Journal of Instrumentation

The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10³⁴ cm⁻² s⁻¹ (10²⁷ cm⁻² s⁻¹). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (|η| ⩽ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m³ with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.

A tau lepton identification algorithm,DeepTau, based on convolutional neural network techniques, has been developed in the CMS experiment to discriminate reconstructed hadronic decays of tau leptons (τ_h) from quark or gluon jets and electrons and muons that are misreconstructed as τ_h candidates. The latest version of this algorithm, v2.5, includes domain adaptation by backpropagation, a technique that reduces discrepancies between collision data and simulation in the region with the highest purity of genuine τ_h candidates. Additionally, a refined training workflow improves classification performance with respect to the previous version of the algorithm, with a reduction of 30–50% in the probability for quark and gluon jets to be misidentified as τ_h candidates for given reconstruction and identification efficiencies. This paper presents the novel improvements introduced in theDeepTau algorithm and evaluates its performance in LHC proton-proton collision data at √(s) = 13 and 13.6 TeV collected in 2018 and 2022 with integrated luminosities of 60 and 35 fb^-1, respectively. Techniques to calibrate the performance of the τ_h  identification algorithm in simulation with respect to its measured performance in real data are presented, together with a subset of results among those measured for use in CMS physics analyses.

The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

The international collaboration designing and constructing the Deep Underground Neutrino Experiment (DUNE) at the Long-Baseline Neutrino Facility (LBNF) has developed a two-phase strategy toward the implementation of this leading-edge, large-scale science project. The 2023 report of the US Particle Physics Project Prioritization Panel (P5) reaffirmed this vision and strongly endorsed DUNE Phase I and Phase II, as did the European Strategy for Particle Physics. While the construction of the DUNE Phase I is well underway, this White Paper focuses on DUNE Phase II planning. DUNE Phase-II consists of a third and fourth far detector (FD) module, an upgraded near detector complex, and an enhanced 2.1 MW beam. The fourth FD module is conceived as a “Module of Opportunity”, aimed at expanding the physics opportunities, in addition to supporting the core DUNE science program, with more advanced technologies. This document highlights the increased science opportunities offered by the DUNE Phase II near and far detectors, including long-baseline neutrino oscillation physics, neutrino astrophysics, and physics beyond the standard model. It describes the DUNE Phase II near and far detector technologies and detector design concepts that are currently under consideration. A summary of key R&D goals and prototyping phases needed to realize the Phase II detector technical designs is also provided. DUNE's Phase II detectors, along with the increased beam power, will complete the full scope of DUNE, enabling a multi-decadal program of groundbreaking science with neutrinos.

The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of  ℒ = 2 × 10³⁴ cm^-2 s^-1 was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of  ℒ = 2 × 10³⁴ cm^-2 s^-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector.

The Large Hadron Collider (LHC) at CERN near Geneva is the world's newest and most powerful tool for Particle Physics research. It is designed to collide proton beams with a centre-of-mass energy of 14 TeV and an unprecedented luminosity of 10³⁴ cm⁻² s⁻¹. It can also collide heavy (Pb) ions with an energy of 2.8 TeV per nucleon and a peak luminosity of 10²⁷ cm⁻² s⁻¹. In this paper, the machine design is described.

Liquid argon time projection chambers (LArTPCs) rely on highly pure argon to ensure that ionization electrons produced by charged particles reach readout arrays. ProtoDUNE Single-Phase (ProtoDUNE-SP) was an approximately 700-ton liquid argon detector intended to prototype the Deep Underground Neutrino Experiment (DUNE) Far Detector Horizontal Drift module. It contains two drift volumes bisected by the cathode plane assembly, which is biased to create an almost uniform electric field in both volumes. The DUNE Far Detector modules must have robust cryogenic systems capable of filtering argon and supplying the TPC with clean liquid. This paper will explore comparisons of the argon purity measured by the purity monitors with those measured using muons in the TPC from October 2018 to November 2018. A new method is introduced to measure the liquid argon purity in the TPC using muons crossing both drift volumes of ProtoDUNE-SP. For extended periods on the timescale of weeks, the drift electron lifetime was measured to be above 30 ms using both systems. A particular focus will be placed on the measured purity of argon as a function of position in the detector.

