The BaBar Drift Chamber

The central drift chamber for the BaBar detector at the PEP-II Bfactory at SLAC is a cylindrical chamber with a length of 280 cm and outer radius of 81 cm. It consists of 40 layers of small hexagonal cells arranged in 10 axial and stereo super-layers. In order to minimize multiple scattering, light materials are used for the mechanical structure, and the gas mixture is Helium based. The pulse-height and timing electronics are mounted directly on the chamber rear end-plate. A full length prototype of the BaBar drift chamber has been built. The analysis of cosmic ray events measures the spatial resolution averaged in the cell to be 130 m and the dE/dx resolution to be 6.8%, meeting the performance goals for the BaBar central tracker. The mechanical assembly and stringing of the chamber was completed in December 1997 and the detector will be integrated into BaBar during summer 1998.