Performance Of Resistive Plate Chambers Research Articles

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.

RPC gap production and performance for CMS RE4 upgrade

CMS experiment built the fourth Resistive Plate Chamber (RPC) trigger station composed of 144 RPCs to enhance the high momentum muon trigger efficiency at both endcap regions. All new CMS endcap RPC gaps are produced in accordance with QA and QC at the Korea Detector Laboratory (KODEL) in Korea. All qualified gaps have been delivered to three assembly sites: CERN in Switzerland, BARC in India, and Ghent University in Belgium for the RPC detector assembly. In this paper, we present the detailed procedures used in the production of RPC gaps adopted for the CMS upgrade.

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].

Performance of the RPC-based ALICE muon trigger system at the LHC

The forward muon spectrometer of ALICE (A Large Ion Collider Experiment) is equipped with a trigger system made of four planes of Resistive Plate Chambers (RPC), arranged in two stations with two planes each, for a total area of about 140 m2. The system provides single and di-muon triggers with suitable transverse momentum selection, optimised for the physics of quarkonia and open heavy flavour.In the first two years of data-taking at the Large Hadron Collider (2010 and 2011) the 72 RPCs were operated in highly saturated avalanche mode in both pp and Pb-Pb collisions. The integrated charge was about 1.3 mC/cm2 on average and 3.5 mC/cm2 for the most exposed detectors.This paper describes two main results. The first result is the determination of the RPC performance, with particular focus on the stability of the main detector parameters such as efficiency, dark current, and dark rate. The second result is the measurement of the muon trigger performance in Pb-Pb collisions at √sNN = 2.76 TeV, in terms of the reliability and stability of the trigger decision logic.

Extreme high-rate capable timing resistive plate chambers with ceramic electrodes

The future Compressed Baryonic Matter experiment to be built at the Facility for Antiproton and Ion Research in Darmstadt, Germany, will create the highest particle densities ever created in a laboratory. One of its components, the Time-of-Flight Wall, will be comprised of Resistive Plate Chambers. The high particle fluxes expected at the most inner region, close to the beam pipe, have led to the research of new low-resistive materials to be used as electrodes. Si3N4/SiC composites are a very good candidate for this function. Their bulk resistivity, in the order of 109–1010 Ω cm, allows for increased rate capabilities up to 106 s−1 cm−2. In this report, the properties of these new materials will be discussed. Also, the performance of resistive plate chambers with ceramic electrodes under irradiation in electron and proton beams will be presented.

The Resistive Plate Chambers of the ATLAS experiment: performance studies

ATLAS (A Toroidal LHC ApparatuS) is one of the four experiments ready for p-p collisions scheduled in autumn 2009 at the LHC at CERN. It is a general purpose experiment, with a physics program that spans from the search of the Higgs Boson to the evidence of physics Beyond the Standard Model (BSM). Events with final state muons are a signature of the most promising physics channels, e.g. the Standard Model Higgs Boson decaying into four muons (H → 4μ). For this reason a completely independent in-air Muon Spectrometer with a toroidal magnetic field for muon track measurement has been realized to trigger and measure the momentum of high energy muons. Resistive Plate Chambers (RPCs) provide the first-level muon trigger and the measurement of the coordinate in the non-bending direction in the barrel region of the Muon Spectrometer. The installation in the experimental hall of RPCs has been completed and extensive tests of their performance have been performed with cosmic-rays muons. An overview of the ATLAS experiment, focusing on the results of the studies on the RPCs performance will be presented.

Results from the PHENIX RPC R&D and long-term performance monitoring

A new Resistive Plate Chamber (RPC) based fast muon trigger system has been developed and partially installed in the PHENIX experiment. This new trigger will allow the PHENIX data acquisition system to efficiently sample high pT (>20GeV/c) muons from W decays in polarized proton+proton collisions at s=500GeV at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. This measurement will significantly improve our knowledge of flavor separated quark and anti-quark polarization in the proton. Since 2005, a multi-institutional effort within the PHENIX Forward Trigger group was devoted to study the properties and performance of bakelite RPCs. In this presentation, the results of the PHENIX RPC R&D will be reported.

A Monte Carlo simulation to study the effect of surface roughness on the performance of RPC

Abstract The electric field inside a Resistive Plate Chamber (RPC) is likely to be influenced by the non-uniform inner surfaces of the RPC electrodes. We have studied the effect of this field perturbation on the performance of the RPC by a Monte Carlo method, which simulates the generation of signal from the detector. For the present study, we have analyzed the effect of the field variation on the time resolution and efficiency of a 0.3 mm single-gap timing RPC. Finally the results obtained from the Monte Carlo study are compared with an analytical calculation.

