Double-end Readout Method Applied in RPC

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.

The Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) uses Resistive Plate Chambers (RPCs) as a trigger-dedicated muon detector. The RPC subdetector presently consists of 912 chambers, providing a ≈3 ns time resolution for the pseudorapidity region |η| <; 1.6. Up to 18 on-detector Front-End Boards (FEBs) per RPC are responsible for signal processing. Each FEB is configured and monitored through its Inter-Integrated Circuit (I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> C) interface to ensure correct and safe detector operation. The resulting ~1.2k I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> C lines, serving 3 to 6 FEBs apiece, are accessible through Control Boards (CBs) in token rings. An online control and monitoring system has recently been developed to automatically configure and continuously monitor FEB parameters. A fine-grained software model of hardware and detector components, organized in a dual hierarchical tree structure, facilitates command and data flow. A novel web-based user-interface allows control of and navigation through the system for efficient problem tracing. This paper covers the front-end control and monitoring system for the RPC subdetector; the online software components that allow for flexible configuration and comprehensive monitoring are described.

Resistive Plate Chamber (RPC) detectors are widely employed in the muon trigger systems of three experiments at the CERN Large Hadron Collider (LHC). They are operated with gas mixture recirculation systems to reduce operational costs and greenhouse gas emissions since their gas mixture is based on C2H2F4, which has a high global warning potential. It is well known that the C2H2F4 molecule can break down under the effect of radiation and electric field. This leads to the creation of several impurities and free fluoride ions (F-), which could accumulate under gas recirculation and potentially attach to the RPC bakelite electrode inner surface. For these reasons, an extensive gas analysis campaign has been performed during LHC Run 2 for the CMS RPC system to verify gas mixture quality and possible accumulation of impurities.During the entire LHC Run 2 period, a gas chromatograph has been used to analyze the RPC gas mixture at different points of the gas system: quality of pure C2H2F4, fresh gas from the mixer, gas at the output of the detectors, and after the purifier module. Several impurities have been found and identified. Few impurities are already present in the C2H2F4 supply, as residuals of the industrial production. Nevertheless, it was found that some of these impurities, as well as others, are created inside the detector gas gap due to the fragmentation of the C2H2F4 molecule under the effects of electric field and radiation.During the 2018 LHC Run several gas analysis points were added to measure the fluoride ions production in different sectors of the RPC detector system. Indeed the products of the C2H2F4 fragmentation do not always recombine and F- species can stay free in the gas mixture. F- analyses were performed on the gas at the output of the detectors both for barrel and endcap regions, where radiation levels and operational conditions were different. In this way, it was possible to correlate the F- production with integrated charge, and gas mixture flow rate. In parallel, the RPC currents have been constantly monitored to look for possible correlations.Fluoride measurements have also been performed at GIF++ to better understand the correlation between F- production, radiation levels and gas volume exchanges.A comprehensive overview of the results obtained from the different types of gas analyses and possible correlation with RPC currents and LHC luminosity will be presented.

We report on a systematic study of double-gap and four-gap phenolic resistive plate chambers (RPCs) for the Phase-2 upgrade of the CMS muon system at high η. 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 with cosmic rays and with 100-GeV muons provided by the SPS H4 beam line at CERN. To examine the rate capability of the prototype RPCs both at Korea University and at the CERN GIF++ facility, the chambers were irradiated with 137Cs sources providing maximum gamma rates of about 1.5 kHz cm−2. For the 1.6-mm-thick double-gap RPCs, we found the relatively high threshold on the produced detector charge 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-η endcap RPCs planned for future phase-II runs of the Large Hadron Collider (LHC).

INO-ICAL is a proposed underground experiment to study the oscillation parameters of neutrinos by detecting those produced in the atmospheric air showers. The Iron CALorimeter (ICAL) is to have 151 layers of iron plates stacked vertically corresponding to a height of ∼14.5 m, with active detector elements inserted between the iron layers. The iron layers will be magnetized with a maximum magnetic field of 1.5 T to enable the measurement of the charge and momentum of the μ - (or μ +) produced by ν μ (or ν̅ μ ) interactions inside the detector throughout the operation. Resistive Plate Chambers (RPCs) have been chosen as the active detector elements as they are amenable to large area coverage, as well as due to their high particle detection efficiency, long-term performance and low cost of production. The major factors that weigh in on the physics potential of the ICAL detector are the efficiency, position resolution and time resolution of the large area RPCs. A prototype detector called mini-ICAL (with 11 iron layers) was commissioned in order to understand the engineering challenges in building the large-scale electromagnet and its ancillary systems, and also to study the performance of the RPC detectors and readout electronics developed by the INO collaboration. As part of the performance study of the RPC detectors, an attempt is made to improve their position and time resolutions. The designed position resolution for the ICAL detector is of the order of 1 cm and the required time resolution is ∼1 ns. Even a small improvement in the position and time resolution will help to improve the measurements of momentum and directionality of the neutrinos in the ICAL detector. In ICAL detector simulation, where muons traverse in all directions with on average 20 RPC layers, a 30 % improvement in position resolution results in ∼10 % improvement in the momentum resolution at 3 GeV. Due to large iron materials in between two RPCs, the resolution is dominated by the effect of multiple scattering at this momentum. Also for a muon with 10 layer hit, the charge ambiguity reduces from 0.04 % to 0.001 % when the time resolution improves from 1 ns to 0.7 ns. The Time-over-Threshold (ToT) of the RPC pulses is recorded by the readout electronics. ToT is a measure of the pulse width and consequently the pulse amplitude. This information is used to improve the time and position resolution of RPCs and consequently INO's physics potential.

