INVESTIGATION OF EFFICIENT DESIGNS OF HOLLOW CATHODES

摘要

This paper investigates modifications to QinetiQ's T6 hollow cathode with the aim of extending lifetime, and discusses results from initial experiments. The modifications aim to streamline the flow of the plasma through the hollow cathode, channelling it out of the exit orifice. It has been shown from previous research (Gandhi, et al and Fearn, et al) that changing the internal profile can increase the efficiency of the hollow cathode and that is a prime candidate for reducing temperature. During a discussion with QinetiQ, it was said that a drop of 40℃ could lead to an extension of cathode lifetime by up to 50 percent. Testing on a control hollow cathode was carried out specifically looking at temperature. It was found that the hollow cathode reached tip temperature in excess of 1200℃ taken using an optical pyrometer. This was confirmed by visual observations of recrystallisation at the tip of the cathode after removing it from the chamber. Further discussions of tip temperature observations, as well as the current-voltage characteristics, are included in this paper.