Patent ID: 8546754

Claim:
An ion trap, comprising a plurality of elongate trapping electrodes, an ion exit aperture for ejecting ions from the trap, and a voltage supply means configured: (a) to supply a trapping voltage to the elongate trapping electrodes so as to trap ions within an ion trapping volume, and (b) subsequently to supply an ejection voltage to the trap so as to cause ions trapped therein to be ejected from the ion exit aperture in a direction which is neither parallel with, nor orthogonal to, the direction of elongation of the trap; and wherein the trapping electrodes and the ejection voltage between them generate an electric field which is non linear along the direction of elongation of the trap, so that ions at different positions along the direction of elongation of the trap upon application of the ejection voltage experience different electric field potentials so as to cause spatial focusing of the ions downstream of the trap.