Balance of the 6 TH and 10 TH spatial harmonics amplitudes of a quadrupole mass filter with round rods

Abstract

The purpose of this work is to find the electrode structure of the analyser with round rods, in which the amplitudes of the 6th and 10th harmonics are equal. For these conditions, we determine the shape of the mass peak and the modified stability diagram. The method is the representation of the electric field in the form of a complex potential which allows to write the equations of ion motion in analytic form. Numerical integration of the motion equations for an ensemble of ions with a given distribution of initial conditions is used to obtain the mass filter transmission contour. It is shown that radial displacement of two opposite rods can be used to balance the amplitudes of the 6th and 10th spatial harmonics and obtain an increase in the resolving power.