see also:

TOF- & MASS- spectroscopy / spectrometry detectors, TOFMS, ion-counting, ionization spectroscopy

In time-of-flight mass spectrometers ions are accelerated in an electric field. The time it takes for the ion to reach a detector is used to determine the mass-to-charge ratio of the ion. With a constant-fraction-discriminator (CFD) and time-to-digital converters, the flight time of the ion can be easily be measured with high precision. In setups where a high number of ions of the same mass is created, an ADC digitizer can be used instead to also obtain information on the pulse height and thus on the number of ions in each measured pulse.

Read more about TOF-MS in this article.