Mass spectrometer

摘要

A mass spectrometer is disclosed comprising a mass selective ion trap such as a 3D quadrupole field ion trap upstream of a pusher electrode 1 of an orthogonal acceleration Time of Flight mass analyser. According to a first embodiment bunches of ions are released from the ion trap and the pusher electrode 1 is energised after a delay time which is progressively varied. According to a second embodiment ions are released from the ion trap in reverse order of mass to charge ratio with the ions having the largest mass to charge ratio being released first. By appropriate release of the ions from the ion trap it is possible to ensure that substantially all of the ions arrive at the pusher electrode 1 at substantially the same time. According to both embodiments it is possible to achieve a duty cycle approaching 100% across a large range of mass to charge ratios.