Excitation of nanosecond waves on positive columns

Abstract

Nanosecond pulses are launched, and propagate on a positive column in the form of electron waves. The dispersion of the pulses is studied experimentally, and is found to be in agreement with monochromatic experiments and theory. Apart from wave attenuation, which is observed to depress signals of higher frequencies, Fourier analysis of the received pulses has revealed that the launching mechanism favours frequencies in the vicinity of 1/6ωp A full-wave theory, based on an extension of Goubau's excitation theorem, is derived, and successfully contrasted with experiment.