Sequencing ion packets for ion time-of-flight mass spectrometry

A method of analyzing ions by determining times of flight comprising:

• selecting a pseudo-irregular sequence for launching packets of ions;
• releasing packets of ions in response to a binary signal corresponding to the pseudo-irregular sequence such that on-the-fly packets of ions have substantially identical volumes;
• electrically affecting each on-the-fly packet of ions such that each on-the-fly packet becomes more compact;
• directing the more compact on-the-fly packets through a propagation path along which ions within an on-the-fly packet vary in velocity in accordance with the mass-charge ratios of the ions, selecting said pseudo-irregular sequence including determining a sequence in which ions of at least some on-the-fly packets spatially overtake ions of other on-the-fly packets;
• measuring the times of flight of ions through the propagation path, including detecting times of arrival of ions at a detector end of the propagation path and including correlating detections of times of arrival with the pseudo-irregular sequence;
• and
• forming a mass spectrum of ions of the released packets in accordance with the correlating of the detections of times of arrival with the pseudo-irregular sequence.

An apparatus for analyzing ions by determining times of flight comprising:

• a source of ions;
• signal generation means for generating a pseudo-irregular signal for launching packets of ions;
• launching means connected to the generating means for releasing packets of ions from the source in response to the signal generation means;
• compact means operatively coupled to the launching means for bunching ions of each packet released by the launching means;
• containment means operatively coupled to the compact means for defining an environment in which the ions in the packets follow a propagation path at velocities dependent upon the masses of the ions, said propagation path having sufficient length to allow packets to overlap along the propagation path;
• detector means for determining the times of arrival of the ions at an end of the propagation path;
• and
• correlation means for correlating the times of arrival with the pseudo-irregular signal to determine a mass spectrum of ions in the packets.