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

Abstract

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 ® 1350-G and PPSX000-ML. Note that over the range of thruster operating conditions the facility backpressure varies from 10 −5 to 6 × 10 −5 mbar. In addition, the effect of discharge chamber wall material on temperature field was also investigated using dielectric BN-SiO 2 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.

Comparison between Mach 2 rarefied airflow modification by an electrical discharge and numerical simulation of airflow modification by surface heating

“…A complete description of the measuring technique can be found in Ref. 20. During the whole experiment, the surface temperature is acquired to ensure us that those measurements are done when the thermal equilibrium is reached ͑surface temperature and pressure measurements͒.…”

Effect of Anode Temperature on Hall Thruster Performance

“…A thermal model in [9] is used to estimate the power deposited on the anode due to collisions with electrons at an electron temperature and discharge current of 15 eV and 13 A, respectively. The result is approximately 500 W. This model does not account for radiative heating of the anode, which is much more difficult to estimate than collisional heating.…”

Impact of discharge chamber geometry on characteristics of a low-power Hall thruster

“…The equilibrium temperature of both the internal and external Al 2 O 3 dielectric channel walls was determined by means of calibrated thermal imaging in the 8-9 μm domain [8]. The discharge voltage was set to 200 V and the xenon flow was adjusted around 1 mg/s to keep the discharge current constant at 1.1 A.…”

“…1 for the three values of the channel width. The temperature of the internal wall T int is always higher than the external wall one T ext because it is more difficult for the former to evacuate heat [8]. The temperature of the two walls decreases with the size.…”