The Effect of Higher Order Multipole Fields on the Property of Quadrupole Mass Filter

The effect of higher order multipole fields on the property of linear quadrupole mass filter were investigated with theoretical simulations. The decapole component A₅, or the mixture of decapole A₅, hexapole A₃ and octopole A₄ fields can be added to the linear quadrupole by using four special shape rods. The A₅ and some other higher order multipole fields can also be added to linear quadupole when four cylindrical rods with different diameters are used. The existence of some small amount of A₅ will change the shape of the first stability diagram, and distort the mass resolution of the linear quadrupole mass filter. When some hexapole A₃, and octopole A₄ field are added besides A₅, the mass resolution will be significantly improved.