The ARGUS vertex drift chamber

This contribution describes the design and the performance of the ARGUS vertex drift chamber. Since spring 1985 it has operated successfully in the high background environment of the DORIS II storage ring. The chamber is filled with pure CO2 at a pressure of 1.5 bar. The spatial resolution, as obtained from Bhabha events, is about 50 μm over a large region of the drift cell. The data from the vertex drift chamber has considerably improved the precision of the measured parameters for charged tracks. Consequently the reconstruction efficiency for secondary vertices from K0S and Λ decays is greatly enhanced, especially in the region close to the beam line. (orig.)