LiquidO is an innovative radiation detector concept. The core idea is to exploit stochastic light confinement in a highly scattering medium to self-segment the detector volume. In this paper, we demonstrate event-by-event muon tracking in a LiquidO opaque scintillator detector prototype. The detector consists of a 30 mm cubic scintillator volume instrumented with 64 wavelength-shifting fibres arranged in an 8 × 8 grid with a 3.2 mm pitch and read out by silicon photomultipliers. A wax-based opaque scintillator with a scattering length of approximately 0.5 mm is used. The tracking performance of this LiquidO detector is characterised with cosmic-ray muons and the position resolution is demonstrated to be 450 μm per row of fibres. These results highlight the potential of LiquidO opaque scintillator detectors to achieve fine spatial resolution, enabling precise particle tracking and imaging.

The Timepix3 detector has been implemented as a miniaturized, low-power payload for spacecraft operation and deployment onboard satellites. This work reports on the development for the JoeySat telecommunication micro-satellite of the One Web EUTELSAT constellation, representing the first-ever spacecraft deployment of the Timepix3 detector. The architecture, customization, and configuration of the device at the HW, SW, and in-orbit operation levels are described. Following launch into LEO orbit at 600 km altitude in May 2023, the detector payload underwent successful in-orbit commissioning. High-resolution radiation data are collected regularly and continuously along the satellite orbit in LEO. We present first results of detailed radiation data acquired by Timepix3 with a silicon sensor, including a preliminary physics-level evaluation in terms of time distributions and Earth orbit maps of total and partial particle fluxes.

The Balloon-borne Instrument for Spectral Scanning of high-altitude Environments (BISSE) is a lightweight gamma-ray measurement system designed as a payload of standard weather balloons which can be retrieved after the flight. Its design enables multiple flights at a relatively low cost. The BISSE system automatically records radiation spectra at different altitudes throughout the flight. The sensor is cadmium zinc telluride (CZT) with a crystal volume of 1 cm³, providing good spectral resolution while maintaining low weight. The system also includes various auxiliary sensors that enable additional measurements during the flight, such as temperature and pressure monitoring. The Light-weight Aranda-borne Gamma-ray and Environmental Radiation detector (LAGER) is a modification of the BISSE system for underwater measurements. In contrast to the BISSE, the primary limitation for the design is overall size rather than weight; consequently the system is more compact. In this contribution, we discuss the designs of BISSE and LAGER as well as the latest improvements to both systems. The BISSE system is also investigated as a payload for a rotary-wing unmanned aerial vehicle. These flights motivated several crucial modifications to the system for future deployments. Planned balloon flight is also studied using Geant4 simulations.

The Low-power Gigabit Transceiver (lpGBT) is a radiation-tolerant ASIC used in high-energy physics experiments for multipurpose high-speed bidirectional serial links. In 2024, almost 270,000 lpGBTs v1 were tested with a production test system that exercises the entire ASIC functionality to ensure its correct operation. Furthermore, qualification tests (Total Ionizing Dose, Single-Event Upsets, etc.) were done on lpGBTs from each production lot. Despite the thorough production and qualification tests, a design issue named “stuck at power-up” was discovered, affecting a maximum of 0.9% of delivered devices simultaneously. The test system setup developed for the characterisation of this behaviour and the results obtained are presented here.

The CMS High Granularity Calorimeter (HGCAL), developed for the High luminosity phase of the LHC (HL-LHC), uses custom ASICs — HGCROC3 and H2GCROC3 — to read out silicon sensors and SiPM-on-tile modules. These chips provide precise charge and timing measurements, digital processing for triggering, and are designed to operate in harsh radiation conditions. Version 3 of the chips implements all final features, with sub-versions a–d addressing bugs and improving radiation tolerance. Extensive testing has been performed in lab and beam environments. The proceedings covers chip design, performance, and SEE-related issues and fixes.

