• 0-D model; plasma model; plasma physics
• electric propulsion
• orificed hollow cathode

The Hollow Cathode (HC) is an electron source device that is widely adopted in electric propulsion systems for satellites. This device can be used to produce electrons to ionize the propellant for the plasma formation inside the thruster chamber, or as a neutralizer for the ion beam ejected by the thruster. The performance of a hollow cathode is strongly related to its geometry and operation conditions, and the plasma diagnostic is difficult to be performed due to its minute size. Thus, a numerical model is needed to determine the optimal geometry and operating conditions for a given mission profile. A zero-dimensional plasma model represents a good compromise between including detailed plasma processes and keeping the model reasonable in terms of flexibility and computational cost. Hence, in this work, a zero dimension (volume averaged) plasma model for orificed hollow cathodes is presented. The model determines the plasma properties and wall temperatures by solving equations of conservation of current, ion mass, and power. To attempt the development of a self-consistent code, a thermal function for the cathode wall temperatures is derived and it is coupled to the plasma model.
The plasma model has been tested for different hollow cathodes configurations and the results have been compared to experimental data derived from literature and from a test campaign at Mars Space Ltd. Finally, after the model validation, a parametric investigation was performed in order to analyse the effects of operation conditions and geometry variation. In addition, for the latter analysis, a power deposition estimation on the cathode walls due to electron and ion bombardment is provided too.