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The collision centrality in the ALICE experiment will be determined by the Zero Degree Calorimeters (ZDCs) that will measure the spectator nucleons energy in heavy ion collisions. The ZDCs detect the Cherenkov light produced by the fast particles in the shower that cross the quartz fibers, acting as the active material embedded in a dense absorber matrix. Test beam results of the calorimeters are presented.
The use of phenolic or melaminic bakelite as RPC electrodes is widespread. The electrode resistivity is an important parameter for the RPC performance. As recent studies have pointed out, the bakelite resistivity changes with temperature and is influenced by humidity. In order to gain a quantitative understanding on the influence of temperature and humidity on RPC electrodes, we assembled an apparatus to measure resistivity in well-controlled conditions. A detailed description of the experimental set-up as well as the first resistivity measurements for various laminates in different environmental conditions are presented.
The trigger system for the ALICE Dimuon Arm will be based on Resistive Plate Chambers. An RPC prototype, with electrodes made of low resistivity bakelite (rho ~ 3.10^9 ? cm) has been tested both at the SPS and at the GIF. The results for operation in streamer mode are presented here.
ALICE (A Large Ion Collider Experiment) is the heavy-ion dedicated experiment at LHC. The Resistive Plate Chamber detector (RPC) with low-resistivity bakelite electrodes was selected for the trigger system of the muon spectrometer. Although the main goal of ALICE is the study of nucleus-nucleus collisions, reference data in p-p interactions will be collected as well. According to the specific aspects of p-p data taking for ALICE and in particular to the ageing requirements, a running mode, referred as highly-saturated avalanche using the same FEE as the one we use for streamer mode was investigated. A detailed study of signal properties was carried out with cosmics rays to get a more precise view of its intrinsic properties (among others the streamer fraction vs. HV). The possibility of detecting avalanche signals with our FEE designed...
ALICE (a large ion collider experiment) is the LHC experiment dedicated to the study of ultra-relativistic heavy ion collisions. The ALICE muon spectrometer covers a large range in pseudo-rapidity and is designed to study quarkonia and heavy flavours decaying into (di-)muons. The high particle multiplicities environment in such collisions require a specific, fast and efficient trigger system, the muon trigger. It consists of four planes of RPC detectors, covering an area of 36 m2 each, 21k front-end channels and a fast-decision electronics. The muon trigger is designed to reconstruct (muon) tracks and deliver a trigger signal each 25 ns (40 MHz) with a total latency of 800 ns. The hit position on the RPC is measured in two orthogonal directions with an accuracy of about 1 cm. The performance measured with the first p–p collisions at sq...
The trigger for the ALICE muon spectrometer will be issued by single-gap, low resistivity bakelite resistive plate chambers (RPCs). The trigger system consists of four 5.5x6.5 m2 RPC planes arranged in two stations, for a total of 72 detectors. One hundred and sixteen detectors have been assembled and tested in Torino. The tests have been performed with the streamer mixture developed for heavy ion data-taking. The tests include: the detection of gas leaks and parasitic currents; the measurement of the efficiency with cosmic rays, with particular regard to the uniformity of the efficiency throughout the whole active surface, with a granularity of about 2x2 cm2; the measurement of the dark current and of the mean and localised noise rate. All the RPCs produced have been characterised. Among them, the detectors to be finally installed in ...
The trigger for the ALICE muon spectrometer will be issued by single-gap, low-resistivity bakelite RPCs. The trigger detector will be made of four 6×6 m2 RPC planes arranged in two stations, for a total of 72 chambers. Strip planes, stiffener planes and mechanical supports are realized and assembled in the INFN Technological Laboratory in Torino (Italy). All the produced volumes are tested before installation in ALICE: gas tightness and spacer gluing are checked at INFN-LNGS, while INFN-Torino Laboratory houses the cosmic rays test station. The tests are made with the ALICE streamer mixture (50.5% Ar, 41.3% C2H2F4, 7.2% i-C4H10, 1% SF6) and include measure of the electrodes resistivity, together with noise and efficiency mapping. These tests provide a complete characterization of the detectors (efficiency, cluster size, absorbed curren...
The Forward Muon Spectrometer is one of the main components of ALICE, the dedicated heavy-ion experiment at the LHC. Its main goal is to measure heavy quarkonia (J/ψ and families) production in their μ+μ− decay channel. The muon trigger has to match the maximum trigger rate of about 1 kHz which can be handled by the DAQ. Therefore an event selection is performed by applying a suitable pt cut on each muon of the pair. The trigger system is based on Resistive Plate Chambers. The experimental conditions, the trigger architecture, its principle and its performance predicted by simulation are presented.
The trigger detectors for the Muon Forward Spectrometer of the ALICE experiment will be single gap RPCs with low–resistivity bakelite electrodes. The detector will take data for different colliding systems resulting in a wide range of working conditions and requirements, especially concerning position resolution and detector lifetime. To this aim we have investigated the possibility to operate the RPCs both in streamer and in highly–saturated avalanche mode with the same FE electronics. In this paper we present the results obtained in a test with cosmic rays, as well as from beam and ageing tests with the gas mixture that allows for highly–saturated avalanche operation.
A dedicated front-end electronics has been developed for the trigger chambers of the ALICE muon spectrometer under construction at the future LHC at CERN. This trigger detector is based on RPCs (Resistive Plate Chambers) working in streamer mode. The number of electronics channels (about 21000) and the fact that RPC signals have specific characteristics have led to the design of an 8 channel front-end ASIC using a new discrimination technique. The principle of the ASIC is described and the radiation hardness is discussed. Special emphasis is put on production characteristics of about 4000 ASICs.
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