Computer simulation of gas-filled separators. II. Ion charge fluctuations

The paper presents a mathematical model of ion charge fluctuations at collisions with gas molecules, which takes into account one-electron trapping and one- or two-electron loss effects. The model is the simplest generalization of the single-electron fluctuation model and gives asymmetrical equilibrium charge distributions. It is shown that for symmetrical charge distributions in the ion beam, ion charge fluctuations lead to an increase in the average radius of curvature of the ion trajectory in a magnetic field. For asymmetrical charge distributions, this radius may either increase or decrease. The results of numerical modeling of ion motion in gas-filled separators show that the allowance for two-electron processes yields substantially different ion distributions in the beam in the focal plane of the separator.