Ion trajectory simulation of linear multipole ion traps for analysis of spatial ion distribution

Abstract

We explore the spatial distribution of ions in a linear multipole radio-frequency ion trap by ion-trajectory simulation using the SIMION software. As a typical example, a two-dimensional column density is characterised for Ag₂⁺ ions stored in several types of the trap. Taking into account the effects of the space charge and ion–buffer He collisions, we are able to reproduce a ring profile of an ion distribution experimentally observed for a linear octopole trap at a high density of ions close to the space-charge limit. This simulation demonstrates also that the profile of the ion distribution is dependent on the number of ions stored and the temperature of a buffer He gas. As for a quadrupole trap, an ion distribution is shown to be located around the central axis of the trap as observed by experiment. An influence of the electrode structure is also discussed for the quadrupole trap.

GRAPHICAL ABSTRACT

KEYWORDS:

• SIMION
• linear ion trap
• atomic and molecular clusters
• ion cloud

Acknowledgements

The authors thank Drs. Takuya Horio, Masashi Arakawa and Tetsuichiro Hayakawa for helpful discussion and Dr. Takuya Majima for sharing their experimental data.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported financially by the Japan Society for the Promotion of Science (JSPS) KAKENHI [grant numbers JP21J21716 and JP22H00317].