the peaks on the detector 22 the flight times at each of the points across the peak on detector 22 are then subtracted from the flight time of the corresponding points on detector 30 the flight time differences are then plotted on a new time graph which is representative of the flight times between the two detectors since the peak widths of the peaks on the two detectors in the described embodiment should be similar the plotted peaks in the differential spectrum will be much narrower alternatively the centroid s of the peak s on detectors 22 and 30 may be calculated and the time difference between the centroids used as the centroid of the peak in the differential spectrum the process may be repeated for each successive pulse and the individual pulses are accumulated in the differential spectrum alternatively a number of pulses may be accumulated and or averaged before any mathematical procedure is used to determine the differential spectrum since the jitter in arrival times at the two detectors will be in the same direction the time position in the differential mass spectrum will be relatively invariant and peak widths should remain narrow narrow peaks mean the accuracy of the m z values assigned to the peaks will be high the differential mass spectrum is used for determining the m z values to high accuracy it will not however reflect the true mass resolution of the mass spectrometer the true mass resolution of the instrument will be evident from individual shots on detector 30 the individual shots on detector 22 can also be accumulated and aligned on the basis of.