B. Gorini

The base-line DataFlow system of the ATLAS trigger and DAQ

The base-line design and implementation of the ATLAS DAQ DataFlow system is described. The main components of the DataFlow system, their interactions, bandwidths, and rates are discussed and performance measurements on a 10% scale prototype for the final ATLAS TDAQ DataFlow system are presented. This prototype is a combination of custom design components and of multithreaded software applications implemented in C++ and running in a Linux environment on commercially available PCs interconnected by a fully switched gigabit Ethernet network.

The trigger for K0→π0π0 decays of the NA48 experiment at CERN

The trigger used for the collection of the samples of K0→π0π0 decays in the NA48 experiment at CERN uses a novel pipeline design in order to satisfy the demanding specifications of a high rate kaon beam. The trigger algorithms, architecture and performance are described.

A 40 MHz-pipelined trigger for K0→2π0 decays for the CERN NA48 experiment

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 [l] experiment, aiming at measuring CP violation in KO -+ 2n decays. The outputs of the 13340 cells of the 10 m3 liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs. This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution. Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.

A 40 MHz pipelined trigger for K/sup 0//spl rarr/2/spl pi//sup 0/ decays for the CERN NA48 experiment

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 experiment, aiming at measuring CP violation in K/sup 0//spl rarr/2/spl pi/ decays. The outputs of the 13340 cells of the 10 m/sup 3/ liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs. This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution. Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.

Performance of the Final Event Builder for the ATLAS Experiment

Event data from proton-proton collisions at the LHC will be selected by the ATLAS experiment by a three level trigger system, which reduces the initial bunch crossing rate of 40 MHz at its first two trigger levels (LVL1+LVL2) to ~3 kHz. At this rate the Event-Builder collects the data from all Read-Out system PCs (ROSs) and provides fully assembled events to the the Event-Filter (EF), which is the third level trigger, to achieve a further rate reduction to ~200 Hz for permanent storage. The Event-Builder is based on a farm of 0 (100) PCs, interconnected via Gigabit Ethernet to 0 (150) ROSs. These PCs run Linux and multi-threaded software applications implemented in C++. All the ROSs and one third of the Event-Builder PCs are already installed and commissioned. Performance measurements have been exercised on this initial system, which show promising results that the required final data rates and bandwidth for the ATLAS event builder are in reach.

Performance of the ATLAS DAQ DataFlow system

The baseline DAQ architecture of the ATLAS Experiment at LHC is introduced and its present implementation and the performance of the DAQ components as measured in a laboratory environment are summarized. It will be shown that the discrete event simulation model of the DAQ system, tuned using these measurements, does predict the behaviour of the prototype configurations well, after which, predictions for the final ATLAS system are presented. With the currently available hardware and software, a system using ~140 ROSs with 3GHz single cpu, ~100 SFIs with dual 2.4 GHz cpu and ~500 L2PUs with dual 3.06 GHz cpu can achieve the dataflow for 100 kHz Level 1 rate, with 97% reduction at Level 2 and 3 kHz event building rate. ATLAS DATAFLOW SYSTEM The 40 MHz collision rate at the LHC produces about 25 interactions per bunch crossing, resulting in terabytes of data per second, which has to be handled by the detector electronics and the trigger and DAQ system [1]. A Level1 (L1) trigger system based on custom electronics will reduce the event rate to 75 kHz (upgradeable to 100 kHz – this paper uses the more demanding 100 kHz). The ________________________________________ #. Also affiliated with University of California at Irvine, Irvine, USA *. On leave from Henryk Niewodniczanski Institute of Nucl. Physics, Cracow +. Presently at CERN, Geneva, Switzerland 91 DAQ system is responsible for: the readout of the detector specific electronics via 1630 point to point read-out links (ROL) hosted by Readout Subsystems (ROS), the collection and provision of “Region of Interest data” (ROI) to the Level2 (L2) trigger, the building of events accepted by the L2 trigger and their subsequent input to the Event Filter (EF) system where they are subject to further selection criteria. The DAQ also provides the functionality for the configuration, control, information exchange and monitoring of the whole ATLAS detector readout [2]. The applications in the DAQ software dealing with the flow of event and monitoring data as well as the trigger information are called “DataFlow” applications. The DataFlow applications up to the EF input and their interactions are shown in Figure 1. Figure 1 ATLAS DAQ-DataFlow applications and their interactions (up to the EventFilter) SFI L2PU L2SV DFM pROS ROS ROI data

A 40 MHz pipelined trigger for {Kappa}{sup 0} {r_arrow} 2{pi}{sup 0} decays for the CERN NA48 experiment

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 experiment, aiming at measuring CP violation in K/sup 0//spl rarr/2/spl pi/ decays. The outputs of the 13340 cells of the 10 m/sup 3/ liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs. This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution. Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.