US Patent 9209006 Mass spectrometry

There is provided an ion guide arrangement comprising a guide assembly comprising a plurality of elongate members arranged so as to be spaced about a common axis. The elongate members are capable of being in electrical association with one another so as to guide a stream of ions along an intended pathway substantially aligned with the axis. The or each elongate member is shaped at or near an end of the ion guide assembly so as to define a region capable of receiving a quantity of ions, whereby the or each elongate member is so shaped so as the region converges substantially toward the axis.