Experimental study of acceleration region in a 2 kW Hall thruster

Measurements with a movable emissive probe in a 2 kW Hall thruster revealed several interesting phenomena: the length of the acceleration region almost does not change when the discharge voltage increases from 200V to 400 V (i), the growth of maximum electron temperature with the discharge voltage in this range is fairly linear (ii), at the discharge voltages above 400 V, the maximum electron temperature saturates at 50 eV (iii) which is accompanied by observed expansion of the acceleration region towards the anode and the plume (iv). These results suggest that the dominant mechanism of the electron mobility is affected by the discharge voltage and may alter at high discharge voltages. A role of the secondary electron emission appears to be less important at moderate discharge voltages (less than 400 V in our thruster).