Patent ID: 8642949

Claim:
An ion transfer arrangement for transporting ions between an atmospheric pressure ion source and a relatively lower pressure region, comprising: an expansion chamber having an inlet which opens to the atmospheric pressure ion source; an ion transfer conduit having an inlet opening towards the expansion chamber, an outlet opening towards the relatively low pressure region which is below the pressure of the expansion chamber, and at least one sidewall surrounding an ion transfer channel, the sidewall extending along a central axis between the inlet end and the outlet end; an evacuable chamber which encloses the ion transfer conduit; a plurality of apertures formed in the longitudinal direction of the sidewall of the conduit; a pumping means for evacuating the evacuable chamber so as to remove a portion of the gas within the ion transfer channel through the plurality of apertures in the conduit to the evacuable chamber, the pumping means being configured to evacuate the evacuable chamber to a pressure below atmospheric pressure, but high enough to maintain a viscous flow of gas and ions through the ion transfer channel; and an aerodynamic and/or electric lens, located within the expansion chamber between the inlet of the expansion chamber and the inlet of the ion transfer conduit, for focusing ions from the atmospheric pressure ion source towards the longitudinal axis of the ion transfer channel.