Since 2019 a collaboration between researchers from various institutes and experiments (i.e. ATLAS, CMS, ALICE, LHCb/SHiP and the CERN EP-DT group), has been operating several RPCs with diverse electronics, gas gap thicknesses and detector layouts at the CERN Gamma Irradiation Facility (GIF++). The studies aim at assessing the performance of RPCs when filled with new eco-friendly gas mixtures in avalanche mode and in view of evaluating possible ageing effects after long high background irradiation periods, e.g. High-Luminosity LHC phase. This challenging research is also part of a task of the European AidaInnova project. A promising eco-friendly gas identified for RPC operation is the tetrafluoruropropene (C_3H_2F_4, commercially known as HFO-1234ze) that has been studied at the CERN GIF++ in combination with different percentages of CO_2. Between the end of 2021 and 2022 several beam tests have been carried out to establish the performance of RPCs operated with such mixtures before starting the irradiation campaign for the ageing study. Results of these tests for different RPCs layouts and different gas mixtures, under increasing background rates are presented here, together with the preliminary outcome of the detector ageing tests.

This document presents an overview of the activities of Brazilian groups on gaseous detectors, with emphasis on resistive plate chambers (RPCs) for the CMS experiment at the CERN LHC and related applications. It summarises the design, performance, maintenance and upgrade of the CMS RPC system, including the installation of improved RPCs for the HL-LHC era and the development of alternative, lower-GWP gas mixtures. It also describes local laboratory infrastructures in Brazil for RPC assembly, testing and gas studies, as well as spin-off projects such as the MARTA cosmic-ray detector and applications in medical imaging and muography. It is intended as a living reference to be periodically updated, documenting the contributions of the Brazilian community to RPC technology and its applications.

Improved resistive plate chambers (iRPCs) will be installed in the challenging forward region of the compact muon solenoid (CMS) during its Phase-2 upgrade. The design target of iRPC time resolution is 1.5 ns. It will help the Level-1 trigger system distinguish the muons from high backgrounds and improve the trigger efficiency. Studying the time resolution after integrating the new backend electronics boards (BEB) is essential for ensuring timely performance. In this system, a time reference (Tref) signal is distributed by the BEB to several frontend electronics boards (FEB) to reset the time-to-digital converters (TDC). In the CMS experiment, the arrangement of the iRPC chambers and on-chamber FEBs is at different positions, resulting in varying Tref arrival times on the FEB side. This paper describes the measures taken to ensure the time resolution of the single path and adjust the time base for multi-paths. Unique designs were implemented in the chamber, FEB, and BEB to ensure a satisfactory time resolution. Tref adjustments for different paths were performed in bunch crossing steps (24.950 ns) in the BEB using shift registers. And the sub-bunch crossing adjustment steps were performed in the FEB using the TDC correction module. Finally, the arrival time differences of Tref on different FEBs were less than 1.25 ns after adjustment. The time resolution of the FEB–BEB system was observed to be 32 ps. The time resolution of the chamber FEB–BEB system was first measured and is 554 ps at an iRPC working point of 7200 V. In addition, the Tref arrival time differences of different paths were adjusted from − 99.923 (− 90.113) ns to 0.073 (− 0.141) ns. The test results revealed that the system time resolution and Tref adjustment performed by the BEB met the Phase-2 upgrade goals.

In view of the High Luminosity upgrade of the CERN LHC, the forward CMS Muon spectrometer will be extended with two new stations of improved Resistive Plate Chambers (iRPC) covering the pseudorapidity range from 1.8 to 2.4. Compared to the present RPC system, the gap thickness is reduced to lower the avalanche charge, and an innovative 2D strip readout geometry is proposed. These improvements will allow iRPC detector to cope with higher background rates. A new Front-End-Board (FEB) is designed to readout iRPC signals with a threshold as low as 30fC and an integrated Time Digital Converter with a resolution of 30ps. In addition, the communication bandwidth is significantly increased by using optical fibers. The history, final design, certification, and calibration of this FEB are presented.

