Design and analysis of a radiation cooling system for hollow cathode testing

Highlights: • A method is proposed for radiation-cooling of hollow cathodes in vacuum. • Four radiative cooling system configurations are suggested and analysed. • The cooling effectiveness of each configuration is quantified numerically. • Cooling effectiveness increases with the addition of Multi-Layer Insulation (MLI). • Post cathode ignition cooling has negligible effect on cathode performance. - Abstract: Thermal analysis is used to determine efficient radiation cooling system geometry in order to reduce the pre-ignition temperature of a hollow cathode for electric propulsion applications. To do so four cooling configurations were modeled and their cooling capability, via radiation, explored. It is found that a horizontal cooling plate positioned above the cathode is insufficient to cool it down to the required temperature of −50 °C. On the other hand three other more suitable configurations, two side plates, open box and half cylinder shaped structures encapsulating the cathode are shown to satisfy the cooling requirement. For the most efficient case of half-cylindrical shaped configuration the required cooling power is computed and found to be below 100 W for all cases simulated; therefore indicating that relatively simple cooling devices may be used for cathode radiative cooling. It is also shown that the addition of Multi-Layer Insulation (MLI) on the walls of the vacuum chamber greatly improves cooling system performance as it reduces both hollow cathode temperatures and the power dissipated into the cooling source. Lastly, sensitivity analysis is performed to quantify the effect of deviations in structure emissivities on hollow cathode temperatures.