Hollow cathode conditioning and discharge initiation

In the framework of developing a fast-starting hollow cathode, one must understand how a cathode is conditioned for operation. The desorption of known contaminates as a function of heater power was measured to quantify cathode conditioning characteristics. In addition to conditioning, a study of hollow cathode emission characteristics under vacuum conditions was performed. Results of these two studies are described herein along with measurements of the temperature of the cathode as a function of time and heater power. The data are used to validate a transient surface diffusion model that describes the migration and surface coverage fraction of low-work-function material from the interior of the hollow cathode to the orifice barrel and to the exterior surface of the orifice plate of the cathode. A sufficiency condition is presented for our cathode geometry of vacuum emission current level and the ability to start a hollow cathode discharge once gas flow is initiated. (c) 2008 American Institute of Physics.