V. Canale

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.

Deflection Monitoring Method Using Fiber Bragg Gratings Applied to Tracking Particle Detectors

This paper proposes the use of fiber Bragg gratings (FBGs) for the deflection monitoring of a micromegas (MM) tracking particle detector to be installed at the European Organization for Nuclear Research during a major upgrade of the experiment ATLAS within 2018. MM detectors are designed to reach high spatial and time resolution, even if the design is not yet finalized. One mandatory issue for the MM detector is a precise monitoring of the deflection of the drift and read-out electrodes and/or of the panel hosting the electrodes. To this aim, FBG strain sensors are proposed and experimentally investigated as a sensing solution to monitor the strain state of the detector support panel hosting the drift and read-out electrodes. Finally, simple postprocessing analysis based on classical beam theory considering a rigid body permits calculating the panel deflection. Preliminary experimental results on first prototypes of small and large detector panels are presented and discussed.

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.

The ATLAS level-1 barrel muon trigger performances

The level-1 muon trigger of ATLAS is expected to select events with high transverse momentum muons and associate them the correct bunch-crossing. For these purposes, dedicated fast detectors provide coarse measurement of the muon transverse momentum and high efficiency in its discrimination, giving also tracking measurements in two orthogonal views. In the barrel region (|eta|<1) it makes use of resistive plate chambers (RPCs) as active detectors. The trigger and readout chain is based on custom ASIC chips, which perform both the time and spatial coincidence with programmable roads and signal time shaping, and the readout, with a time resolution of 1/8 of a bunch crossing. A calibration procedure will allow to align signals in time and improve the background rejection of the system. The trigger system performances have been studied, testing multiple trigger configurations, on a cosmics test-stand using a full trigger tower of the ATLAS muon barrel spectrometer and the complete ATLAS trigger chain

Test beam results from the ATLAS LVL1 muon barrel trigger and RPC readout slice

The ATLAS barrel level-1 muon trigger system has the following main requirements: coarse measurement and discrimination of the muon transverse momentum PT; bunch crossing identification; fast and coarse tracking to identify tracks in the precision chambers that are related to the muon candidate; 2nd-coordinate measurement with a required resolution of 5-10 mm. Integration tests have been carried out between the various components of the system and in conjuction with the detector, front-end and other general sub-systems of the experiment. Results from test beam measurements have been performed in the CERN H8 test beam area, where production detectors from one full trigger tower have been installed.

Ageing test of ATLAS RPCs at CERN's Gamma Irradiation Facility

An ageing test of three ATLAS production RPC stations is in progress at X5 GIF, the CERN irradiation facility. The chamber efficiency as a function of the operating voltage is measured at different source intensities, up to a maximum counting rate of about 700 Hz/cm/sup 2/. All along the test, plate resistivity has been monitored using two different methods: by measuring the I-V characteristics in pure Ar, and by comparing the efficiency vs high voltage curves at different source intensities. The increase in plate resistivity, which is one of the dominant ageing effects for RPCs with phenolic-melaminic electrodes, has been shown to be strongly dependent on environmental relative humidity. Indeed, after setting to values between 40% and 50% the relative humidity of both the operating gas and the air surrounding the chambers, a significant decrease of the plate resistivity has been observed.

Small-Pad Resistive Micromegas for Operation at Very High Rates

Resistive strip Micromegas detectors have already proved to be suitable for precision tracking in dense particle rate environment up to few kHz/cm2. In order to achieve higher rate capability, with low occupancy, fine-segmented strips could be replaced by few mm2 pads. A first prototype, with readout and resistive pads connected by resistors embedded in an insulating layer, has been constructed at CERN and first performance studies are presented.