Simulation Research And Structure Optimization Of The Quadrupole Mass Spectrometer Based On COMSOL

Quadrupole mass spectrometer is a widely used mass spectrometer.Further research on the structure,field and processing technology of quadrupole mass spectrometer will improve its performance.In this paper,a research method is introduced based on the theoretical derivation and finite element analysis software COMSOL Multiphysics5.2.In addition,the quadrupole mass spectrometer has been studied and simulated according to the technical requirement of quadrupole mass spectrometer.The main contents are listed as the following:1)According to the requirement of a quadrupole mass spectrometer,based on the ions movement theory and particle collision theory,the simulation theory of charged particles movement in quadrupole mass spectrometer has been established,the finite element simulation theory of quadrupole mass spectrometer has also been established combined with the simulation software.2)The simulation model of quadrupole mass spectrometer has been established.The distribution of electric field and ions trajectories of quadrupole mass spectrometer have been analyzed by COMSOL Multiphysics5.2.The effects of pressure on the ion trajectory have been analyzed by using collision frequency replace the pressure.It has been found that transmission probability will decrease when the pressure is higher than10^-2Pa.The effect of Mathieu parameter a and q on the ion trajectory have been analyzed,which indicates that both a and q should be considered during the parameter selection.The effects of ion incident angle and energy have been analyzed.The effect of ion release position is also discussed.It has been found that collimate ions will increase transmission probability.The effect of ion charge on the ion trajectory has also been studied.Based on the relationship between the phase of RF voltage and time,the effects of the RF voltage phase and entrance aperture radius have been studied.It has been found that when the entrance aperture radius smaller than 0.05R_0,the transmission probability is the best.3)According to the requirements of quadrupole mass spectrometer and the simulation results.the focusing lens system has been simulated and optimized based on theory of the focusing lens for improving the transmission probability.There are three kinds of structures,including the structure without focusing lens,the structure with focusing lens while no electrostatic shield,and the structure both with focusing lens and electrostatic shield,have been simulated.According to the simulation results,it has been found that put a focusing lens with electrostatic shielding in front of the quadrupole mass spectrometer analyzer can significantly improve transmission probability and the performance of mass spectrum.The simulation method provides theoretical and simulation supports for the design of quadrupole mass spectrometer.Meanwhile,the simulation results will provide future reference for the parameter selection and the optimization of the structure of quadrupole mass spectrometer.