| 摘要 |
The present invention provides a mass spectrometer including an ion source for generating pre-cursor ions, ion fragmentation means for generating fragment ions from the pre-cursor ions, a reflectron for focusing the kinetic energy distribution of the ions, and an ion detector wherein the mass spectrometer also includes axial spatial distribution focusing means which in use acts on the ions after the ion fragmentation means and before the reflectron, the axial spatial distribution focusing means being operable to reduce the spatial distribution of the ions in the direction of the ion optical axis of the spectrometer. Suitably the axial spatial distribution focusing means comprising a cell with two electrodes 52, 54 which may be apertures or high transmission grids. A pulsed electrostatic field is generated by applying a high voltage pulse 60 to the first electrode 52 at the time when the pre-cursor ions of interest 56, 58 have just passed into the pulser 50. The second electrode 54 is maintained at 0V during this time.
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