SIMION ion optics simulations at atmospheric pressure

A method for simulating the motions of charged particles in atmospheric pressure conditions in electrostatic and magnetic fields has been developed and implemented in a user program for SIMION 7.0 and the predictive capability of the model tested against experiment. The statistical diffusion simulation (SDS) user program avoids the computationally intensive issues of high collision rates by employing collision statistics to simulate the effects of millions of collisions per time step. Ion motions are simulated by a combined viscous ion mobility and random ion jumping approach. Comparison of the model predictions against measurement of Cs+ transport through room air, N2, Xe, Ar, and He collision gases in a simple drift cell at pressures from 6 to 640 Torr are favorable and provide confidence that the approach is viable.