A calibrated infrared imaging study on the steady state thermal behaviour of Hall effect thrusters

The thermal behaviour of Hall effect thrusters was investigated by means of calibrated infrared thermal imaging performed in the 8-9 μm spectral domain. Study on the variation of the steady state temperature of Hall thruster elements like discharge chamber (channel) walls and anodes along with discharge voltage and propellant (xenon) mass flow rate confirms that energy loss mechanisms, which are responsible for the heating of the thrusters, are a direct consequence of interactions between charged particles and surfaces. In order to obtain new insights into plasma surface interactions inside a thruster, the channel wall temperature was monitored over a broad range of electrical power stretching from 400 W to 5.5 kW for three types of thrusters with different designs, dimensions and operation domains, namely SPT100-ML, PPS (registered) 1350-G and PPSX000-ML. Note that over the range of thruster operating conditions the facility backpressure varies from 10-5 to 6 x 10-5 mbar. In addition, the effect of discharge chamber wall material on temperature field was also investigated using dielectric BN-SiO2 and AlN walls as well as conducting graphite walls. For a given thruster geometry and material, a simple relationship between the mean wall temperature and the input electrical power can be established, in contradiction to the complex dynamics of such a magnetized plasma medium. Besides, thruster thermal history and degree of wear do not have a strong impact on power losses inside the channel