Computer simulation of charged particle beam trajectories in a quadrupole ion trap mass spectrometer

A numerical simulation method has been developed for the analysis of ion motion in an ion trap mass spectrometer. In this method, ion motion can be simulated with the interaction of ion — bath gas and ion — space charge during mass analysis scan. By applying this method, the influence of the bath gas pressure and the space charge density on mass spectra is clarified. Furthermore, the relationship between the scan speed and the degree of the mass shift is obtained. Based on these relationships, an advanced scanning method is obtained, in which the scan speed is reduced gradually over the scan time. The feasibility of achieving high resolution without mass shift or scan time expansion is also examined.