Numerical simulation for the effect of wall material on near wall conductivity in Hall Thrusters

The wall material plays an important role for the electron current due to near wall conductivity in Hall Thrusters. A Monte Carlo method combined with a one dimensional steady sheath model is presented and is applied to simulate the electron conductive current due to near wall conductivity for the different channel wall materials of Hall thruster. The simulation results show that the higher the secondary electron emission (SEE) coefficient of the channel wall material is, the greater the electron conductive current is. Based on the simulation, a physical explanation is given from the viewpoint of near wall conductivity. For the channel wall material with low SEE coefficient, the secondary electrons taking part in the near wall conductivity becomes less. In addition, the absolute potential drop in the sheath near the wall increases, which means that the sheath can stop more electrons from colliding with the channel wall. And consequently the electron conductive current due to near wall conductivity is much less. The situation is vice verse for the channel wall material with high SEE coefficient. The simulation results are qualitatively in accordance with the experiments. The results can help to choose and design the wall material of the Hall Thrusters with a high performance.