US Patent 7893407 High performance micro-fabricated electrostatic quadrupole lens

A method of aligning sets of cylindrical electrodes in the geometry of a miniature quadrupole electrostatic lens, which can act as a mass filter in a quadrupole mass spectrometer is provided. The electrodes are mounted in pairs on microfabricated supports, which are formed from conducting parts on an insulating substrate. Complete segmentation of the conducting parts provides low capacitative coupling between co-planar cylindrical electrodes, and allows incorporation of a Brubaker prefilter to improve sensitivity at a given mass resolution. A complete quadrupole is constructed from two such supports, which are spaced apart by further conducting spacers. The spacers are continued around the electrodes to provide a conducting screen.