Patent ID: 8288720
Filing Date: 2012-10-16
Classification: H01J

Abstract:
1. An ion trap mass spectrometer having an ion trap for capturing ions into a space surrounded by three or more electrodes including a first electrode, a second electrode and a third electrode, the second electrode and the third electrode facing each other apart from the first electrode, the mass spectrometer capable of resonant ejection of unnecessary ions from among the captured ions by applying a signal for resonant excitation of ions to each of the second and third electrodes while applying an ion-capturing rectangular-wave voltage to the first electrode, comprising: a) a data memory for storing a waveform data obtained by digitizing a broad-band signal representing a frequency spectrum having a notch at a predetermined frequency or over a predetermined frequency range; b) a rectangular-wave voltage generator for generating, in an ion-selecting process for selectively leaving an ion having a specific mass-to-charge ratio or ions belonging to a specific mass-to-charge ratio range in the ion trap, an ion-capturing rectangular-wave voltage adjusted to a frequency corresponding to the aforementioned specific mass-to-charge ratio or mass-to-charge ratio range, and for applying this rectangular-wave voltage to the first electrode; and c) a broad-band signal generator for generating a broad-band signal for resonantly exciting ions, excluding at least the ion having the specific mass-to-charge ratio or the ions belonging to the mass-to-charge ratio range, by sequentially retrieving waveform data stored in the data memory and converting the retrieved data to analogue data at a timing synchronized with the frequency of the rectangular-wave voltage generated by the rectangular-wave voltage generator in the ion-selecting process, and for applying the broad-band signal to the second and third electrodes.