X-ray micro-CT (µCT) is a widely used technique for non-destructive imaging, yet optimal selection of acquisition parameters remains challenging. X-ray tube power is often constrained by focal spot size requirements, and for weakly attenuating samples the choice of tube voltage (kVp) at constant tube power represents a key trade-off: lower kVp increases attenuation contrast, while higher kVp increases photon flux and reduces noise. Recent simulations with PEPIsim, the MATLAB-based simulation tool developed for X-ray phase-contrast, spectral μCT with a small-pixel photon-counting detector, demonstrated that, under constant power conditions, higher tube voltages can yield improved signal-to-noise ratio (SNR) in both attenuation and phase-retrieved images of weakly attenuating plastics. Building on these findings, we performed exploratory acquisitions at the PEPI Lab of a formalin-fixed, paraffin-embedded pedunculated colonic polyp with adenocarcinoma, scanned across a range of tube voltages (45–100 kVp) at constant power for the purpose of virtual histology. Consistent with the simulation predictions, the measured SNR values tended to increase with tube voltage for both attenuation and phase-retrieved images. While the dataset is limited and further work is required to confirm broader applicability, these results suggest that PEPIsim can provide useful guidance for acquisition parameter selection and may help establish simple experimental guidelines, such as minimum kVp thresholds, for biological samples.

Particle identification (PID) is one of the main strengths of the ALICE experiment at the LHC. It is a crucial ingredient for detailed studies of the strongly interacting matter formed in ultrarelativistic heavy-ion collisions. ALICE provides PID information via various experimental techniques, allowing for the identification of particles over a broad momentum range (from around 100 MeV/c to around 50 GeV/c). The main challenge is how to combine the information from various detectors effectively. Therefore, PID represents a model classification problem, which can be addressed using Machine Learning (ML) solutions. Moreover, the complexity of the detector and richness of the detection techniques make PID an interesting area of research also for the computer science community. In this work, we show the current status of the ML approach to PID in ALICE. We discuss the preliminary work with the Random Forest approach for the LHC Run 2 and a more advanced solution based on Domain Adaptation Neural Networks, including a proposal for its future implementation within the ALICE computing software for the upcoming LHC Run 3.

A fast wave interferometer (FWI), which can measure ion mass density, has been developed on DIII-D for its use on future fusion reactors, as well as for the study of ion behavior in current plasma devices. The frequency of the fast waves used for the FWI is around 60 MHz, and require antennas and coaxial cables or waveguides, which, unlike traditional mirror-based optical interferometers, are less susceptible to neutron/gamma-ray radiation and are relatively immune to impurity deposition and erosion as well as alignment issues. The bulk ion density evaluated using FWI show good agreement with that derived from CO₂ interferometry within about 15%. When the ion mass density measurement by FWI is combined with an electron density measurement from CO₂ interferometry, Z_eff measurements are also enabled and are in agreement with those from visible Bremsstrahlung measurements. Additionally, large-bandwidth FWI measurements clearly resolve 10–100 kHz coherent modes and demonstrate its potential as a core fluctuation diagnostic, sensitive to both magnetic and ion density perturbations.

KM3NeT (Cubic Kilometer Neutrino Telescope) is a research infrastructure that comprises two underwater neutrino detectors located at different sites in the Mediterranean Sea: KM3NeT-Fr (ORCA) (offshore the coast of Toulon, France, at a depth of around 2500 m) and KM3NeT-It (ARCA) (off Capo Passero, Sicily, Italy, at a depth of around 3500 m). The experiment consists of vertical structures, called strings, along which the optical modules are positioned. A hydrophone, located on the base of each string, is used for the reconstruction of the position of the KM3NeT elements with an accuracy of 10 cm. The presence of acoustic sensors in an underwater environment gives the opportunity to detect and study the sound emissions of marine mammals present in the area. The presented work describes the identification programs of the signals emitted by dolphins (clicks and whistles) and sperm whales (clicks) and the results of the analysis of real data collected between spring 2020 and spring 2021.

