Laser probe investigations of the initial stage of spark discharge in air in the tip (cathode)–plane gap

A spark discharge in a 1.5-mm-long tip (cathode)-plane gap in the time interval from the breakdown onset to 200 ns has been studied. Тhe discharge has been found to arise in the form of a bundle of microchannels. The dynamics of the discharge spatial structure, the electron concentration, the gas temperature in the channel, and the velocity of its radial expansion have been determined.