Crowd control of ions in the Astral analyzer

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, while 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.

A High Dynamic Range Ion Detector for Multireflection Time-of-Flight Analyzers

“…At 5000 ions, although the peak is clearly more intense, the low-gain channel has not become saturated to the ∼4.5 V equivalent level. Here space charge effects have continued to broaden the peak, which is obviously deleterious for resolution, with trends reported previously, but also very helpful for dynamic range. This serendipitous effect extends the in-spectrum dynamic range well beyond what might be anticipated just by looking at the bit-depth of the digitizer system.…”