Characterization of linear quadrupoles operated with amplitude-asymmetric sinusoidal waveforms.

Abstract

The stability regions formed by the asymmetric sinusoidal shape of the periodic supply potential of the quadrupole mass filter are calculated, with the signal duty cycle $d=0.5$. Two cases are considered, when $A_1<A_2$ and $A_1>A_2$, where $A_1$ and $A_2$ are the amplitudes of the positive and negative parts of the sinusoid. Stability islands are revealed, where the QMF operation is possible by changing amplitude $A_2$ without DC potential. For the values $A_1=1$ and $A_2=0.8$, the mass selected instability mode with a resolution of about 7000 is found. In this island, the potential well depth reaches its maximum along the Y coordinate. At the amplitudes $A_1=1$ and $A_2=1.8-2.0$, stability regions are formed, the operation in which allows reaching $R_{0.5}=2000$. The results of the transmission and excitation contours modeling confirm the validity of the method for calculating the stability diagrams of a linear quadrupole with asymmetric sinusoidal waveform.