On-Line Measurement of Ion Density in Atmospheric Nitrogen Discharge Filaments via Radiation Signals from Plasma Oscillation

Diagnosis of the particle number density of plasma plays an important role in the understanding of plasma sources and processing. Regular radiation signals from plasma oscillation in fllaments of atmospheric nitrogen discharge, which were excited by the injection of secondary electron beams during the propagation of the streamer, are employed to determine the ion density of plasma and its evolution in the fllaments. Results show that the density of N + in a fllament of atmospheric nitrogen discharge is of the order of 10 13 cm i3 . It is also found that the re- combination processes play a dominant role in plasma decay, and that the ion density decreases non-monotonically with time during streamer propagation.