THE DRIFT CHAMBER ELECTRONICS AND READOUT FOR THE NA48 EXPERIMENT AT THE CERN SPS

A drift chamber readout system for about 8000 channels with continuous sensitivity, i.e. concurrent data recording and readout, is described , Drift times are measured in bins of 1.56 ns with respect to a contin uously running 40 MHz clock. The clock interval of 25 ns is divided in to 16 bins by means of a 16-element delay chain. The length of this ch ain is linked to the clock interval by a phase-locked loop, An ASIC ch ip was developed to perform time measurements and data storage for 16 channels. in an asynchronous readout of this chip, data are tranferred to intermediate buffers, for use in a first-level trigger and eventua l final readout. The design of the electronics is described and result s from data-taking runs are presented. (C) 1998 Elsevier Science B.V. All rights reserved.