Directional probe measurement of plume divergence angle in Hall thrusters

In view of the focused ion beam of Hall thrusters, a method for fast measuring and calculating the plume divergence angle with a directional probe in the near-field region is proposed. The distribution and diffusion of the ion beam density can be also obtained through the measurement. The uncertainty analysis shows that the deviation of plume divergence angle obtained with this method mainly comes from the radial cut of measured ion current. However, when the probe position is chosen appropriately for a focused ion beam, the measurement uncertainty can reach ±1% of the minimum.