M. Della Pietra

Strategies and Tools for ATLAS Online Monitoring

ATLAS is one of the four experiments under construction along the Large Hadron Collider (LHC) ring at CERN. The LHC will produce interactions at a center-of-mass energy equal to radics = 14 TeV with a frequency of 40 MHz. The detector consists of more than 140 million electronic channels. The challenging experimental environment and the extreme detector complexity impose the necessity of a common, scalable, distributed monitoring framework, which can be tuned for optimal use by different ATLAS sub-detectors at the various levels of the ATLAS data flow. This paper presents the architecture of this monitoring software framework and describes its current implementation, which has already been used at the ATLAS beam test activity in 2004. Preliminary performance results, obtained on a computer cluster consisting of 700 nodes, will also be presented, showing that the performance of the current implementation is within the range of the final ATLAS requirements.

The Read-Out Driver for the RPC of the ATLAS Muon Spectrometer

The spectrometer of the ATLAS experiment has been designed to identify muon tracks with transverse momenta up to 1 TeV/c. Its barrel section is made of monitored drift tubes and resistive plate chambers (RPCs) arranged into 32 sectors, to form two wheels surrounding the interaction point. The RPC subsystem provides the level-1 trigger in the barrel and it is read out by a specific DAQ system. On-detector electronics pack the RPC data in frames with an event number assigned by the trigger logic and transmit them to the counting room optically. Data from each sector are then routed together to a read-out driver (ROD) board. This is a custom processor that parses the frames, checks their coherence and builds a data structure for all the RPCs of one of the 32 sectors of the spectrometer. Each ROD sends the event fragments to a read-out buffer for further event building and analysis. The ROD is a VME64x board, designed around two Xilinx Virtex-II FPGAs and an ARM7 microcontroller. In this paper we describe the system architecture, the event binding algorithms and the monitoring features embedded into the design. The board is in production and will be deployed in the first ATLAS runs.

New results on ATLAS RPC's aging at CERN's GIF

In order to ensure that the resistive plate chambers used in the ATLAS experiment will not show, during their operation, any abnormal aging effect which could degrade their performances, an aging test is being performed at X5-GIF, CERNs gamma irradiation facility. In this paper, the latest results are presented, together with an example of successful damage recovery technique.

Test beam results and integration of the ATLAS level-1 muon barrel trigger

The ATLAS level-1 muon trigger will be crucial for the online selection of events with high transverse momentum muons and for its correct association to the bunch-crossing corresponding to the detected events. This system uses dedicated coarse granularity and fast detectors capable of providing measurements in two orthogonal projections. The resistive plate chambers (RPCs) are used in the barrel region (|/spl eta/| < 1). The associated trigger electronics is based on a custom chip, the coincidence matrix, that performs space coincidences within programmable roads and time gates. The system is highly redundant and communicates with the ATLAS level-1 trigger processor with the MUCTPI interface. The trigger electronics provides also the readout of the RPCs. Preliminary results achieved with a full trigger tower with production detectors in the H8 test beam at CERN will be shown, in particular preliminary results on the integration of the barrel muon trigger electronics with the MUCTPI interface and with the ATLAS DAQ system will be discussed.

The RPC LVL1 trigger system of the muon spectrometer of the ATLAS experiment at LHC

The Atlas Trigger System has been designed to reduce the LHC interaction rate of about 1 GHz to the foreseen storage rate of about 100 Hz. Three trigger levels are applied in order to fulfill such a requirement. A detailed simulation of the ATLAS experiment including the hardware components and the logic of the Level-1 Muon trigger in the barrel of the muon spectrometer has been performed. This simulation has been used not only to evaluate the performances of the system but also to optimize the trigger logic design. In the barrel of the muon spectrometer the trigger will be given by means of resistive plate chambers (RPCs) working in avalanche mode. Before being mounted on the experiment, accurate quality tests with cosmic rays are carried out on each RPC chamber using the test station facility of the INFN and University laboratory of Napoli. All working parameters are measured and the uniformity of the efficiency on the whole RPC surface is required. A summary of the Napoli cosmic rays tests, together with a brief description of the Atlas Trigger, in particular of the Level-1 Muon Trigger in the barrel, and the results of the trigger simulation will be given.

