Patent ID: 7935923

Claim:
A quadrupole mass filter (QMF) comprising: a plurality of rectangular shaped electrodes aligned in a symmetric manner to generate a quadrupole field; an aperture region positioned in a center region parallel to and adjacent to each of said rectangular shaped electrodes, an incoming ion stream enters said aperture region so as to be controlled by said quadrupole field; a housing unit having a hollow rectangular cross-section that encloses said QMF, the inner surfaces of the housing unit being parallel to said rectangular shaped electrodes; a plurality of voltage sources providing a r.f. and d.c. signal to said rectangular shaped electrodes for generating said quadrupole field; and an auxiliary voltage source applying an auxiliary drive signal to said r.f. and d.c. signal to create new stability boundaries with high resolution within the standard Mathieu stability regions around operating conditions where there are approximately no higher-order resonances.