A power pulsed low-pressure argon microwave plasma investigated by Thomson scattering : evidence for molecular assisted recombination

A squared-wave power pulsed low-pressure plasma is investigated by means of Thomson scattering. By this method the values of the electron density and temperature are obtained, directly. The plasma is created by a surfatron launcher in pure argon at gas pressures of 8–70 mbar. Features of the pulse rise and decay are studied with microsecond time resolution. During the pulse rise we observe initial high temperature values, while the density is still rising. At power switch-off we find decay times of the electron density that are smaller than what is expected on the basis of diffusion losses. This implies that the dominant decay mechanism in the studied pressure regime is provided by molecular assisted recombination.