Analytical studies of the plasma extraction electrodes and ion beam formation

In this work, a theoretical and computational study on the space charge dominated beams, extracted from a plasma ion source through a spherical and planer electrode is simulated and optimized. The influence of some electrode parameters—axial position, electrode diameter, material and shape—on ion current extracted from a plasma source were investigated and compared. The optimum values and conditions of the curvature of the plasma boundary, angular divergence, perveance, and the extraction gap were optimized to extract high quality beams. It has been shown that for a planar electrode system there is usually a minimum for optimum perveance versus angular divergence at about ≈0.6 for corresponding aspect ratios. This was assured by experimental data. The appropriate spherical electrode system focus the beam to a minimum value located at a distance equal to the focal length of the spherical extraction electrode.