The Tracking Ultraviolet Set-up (TUS) is the world’s first orbital imaging detector of Ultra High Energy Cosmic Rays (UHECR) and it operated in 2016–2017 as part of the scientific equipment of the Lomonosov satellite. The TUS was developed and manufactured as a prototype of the larger project K-EUSO with the main purpose of testing the efficiency of the method for measuring the ultraviolet signal of extensive air shower (EAS) in the Earth’s night atmosphere. Despite the low spatial resolution (∼5 × 5  km² at sea level), several events were recorded which are very similar to EAS as for the signal profile and kinematics. Reconstruction of the parameters of such events is complicated by a short track length, an asymmetry of the image, and an uncertainty in the sensitivity distribution of the TUS channels. An advanced method was developed for the determination of event kinematic parameters including its arrival direction. In the present article, this method is applied for the analysis of 6 EAS-like events recorded by the TUS detector. All events have an out of space arrival direction with zenith angles less than 40°. Remarkably they were found to be over the land rather close to United States airports, which indicates a possible anthropogenic nature of the phenomenon. Detailed analysis revealed a correlation of the reconstructed tracks with direction to airport runways and Very High Frequency (VHF) omnidirectional range stations. The method developed here for reliable reconstruction of kinematic parameters of the track-like events, registered in low spatial resolution, will be useful in future space missions, such as K-EUSO.

We review the current status of liquid noble gas radiation detectors with energy threshold in the keV range, which are of interest for direct dark matter searches, measurement of coherent neutrino scattering and other low energy particle physics experiments. Emphasis is given to the operation principles and the most important instrumentation aspects of these detectors, principally of those operated in the double-phase mode. Recent technological advances and relevant developments in photon detection and charge readout are discussed in the context of their applicability to those experiments.

The Balloon-borne Instrument for Spectral Scanning of high-altitude Environments (BISSE) is a lightweight gamma-ray measurement system designed as a payload of standard weather balloons which can be retrieved after the flight. Its design enables multiple flights at a relatively low cost. The BISSE system automatically records radiation spectra at different altitudes throughout the flight. The sensor is cadmium zinc telluride (CZT) with a crystal volume of 1 cm³, providing good spectral resolution while maintaining low weight. The system also includes various auxiliary sensors that enable additional measurements during the flight, such as temperature and pressure monitoring. The Light-weight Aranda-borne Gamma-ray and Environmental Radiation detector (LAGER) is a modification of the BISSE system for underwater measurements. In contrast to the BISSE, the primary limitation for the design is overall size rather than weight; consequently the system is more compact. In this contribution, we discuss the designs of BISSE and LAGER as well as the latest improvements to both systems. The BISSE system is also investigated as a payload for a rotary-wing unmanned aerial vehicle. These flights motivated several crucial modifications to the system for future deployments. Planned balloon flight is also studied using Geant4 simulations.

The Low-power Gigabit Transceiver (lpGBT) is a radiation-tolerant ASIC used in high-energy physics experiments for multipurpose high-speed bidirectional serial links. In 2024, almost 270,000 lpGBTs v1 were tested with a production test system that exercises the entire ASIC functionality to ensure its correct operation. Furthermore, qualification tests (Total Ionizing Dose, Single-Event Upsets, etc.) were done on lpGBTs from each production lot. Despite the thorough production and qualification tests, a design issue named “stuck at power-up” was discovered, affecting a maximum of 0.9% of delivered devices simultaneously. The test system setup developed for the characterisation of this behaviour and the results obtained are presented here.

