The dependence of ion transmission on the initial r.f. phase of a quadrupole mass filter

Abstract

A time-of-flight technique has been developed in order to measure the dependence of ion transmission efficiency through a quadrupole mass filter upon the phase of the r.f. field at the entrance to the analyser. The technique is such that the collection of a stray signal due to the analyser supplies is avoided. A high gain channel multiplier detects individual ions, producing an output pulse with an amplitude at least fifty times greater than the background noise level. The modulation of the ion beam is found to vary from zero to 60% depending upon the ion injection energy and the quadrupole resolution setting. Correlation with existing theoretical data is demonstrated.