MULTIPOLE ION GUIDE HAVING LONGITUDINALLY ROUNDED ELECTRODES

摘要

An ion guide having a plurality of spheroidal or similarly shaped electrodes is disclosed. The electrodes are arranged in pairs about a central ion flow axis, and an RF voltage is applied in a prescribed phase relation to create an electric field that focuses and radially confines an ion beam. A defocusing effect associated with the electrode shape may be reduced by placement of a separate skirt electrode immediately downstream in the ion path, or by forming the electrodes in a composite structure, whereby the trailing portion of the electrode is fabricated from or coated with an insulative material.