The CMS High Granularity Calorimeter (HGCAL), developed for the High luminosity phase of the LHC (HL-LHC), uses custom ASICs — HGCROC3 and H2GCROC3 — to read out silicon sensors and SiPM-on-tile modules. These chips provide precise charge and timing measurements, digital processing for triggering, and are designed to operate in harsh radiation conditions. Version 3 of the chips implements all final features, with sub-versions a–d addressing bugs and improving radiation tolerance. Extensive testing has been performed in lab and beam environments. The proceedings covers chip design, performance, and SEE-related issues and fixes.

X-ray micro-CT (µCT) is a widely used technique for non-destructive imaging, yet optimal selection of acquisition parameters remains challenging. X-ray tube power is often constrained by focal spot size requirements, and for weakly attenuating samples the choice of tube voltage (kVp) at constant tube power represents a key trade-off: lower kVp increases attenuation contrast, while higher kVp increases photon flux and reduces noise. Recent simulations with PEPIsim, the MATLAB-based simulation tool developed for X-ray phase-contrast, spectral μCT with a small-pixel photon-counting detector, demonstrated that, under constant power conditions, higher tube voltages can yield improved signal-to-noise ratio (SNR) in both attenuation and phase-retrieved images of weakly attenuating plastics. Building on these findings, we performed exploratory acquisitions at the PEPI Lab of a formalin-fixed, paraffin-embedded pedunculated colonic polyp with adenocarcinoma, scanned across a range of tube voltages (45–100 kVp) at constant power for the purpose of virtual histology. Consistent with the simulation predictions, the measured SNR values tended to increase with tube voltage for both attenuation and phase-retrieved images. While the dataset is limited and further work is required to confirm broader applicability, these results suggest that PEPIsim can provide useful guidance for acquisition parameter selection and may help establish simple experimental guidelines, such as minimum kVp thresholds, for biological samples.

Computed Tomography (CT) is a cornerstone of diagnostic imaging but conventional systems, equipped with energy-integrating detectors (EIDs), present limitations in spatial resolution, noise, and tissue contrast. Photon-Counting CT (PCCT) addresses these limitations using photon-counting detectors (PCDs) that directly convert incoming X-ray photons into electric signals, enabling energy discrimination, material quantification, and virtual monoenergetic image reconstruction. Clinical applications have already included cardiovascular, thoracic, and neuroimaging examinations. We performed a characterization of the spatial resolution of the first clinical PCCT scanner, the Naeotom Alpha® (Siemens Healthineers), equipped with CdTe PCDs. High-contrast presampled Modulation Transfer Function (MTF) was measured using a custom-built tungsten wire phantom tilted by 3^∘C. Spatial resolution in radial and tangential was evaluated by shifting the phantom within the field of view. Three acquisition protocols were tested (head, abdomen/thorax, inner ear), including standard and Ultra-High Resolution (UHR) modes. Images were reconstructed with multiple iterative algorithms and kernels, and MTF analysis was automated via Python. Results showed that spatial resolution increases with sharper reconstruction kernels across all anatomical protocols, with negligible differences between standard and vascular algorithms. UHR mode significantly improved resolution in the inner ear protocol (f_50% from 0.56 to 0.73 mm^-1; f_10% from 0.87 to 1.09 mm^-1). In conclusion, this work provides an initial assessment of PCCT spatial resolution for acquisition protocols and reconstructions usually adopted in clinical routine. Future investigations will employ standardized phantoms and comparisons with other CT systems to further validate performance and assess its potential to enhance diagnostic imaging quality.

To address new applications in the 18–30 keV photon energy range at the European XFEL, where silicon sensors lose quantum efficiency, the AGIPD Collaboration has developed an AGIPD detector prototype with high-Z sensor materials. An electron-collecting version of the chip (ecAGIPD) was designed to leverage from the higher mobility and longer lifetime of electrons with respect to holes in the candidate materials: chromium-doped gallium arsenide (GaAs:Cr) and high-flux cadmium zinc telluride (CdZnTe). This work reports on the characterization of GaAs and high-flux CdZnTe ecAGIPD prototypes at the HED instrument at the European XFEL. Their time response, linearity and performance at 2.2 and 4.5 MHz frame rates were evaluated. Preliminary results demonstrate good linearity of both materials up to 1.6e+03 15 keV photons/mm²/pulse, and a residual after-pulse signal corresponding to less than one photon on CdZnTe, up to an estimated flux of 1.2e+05 24 keV photons/mm²/pulse.

