Effect of beamlet-beamlet interaction on ion optics of multiaperture sources

Space-charge effects of beamlet-beamlet interaction in the unneutralized accelerator region of intense ion sources have been computed. If shielding effects of the electrodes are neglected, the radial space charge of a typical ion source is so great that most of the beam will hit the second electrode or will undergo nonlinear steering. Beam divergence will be an order of magnitude larger than that expected from considerations of spherical aberrations of a single beamlet caused by deviations from Pierce geometry. If shielding effects of the electrodes are sufficiently great that only nearest-neighbor beamlet-beamlet interactions are important, then the outermost beamlets (or those near a water line) will cause a total beam divergence which is the same order of magnitude as that due to single-beamlet spherical aberrations, and far more than the divergence expected from source ion temperature. A solution to this problem is proposed.