| 摘要 |
An ion entrance opening (15) for introducing ions into an orbit (C) along a sector-shaped electric field entrance optical axis (A) from outside is provided in an outer electrode (11a) of a main electrode (11) for producing a sector-shaped electric field for forming the orbit (C). In order to correct the disturbance in the sector-shaped electric field due to the provision the ion entrance opening (15), three electrode correction electrodes (20) are aligned in the direction of the sector-shaped electric field entrance optical axis (A). By appropriately adjusting each of the direct-current voltages applied to the electrode correction electrodes (20), the equipotential lines in the sector-shaped electric field can be substantially the same as in the case where the ion entrance opening (15) is not provided. This configuration can alleviate the shift of the orbit of ions flying along the orbit (C). And, by halting the voltage application to the electrodes (11) and (20), ions can be placed into orbit through the ion entrance opening (15). |
