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Abstract
Space charge effects are the Achilles’ heel of all high-resolution ion optical devices. In time-of-flight mass analyzers these may manifest as reduction of resolving power, mass measurement shift, peak coalescence and/or transmission losses, whilst highly sensitive modern ion sources and injection devices ensure that such limits are easily exceeded. Space charge effects have been investigated, by experiment and simulation study, for the Astral multi-reflection analyzer, incorporating ion focusing via a pair of converging ion mirrors, and fed by a pulsed extraction ion trap. Major factors were identified as the resonant effect between ~103 ions of similar m/z in-flight, and the expansion of trapped packets of ~104-5 ions prior to extraction. Optimum operation and compensated ion mirror calibration strategies were then generated and described based on these findings.
Supplementary materials
Title
Crowd Control of Ions in the Astral Analyzer: Supplementary Results
Description
Contains results from a series of supporting experiments, including the effect of varying RF pseudopotential well depth; peak shape measurements prior to full mirror optimisation; additional FlexMix resolution and mass accuracy trends; supporting MRFA isotope coalescence measurements; caffeine isotope coalescence simulations; the positions of overtones; influence of charge state. Furthermore, advice is given for the use of the AGC parameter in the design of real experiments.
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