On the relation between ion oscillations and travelling double layers in a positively biased single-ended Q-machine

As is known low-frequency oscillations can be excited in a low-density single-ended Q-machine between the hot plate (HP) and an ''exciting'' electrode (E) biased positively with respect to HP. For large positive bias (>2V) the oscillations of the ion component have been shown to exhibit for fundamental frequency the character of a standing wave with half a wavelength corresponding to the distance between HP and E. The authors present an experimental result which shows the presence of a small travelling phenomenon which is superimposed on a dominant standing wave behaviour of the ions. (Auth.)