Environmental dependence of the performance of resistive plate chambers

This paper reports on the performance of Resistive Plate Chambers (RPCs) as function of the gas flow rate through the chambers and of environmental conditions, such as atmospheric pressure, ambient temperature and air humidity. The chambers are read out by pads with an area of 1 × 1 cm2 and 1-bit resolution per pad (binary readout). The performance measures include the noise rate as well as the detection efficiency and pad multiplicity for cosmic rays. The measurements extended over a period of almost one year and are sensitive to possible long-term aging effects.

The BESIII muon identification system

The muon identification system of BESIII experiment at the IHEP is described. The muon counter (MUC) is composed of resistive plate chambers (RPCs) working in self-quenching streamer mode with the gas mixture Ar/C 2F 4H 2/C 4H 10=50/42/8. The design, the construction, the mass production and the quality control result of the detectors are described in detail. The paper also presents the performance of the bare RPCs and the superlayer modules with cosmic rays. Finally, the subsystems of MUC, including the RPC superlayer modules, the gas systems, the HV and LV system and the readout electronic system, are also presented.

Performances of 4-gap timing RPCs for relativistic ions in the range Z = 1–6

Results from 4-gap Resistive Plate Chambers (RPCs) under irradiation by fully stripped relativistic ions (normalized momentum p/M = γβ = 2.7, atomic charge Z = 1−6) are presented. A time resolution of 80 ps at high efficiency has been obtained by using standard `off the shelf' 4-gap timing RPCs from the new HADES time-of-flight wall. The resolution worsened to 100 ps for ∼ 1 kHz/cm2 proton flux and for ∼ 100 Hz/cm2 carbon flux. The chambers were operated at a field E = 100 kV/cm, showing a high stability during the measurements. It seems to exist ample room for improvement, in particular regarding the time resolution.

Resistive Plate Chambers performance with Cosmic Rays in the CMS experiment

The Resistive Plate Chambers [M. Abbrescia, et al., Nucl. Instr. and Meth. A 550 (2005) 116] are used in the CMS experiment [CMS Collaboration, The CMS experiment at the CERN LHC 2008, J. Inst. 3 (2008) S08004] as a dedicated muon trigger both in barrel and endcap system. About 4000 m 2 of double gap RPCs have been produced and have been installed in the experiment since more than one and half Years. The full barrel system and a fraction of the endcaps have been monitored to study dark current behaviour and system stability, and have been extensively commissioned with Cosmic Rays collected by the full CMS experiment.

Measurement of the rate capability of Resistive Plate Chambers

This paper reports on detailed measurements of the performance of Resistive Plate Chambers in a proton beam with variable intensity. Short term effects, such as dead time, are studied using consecutive events. On larger time scales, for various beam intensities the chamber's efficiency is studied as a function of time within a spill of particles. The correlation between the efficiency of chambers placed in the same beam provides an indication of the lateral size of the observed effects. The measurements are compared to the predictions of a simple model based on the assumption that the resistive plates behave as pure resistors.

Construction and performance of multigap RPC in streamer and avalanche modes

We have constructed the multigap RPC and investigated its performance in counting efficiency and the time response for the cosmic-ray muons. The multigap structure of resistive plate chamber (RPC) is supposed to be helpful to obtain reasonably large signal without degrading the time resolution. We found that an average time resolution for 3 gap RPC in avalanche mode was about 0.48 ns. The time resolution is considered to be inversely proportional to the gap size.

Quantitative aging study with intense irradiation tests for the CMS forward RPCs

A systematic study with a series of irradiation tests was performed for the forward resistive plate chambers (RPCs) of the Compact Muon Solenoid (CMS) in the Large Hadron Collider (LHC) experiment. Small double-gap RPCs were manufactured and tested by the gamma rays emitted from a 200 mCi 137Cs source at Korea University and by the fast neutrons provided by the MC50 proton cyclotron at the Korea Institute Radiological and Medical Science (KIRAMS). We found no significant symptom of aging in the performance of the prototype RPCs, as a consequence of the neutron irradiation, whose total equivalent dose was approximately 45 Gy. However, a fast degradation was observed in the RPCs when the gamma signal rates were higher than 3 kHz cm − 2 . Furthermore, we observed from the chemical analysis for the RPC electrode that the long-term performance of the RPCs was stable in spite of absorbing the high-level fluorine when the signal rates were lower than 2 kHz cm − 2 .