Cosmic ray test station for ATLAS RPC

Abstract We describe the facility for RPC test with cosmic rays, designed and built at the laboratory of INFN and University of Naples. Trigger and tracking systems consist of a scintillator hodoscope and two drift chambers with track reconstruction resolution of ∼400 μm . Trigger is provided by the twofold coincidence of scintillators covering a surface of 1 m 2 . Two step motors move chambers synchronously along the station for RPC scanning. Up to eight RPCs can be tested simultaneously.

Design, implementation and test of the timing trigger and control receiver for the LHC

The Timing Trigger and Control (TTC) system is an optical network which distributes the timing and synchronization signals of the Large Hadron Collider (LHC) machine to the LHC experiments. It is also used to transmit the trigger information of each experiment to the on-detector electronics. The TTC system has been designed in the late 90s, by using VLSI processes available at that time. Thus, some elements of the system are now obsolete and, in particular, only a small number of the network receivers (TTCrx) is presently available to be deployed in the LHC experiments. In this paper we describe a possible implementation of the TTCrx, which should be used to replace the TTCrx chips on the off-detector electronics, where radiation is not a concern. Our design is based on the Xilinx Virtex-5 FPGAs, and uses fabric resources and embedded high speed serial link transceivers, in order to emulate the architecture and the main features of the TTCrx. By using our approach, the receiver part of the TTC can be easily implemented in commercial FPGAs, thus resulting in a fast design implementation, a simple layout and a cost-effective solution. In this paper, we present the details of the implementation and the test results.

The ATLAS LVL1 Barrel Muon Trigger Commissioning with Cosmic Rays

The ATLAS muon spectrometer, currently in the installation phase, uses dedicated detectors to be able to trigger on high transverse momentum muons in the range 6-20 GeV/c resistive plate chambers (RPC) are equipping the barrel region in the middle and outer station, while precision chambers (monitored drift tubes, MDT) are present also in the inner layer. The RPCs have the required timing and spatial resolution of about 2 ns times 1 cm, to be able to associate the muon to the correct bunch crossing and provide the second coordinate measurements to the MDTs. In order to successfully commission the chambers, cosmic runs are taken to check and validate the readout and trigger chain, and cosmic rates are measured and compared against values obtained with a cosmic ray Monte Carlo generator and full detector simulation. The first part of the detector under commission is the set of horizontal chambers positioned between the feet of the detector. The first results obtained in the ATLAS cavern will be presented. The first cosmic data taking collects signals from chambers arranged in six trigger towers, covering about one quarter of the full detector length. The experience gained on this small part of the detector will be very useful to define the commissioning work for the whole detector.

PERFORMANCES OF THE ATLAS LEVEL-1 MUON TRIGGER PROCESSOR IN THE BARREL

The ATLAS level-1 muon trigger will select events with high transverse momentum and tag them to the correct machine bunch-crossing number with high efficiency. Three stations of dedicated fast detectors provide a coarse pT measurement, with tracking capability on bending and non-bending projections. In the Barrel region, hits from doublets of Resistive Plate Chambers are processed by custom ASIC, the Coincidence Matrices, which performs almost all the functionalities required by the trigger algorithm and the readout. In this paper we present the performance of the level-1 trigger system studied on a cosmic test stand at CERN, concerning studies on expected trigger rates and efficiencies.

Study of the performances of the level-1 trigger system for muons in the barrel of ATLAS with cosmic rays

The muon trigger in ATLAS is crucial for all the main physics channels to be studied at the design center of mass energy and luminosity of LHC and also for the initial phase of data taking with beams for the calibration of all the detectors. The level-1 trigger system for muons in ATLAS is performed using dedicated RPC chambers in the |η| ≪ 1 region. The trigger electronics provides both trigger and readout information. This system is being commissioned using cosmic rays with the full trigger and data acquisition chains. Monitoring tools have been developed in order to spot problems during data taking and determine the quality of the data and the trigger performance. Moreover, using the data taken during the commissioning phase, with partial availability of the detector, some studies have been performed to allow the optimization of the trigger system, based on different choises of the configuration parameters, also as a function of the detector working point. In this paper we would like to describe the extensive tests performed on the system and illustrate the possible performances with different conditions.