ION SEPARATION IN IMPERFECT FIELDS ON THE QUADRUPOLE MASS ANALYZER .5. EXPERIMENTAL-VERIFICATION

The experimental aspects of ion separation in imperfect fields of the quadrupole mass analyser is the subject of this paper. The results of the experimental verification of techniques which can be used to avoid the transmission losses caused by field distortions prove the validity of the simulation results. The distribution of the ion energies analysed at the mass analyser exit confirms that the distortions cause an additional increase in the energy spread when the ions pass through fringing fields. This phenomenon leads to the appearance of peak ''shadows''. An injection efficiency study demonstrates the advantage of ion injection into the mass analyser at zero phase in each cycle in an r.f. field. This technique has been realized by a heterogeneous standing wave voltage applied to the mass analyser with a linear distribution of amplitude along the ion transit axis.