Production of seed electrons in N2

This paper deals with the nature of seed electrons source in compressed N₂ for positive polarity. We present an experimental procedure which gives evidence of the fact that collisional detachment from negative ions play the major role in the supply of seed electrons. The order of magnitude of the delay needed by the ion density to recover its background equilibrium level was evaluated experimentally. The role of impurities, especially water vapour and oxygen, are emphasized. The results are presented as Von Laue diagrams and interpreted in terms of the critical volume concept