Results in online data processing in the data acquisition system of the ALEPH TPC

Abstract

The performance and implementation of the TPC (time projection chamber) DAQ (data acquisition chamber) system are presented. It is shown how online data processing is used to obtain a substantial reduction of the data volume. The TPC DAQ system has performed in a satisfactory way since the beginning of LEP physics in 1989. The task of reliably initializing steering, and testing several hundred complex electronic modules has been achieved. Experience has shown that the complete system can operate reliably, provided it is properly monitored. The design requirements on TPPs (triple-width FASTBUS modules) and TPDs (double-width FASTBUS modules) were fulfilled, and their measured performance seems appropriate for the highest physics event rates expected at LEP. A substantial online reduction of the data volume has been obtained by making use of the processing power of 36 TPPs in parallel.<>