| 摘要 |
A mass spectrometer is disclosed comprising a quadrupole rod set ion trap 2 and 3 wherein a radially dependent DC potential barrier is created at the exit of the ion trap 4 and 5 , said potential decreasing with increasing radius in one radial direction (see Figure 3). Ions within the ion trap are mass selectively excited in a radial direction until they experience a potential field which no longer confines the ions axially within the ion trap, but which instead acts to extract the ions and hence causes the ions to be ejected axially from the ion trap. Alternatively, or additionally, the linear quadrupole ion trap is provided with axially segmented vane electrodes (6 and 7 in Figures 4 and 5) disposed between the main rod electrodes 2 and 3, to which transient DC voltages are applied (see Figure 6 and 7) such that radially excited ions are urged through the ion trap, while ions located upon the central longitudinal axis experience no net force. |
