The CMS muon system consist of Drif Tubes (DTs) in barrel region, Cathode Strip Chambers (CSCs) in the end-cap region and Resistive Plate Chambers (RPCs) in both regions. The RPCs with their ...excellent time resolution were chosen as dedicated muon trigger detector for the CMS experiment. After the Long Shutdown 1 (LS1) the LHC luminosity should reach 1034cm-2s-1 thus it is necessary to improve the level 1 trigger efficiency of the CMS detector for this high luminosity, to achieve that a 4th RPCs layer (RE4) in both end-caps of the CMS detector and all the components must be installed and completely validated. Based on the valuable experience (Barrel & Endcap) are defined several steps of Quality Certification (QC): QC1 (Components), QC2 (Gaps), QC3 (Chambers), QC4 (chambers & Super Modules), QC5 (Commissioning at P5). In this work is presented some results of QC4.
The high pseudo-rapidity region of the CMS muon system is covered by Cathode Strip Chambers (CSC) only and lacks redundant coverage despite the fact that it is a challenging region for muons in terms ...of backgrounds and momentum resolution. In order to maintain good efficiency for the muon trigger in this region additional RPCs are planned to be installed in the two outermost stations at low angle named RE3/1 and RE4/1. These stations will use RPCs with finer granularity and good timing resolution to mitigate background effects and to increase the redundancy of the system.
The CMS experiment, located at the CERN Large Hadron Collider, has a redundant muon system composed by three different detector technologies: Cathode Strip Chambers (in the forward regions), Drift ...Tubes (in the central region) and Resistive Plate Chambers (both its central and forward regions). All three are used for muon reconstruction and triggering. During the first long shutdown (LS1) of the LHC (2013-2014) the CMS muon system has been upgraded with 144 newly installed RPCs on the forth forward stations. The new chambers ensure and enhance the muon trigger efficiency in the high luminosity conditions of the LHC Run2. The chambers have been successfully installed and commissioned. The system has been run successfully and experimental data has been collected and analyzed. The performance results of the newly installed RPCs will be presented.
We report on a systematic study of double-gap and four-gap phenolic resistive plate chambers (RPCs) for future high-{\eta} RPC triggers in the CMS. In the present study, we constructed real-sized ...double-gap and four-gap RPCs with gap thicknesses of 1.6 and 0.8 mm, respectively, with 2-mm-thick phenolic high-pressure-laminated (HPL) plates. We examined the prototype RPCs for cosmic rays and 100 GeV muons provided by the SPS H4 beam line at CERN. We applied maximum gamma rates of 1.5 kHz cm-2 provided by 137Cs sources at Korea University and the GIF++ irradiation facility installed at the SPS H4 beam line to examine the rate capabilities of the prototype RPCs. In contrast to the case of the four-gap RPCs, we found the relatively high threshold was conducive to effectively suppressing the rapid increase of strip cluster sizes of muon hits with high voltage, especially when measuring the narrow-pitch strips. The gamma-induced currents drawn in the four-gap RPC were about one-fourth of those drawn in the double-gap RPC. The rate capabilities of both RPC types, proven through the present testing using gamma-ray sources, far exceeded the maximum rate expected in the new high-{\eta} endcap RPCs planned for future phase-II LHC runs.
Based on previous experience and attempt, a real-size mosaic Multi-gap Resistive Plate Chamber (MRPC) has been developed within the framework of the CMS muon upgrade efforts. The chamber is a 5-gap ...with plates made each of 6 pieces of low resistive glass. Cosmic ray test at CERN 904 shows that its efficiency can reach above 95% with a gas mixture of 90% C2H2F4, 5% i-C4H10 and 5% SF6. The chamber was also tested with CMS dry gas(95.2% C2H2F4, 4.5% i-C4H10, 0.3% SF6) at the CERN Gamma Irradiation Facility (GIF++). Efficiency results calculated by a simple tracking method show that the good performance is maintained at rates up to 10 kHz/cm2.
The RPC muon detector of the CMS experiment at the LHC (CERN, Geneva, Switzerland) is equipped with a Gas Gain Monitoring (GGM) system. A report on the stability of the system during the 2011-2012 ...data taking run is given, as well as the observation of an effect which suggests a novel method for the monitoring of gas mixture composition.
The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous ...luminosity would also increase by an order of magnitude up to 6 middot 10 super(34) cm super(-2)s super(-1). The region of the forward muon spectrometer (eta > 1.6) is not equipped with RPC stations. The increase of the expected particles flux up to 2 kHz/cm super(2) (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The current CMS RPC technology cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provide a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity glass is proposed to equip at least the two most far away of the four high eta muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux are presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.
The High Luminosity LHC (HL-LHC) phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. The foreseen gradual increase of the instantaneous ...luminosity of up to more than twice its nominal value of \(10\times10^{34}\ {\rm cm}^{-1}{\rm s}^{-2}\) during Phase I and Phase II of the LHC running, presents special challenges for the experiments. The region with high pseudo rapidity (\(\eta\)) region of the forward muon spectrometer (\(2.4 > |\eta| > 1.9\)) is not equipped with RPC stations. The increase of the expected particles rate up to 2 kHz cm\(^{-1}\) ( including a safety factor 3 ) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The current CMS RPC technology cannot sustain the expected background level. A new generation of Glass-RPC (GRPC) using low-resistivity glass was proposed to equip the two most far away of the four high \(\eta\) muon stations of CMS. In their single-gap version they can stand rates of few kHz cm\(^{-1}\). Their time precision of about 1 ns can allow to reduce the noise contribution leading to an improvement of the trigger rate. The proposed design for large size chambers is examined and some preliminary results obtained during beam tests at Gamma Irradiation Facility (GIF++) and Super Proton Synchrotron (SPS) at CERN are shown. They were performed to validate the capability of such detectors to support high irradiation environment with limited consequence on their efficiency.
The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous ...luminosity would also increase by an order of magnitude up to \(6.10^{34} cm^{-2} s^{-1}\) . The region of the forward muon spectrometer (\(|{\eta}| > 1.6\)) is not equipped with RPC stations. The increase of the expected particles rate up to \(2 kHz/cm^{2}\) (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The actual RPC technology of CMS cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provides a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity (LR) glass is proposed to equip at least the two most far away of the four high \({\eta}\) muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux is presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.
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