Data Aquisition System
Event Filter and Data Acquisition
For LVL2-selected events, event building is performed. Each readout buffer contains fragments of many events for a small part of one subdetector. The event builder collects all the fragments from one event into a single memory - the memory of an Event Filter processor. The event building is performed using a data switch.
Event Filter processing is performed using farms of processors acting on the full-event data. The complicated selection criteria of the off-line analysis will be used in a real-time environment. The processing time per event could be about 1 second on a 1000 MIPS (Million Instructions Per Second) processor (today's processors are typically 100-200 MIPS)
The figure above shows, on the left, a fuctional view of the trigger and DAQ systems, on the right is an implementation view emphasising the trigger levels and their interaction with the DAQ system.
DAQ prototype "-1"
A project is in progress to study the full fuctionality of the DAQ and Event Filter systems.
The goal of this project is to produce a prototype system representing a "full slice" of a DAQ system, and suitable for evaluating candidate technologies and architectures for the final ATLAS DAQ system.
Work started on defining the requirements in Spring 1996 and it is
expected that the prototype will be running in 1998. Each phase of the
project is reviewed by the ATLAS Trigger/DAQ community.