The compact muon solenoid (CMS) is a multipurpose detector at the large hadron collider (LHC) at CERN. One of the main goals of the CMS design is to ensure efficient and accurate identification and reconstruction of muons. The CMS muon spectrometer is based on three kinds of gaseous detectors placed inside the iron return yoke of a 4 Tesla superconducting solenoid: Drift Tube Chambers (DT), Cathode Strip Chambers (CSC) and the Resistive Plate Chambers (RPC). The detector is currently being assembled and commissioned with cosmics to be ready to take data in 2008. At the end of 2006 a fraction of the whole CMS including several sectors of the muon system were tested together with the magnet at the nominal field. A description of the main features of the system, with more emphasis on the DT detectors will be presented.

Cosmic Ray Test Certification of the First 100 CMS Endcap RPCs and the Corresponding Construction Database

Commissioning and first performances of the ALICE MID RPCs

Resistive plate chambers (RPCs) have been chosen as a part of the muon trigger detector, in both the endcap and barrel regions of a compact muon solenoid (CMS) experiment, which will work in extreme radiation backgrounds. In order to evaluate the response of the RPC detector in the CMS background environment, the RB1 barrel region has been investigated. The present simulation for e+/e− using GEANT3.21 code predicts hit rates of 0.048 (0.045) and 0.040 (0.038) Hz cm−2 using a bakelite and glass-based RPC setup. A similar trend in the results of GEANT4 Monte Carlo code with the same RPC configurations is also reported.

The Muon Upgrade Phase II of the Compact Muon Solenoid (CMS) aims to guarantee the optimal conditions of the present system and extend the η coverage to ensure a reliable system for the High Luminosity Large Hadron Collider (HL-LHC) period. The Resistive Plate Chambers (RPCs) system will upgrade the off-detector electronics (called link system) of the chambers currently installed chambers and place improved RPCs (iRPCs) to cover the high pseudo−rapidity region, a challenging region for muon reconstruction in terms of background and momentum resolution. In order to find the best option for the iRPCs, an R&D program for new detectors was performed and real size prototypes have been tested in the Gamma Irradiation Facility (GIF++) at CERN. The results indicated that the technology suitable for the high background conditions is based on High Pressure Laminate (HPL) double-gap RPC. The RPC Upgrade Phase II program is planned to be ready after the Long Shutdown 3 (LS3).

Resistive Plate Chambers (RPCs) are widely used in particle physics applications, including the CERN LHC experiments. RPCs are often operated with a gas mixture containing C2H2F4 and SF6, both greenhouse gases (GHGs) with a high global warming potential (GWP). The reduction of GHG emissions and the search for eco-friendly alternatives are crucial for use of RPCs in future since F-gases are being phased out in Europe. The best way to immediately reduce GHG emissions is to use gas recirculation systems. In parallel, CERN gas team is developing a new recuperation system specifically conceived for C2H2F4 and SF6, where good performance has been achieved. For long-term operation, low GWP gases are studied. Hydrofluoroolefins (HFO), chlorofluorocarbons and 3M Novec are identified as possible replacements for C2H2F4 and SF6. Several eco-friendly gas mixtures were investigated on 2 mm gap RPCs, by measuring detector performance, i.e. efficiency, streamer probability, induced charge, cluster size and time resolution. Studies were done in laboratory and at the CERN Gamma Irradiation Facility (GIF++), which provides a muon beam combined with a gamma source. Comparative analyses were performed between RPC operated with standard mixture and mixtures containing HFO with the addition of He or CO2 or mixtures with alternatives to SF6.

Operations and performance of the CMS RPC muon system at LHC

Resistive Plate Chambers (RPCs) are widely used as tracking detectors in many high-energy physics experiments. It has been observed that low-resistive bakelite RPC prototypes frequently exhibit a secondary hit component, appearing as a long tail or an additional peak in the time-correlation spectra relative to the trigger detector. These secondary hits, which affect both the time and spatial resolution, are difficult to distinguish from genuine signals in high-rate environments without an external trigger. As a result, they can significantly degrade track reconstruction efficiency and increase processing time. We present a machine-learning-based strategy to separate signal and background hit clusters using fifteen cluster-level descriptors that encode both statistical properties (histogram mean, width, cluster size) and fit-based parameters (Gaussian-fit mean, width, amplitude, χ2, NDF) of the time and ADC distributions. Using laboratory data collected from a single-gap low resistive RPC with a three-scintillator master trigger, we trained and evaluated three classifiers-DNN, 1D-CNN, and XGBoost-on balanced signal/background samples. All models demonstrate strong discrimination capability, with XGBoost showing the most robust generalization performance. Feature-importance analysis indicates that cluster size and temporal-shape descriptors are the dominant discriminants. These results highlight that compact, interpretable cluster-level features combined with machine-learning classifiers offer a practical and effective approach to suppress background in self-triggering low resistive RPC detectors.

A dual threshold technique to improve the time resolution of resistive plate chambers in streamer mode

The main task of the RPC (Resistive Plate Chamber) Muon Trigger monitoring system design for the CMS (Compact Muon Solenoid) experiment (at LHC in CERN Geneva) is the visualization of data that includes the structure of electronic trigger system (e.g. geometry and imagery), the way of its processes and to generate automatically files with VHDL source code used for programming of the FPGA matrix. In the near future, the system will enable the analysis of condition, operation and efficiency of individual Muon Trigger elements, registration of information about some Muon Trigger devices and present previously obtained results in interactive presentation layer. A broad variety of different database and programming concepts for design of Muon Trigger monitoring system was presented in this article. The structure and architecture of the system and its principle of operation were described. One of ideas for building this system is use object-oriented programming and design techniques to describe real electronics systems through abstract object models stored in database and implement these models in Java language.