Patent ID: 7417224

Claim:
An ion mobility spectrometer, comprising: an ionization chamber, through which analyte-containing gas can flow; a radiation source, from which ionizing radiation, which is suitable for at least partially ionizing the analyte-containing gas, enters said ionization chamber; a separation area located behind said ionization space in the direction of flow, into which the partially ionized gas as an ion carrier gas and a nearly ion-free gas as a drift gas are introduced in such a way that a flow becomes established at least in an inlet area of said separation area, said flow comprising an ion carrier gas cross-sectional area through which predominantly said ion carrier gas flows and drift gas cross-sectional areas through which predominantly said drift gas flows, with said drift gas and said ion carrier gas flowing unidirectionally, said ion carrier gas cross-sectional area being smaller in at least one dimension than said drift gas cross-sectional areas; a detector electrode; an auxiliary electrode; and a counterelectrode, said detector electrode, said auxiliary electrode and said counterelectrode being arranged in said separation area such that an electric field can develop between them, said electric field having at least one field component that is not parallel to the direction of flow in said separation area, at least one of said drift gas cross-sectional areas being located between said ion carrier gas cross-sectional area and said detector electrode.