ABSTRACT
This work covers the experimental activity on a hollow cathode designed for the 5kW HET and the theoretical-numerical study of the process discharge of it in the test configuration.
This hollow cathode represents the first prototype for HETs, designed completely at the Centrospazio in a previous work, so the experimental activity has been focused on the start modes according to a typical procedure of activation of hollow cathodes and on the discharge stability for some mass flow rates and anode voltage. Therefore, the hollow cathode has been tested through a simple diode configuration. In order to carried out these tests a support has been designed to fix the hollow cathode on the ALTA IV4 vacuum facility and to connect it at xenon feed pipe and power supply.
The experimental data have allowed to calculate the electrical characteristic hollow cathode and to put in evidence, at the moment of the start-up, a certain instability of the arc discharge between the cathode and keeper just turned-off the heater. However, the arc discharge between cathode and anode has been resulted fairly stable and to avoid an overheating of the anode the hollow cathode has been turned off.
At last, in the study of the physical model on the region discharge between cathode and anode the plasma has been considered as a continuum multi-fluid (electrons, ions monovalent and neutrals) at high ionization. The numerical data have allowed to calculate the trend of number density, temperature and pressure for the three species of plasma. The good agreement of the theoretical electrical characteristic with the experimental one can be considered a partial validation of the physical model developed.
