Resistive Plate Chambers System Research Articles

First results of CMS RPC performance at 13 TeV

The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the Large Hadron Collider (LHC) is equipped with a redundant system made of Resistive Plate Chambers (RPCs) and Drift Tube (DT) chambers in the barrel, RPC and Cathode Strip Chambers (CSCs) in the endcap region. In this paper, the first results of the performance of the RPC system during 2015 with the LHC running at 13 TeV is presented. The stability of the RPC performance, in terms of efficiency, cluster size and noise, is reported.

Eco-friendly gas mixtures for Resistive Plate Chambers based on tetrafluoropropene and Helium

Due to the recent restrictions deriving from the application of the Kyoto protocol, the main components of the gas mixtures presently used in the Resistive Plate Chambers systems of the LHC experiments will be most probably phased out of production in the coming years. Identifying possible replacements with the adequate characteristics requires an intense R&D activity, which was recently started, in collaborations with various experiments. Possible new gases have been proposed and are thoroughly investigated. Some tests on one of the most promising candidate—HFO-1234ze, an allotropic form of tetrafluoropropane—have already been reported. Here an innovative approach, based on the use of Helium, to solve the problem related to the high operating voltage needed to operate the chambers with HFO-1234ze based gas mixtures, is discussed and the first results are shown.

Characterization of RPC operation with new environmental friendly mixtures for LHC application and beyond

The large muon trigger systems based on Resistive Plate Chambers (RPC) at the LHC experiments are currently operated with R134a based mixture. Unfortunately R134a is considered a greenhouse gas with high impact on the enviroment and therefore will be subject to regulations aiming in strongly reducing the available quantity on the market. The immediat effects might be instability on the price and incertitude in the product availability. Alternative gases (HFO-1234yf and HFO-1234ze) have been already identified by industry for specific applications as replacement of R134a. Moreover, HFCs similar to the R134a but with lower global warming potential (GWP) are already available (HFC-245fa, HFC-32, HFC-152a). The present contribution describes the results obtained with RPCs operated with new enviromemtal friendly gases. A particular attention has been addressed to the possibility of maintening the current operation conditions (i.e. currently used applied voltage and front-end electronics) in order to be able to use a new mixture for RPC systems even where the common infrastructure (i.e. high voltage and detector components) cannot be replaced for operation at higher applied voltages.

CMS RPC muon detector performance with 2010-2012 LHC data

The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the Large Hadron Collider (LHC) is equipped with a redundant system made of Resistive Plate Chambers (RPCs) and Drift Tube (DT) chambers in the barrel, RPC and Cathode Strip Chambers (CSCs) in the endcap region. In this paper, the operations and the performance of the RPC system during the first three years of LHC activity are presented. The stability of the RPC performance, in terms of efficiency, cluster size and noise, is also reported. Finally, the radiation background levels on the RPC system have been measured as a function of the LHC luminosity. Extrapolations to the High Luminosity LHC conditions are also discussed.

Performance and operation of the ATLAS Resistive Plate Chamber system in LHC Run-1

The barrel region of the ATLAS muon spectrometer is instrumented with a Resistive Plate Chamber (RPC) system covering the pseudo-rapidity range |η| < 1.05 with a detector surface of almost 4000m2. The RPCs, providing the first level trigger signal and the track coordinate in the non-bending plane for the candidate muons, have played a fundamental role in the physics studies carried out by ATLAS, culminated with the discovery of the Higgs boson. During the LHC Run-1 the RPC have shown excellent performance up to the maximum instantaneous luminosity of 0.7 × 1034cm-2s-1, corresponding approximately to 70% of the design value. The detector operation in the challenging background and pileup conditions of the LHC environment are presented together with the problems encountered and their corresponding solutions. The plans for the maintenance and consolidation of the ATLAS RPC system during the current LHC shutdown, in view of the increased luminosity expected in Run-2, are also presented.

Boltzmann equation and Monte Carlo studies of electron transport in resistive plate chambers

A multi term theory for solving the Boltzmann equation and Monte Carlo simulation technique are used to investigate electron transport in Resistive Plate Chambers (RPCs) that are used for timing and triggering purposes in many high energy physics experiments at CERN and elsewhere. Using cross sections for electron scattering in C2H2F4, iso-C4H10 and SF6 as an input in our Boltzmann and Monte Carlo codes, we have calculated data for electron transport as a function of reduced electric field E/N in various C2H2F4/iso-C4H10/SF6 gas mixtures used in RPCs in the ALICE, CMS and ATLAS experiments. Emphasis is placed upon the explicit and implicit effects of non-conservative collisions (e.g. electron attachment and/or ionization) on the drift and diffusion. Among many interesting and atypical phenomena induced by the explicit effects of non-conservative collisions, we note the existence of negative differential conductivity (NDC) in the bulk drift velocity component with no indication of any NDC for the flux component in the ALICE timing RPC system. We systematically study the origin and mechanisms for such phenomena as well as the possible physical implications which arise from their explicit inclusion into models of RPCs. Spatially-resolved electron transport properties are calculated using a Monte Carlo simulation technique in order to understand these phenomena.

