Patent ID: 6900430
Filing Date: 2005-05-31
Classification: H01J

Abstract:
1. A mass spectrometer, comprising: an ion source; an ion trap for accumulating the ions formed in said ion source and ejecting the same, said ion trap comprising a ring electrode and endcap electrodes; a voltage applying means for applying a voltage, in a transverse direction relative to the direction of ion ejection, to ions ejected from said ion trap in the axial direction of said ion trap; a third electrode which is disposed between the ion trap and said voltage applying means and to which a voltage is applied to form a decelerating electric field between an outside of said ion trap and said third electrode; a detector for detecting the ions to which the voltage has been applied in the transverse direction, wherein an accelerating electric field is formed within said ion trap to eject the ions accumulated in said ion tray after termination of AC voltage application to said ring electrode, and the gradient of said decelerating electric field is decreased, during passage of the ions between said endcap electrode on an outlet side of said ion trap and said third electrode, by changing the potential of said third electrode or said endcap electrode on the outlet side of said ion trap such that a ratio in kinetic energy between preceding ions ejected and succeeding ions ejected between said ion trap and said first electrode is reduced.