We report optical evidence of cesium (Cs) evaporation from a bialkali (SbKCs) photocathode during controlled heating of a photomultiplier tube (PMT). A DFB laser scanned across the 852.113 nm Cs D2 line reveals absorption features only above 60 ^∘C, indicating thermal desorption. The absorption correlates with temperature and offers a non-invasive method to monitor photocathode degradation in sealed detectors.

The reliability of large-area Resistive Plate Chambers (RPCs) operated under High-Luminosity Large Hadron Collider (HL-LHC) conditions is governed by the long-term stability and radiation tolerance of screen-printed graphite/phenoxy coatings on high-pressure-laminate (HPL) electrodes. This work presents a comprehensive, end-to-end qualification of such coatings that integrates industrial process control and metrology with controlled humidity/temperature campaigns, extended high-voltage stress testing to decade-scale charge levels, and representative neutron and gamma irradiation at CERN facilities. The results establish reproducible industrial coating production, stable performance under sustained operation and irradiation, and practical acceptance criteria with operating and monitoring guidelines. The study provides a transferable quality-assurance framework for graphite-based resistive coatings on HPL electrodes, enabling reproducible production and reliable RPC performance for the HL-LHC upgrades and for future high-rate collider experiments.

This paper presents pixcore, which is a 32-bit RISC-V microprocessor with an integrated pixel matrix management coprocessor. The integration of the coproccessor with a RISC-V core enabled the management of the pixel matrix using custom RISC-V instructions, allowing for high performance and flexibility. The presented solution was designed in a 16 nm FinFET CMOS process, and the results of the chip implementation were used in post-layout simulations. The conducted simulations confirmed that the developed coproccessor can be successfully used for managing and readout of the hybrid pixel detector. A comparison was made between the proposed solution and the microprocessor-based system that utilized a dedicated peripheral device for the purpose of controlling the pixel matrix. The comparison indicates a reduction in the execution time of the selected algorithms by a factor of 14, measured in terms of clock cycles.

High particle rates in current and future experiments make pile-up phenomena a critical issue for extracting useful information. In this context, timing serves as a crucial fourth dimension for triggering and event reconstruction. The PICOSEC Micromegas detector has demonstrated precise timing capabilities on the order of tens of picoseconds. In this work, we develop and evaluate novel signal-processing algorithms to demonstrate the detector's potential for online precise timing. In particular, we propose an algorithm based on Artificial Neural Networks (ANNs), trained using a physically motivated model. The performance of the different algorithms is assessed using experimental data recorded during laser beam tests at the IRAMIS Facility of CEA Saclay. A timing resolution of 18.3 ± 0.6 ps, corresponding to 7.8 photoelectrons in the gas volume, is achieved — comparable to results obtained with the standard Constant Fraction Discrimination (CFD) technique. Additionally, we present an alternative algorithm that uses the integrated charge of the pulse exceeding a defined threshold as a parameter to correct for systematic effects.

The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10³⁴ cm⁻² s⁻¹ (10²⁷ cm⁻² s⁻¹). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (|η| ⩽ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

The Large Hadron Collider (LHC) at CERN near Geneva is the world's newest and most powerful tool for Particle Physics research. It is designed to collide proton beams with a centre-of-mass energy of 14 TeV and an unprecedented luminosity of 10³⁴ cm⁻² s⁻¹. It can also collide heavy (Pb) ions with an energy of 2.8 TeV per nucleon and a peak luminosity of 10²⁷ cm⁻² s⁻¹. In this paper, the machine design is described.

The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) collisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, τ lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algorithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described.

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m³ with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.

At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13\TeV. During Run 2 (years 2015–2018) the LHC eventually reached a luminosity of 2.1× 10³⁴ cm^-2s^-1, almost three times that reached during Run 1 (2009–2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016–2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals.

