Patent ID: 8212208
Filing Date: 2012-07-03
Classification: H01J

Abstract:
1. An ion trap comprising: a first quadrupole rod set comprising a plurality of first electrodes; a second quadrupole rod set comprising a plurality of second electrodes, said second quadrupole rod set being arranged downstream of said first quadrupole rod set; a first device which is arranged and adapted to apply a first RF voltage to at least some of said first electrodes and at least some of said second electrodes such that in a first mode of operation a non-zero phase difference is maintained between at least some of said first electrodes and at least some corresponding axially adjacent second electrodes so that an axial pseudo-potential barrier is created between said first quadrupole rod set and said second quadrupole rod set; and a second device which is arranged and adapted to apply one or more supplementary AC voltages to at least some of said first electrodes so that at least some ions within said first quadrupole rod set are resonantly excited in a radial direction so that they interact with the pseudopotential barrier at a point where the pseudopotential approximation no longer holds and are subsequently ejected in an axial direction from said first quadrupole rod set.