THE EVOLUTION OF THE DELPHI EXPERIMENT CONTROL SYSTEM OR HOW TO SURVIVE TEN YEARS OF RUNNING
A. Augustinus, M. Dönszelmann, C. Gaspar, Ph. Gavillet, M. Jonker, T. Adye, B.J. Franek, R. Sekulin, G.R. Smith · 1999
The DELPHI experiment at CERN’s LEP collider [1] started taking data in august 1989. During these ten years of running, the DELPHI Experiment Control System (ECS) has been in permanent evolution. However the initial concepts are still present despite upgrades and reengineering. This is mainly due to a careful architecture and design which allowed a smooth evolution with far better functionality but minor changes for the users (programmers and operators).. 1 BASIC CONCEPTS DELPHI is one of the four large experiments at the LEP electron positron collider. Its readout electronics consists in over 250 000 channels (after multiplexing) and its slow controls system handles several thousands channels (power supplies, temperature and pressure probes…). The Data Acquisition System (DAS) [2] and the Slow Controls System (SC) [3] are the two main components of the Experiment Control System (ECS). Both are organized in a hierarchy of processors and processes (front-end level, sub-detector level and central level). Besides these two majors system, the ECS integrates the control of the trigger system [4] (two levels of triggering, local and central timing configurations) as well as the LEP Communications System (LCP). 1.1 The Data Acquisition System The DELPHI Data acquisition System (DAS) [2] is organized as a set of 20 predefined partitions (equivalent to a sub-detector or part of it) and a so-called Central Partition which builds events and performs a software selection of events (Third Level trigger). Each partition is itself split at the front-end level into between 1 and 13 entities controlled each by a Crate Processor (CP). The standard for front-end electronics and processing is Fastbus. DELPHI has about 150 Fastbus crates. The partitions are controlled by a Local Event Supervisor (LES) while the Central Partition is under control of the Global Event Supervisor (GES). The CP, LES and GES software are running in the same type of embedded processor, the Fastbus Inter-segment Processor