Spatial and temporal spectroscopy of a streamer discharge in nitrogen

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Abstract
The light emitted during the different stages of the spark development in nitrogen has been observed with spectroscopic methods. The first detectable light is emitted with sufficient intensity just after the critical amplification. This type of radiation continues till the start of the heating of the plasma in the predischarge channel. It allows one to determine the electron density and to calculate the current in the predischarge channel. At about 170 ns after the start of the avalanche the dissociation of the molecules and the ionization of the atoms takes place near xcrit in times of a few ns. This causes a rapid increase of the current and the emission of a strong continuum intensity as well as the emission of atom and ion lines. Now the predischarge channel transforms into a plasma channel at a current of about 10 A. Applying plasma diagnostic methods in the spectral range of 3000-8600 AA the temperatures and the electron densities as function of time and radius of the channel can be derived in the plasma channel.