Method and system for operating a time of flight mass spectrometer detection system

A method of operating a time of flight mass spectrometer to process ions having a plurality of mass to charge ratios to determine a plurality of ion intensities, the method comprising:

• a) introducing the ions into the time of flight mass spectrometer;
• b) subjecting the ions to an electric field to push the ions through a drift chamber to a detector as a sequence of groups of ions for detection by the detector, wherein each group of ions in the sequence of groups of ions comprises ions having a different mass to charge ratio in the plurality of mass to charge ratios;
• c) detecting ions contacting the detector to generate a sequence of detection signals;
• d) determining a higher timing resolution data stream by providing the sequence of detection signals to a higher timing resolution digital converter configured to resolve high peak multiplicities, and for each group of ions in the sequence of groups of ions,
• i) determining at least one associated detection signal in the sequence of detection signals generated by the detector on detection of that group of ions, and
• ii) determining a corresponding time and intensity pair representing a flight time and an intensity of that group of ions, wherein the intensity in the time and intensity pair is determined from a plurality of lower range intensities measured over a plurality of high resolution time intervals;
• and
• e) determining a lower timing resolution data stream by providing the sequence of detection signals to a lower timing resolution digital converter to determine a plurality of higher range intensity measurements of the sequence of detection signals over a plurality of low resolution time intervals;
• wherein the lower timing resolution digital converter is operable to measure intensities above a maximum intensity determinable by the higher timing resolution digital converter;
• and wherein the higher timing resolution digital converter operates at a higher timing resolution that is higher than a lower timing resolution of the lower timing resolution digital converter.

A time of flight mass spectrometer system comprising a drift chamber for receiving ions from an ion source, the ions having a plurality of mass to charge ratios;

• a detector for generating a sequence of detection signals representing ions contacting the detector;
• a field generator for generating an electric field to push the ions through the drift chamber for detection by the detector;
• a higher timing resolution digital converter linked to the detector to receive the sequence of detection signals from the detector, the higher timing resolution digital converter being configured to resolve high peak multiplicities, and operable to generate a higher timing resolution data stream by, for each group of ions detected by the detector, i) determining at least one associated detection signal in the sequence of detection signals generated by the detector on detection of the group of ions, and ii) determining corresponding arrival time data for the at least one associated detection signal, the corresponding arrival time data being determined at high resolution time intervals;
• a lower timing resolution digital converter linked to the detector to receive the sequence of detection signals from the detector, the lower timing resolution digital converter being operable to generate a lower timing resolution data stream by sampling the sequence of detection signals at low resolution time intervals;
• and a processor linked to the higher timing resolution digital converter and the lower timing resolution digital converter, the processor being operable to:
• i) process the higher timing resolution data stream to determine a plurality of time and intensity pairs, each time and intensity pair representing a flight time and intensity of ions having a corresponding different mass to charge ratio in the plurality of mass to charge ratios;
• and
• ii) process the lower timing resolution data stream to determine a plurality of higher range intensity measurements of the sequence of detection signals;
• wherein the lower timing resolution digital converter is operable to measure intensities above a maximum intensity determinable by the higher timing resolution digital converter;
• and wherein the higher timing resolution digital converter operates at a higher timing resolution that is higher than a lower timing resolution of the lower timing resolution digital converter.