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

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 similar to 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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3592251]