ALICE (A Large Ion Collider Experiment) studies the Quark-Gluon Plasma (QGP): a deconfined state of nuclear matter obtained in ultra-relativistic heavy-ion collisions. One of the key probes for QGP characterization is the study of quarkonia and open heavy flavor production, of which ALICE exploits the muonic decay. In particular, a set of Resistive Plate Chambers (RPCs), placed in the forward rapidity region of the ALICE detector, is used for muon identification purposes. The correct operation of these detectors is ensured by the choice of the proper gas mixture. Currently they are operated with a mixture of C2H2F4, i-C4H10 and SF6 but, starting from 2017, new EU regulations have enforced a progressive phase-out of C(2)H(2)F(4 )because of its large Global Warming Potential (GWP), which is making it difficult and costly to purchase. Moreover, CERN asked LHC experiments to reduce greenhouse gases emissions, to which RPC operation contributes significantly. A possible candidate for C(2)H(2)F(4 )replacement is the C3H2F4 (diluted with other gases, such as CO2), which has been extensively tested using cosmic muons. Promising gas mixtures have been devised; the next crucial steps are the detailed in-beam characterization of such mixtures as well as the study of their performance under increasing irradiation levels. This contribution will describe the methodology and results of beam tests carried out at the CERN Gamma Irradiation Facility (equipped with a high activity Cs-137 source and muon beam) with an ALICE-like RPC prototype, operated with several mixtures with varying proportions of CO2, C3H2F4, i-C4H10-and SF6 Absorbed currents, efficiencies, prompt charges, cluster sizes, time resolutions and rate capabilities will be presented, both from digitized (for detailed shape and charge analysis) and discriminated (using the same front-end electronics as employed in ALICE) signals.

The improved Resistive Plate Chambers (iRPC) are designed using thin low resistivity High-Pressure Laminate (HPL) gaps. They are proposed to equip the very forward region of the Compact Muon Solenoid (CMS) detector, as they can stand rates ∼2kHz/cm2. To withstand 3 times higher rates than the installed CMS RPC chambers, the HPL electrode thickness was reduced from 2 mm to 1.4 mm. The gas gain of the detector is dependent on the gas pressure and temperature which requires correcting for the applied voltage to keep detector operational characteristics such as efficiency, cluster size and noise rate constant. Herein, we study the pressure correction at constant temperature for CMS iRPC and compare its correction coefficient with the one for the 2 mm RPC gap technology. Pressure correction parameters for both technologies are found compatible.

In view of the High Luminosity LHC, the CMS Muon system will be upgraded to sustain its efficient muon triggering and reconstruction performance. Resistive Plate Chambers (RPC) are dedicated detectors for muon triggering due to their excellent timing resolution. The RPC system will be extended up to 2.4 in pseudorapidity. Before the LHC Long Shutdown 3, new RE3/1 and RE4/1 stations of the forward Muon system will be equipped with improved Resistive Plate Chambers (iRPC) having, compared to the present RPC system, a different design and geometry and 2D strip readout. This advanced iRPC geometry configuration allows the rate capability to improve and hence survive the harsh background conditions during the HL-LHC phase. Several iRPC demonstrator chambers were installed in CMS during the recently completed 2nd Long Shutdown to study the detector behaviour under real LHC conditions. This paper summarizes the iRPC project and its schedule, including the status of the iRPC production sites, details of the chamber quality control procedures and results of the commissioning of the demonstrator chambers.

The CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ( ℒ ) of 1 × 10^34 cm ^-2 s ^-1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of ℒ = 5 ×10^34 cm^-2 s^-1 and increasing ultimately to ℒ = 7.5 ×10^34 cm^-2 s^-1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

