Analysis and Simulation of ion-laden gas flow through capillaries

• Applicant: Professor Dr. Julius Reiss
• Subject Area: Fluid Mechanics
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 268758079

Electrospray ion sources (ESI) generate ions of sensitive, organic molecules for vacuum applications. An important vacuum application is for example mass spectrometry, which allows to analyze biochemical samples. Other applications are found in chemical analysis or in material science, for instance the coating of surfaces, where complex molecules allow to tailor the electronic, mechanical or chemical properties, which enables new electronic elements or catalytic converters.The transfer efficiency of ESI sources, i.e. the ion loss and the ion flux, is crucial for all applications. Existing electrospray ion sources show either very low ion flux or high loss rates. The central element for the vacuum transfer is a capillary in which ions are transported by a gas flow. The gas flows at near sonic velocities and can be laminar or turbulent.The transfer capillary is the bottleneck to higher ion fluxes but the details of the ion loss are not well understood.Especially the gas flow, albeit dominating the ion transport, is not properly taken into account in existing studies.This project aims at a detailed simulation of the capillary gas flow in combination with the ion dynamic and the electric field. By this the relevant loss process of the ESI are analyzed and quantified. A validation is provided by a comparison with experiments. This allows the improvement of existing ion sources. It can also help to identify new design approaches.An improvement of electrospray ion sources would increase the sensitivity of existing mass spectrometers. A substantially increased ion flux could even allow coating with non volatile molecules on an industrial level.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Stephan Rauschenbach