Experimental Comparison of Conventional-Hollow and Coaxial-Hollow Cathode Low-Pressure Arcs

摘要

A one-meter coaxial-hollow cathode argon arc was investigated experimentally and the results obtained were compared with already-documented data on conventional-hollow cathode low-pressure argon arcs. The outer diameter and inner diameter of the hollow cathode, used for comparison purposes, were 1.91 and 0.953 centimeters, respectively, while the outer diameter of the coaxial cathode was 1.91 centimeters and its inner diameter was 1.27 centimeters. Radial profiles of the electron temperature and density in the arc plasma were measured by a Langmuir probe; current profiles were measured by an electrical profile scanner device. A plasma sweeper provided data on electron density. The data obtained by all methods for the low-pressure arc of the coaxial-hollow cathode were consistent in repeated tests and consistent with the data available on the low-pressure arc of the conventional-hollow cathode. The maximum electron temperature was 4.8 electron volts; the electron density average for the arc column was 3 x 10 to the 12th power per cu cm. With the coaxial arrangement for a cathode of any fixed dimensions, the coaxial type can be run at higher power than a conventional single-element hollow cathode of the same dimensions. (Author)