Performance of the AFS vertex detector at the CERN ISR

The central detector of the Axial Field Spectrometer (AFS) is a cylindrical drift chamber using a bicycle-wheel geometry. Its design has been optimized for jet-like events with high track densities. This is accomplished through a high degree of azimuthal segmentation (4/sup 0/ sectors) with up to 42 space points per track, using measurements of drift time and charge division. Particle identification in the non-relativistic region is obtained by (dE/dx) sampling. The detector is operated in an inhomogeneous magnetic field at event rates of typically 5 x 10/sup 5/ collisions per second. Preliminary results will be presented on the detector performance achieved after one year of operation at the ISR.