The influence of the aperture size of the ion source grid includes: focusing, energy dispersion, etc.

1. Focusing: The smaller the aperture size, the better the focusing of the ion beam, because the small aperture can effectively limit the divergence angle of the ion beam and improve the collimation of the ion beam.

2. Energy dispersion: The aperture size also affects the energy dispersion of the ion beam. A smaller aperture size can reduce the energy dispersion of the ion beam, because when ions pass through a small aperture, only ions with a certain energy and direction can pass through, thereby screening out ion beams with a narrower energy distribution.