The KLOE drift chamber readout system

The tracking detector of the KLOE experiment is a large volume drift chamber designed to identify with high efficiency K_L-K _S decays produced on the Φ resonance at the DAΦNE 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 10³³ cm^-2 s^-1, bunch crossing period of 2.7 ns, at an expected trigger rate of 10 KHz, with low deadtime (~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 DAΦNE runs