Patent ID: 8247763

Claim:
An ion trap time-of-flight mass spectrometer which includes an ion trap for capturing ions by an ion-capturing electric field formed in a space surrounded by a plurality of electrodes and a time-of-flight mass analyzer for mass separation and detection of ions which have been expelled from the ion trap, comprising: a) a main voltage generator for applying a rectangular-wave radio-frequency voltage to at least one electrode among the plurality of electrodes in order to form the ion-capturing electric field; b) an auxiliary voltage generator for applying a voltage to at least one electrode, other than the aforementioned one electrode, among the plurality of electrodes in order to expel ions from the ion trap; c) an operation unit that allows an operator to set a predetermined phase at which the rectangular-wave radio-frequency voltage is set to a constant voltage value; and d) a controller for controlling the main voltage generator in such a manner as to change the voltage into the constant voltage value at a timing when the rectangular-wave radio-frequency voltage is at the predetermined phase, and for controlling the auxiliary voltage generator in such a manner as to apply a voltage for expelling ions simultaneously with or later than the timing, in order to collectively expel ions in a state where the ions are captured in the ion trap by the ion-capturing electric field; wherein the predetermined phase at which the rectangular-wave radio-frequency voltage is changed into the constant voltage value can be selected continuously or from a plurality of steps.