Post-Acceleration and Conversion Dynode

Discrimination of slower ions as compared to faster ions is observed with SEMs [254], CEMs, and MCPs as well [250,255,256]. This means a reduction in sensitivity upon reduction of the acceleration voltage of a mass spectrometer, and of course, with increasing ion mass. Post-acceleration detectors can reduce such effects and especially help to improve the sensitivity for high-mass ions [247,256]. In post-acceleration detectors the ions are accelerated immediately in front of the detector by a voltage of 10-30 kV before they hit the first dynode or the first MCP. 

The electron output of ion-counting detectors is usually measured with reference to ground potential, i.e., the first dynode is set to negative high voltage as to achieve acceleration of the electrons down the dynode assembly. In case of sector 

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