A model of transition field between quadrupole mass filter and pre-filter

Analytical function, which describes transition field in the area between quadrupole mass filter (QMF) and prefilter, was proposed. The function was obtained by means of potential distribution in the QMF-to-prefilter connection area numeric model, which was built using SIMION 8 software, and followed potential distribution function least-square fitting. Fitting was based on exponential function, as described for fringing field model earlier. Two variants of the model was proposed: full variant of three coordinates, which takes into account transverse x -, y -coordinates and axial z -coordinate, and simplified variant of single axial z -coordinate. Availability of transition field function together with fringing field function allows analytical description of ion motion in QMF-prefilter electrode system, facilitating in characteristics research of such a system using phase-space dynamics methods.