Zur Entwicklung einer Elektronenlawine bei Überspannung in N2Teil 2. Kanalaufbau

Abstract

In N2 and N2 with a small amount of CH4 the transition of an electron avalanche into the streamer formation (anode- and cathode directed streamers) was investigated under pulsed homogeneous field conditions. The temporal development of this transition was measured at different overvoltages using photomultiplier techniques and by photographing the discharge itself. By comparison of oscillograms and photographs the velocities of the anode directed streamers, which start at carrier amplifications of ≅108. as well as the velocities of the cathode directed streamers were determined confirming the cloud chamber measurements. The anode directed streamer starts already in the region in which the carrier amplification is still reduced by the space charge of the avalanche itself. The cathode directed streamer always starts some nsec later. At the beginning of the development of the cathode directed streamer a small brightly shining neck appears in the region of the increased ionic space charge field of the avalanche, which can still be seen in later stages of the spark development.