Performance of the forward drift chambers for the D[phi] detector

The Forward Drift Chambers (FDCs) provide tracking in the forward region for the D[phi] experiment at Fermilab. The chambers must perform precision track position measurement in a high multiplicity environment. In addition, the measurement of track energy loss by ionization aids in identification of electron pairs resulting from photon conversion. Before being installed at D[phi] for the current Tevatron colliding beam run, these chambers were extensively tested in the Fermilab NWA test beam area, in beams of 10--150 GeV pions and electrons. The beam line was instrumented with PWCs to define the beam position, and with Cerenkov counters to select clean pions or electrons. Measurements included the position resolution, hit finding efficiency, two track resolution and ionization measurement resolution. The authors present here the results of these tests.