| abstract |
A method and apparatus for manipulating ions using a two-dimensional substantially quadrupole field, and a method of manufacturing an apparatus for manipulating ions using a two-dimensional substantially quadrupole field are described. The field has a quadrupole harmonic with amplitude A 2 , an octopole harmonic with amplitude A 4 , and higher order harmonics with amplitudes A 6 and A 8 . The amplitude A 8 is less than A 4 . The A 4 component of the field is selected to improve the performance of the field with respect to ion selection and ion fragmentation. The selected A 4 component can be added by selecting a degree of asymmetry under a 90° rotation about a central axis of the quadrupole. The degree of asymmetry is selected to be sufficient to provide the selected A 4 component. |