, outside this region, similarity rules seem not to be fulfilled. The main ions detected during the Townsend-like disch arge are O-2(+) and NO+ while, after breakdown, dissociation products such as O+ and N+ as well as N-2(+) ions are detected. It has been fou nd that ion detection depends strongly upon cathode dark space structu re.