Patent ID: 8754368

Claim:
A mass spectrometer comprising: an ion trap having a ring electrode and a pair of end cap electrodes opposing each other with the ring electrode disposed therebetween; a time-of-flight mass spectrometer unit for mass analyzing ions ejected from the ion trap; a ring voltage applier for applying an ion-capturing radio-frequency high voltage to the ring electrode; an end cap voltage applier for selectively applying a radio-frequency high voltage having an amplitude of 100V or more, or a direct-current voltage to the end cap electrodes; a gas introducer for introducing a cooling gas into the ion trap; and a controller, wherein the controller controls the ring voltage applier to apply the ion-capturing radio-frequency high voltage to the ring electrode to trap ions, conducts a cooling of ions by introducing a cooling gas into the ion trap by the gas introducer while ions to be analyzed are captured in the ion trap, halts an application of the ion-capturing radio-frequency high voltage to the ring electrode by the ring voltage applier, sets the ring electrode at a ground potential, applies the radio-frequency high voltage having the amplitude of 100V or more to the pair of the end cap electrodes, both having the same phase, by the end cap voltage applier and applies the direct current voltage to the end cap electrodes by the end cap voltage applier to give a kinetic energy to the ions to eject the ions from the ion trap.