Impact of discharge voltage on wall-losses in a Hall thruster

Abstract

Calibrated infrared thermal imaging is used to investigate the temperature of the BN-SiO2 discharge chamber walls of the high-power PPSX000-ML Hall thruster over a broad voltage range. The energy flux deposited by charged particles onto the channel walls is assessed by means of a semi-empirical time-dependent thermal model. Equilibrium temperature as well as power losses onto the channel walls are determined for low and high voltage operation states. For a given input power, the two quantities strongly depend upon the discharge voltage. Above ~ 500 V, losses augment in an exponential way whereas they vary linearly at low voltages. As suggested by many theoretical works, secondary electron emission yield and associated near-wall sheath potential lowering could explain experimental outcomes. The contribution of ion bombardment, however, cannot be fully ruled out, as shown here.