Patent ID: 7547880

Claim:
A drift tube for use in an ion mobility spectrometer, having an axis and comprising: a plurality of tube segments, each of the tube segments having a first aperture and a second aperture, unconnected to the first aperture, both apertures passing through that tube segment; means for connecting the tube segments in a stack with gas-tight connections between the tube segments so that the first apertures line up to form a drift region having a constant cross-section and extending along the axis of the drift tube and the second apertures line up to form a gas channel extending parallel to the axis of the drift tube; and wherein at least one tube segment having a first aperture and a second aperture connected to the first aperture by a gas channel that extends transverse to the axis of the drift tube, is inserted into the stack so that the first aperture lines up with the drift region and the second aperture lines up with the gas channel and the drift region is connected to the gas channel at the location of that tube segment.