Web-based monitoring tools for Resistive Plate Chambers in the CMS experiment at CERN

The Resistive Plate Chambers (RPC) are used in the CMS experiment at the trigger level and also in the standard offline muon reconstruction. In order to guarantee the quality of the data collected and to monitor online the detector performance, a set of tools has been developed in CMS which is heavily used in the RPC system. The Web-based monitoring (WBM) is a set of java servlets that allows users to check the performance of the hardware during data taking, providing distributions and history plots of all the parameters. The functionalities of the RPC WBM monitoring tools are presented along with studies of the detector performance as a function of growing luminosity and environmental conditions that are tracked over time.

CMS RPC commissioning of the existing detector during the long shutdown

February 1 th 2013 marked the end of the first period of running of the Large Hadron Collider (LHC) and the start of a two-year break from operation (LS1) aimed at consolidating both the accelerator as well as the detectors. By the end of LS1, the LHC is expected to provide collisions at 13 Tev. While, by 2020, the ultimate instantaneous luminosity is expected to be 1034/cm2/s. To prepare for this scenario, the Resistive Plate Chamber system at the CMS experiment is planning several detector maintainance and consolidation interventions. These include High Voltage and Low Voltage system reparations, gas leak identification and reparation, signal channel connectivity and functionality. Commissioning and upgrade plans for the existing CMS RPC system are presented here.

CMS endcap RPC performance analysis

The Resistive Plate Chamber (RPC) detector system in LHC-CMS experiment is designed for the trigger purpose. The endcap RPC system has been successfully operated since the commissioning period (2008) to the end of RUN1 (2013). We have developed an analysis tool for endcap RPC performance and validated the efficiency calculation algorithm, focusing on the first endcap station which was assembled and tested by the Peking University group. We cross checked the results obtained with those extracted with alternative methods and we found good agreement in terms of performance parameters [1]. The results showed that the CMS-RPC endcap system fulfilled the performance expected in the Technical Design Report [2].

Operation, performance and upgrade of the CMS Resistive Plate Chamber system at LHC

The Resistive Plate Chambers are used in CMS as dedicated muon trigger detectors in both barrel and endcap regions. They also contribute to the identification, reconstruction and tracking of the muons, together with Drift Tubes in the barrel and Cathode Strip Chambers in the endcaps.In this paper a detailed report about the operation and performance of the system after three years of LHC activities with increasing instantaneous luminosity is given. This period allowed to accumulate enough statistics to measure the detector performance with an unprecedented accuracy on such a large amount of chambers. This provided new insights both on the detector fundamentals and on the related operational aspects.Special attention was devoted to the working point calibration procedures and to the stability of the system. A comparison between the initial and present performance is made, and an overview is given of what has been learned in almost three years of operation of one of the largest systems based on RPCs.

CMS reconstruction improvement for the muon tracking by the RPC chambers

The contribution of Resistive Plate Chamber (RPC) to muon reconstruction in CMS has been studied on a sample of muons collected in proton-proton collisions at √s = 7 TeV at the LHC in 2011. Muon reconstruction is performed using the all-silicon inner tracker and with up to four stations of gas-ionization muon detectors. Drift Tubes and Cathode Strip Chambers detect muons in the barrel and endcap regions, respectively, and are complemented by the RPC system. Measured distributions of reconstructed hits in the RPCs crossed by muons from Z0 decays with a transverse momentum pT above 20 GeV/c are well reproduced by the Monte Carlo simulation. From the samples of J/ψ and Z0 events, the efficiencies for muons with and without the inclusion of the RPC hits in the muon track reconstruction are measured and compared with the simulation. Using RPC information in track reconstruction improves up to about 3% of offline reconstruction efficiency for the muons in the region of pT above 7 GeV/c, in good agreement with simulation.

Operations and performance of the CMS RPC muon system at LHC

The Compact Muon Solenoid (CMS) experiment is one of the two general-purpose detectors at the CERN Large Hadron Collider. CMS combines three different gaseous detector technologies to trigger and reconstruct muons: Drift Tubes in the barrel region (|η|<1.2), Cathode Strip Chambers in the endcaps (0.9<|η|<2.4) , and Resistive Plate Chambers (RPCs) in both regions, as a dedicated muon trigger. We report on the operations and performance of the RPC system after 2 years of LHC running with increasing instantaneous luminosity. Special attention is given to the stability of the system and to the working point calibration procedures.

