Performance of a large scale scintillating fiber tracker using VLPC readout

We report on results of a cosmic ray test of a scintillating fiber tracker using Visible Light Photon Counter (VLPC) readout. Two different detector configurations have been constructed and operated, the first with a total of 3072 channels and the second with 1,785 channels. The 3072 channel system is a prototype for the DO detector tracking upgrade and represents a configuration that is similar to that in the final detector. The second, smaller test was specifically designed to study the position resolution capabilities of the fiber tracker. A description of the cosmic ray test including trigger, fiber configuration, undoped lightguides, VLPC cassettes and cryogenics, and calibration system is given. Final results from the 3072 channel test will be presented, including measurements of resolution, light yield per minimum ionizing particle, singlet and doublet efficiency, and long-term stability. Resolution results from the second, 1785 channel test will be compared to the predicted resolution from Monte Carlo studies.