The Compact Muon Solenoid (CMS) experiment will undergo phase-II upgrade to enhance the capacity of detectors in the High-Luminosity Large Hadron Collider era. An important extension involves the installation of the Improved Resistive Plate Chambers (iRPC) in the most forward part of the endcap muon system. The iRPC detector addresses the efficiency drop experienced by the current CMS trigger system for single muon triggers in the high pseudorapidity region. It features a double-ended read-out method, allowing the determination of the hit position along the strip using the time difference between signals from both ends. This feature provides precise spatial information for clustering. To utilize this feature and integrate iRPC cluster information into the CMS trigger system, this paper proposes a 2-Dimensional (2D) cluster-finding algorithm. This algorithm provides the 2D coordinates to CMS trigger system, with each cluster being timestamped to reduce time ambiguity in endcap trajectory reconstruction. The proposed algorithm was implemented in the firmware of the iRPC Back-End Electronics and evaluated using a dedicated cosmic muon setup. The results show a position precision of 2.55 cm and an algorithm efficiency better than 99%, demonstrating the algorithm's potential to improve muon detection and trigger efficiency in the CMS endcap region.

AbstractThe CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ($$\mathcal {L}$$ L ) of $$1 \times 10^{34}$$ 1 × 10 34 cm$$^{-2}$$ - 2 s$$^{-1}$$ - 1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of $$\mathcal {L} = 5 \times \text {10}^\text {34}\,\text {cm}^\text {-2}\,\text {s}^\text {-1}$$ L = 5 × 10 34 cm -2 s -1 and increasing ultimately to $$\mathcal {L} = 7.5 \times \text {10}^\text {34}\,\text {cm}^\text {-2}\,\text {s}^\text {-1}$$ L = 7.5 × 10 34 cm -2 s -1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

Resistive Plate Chambers (RPCs) are gaseous detectors widely used in high energy physics experiments, operating with a gas mixture primarily containing Tetrafluoroethane (C2H2F4), commonly known as R134a, which has a global warming potential (GWP) of 1430. To comply with European regulations, the RPC EcoGas@GIF++ collaboration, involving ALICE, ATLAS, CMS, LHCb/SHiP, and EP-DT communities, has undertaken intensive R&D efforts to explore new environmentally friendly alternative gas mixtures for RPC technology. A leading alternative under investigation is HFO1234ze, boasting a low GWP of 6 and demonstrating reasonable performance compared to R-134a. Over the past few years, RPC detectors with slightly different characteristics and electronics have been studied using HFO and CO2-based gas mixtures at the CERN Gamma Irradiation Facility. An aging test campaign was launched in August 2022, and during the latest test beam in July 2023, all detector systems underwent evaluation. This contribution will report the results of the aging studies and the performance evaluations of the detectors with and without irradiation.

This paper reports the latest developmental efforts for a position-sensitive glass-based Resistive Plate Chamber (RPC) and a multi-channel Data AcQuisition (DAQ) system tailored for muon tracking in muography applications. The designed setup prioritizes portability, aiming for field applications where both the detector and the DAQ operate effectively in external environmental conditions. Comprehensive discussions on hardware development activities and signal processing techniques are included, incorporating noise filtering to enhance the accurate detection of real muons. A muon absorption measurement has also been carried out to understand the behavior of these detectors from an application perspective.

Results obtained by the RPC ECOgas@GIF++ Collaboration, using Resistive Plate Chambers operated with new, eco-friendly gas mixtures, based on Tetrafluoropropene and carbon dioxide, are shown and discussed in this paper. Tests aimed to assess the performance of this kind of detectors in high-irradiation conditions, analogous to the ones foreseen for the coming years at the Large Hadron Collider experiments, were performed, and demonstrate a performance basically similar to the one obtained with the gas mixtures currently in use, based on Tetrafluoroethane, which is being progressively phased out for its possible contribution to the greenhouse effect. Long term aging tests are also being carried out, with the goal to demonstrate the possibility of using these eco-friendly gas mixtures during the whole High Luminosity phase of the Large Hadron Collider.

In the last few years, an intense R D activity on particle detectors for future HEP applications has been carried on with the aim of developing new techniques as well as studying the performance of already existing detectors when operated in a high rate environment. As for Resistive Plate Chamber detectors, the main challenges to face are the improvement of their detection capabilities and longevity at very high-rates, and the search for new eco-friendly gasmixtures free from greenhouse components. Results obtained in the framework of the RPC ECOGas@GIF++ Collaboration on a thin-Resistive Plate Chamber exposed at the CERN Gamma Irradiation Facility and operated with eco-friendly gas mixtures based on Tetrafluoropropene and Carbon dioxide will be discussed in this paper.

