| 摘要 |
In conventional mass spectrometers, if ions are converged by a radio-frequency electric field under the condition of relatively high gas pressure, the ions are decelerated and are delayed, or stagnated in an extreme case, to cause a decrease in the detection sensitivity or an appearance of a ghost peak. By contrast, in the mass spectrometer according to the present invention, lens electrodes 40 comprises four plate-shaped electrodes 41a through 41d, which are radially arranged around the ion optical axis C at intervals of 90 degrees from each other; the four electrodes placed in the plane being approximately perpendicular to the ion optical axis C form a group, and a plurality of the groups are arranged along the ion optical axis C direction at approximately even intervals. The radio-frequency voltages each applied to each of any pair of electrodes adjacent along the direction of the ion optical axis C have a given amount of phase shift. With this configuration, when ions enter the lens electrode 40, an ion acceleration effect is exerted in accordance with the amount of phase shift of the adjacent radio-frequency electric fields, and the ions are sequentially accelerated as they travel through the lens electrode 40. Consequently, a delay or stagnation of the ions can be avoided.
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