Study the effect of humidity on the RPC performance

The effect of water vapor on the performance of a resistive plate chamber (RPC) has been studied by simulating the dependency of avalanche multiplication on the amount of humidity in the RPC gas mixture. Also, the change of plates’ resistivity with humidity has been considered in the simulation. The results of simulation show that at the room temperature, the addition of water vapor to the gas mixture even up to 100% relative humidity (RH), has no practical influence on the avalanche multiplication process inside the RPC gap. The humidity effect on the avalanche multiplication appears for high-temperature operation where the induced signal increases with humidifying the gas mixture. The simulation was also performed for high-particles flux densities and the results show that the degradation of plates’ resistivity with humidity improves the efficiency as well as rate capability of the detector in agreement with experimental reports.

Simulation of RPC performance for 511 keV photon detection

Measurements of the time resolution of timing Resistive Plate Chambers (RPCs) reveal some differences when comparing the results for 511 keV photons and for particle beams. The subject is of interest, since timing RPCs are currently considered for Positron Emission Tomography (PET), where the sensitivity of the system depends largely on the time resolution of the detector. In this publication we discuss possible explanations, in particular the statistical fluctuations of the deposited charge and the Compton electron flight time distributions. Moreover, we rediscuss the reduction of the Townsend coefficient due to the space charge effect inside the avalanches as a function of the avalanche size. We shall see that the dependence assumed by different analytic models differs significantly from what is predicted by detailed Monte Carlo avalanche simulations.

Aging Study with High-Level Radiation Sources for the CMS Forward RPCs

An aging study with intensive radiation sources was performed for the forward resistive plate chambers (RPCs) of the Compact Muon Solenoid (CMS) detector in the Large Hadron Collider experiment (LHC). The expected rate of the radiation background to be induced in the forward RPCs ranges from a few tens of Hz/cm to as much as ∼1 kHz/cm. Therefore, the radiation hardness for the forward RPCs should be sufficient to ensure the safe operation of the CMS and successful achievement of the LHC physics. Two oil-coated and one plain double-gap RPCs were manufactured and tested with the neutron beam provided by the MC50 cyclotron of the Korea Institute of Radiological and Medical Science (KIRAMS) and with gamma rays from a 200-mCi Cs source. The estimated radiation dose induced by the fast neutrons was approximately 50 Gy. No significant aging effect was found to be a consequence of the neutron irradiation, However, a degradation of the RPC performance was observed after intense gamma irradiation for a total of 32.5 days. The mean gamma-signal rate drawn in each RPC was 4.0 kHz/cm, which was approximately two times the maximum rate expected in the highest η-region covering the particle trigger. Increases in the noise rates and the currents accounted for the degradation in the efficiencies for the RPCs. As a result, safe operation of the forward RPCs in the avalanche mode was ensured for signal rates up to 2 kHz/cm.

Analysis and interpretation of the performance degradation of glass Resistive Plate Chambers operated in streamer mode

The long-term stability of Resistive Plate Chambers (RPCs) with glasselectrodes was studied for one year with a dedicated test stationhosting about 10 m2 of detectors. RPCs were operated in streamer mode with a ternary gas mixture containing argon (27%), isobutane (9%) and tetrafluoroethane (64%). Environmental conditions were kept undercontrol and, in particular, the water pollution in the gas, deemedresponsible for the degradation of glass RPC performance, was monitored never to exceed 30 ppm in the exhaust line. Evidence for a substantial aging of the detectors was observed, resulting in a loss of efficiency correlated to an increased rate of spurious streamers. This can be ascribed to the chemical attack of the glass surface by hydrofluoric acid formed in the streamer process, as confirmed bydetailed morphological and chemical analyses of the electrodesurface. Our results strengthen the indication that the instability ofglass RPCs in the long term is related to the use of fluorocarbons asquenching medium and is not due to external pollutants.

Application of Gas Chromatographic analysis to RPC detectors in the ATLAS experiment at CERN-LHC

Starting from 2007 a large number (1200) Resistive Plate Chambers (RPC) detectors will be used as muon trigger detectors in the ATLAS Experiment at CERN-LHC accelerator. RPC are gaseous detector in which the quality and the stability of the gas mixture as well as the design of the gas supplying system, play a fundamental role in their functioning. RPC are foreseen to work more than ten years in the high radiation environment of ATLAS and the gas mixture acts really as a "lifeguard" for the detectors. For this reason a great attention has been devoted to the gas studies in order to optimize RPC performance, robustness and reliability in a high radiation environment.In this paper we describe the work done to decide how to supply and control in an optimal way the gas to the detectors, in order to ensure their best performance for a long time. The activity, based on Gas Chromatographic (GC) analysis, has been carried on a sample of final RPC working in radiation conditions much more intense than those foreseen for the ATLAS experiment. This has been possible using a high Gamma ray radiation facility available at CERN (GIF). The gas has been supplied using a system similar but at a reduced scale with respect to the final one and including: a recirculation circuit, a humidification module and a three stages purification subsystem.