The acceptance of the quadrupole mass filter

Abstract The acceptance of the quadrupole mass filter in the presence of realistic fringing fields is examined using phase-space dynamics. Parameters are obtained which characterize the ion transmission in terms of instrument radius, ion mass, ion energy and frequency of the applied field. These parameters can be used to evaluate ion-source designs or to optimize lens systems coupling ion sources to quadrupoles. Some examples are given. Consideration of the three-dimensional variation of the fringing fields shows that ion trapping and ion reflection are possible for slow-moving ions at both the entrance and the exit.