Architecture of the DELPHI on-line data acquisition control system

Since LEP (Large Electron-Positron storage ring) started running in August 1989, the DELPHI (Detector with Lepton, Photon, and Hadron Identification) experiment has recorded the production of over 400000 Z/sup 0/ vector bosons. The basic design of the process control system of the on-line data acquisition is described. The approach adopted is based on the state manager concept, in which the experiment is described in terms of objects in well-defined states. Commands can be sent to these objects causing them to perform actions and to change state. The complete description of all objects in a simple language is used to generate a set of executable images which run as VMS processes distributed over 20 VAXes and control the 16 subdetectors of DELPHI.<
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