Thermalisierung und zeitliche Entwicklung der Elektronendichte und Temperatur von Funkenkanälen in Wasserstoff

Abstract

In a streamer initiated pre-discharge channel in H2 the axial and radial electron density distributions were measured at different times of the channel development. It was found that at any point in the channel where the electron density reaches ≅ 2 - 1017 cm-3 an immediate thermalisation of the plasma at this point takes place in a time of ≅ 10 nsec. Due to the inhomogeneous radial and axial electron density distribution in a streamer initiated discharge channel the thermalisation begins at first in a constricted region of the channel. The further development of the electron density and temperature distributions in the thermalized channel was studied by means of spectroscopic plasma diagnostic methods in channels initiated by different overvoltages. These experiments have shown that the inhomogeneous axial electron density distribution is equalized after a time of ≅ 100 nsec. The maximum electron density of ≅ 1 - 2 - 1018 cm-3 is reached in the channel axis immediately after the thermalisation of the channel whereas the temperature increases during the time of the highest energy input to the maximum of ≅ 5 - 6 • 104 °K