| 摘要 |
An ion trap comprises substantially elongate electrodes 10, 20 some of wh ich are curved along their axis of elongation and which define a trapping vo lume between them. The sectional area of this trapping volume towards the ex tremities of the trap in the direction of elongation is different to the sec tional area away from its extremities (eg towards the middle of the trap). I n a preferred embodiment, the trap has a plurality of elongate electrodes, w herein opposed electrodes have different radii of curvature so that the trap splays towards its extremities. Thereby, a wider mass range of ions can be trapped and ejected, a higher space charge capacity (for a given trap length ) is provided, and sharper ion beam focussing on ejection is possible.
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