Published online by Cambridge University Press: 15 October 2001
The aim of the present work is to provide data to understand better and quantify the dielectric strength of pure compressed N2 (1 < P < 8 bar). The lack of agreement of results found in the literature leads us to study the electrical and physical characteristics of this gas as a function of a wide set of parameters. Experiments are mainly performed in point to plane nitrogen gaps up to 40 mm length using three different rod radii. Gas conditioning phenomenon in positive polarity and corresponding change in characteristics of discharge mechanism are demonstrated here. In our experimental conditions, no leader is involved in the discharge development whatever the polarity is. The values of the breakdown reduced field $E_{\rm b}/P$ are determined as a function of the pressure. Two different experiments are performed in order to take into account the mechanisms of initiatory electron production: the influence of the γ-ray irradiated N2 and that of the surface roughness of the HV electrode. In negative polarity, the free electrons are provided from the cathode whereas they are provided from the gas under positive polarity. Voltage waveform influences on the U50 breakdown voltage are dealt with in a large pressure range (1 < P < 12 bar). The role of the non-uniformity of the applied electric field on the U50 value is pointed out in both polarities. Finally, the reduced guiding field of negative streamer is experimentally measured.