G. Carlino

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.

Long-term performance of the L3 RPC system

Abstract Started in 1994 the L3 experiment has been equipped with a forward–backward muon spectrometer triggered by an RPC system. Made of 192 double-gap RPCs, it has been working for six years in streamer mode and it will continue to run at least one year more. We monitored the behaviour of the system during the L3 run periods and in this paper we report on its present status and long-term performance.

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.

The L3 forward-backward muon RPC trigger system

Abstract We describe the trigger system for the Forward-Backward muon spectrometer of L3 detector. The trigger uses double gap Resistive Plate Counters (RPC) covering an area of 300 m2. This is the first large scale application of this kind of detectors in high energy physics. The main features of these detectors, the trigger architecture and preliminary results are reported.

The muon spectrometer barrel level-1 trigger of the ATLAS experiment at LHC

The proton-proton beam crossing at the LHC accelerator at CERN will have a rate of 40 MHz at the project luminosity. The ATLAS Trigger System has been designed in three levels in order to select only interesting physics events reducing from that rate of 40 MHz to the foreseen storage rate of about 200 Hz. The First Level reduces the output rate to about 100 kHz. The ATLAS Muon Spectrometer has been designed to perform stand-alone triggering and measurement of Muon transverse momentum up to 1 TeV/c with good resolution (from 3% at 10 GeV/c up to 10% at 1 TeV/c). In the Barrel region of the Muon Spectrometer the Level-1 trigger is given by means of three layers of resistive plate chamber detectors (RPC): a gaseous detector working in avalanche mode composed by two plates of high-resistivity bakelite and two orthogonal planes of read-out strips. The logic of the Level-1 barrel Muon trigger is based on the search of patterns of RPC hits in the three layers consistent with a high transverse momentum Muon track originated from the interaction vertex. The associated trigger electronics is based on dedicated processors, the Coincidence Matrix boards, performing space coincidences and time gates and providing the RPC readout as well. A detailed simulation of the ATLAS Experiment and of both 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 define the hardware set-up such as the cabling of both the trigger detectors and the trigger electronics modules. A description of both the Level-1 Muon Trigger system in the barrel and the RPC detectors, with their cosmic rays quality tests, will be presented together with the trigger performances and rates calculations evaluated for Muons over a wide range of pT and preliminary studies on the impact of accidental triggers due to low energy background particles in the experimental area

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.

Enabling data analysis à la PROOF on the Italian ATLAS Tier-2s using PoD

We describe our experience using PROOF for data analysis on the Italian ATLAS-Tier2 in Frascati, Napoli and Roma1. To enable PROOF on the cluster we used PoD, Proof-on-Demand. PoD is a set of tools designed to interact with any Local Resource Management System (LRMS) to start the PROOF daemons. In this way any user can quickly setup its own PROOF cluster on the resources, with the LRMS taking care of scheduling, priorities and accounting. Usage of PoD has steadily increased in the last years, and the product has now reached a production level quality. PoD features an abstract interface to LRMSs and provides plugins for several LRMSs. In our tests we used both the gLite and PBS plug-ins, the latter being the native LRMS handling the resources under test. Data were accessed via XRootD with file discovery provided by the standard ATLAS tools. The Storage Element was Disk Pool Manager (DPM) which traditionally uses RFIO rfio data access protocol; we added XRootD on top of this system so PoD could access the data. We describe the configuration and setup details and the results of some benchmark tests we run on the facility.

Deployment of job priority mechanisms in the Italian Cloud of the ATLAS experiment

An optimized use of the Grid computing resources in the ATLAS experiment requires the enforcement of a mechanism of job priorities and of resource sharing among the different activities inside the ATLAS VO. This mechanism has been implemented through the VOViews publication in the information system and the fair share implementation per UNIX group in the batch system. The VOView concept consists of publishing resource information, such as running and waiting jobs, as a function of VO groups and roles. The ATLAS Italian Cloud is composed of the CNAF Tier1 and Roma Tier2, with farms based on the LSF batch system, and the Tier2s of Frascati, Milano and Napoli based on PBS/Torque. In this paper we describe how test and deployment of the job priorities has been performed in the cloud, where the VOMS-based regional group /atlas/it has been created. We show that the VOViews are published and correctly managed by the WMS and that the resources allocated to generic VO users, users with production role and users of the /atlas/it group correspond to the defined share.

The RPC Level-1 muon trigger of the ATLAS experiment at the LHC

The three-level ATLAS trigger system has been designed to reduce the initial LHC interactions rate from 1 GHz, to ~100 Hz in order to allow permanent data storage. This result must be achieved preserving the less probable physics signals against a large background therefore providing a challenge task for the trigger and DAQ system. The level-1 muon trigger in the barrel region of the muon spectrometer is provided by resistive plate chambers (RPC) working in avalanche mode. More than 1000 RPC units of different sizes will he installed covering a surface of about 3650 m2 with a 350000 readout channels. A detailed simulation of the level-1 has been developed in order to optimize the trigger logic design and to study its performances. A description of the level-1 trigger in the barrel and preliminary results of its performances are presented.