| 摘要 |
Selective trapping of ions from an external source into a quadrupole trap is accomplished by applying a parametric pump voltage to the quadrupole trap electrodes in such a phase as to extract energy from the ions, causing the ions to accumulate in the center of the trap. Pump voltage phase is controlled by the timing of the injection of ions into the trap relative to the absolute phase of the pump voltage. Optimum phasing results when the ion packet allowed into the trap through gating of the ion beam optics is sufficiently opposed by the field produced by the parametric pump voltage. The ions are also subjected to a normal RF trapping field.
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