DC POINT-TO-PLANE DISCHARGE IN PURE OXYGEN IN THE 50-760 TORR PRESSURE RANGE

The present work is a part of a general study dealing with pure gases at pressures in the 50-760 Torr range. This experimental study concern s discharges occurring in oxygen, between a 100 mu m curvature radius rhodium point and a stainless steel plane 1 cm distant. A positive de high voltage is applied to the point using a 0-30 kV, 0-10 mA power su pply. Electrical measurements are performed so that voltage-current ch aracteristic curves can be drawn for the whole pressure range. Current impulses are recorded at the earthed plane in each typical regime of the discharge. These electrical impulses are compared with the simulta neous optical signals obtained from a photomultiplier. A focalization on the photomultiplier of various precise spots in the interelectrode gap allows one to get some information about the propagation of an ion izing front from the high-voltage electrode to the grounded plane. Fro m comparison with previous studies, it may be inferred that the glow r egime is more difficult to visualize on the characteristic curves than it is in the case of nitrogen. However, 'streamer-like' impulses are observed for oxygen in the whole pressure range, which is not the case for nitrogen. The continuity between these streamer-like impulses and the 'classical' streamers observed at atmospheric pressure seems to b e established and confirms the important role played by electronegativ ity in the inception of ionizing fronts.