Resistive Plate Chamber (RPCs) detectors in the Compact Muon Solenoid operate with a gas mixture composed of 95.2% of C 2 H 2 F 4 , which provides a high number of ion-electron pairs, 4.5% of iC 4 H 10 , which ensures the suppression of photon-feedback effects, and 0.3% of SF 6 , used as an electron quencher to further operate the detector in streamer-free mode. C 2 H 2 F 4 is known to be a Greenhouse gas with a global warming potential (GWP) of 1430. Consequently, several ECO-friendly alternatives to C 2 H 2 F 4 have been investigated in recent years. In this context, a short-mid term approach for the upcoming years of Large Hadron Collider (LHC) operation could be to focus on reducing the GWP of the RPC gas mixture by replacing C 2 H 2 F 4 with CO 2 . The studies are conducted at the CERN Gamma Irradiation Facility in the North Area of the Super Proton Synchrotron (SPS), where a 13.6 TBq radiation source and a muon beam from SPS mimic the conditions of Phase-II (i.e. High-Luminosity (HL)) of the LHC. This paper presents the performance of a 1.4 mm gap RPC with three different CO 2 based mixtures (30 and 40% of CO 2 ; 0.5 and 1% of SF 6 ) under high gamma background conditions with the perspectives for the longevity campaign.

Abstract The CMS detector, including its muon system, has been operating at the CERN LHC in increasingly challenging conditions for about 15 years. The muon detector was designed to provide excellent triggering and track reconstruction for muons produced in proton–proton collisons at an instantaneous luminosity ( $$\mathcal {L}$$ L ) of $$1 \times 10^{34}$$ 1 × 10 34 cm $$^{-2}$$ - 2 s $$^{-1}$$ - 1 . During the Run 2 data-taking period (2015–2018), the LHC achieved an instantaneous luminosity of twice its design value, resulting in larger background rates and making the efficient detection of muons more difficult. While some backgrounds result from natural radioactivity, cosmic rays, and interactions of the circulating protons with residual gas in the beam pipe, the dominant source of background hits in the muon system arises from proton–proton interactions themselves. Charged hadrons leaving the calorimeters produce energy deposits in the muon chambers. In addition, high-energy particles interacting in the hadron calorimeter and forward shielding elements generate thermal neutrons, which leak out of the calorimeter and shielding structures, filling the CMS cavern. We describe the method used to measure the background rates in the various muon subsystems. These rates, in conjunction with simulations, can be used to estimate the expected backgrounds in the High-Luminosity LHC. This machine will run for at least 10 years starting in 2029 reaching an instantaneous luminosity of $$\mathcal {L} = 5 \times \text {10}^\text {34}\,\text {cm}^\text {-2}\,\text {s}^\text {-1}$$ L = 5 × 10 34 cm -2 s -1 and increasing ultimately to $$\mathcal {L} = 7.5 \times \text {10}^\text {34}\,\text {cm}^\text {-2}\,\text {s}^\text {-1}$$ L = 7.5 × 10 34 cm -2 s -1 . These background estimates have been a key ingredient for the planning and design of the muon detector upgrade.

Resistive Plate Chamber detectors are largely used in current High Energy Physics experiments, typically operated in avalanche mode with large fractions of Tetrafluoroethane (C2H2F4), a gas recently banned by the European Union due to its high Global Warming Potential (GWP). An intense R D activity is ongoing to improve RPC technology in view of future HEP applications. In the last few years the RPC EcoGas@GIF++ Collaboration has been putting in place a joint effort between the ALICE, ATLAS, CMS, LHCb/SHiP and EP-DT Communities to investigate the performance of present and future RPC generations with eco-friendly gas mixtures. Detectors with different layout and electronics have been operated with ecological gas mixtures, with and without irradiation at the CERN Gamma Irradiation Facility (GIF++). Results of these performance studies together with plans for an aging test campaign are discussed in this article.