Extended Data Acquisition Support at GSI

The Experiment Data Acquisition and Analysis System (EDAS) of GSI, designed to support the data processing associated with nuclear physics experiments, provides three modes of operation: real-time, interactive replay and batch replay. The real-time mode is used for data acquisition and data analysis during an experiment performed at the heavy ion accelerator at GSI. The computing resources provided by dedicated Experiment Computers are insufficient for the more complex experiments performed today. To meet demands for higher data rates, more computing power and more support for data analysis during an experiment, a distributed system was conceived. The GSI High Speed Data Acquisition Network provides the hardware support for the system; it consists of a number of dedicated Experiment Computers which directly control experiments, a multi-user mainframe which performs the data analysis and data storing for all experiments, and a concentrator to connect all Experiment Computers to the mainframe. Three software sub-systems were designed, one for each component of the distributed system. An experiment may be performed either in Stand Alone Mode, using only the Experiment Computers, or in Extended Mode using all computing resources available. The Extended Mode combines the advantages of the real-time response of a dedicated minicomputer with the availability of computing resources in a large computing environment. This paper first gives an overview of EDAS and presents the GSI High Speed Data Acquisition Network. Data Acquisition Modes and the Extended Mode are then introduced.