SPACE-CHARGE ION OPTICS INCLUDING EXTRACTION FROM A PLASMA.

The effect of source plasma properties and extraction electrode dimensions on ion-beam optics is examined theoretically using an algorithm for a solution to the Poisson-Vlasov equation with explicit consideration of the cylindrically symmetric two-dimensional collisionless sheath. Ion optics as a function of source plasma density, electron temperature, fluctuations, and plasma potential are examined as well as the effect of electrode dimensions such as aspect ratio and thickness. The ion properties examined are beam divergence with relative contributions of aberrations, nonoptimum perveance, sensitivity to non-optimum conditions. Also considered is actual transmission including non-geometric electrode absorption.