The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy neutrino detector built into the ice at the South Pole. Construction of IceCube, the largest neutrino detector built to date, was completed in 2011 and enabled the discovery of high-energy astrophysical neutrinos. We describe here the design, production, and calibration of the IceCube digital optical module (DOM), the cable systems, computing hardware, and our methodology for drilling and deployment. We also describe the online triggering and data filtering systems that select candidate neutrino and cosmic ray events for analysis. Due to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are operating and collecting data. IceCube routinely achieves a detector uptime of 99% by emphasizing software stability and monitoring. Detector operations have been stable since construction was completed, and the detector is expected to operate at least until the end of the next decade.

This paper describes the reconstruction of electrons and photons with the ATLAS detector, employed for measurements and searches exploiting the complete LHC Run 2 dataset. An improved energy clustering algorithm is introduced, and its implications for the measurement and identification of prompt electrons and photons are discussed in detail. Corrections and calibrations that affect performance, including energy calibration, identification and isolation efficiencies, and the measurement of the charge of reconstructed electron candidates are determined using up to 81 fb⁻¹ of proton-proton collision data collected at √s=13 TeV between 2015 and 2017.

The Timepix3, hybrid pixel detector (HPD) readout chip, a successor to the Timepix \cite{timepix2007} chip, can record time-of-arrival (ToA) and time-over-threshold (ToT) simultaneously in each pixel. ToA information is recorded in a 14-bit register at 40 MHz and can be refined by a further 4 bits with a nominal resolution of 1.5625 ns (640 MHz). ToT is recorded in a 10-bit overflow controlled counter at 40 MHz. Pixels can be programmed to record 14 bits of integral ToT and 10 bits of event counting, both at 40 MHz. The chip is designed in 130 nm CMOS and contains 256 × 256 pixel channels (55 × 55 μm²). The chip, which has more than 170 M transistors, has been conceived as a general-purpose readout chip for HPDs used in a wide range of applications. Common requirements of these applications are operation without a trigger signal, and sparse readout where only pixels containing event information are read out.

A new architecture has been designed for sparse readout and can achieve a throughput of up to 40 Mhits/s/cm². The flexible architecture offers readout schemes ranging from serial (one link) readout (40 Mbps) to faster parallel (up to 8 links) readout of 5.12 Gbps. In the ToA/ToT operation mode, readout is simultaneous with data acquisition thus keeping pixels sensitive at all times. The pixel matrix is formed by super pixel (SP) structures of 2 × 4 pixels. This optimizes resources by sharing the pixel readout logic which transports data from SPs to End-of-Column (EoC) using a 2-phase handshake protocol.

To reduce power consumption in applications with a low duty cycle, an on-chip power pulsing scheme has been implemented. The logic switches bias currents of the analog front-ends in a sequential manner, and all front-ends can be switched in 800 ns. The digital design uses a mixture of commercial and custom standard cell libraries and was verified using Open Verification Methodology (OVM) and commercial timing analysis tools. The analog front-end and a voltage-controlled oscillator for 1.5625 ns timing resolution have been designed using full custom techniques.

The ATLAS luminosity monitor, LUCID (LUminosity Cherenkov Integrating Detector), had to be upgraded for the second run of the LHC accelerator that started in spring 2015. The increased energy of the proton beams and the higher luminosity required a redesign of LUCID to cope with the more demanding conditions. The novelty of the LUCID-2 detector is that it uses the thin quartz windows of photomultipliers as Cherenkov medium and a small amounts of radioactive ²⁰⁷Bi sources deposited on to these windows to monitor the gain stability of the photomultipliers. The result is a fast and accurate luminosity determination that can be kept stable during many months of data taking. LUCID-2 can also measure the luminosity accurately online for each of the up to 2808 colliding bunch pairs in the LHC . These bunch pairs are separated by only 25 ns and new electronics has been built that can count not only the number of pulses above threshold but also integrate the pulses.