Simulation of ion transport through curved-solenoid macroparticle filters

Ion transport through curved-solenoid macroparticle filters is investigated using a parabolic potential model of the electric field. Consideration of the ion equations of motion shows that the filter efficiency will increase with the relative radius of curvature of the solenoid and decrease with the relative length of the input region. If the magnetic field is constant in the input region, transport efficiencies of up to 100% are predicted. We argue that the observed effect of axial magnetic field on the angular distribution of ions emitted from the cathode spot can be explained by electric fields changing ion trajectories after emission, rather than a change in spot behavior. Detailed calculations give the energy and angular distributions with which the ions exit the filter. Focusing effects are observed and seen to affect the ion transport−particularly when the ions are not emitted on the filter axis.