An optimised compact electron impact ion storage source for a time-of-flight mass spectrometer

In the ion source of an ion trap time-of-flight (TOF)-mass spectrometer, an effective electrostatic field separation of the region of ion generation and ion acceleration, which have different electric field strengths, is necessary for optimal operation. At the same time, the electrostatic field separation has to have a high transmission for ions, permitting for a high sensitivity of the mass spectrometer. Usually, a single mesh is used for such an application. In our case of a compact yet high-performance system, the field separation requirements are too tight for using only a single mesh. We systematically performed ion-optical simulations, which showed that only a double grid configuration promises satisfying results. The modifications of the instrument, based on the simulations, increased the performance significantly by reducing the baseline and improving the storage of the ions; the dynamic range of the modified spectrometer after the improvements covered - in a 1 min record time - about six orders of magnitude. Systematic studies performed using the laboratory instrument confirm the results of the simulations. (C) 2010 Elsevier B.V. All rights reserved.