A data-driven performance evaluation method for CMS RPC trigger through CMS muon trigger

Abstract The muon system of the CMS (Compact Muon Solenoid) experiment at the LHC (Large Hadron Collider, Geneva-CH) consists of three gaseous detectors with complementary features: the Drift Tube Chambers (DT) in the barrel and the Cathode Strips Chambers (CSC) in the forward region provide good spatial resolution while the Resistive Plate Chambers (RPC), in both barrel and forward region, have an excellent time resolution. The measurements of these detectors are employed for triggering on muons in the hardware-based Level-1 trigger stage. In such scenario an algorithm has been developed, the Global Muon Trigger (GMT), which is in charge of collecting and merging the information provided by the three detectors and outputs muon trigger candidates (GMT candidates). The GMT candidates are henceforth transmitted to the L1 Global Trigger Logic which performs the final decision of accepting or rejecting the muon candidates. The GMT algorithm allows to trace back the detectors whose measurements have been used for each GMT candidate: such feature has been exploited in developing a method for the performance evaluation of muon trigger provided by the RPC system.

The detector control systems for the CMS Resistive Plate Chamber

The Resistive Plate Chamber system is composed by 912 double-gap chambers equipped with about 104 front-end boards. The correct and safe operation of the RPC system requires a sophisticated and complex online Detector Control System, able to monitor and control 2·104 hardware devices distributed on an area of about 5000 m2. The RPC DCS acquires, monitors and stores about 105 parameters coming from the detector, the electronics, the power system, the gas, and cooling systems. The DCS system and its first results, obtained during the 2007 and 2008 CMS cosmic runs, will be described in this paper.

Performance study of the CMS barrel resistive plate chambers with cosmic rays

In October and November 2008, the CMS collaboration conducted a programme of cosmic ray data taking, which has recorded about 270 million events. The Resistive Plate Chamber system, which is part of the CMS muon detection system, was successfully operated in the full barrel. More than 98% of the channels were operational during the exercise with typical detection efficiency of 90%. In this paper, the performance of the detector during these dedicated runs is reported.

First measurements of the performance of the Barrel RPC system in CMS

During the summer 2006, a first integrated test of a part of the CMS experiment was performed at CERN collecting a data sample of several millions of cosmic rays events. A fraction of the Resistive Plate Chambers system was successfully operated. Results on the RPC performance are reported.

Summary of RPC 2007 the IX International Workshop

This summary highlights the success stories and open issues for the widely employed Resistive Plate Chamber (RPC). Many experiments were represented, each having its own specific requirements for the operation of the detector. The general focus is on the understanding of operational characteristics, namely studies of electrode material, gas systems, aging and long term performance. Simulations of electric field and transport parameters are reported, along with performance at high rates, focused on timing and time-of-flight systems. There are important issues related to operation of large RPC systems and their commissioning, QA and QC procedures. Finally, RPCs are now being used in diverse applications such as in Calorimetry with analogue readout and in Astrophysics.

The time response of glass Resistive Plate Chambers to heavily ionizing particles

The HARP system of resistive plate chambers (RPCs) was designed toperform particle identification by the measurement of the difference in the time-of-flight of differentparticles. In previous papers an apparent discrepancy was shown between theresponse of the RPCs to minimum ionizing pions and heavily ionizingprotons. Using the kinematics of elastic scattering off a hydrogen target acontrolled beam of low momentum recoil protons was directed onto the RPCchambers. With this method the trajectory and momentum, and hence thetime-of-flight of the protons can be precisely predicted without needfor a measurement of momentum of the protons.It is demonstrated that the measurement of the time-of-arrival ofparticles by the thin gas-gap glass RPC system of the HARP experimentdepends on the primary ionization deposited by the particle in thedetector.

RPC cosmic ray tests in the ATLAS experiment

Extensive tests with cosmic rays were performed with Resistive Plate Chamber (RPC) trigger chambers belonging to 6 muon stations of sector 13 installed in the ATLAS muon spectrometer. We illustrate the results of this pre-commissioning phase, which represents a test bench for the final commissioning of the ATLAS RPC system with cosmic rays.

Physics Performance of the Barrel RPC System of the HARP Experiment

The physics performance of the barrel RPC system of the HARP experiment is described. In the barrel two sets of fifteen identical resistive plate chambers (RPCs) have been operated in 2001 and 2002 as a part of the HARP experiment at the CERN PS accelerator. For the first time under real experimental conditions RPCs have bean applied for particle identification (PID) by measuring the particle's time-of-flight (ToF). The procedure developed for the RPC calibration, based on reconstructed tracks in the HARP Time Projection Chamber (TPC), is described in detail. Intrinsic RPC time resolutions of 141 ps and a combined time resolution of the large angle TOF system of 180 ps are obtained. The effective resolution of the comparison of predicted and measured ToF is 305 ps in the region of interest for this experiment. The PID capabilities of the system are demonstrated. An average efficiency of the RPC counters of about 97% is measured