Hall-Effect Thruster Channel Surface Properties Investigation

Modification of Boron Nitride Ceramic to Replicate Hall Effect Thruster Surface Wear

“…[14][15][16][17] Current HET models do not integrate a realistic wall microstructure, but instead rely on sputter yield or SEE coefficients derived from idealized material tests. 5,9,18 Our results presented below show that through various 1 Properties of the HET channel wall affect SEE, anomalous electron transport, and near-wall conductivity, and erosion rate, thereby altering HET performance. 10,11 The roughness of HET channel walls has been shown to affect the equipotential contours of the plasma sheath near the channel wall reducing overall thruster performance.…”

“…These measurements agree closely with those by Zidar. [1][2][3] Figure 2 shows that as the distance the weight is dragged across the sample increases, surface roughness increases. While grade HP is initially smoother than M26, after 3 cm, HP is 26% rougher than M26.…”

“…H Many current HET efforts are focused on developing and benchmarking models that integrate the important role of surface properties of the annular channel that contains the plasma discharge. [1][2][3][4][5][6][7][8][9] Wall-effects play an important role in both the lifetime and overall performance of the thruster. Properties of the channel wall can affect secondary electron emission (SEE), anomalous electron transport, and nearwall conductivity, thereby altering HET performance.…”

“…Zidar and Rovey compared pristine and worn grade HP and M26 boron nitride channel material from various locations within thrusters and showed that surface changes occur on multiple length scales and vary depending on the location. [1][2][3] At the macroscopic level, surface roughness increases, especially near the exit plane where angled striations in the channel are formed. Near the anode deposition of metallic materials was evident.…”

“…At the microscopic level, metallic atoms are deposited on the BN channel close to the anode and individual BN grains become smoother. Both Garnier, et.al., [23][24] and Zidar, et.al., [1][2][3] show that the chemical composition of the BN channel surface changes, with the fraction of silicon dioxide binding agent decreasing with proximity to the exit plane of the thruster. It is currently unclear how these surface changes affect SEE and sputter yield, and indirectly affect performance and lifetime.…”