Analysis of Ion Trajectory Stability in Second Order Cassinian Ion Traps

Abstract

High precision instruments are a requirement in a lot of scientific disciplines. Environmental research is no difference in this regard. Often, it is necessary to know which substances are present in gaseous form, e.g. for exhaust gas analysis, or contamination management. Mass spectrometry is a technique that yields the molecular mass of analytes present in the device. If the resolving power is too low, the molecular mass is not sufficient to identify a substance. Other techniques have then to be used in order to obtain further information. However, if the mass resolving power is high enough, it can lower the number of candidates that might be present in a sample based on the molecular mass alone. Ion traps are devices that can be used as mass analyzers with very high resolving power. A relatively new representative of ion traps for mass analysis is the Cassinian ion trap. Although offering already very high mass resolving power, it can be further increased by changing the geometric and electric parameters. Ion traps work by letting ions fly on a closed trajectory for very long times (up to a few seconds). Changing geometric or electric parameters can possibly change the trajectories so that the ions do not fly for long times, but collide with the housing or electrodes instead. In this paper, we have analyzed how the geometry and electrode voltage influence the stability of ion trajectories when the ions are injected via a small tunnel from the outside. For this, the known differential equations describing the ion trajectories have been solved numerically. This knowledge can then be used to design Cassinian Traps with increased resolving power.