Parameters of electric spark microchannels in the near-anode region of the discharge

We consider the formation of an electric spark from a point anode in atmospheric air when the primary spark channel from a very early stage of its evolution immediately begins to develop in the form of a cluster of highly ionized plasma microchannels. Using laser probing at a wavelength of 1064 nm, spark microchannels are resolved in the near-anode region of the discharge, and the data on the magnitude and distribution of the plasma electron density of single microchannels are obtained. It is shown that during the first nanoseconds after the discharge gap breakdown, the electron density in individual microchannels is distributed nonuniformly and ranges from 10¹⁸ to 5 × 10¹⁹ cm^–3, with characteristic microchannel diameters being of 20 – 50 μm.