A radial TPC for heavy ions

The CERES experiment at the CERN SPS has been recently upgraded with a TPC with radial drift field, the first one of its sort. Constructed during 1998, it has been successfully operated in commissioning and physics runs, with muon, proton, and heavy-ion beams. A high voltage electrode of about 0.5 m radius is surrounded by sixteen 2 m long readout chambers, placed at a radius of 1.3 m, with chevron-shaped readout pads. The field cage is enclosed by two low-mass voltage degraders at each end of the cylindrical structure. A Ne-CO/sub 2/ [80-20] gas mixture allows for a safe operation and good transport properties under drift fields ranging from 200 to 600 V/cm. A spatial resolution better than 700 microns and 350 microns in r and rdelta(phi), respectively, has been achieved in a highly inhomogeneous magnetic field. Details of its construction as well as results of the operation and performance in a high multiplicity environment are presented.