The KLOE drift chamber readout system.

The tracking detector of the KLOE experiment [1] is a large volume drift chamber designed to identify with high efficiency KLKS decays produced on the Phi resonance at the DA Phi NE factory, for a precise measurement of the CP-symmetry violation parameters. The chamber's readout system is designed to run at a peak luminosity of 10(33) cm(-2) s(-1), bunch crossing period of 2.7 ns, at an expected trigger rate of 10 KHz, with low deadtime (similar to 2%). Each of the 12582 readout channels consists of an on-detector preamplifier and a shaper-discriminator circuit which feeds a custom built integrated TDC. Zero-suppressed data collected by the front-end electronics are sent, through a two-level data concentrator, to an online farm and finally are written to tape. The concentrator system is based on custom-design and VME busses, on an FDDI switch and commercial processors. A description of the readout system is presented, together with results from KLOE cosmic rays and commissioning at DA Phi NE runs.