Journal of Instrumentation

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.

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.

A multi-TeV muon collider offers a spectacular opportunity in the direct exploration of the energy frontier. Offering a combination of unprecedented energy collisions in a comparatively clean leptonic environment, a high energy muon collider has the unique potential to provide both precision measurements and the highest energy reach in one machine that cannot be paralleled by any currently available technology. The topic generated a lot of excitement in Snowmass meetings and continues to attract a large number of supporters, including many from the early career community. In light of this very strong interest within the US particle physics community, Snowmass Energy, Theory and Accelerator Frontiers created a cross-frontier Muon Collider Forum in November of 2020. The Forum has been meeting on a monthly basis and organized several topical workshops dedicated to physics, accelerator technology, and detector R&D. Findings of the Forum are summarized in this report.

Recent experiments with high-intensity lasers have shown record production of α-particles by irradiating boron-hydrogen targets. This opened the way to completely new studies on proton-boron fusion with multiple goals:

i) studies related to nuclear fusion. The proton-boron fusion reaction produces 3 α-particles and releases a large energy. It is considered an interesting alternative to deuterium-tritium fusion because it produces no neutrons, therefore no activation and radioactive wastes.

ii) generation of novel laser-driven α-particle sources. Laser-driven α-particle sources are promising for their potential high brightness while remaining compact. They could be used for multidisciplinary applications, including medical ones.

The COST Action CA21128 — PROBONO (PROton BOron Nuclear fusion: from energy production to medical applicatiOns) is the first international programme which aims at understanding the physics involved in laser-driven pB fusion, including the study of Equation of State of boron and boron compounds. Action's goals are to facilitate access to experimental infrastructures, maximize production of new knowledge, boost the career of young researchers by fostering opportunities for training, and finally interconnect researchers across countries building a well-organized community focused on pB research.

Timepix4 is a 24.7 × 30.0 mm² hybrid pixel detector readout ASIC which has been designed to permit detector tiling on 4 sides. It consists of 448 × 512 pixels which can be bump bonded to a sensor with square pixels at a pitch of 55 µm. Like its predecessor, Timepix3, it can operate in data driven mode sending out information (Time of Arrival, ToA and Time over Threshold, ToT) only when a pixel has a hit above a pre-defined and programmable threshold. In this mode hits can be tagged to a time bin of <200 ps and Timepix4 can record hits correctly at incoming rates of ∼3.6 MHz/mm²/s. In photon counting (or frame-based) mode it can count incoming hits at rates of up to 5 GHz/mm²/s. In both modes data is output via between 2 and 16 serializers each running at a programmable data bandwidth of between 40 Mbps and 10 Gbps. The specifications, architecture and circuit implementation are described along with first electrical measurements and measurements with radioactive sources. In photon counting mode X-ray images have been taken at a threshold of 650 e⁻ (with <10 masked pixels). In data driven mode images were taken of ToA/ToT data using a ⁹⁰Sr source at a threshold of 800 e⁻ (with ∼120 masked pixels).

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.

User Datagram Protocol (UDP) is a commonly used protocol for data transmission in small embedded systems. UDP as such is unreliable and packet losses can occur. The achievable data rates can suffer if optimal packet sizes are not used. The alternative, Transmission Control Protocol (TCP) guarantees the ordered delivery of data and automatically adjusts transmission to match the capability of the transmission link. Nevertheless UDP is often favored over TCP due to its simplicity, small memory and instruction footprints. Both UDP and TCP are implemented in all larger operating systems and commercial embedded frameworks. In addition UDP also supported on a variety of small hardware platforms such as Digital Signal Processors (DSP) Field Programmable Gate Arrays (FPGA). This is not so common for TCP. This paper describes how high speed UDP based data transmission with very low packet error ratios was achieved. The near-reliable communications link is used in a data acquisition (DAQ) system for the next generation of extremely intense neutron source, European Spallation Source. This paper presents measurements of UDP performance and reliability as achieved by employing several optimizations. The measurements were performed on Xeon E5 based CentOS (Linux) servers. The measured data rates are very close to the 10 Gb/s line rate, and zero packet loss was achieved. The performance was obtained utilizing a single processor core as transmitter and a single core as receiver. The results show that support for transmitting large data packets is a key parameter for good performance. Optimizations for throughput are: MTU, packet sizes, tuning Linux kernel parameters, thread affinity, core locality and efficient timers.

This paper describes the experience with the calibration, reconstruction and evaluation of the timing capabilities of the CMS HGCAL prototype in the beam tests in 2018. The calibration procedure includes multiple steps and corrections ranging from tens of nanoseconds to a few hundred picoseconds. The timing performance is studied using signals from positron beam particles with energies between 20 GeV and 300 GeV. The performance is studied as a function of particle energy against an external timing reference as well as standalone by comparing the two different halves of the prototype. The timing resolution is found to be 60 ps for single-channel measurements and better than 20 ps for full showers at the highest energies, setting excellent perspectives for the HGCAL calorimeter performance at the HL-LHC.

The Phase-2 Upgrade [1] of the CMS Outer Tracker [2] requires the production of 7608 Strip-Strip (2S) and 5592 Pixel-Strip (PS) modules, altogether incorporating 45 192 hybrid circuits of 15 design variants. The module design makes the potential repairs impractical; therefore, performing production-scale testing of the hybrids is essential. Accordingly, a scalable, crate-based test system was designed and manufactured, allowing for parallel, high-throughput testing. To reproduce the operating conditions, the system was integrated within a climate chamber, which required the development of a remote control interface and the calibration of thermal cycles. The results and lessons learned from the test system integration and commissioning will be presented.

Fast simulation of the energy depositions in high-granular detectors is needed for future collider experiments at ever-increasing luminosities. Generative machine learning (ML) models have been shown to speed up and augment the traditional simulation chain in physics analysis. However, the majority of previous efforts were limited to models relying on fixed, regular detector readout geometries. A major advancement is the recently introduced CaloClouds model, a geometry-independent diffusion model, which generates calorimeter showers as point clouds for the electromagnetic calorimeter of the envisioned International Large Detector (ILD). In this work, we introduce CaloClouds II which features a number of key improvements. This includes continuous time score-based modelling, which allows for a 25-step sampling with comparable fidelity to CaloClouds while yielding a 6× speed-up over Geant4 on a single CPU (5× over CaloClouds). We further distill the diffusion model into a consistency model allowing for accurate sampling in a single step and resulting in a 46× speed-up over Geant4(37× over CaloClouds). This constitutes the first application of consistency distillation for the generation of calorimeter showers.

In order to extract intense ion beams with good beam optics from hydrogen negative ion sources, it is important to control the shape of the plasma meniscus (i.e. beam emission surface). Recently, it is suggested experimentally that the degradation of beam optics in the RF negative ion sources may be due to the fluctuation of the distance d_eff between the meniscus and the extraction grid caused by the fluctuation of the plasma density n_p. The purpose of this study is to make clear the dependence of d_eff on n_p in the presence of a large amount of surface produced H^- ions in order to understand such fluctuation of beam optics in RF sources For the purpose, 3D electrostatic PIC simulation was conducted taking the bulk plasma density as a parameter, investigating the extraction region of a H^- ion source. A large amount of the surface H^- production on the PG has been taken into account under the assumption that the H^- production rate is proportional to the bulk plasma density. The result shows that the effective distance d_eff is proportional to n_p^-1/2 even for a large amount of surface H^- production. This dependence suggests that the bulk plasma density  n_p is the key parameters to control d_eff and the resultant beam optics extracted from the negative ion source.

The ECAL Barrel and MTD Barrel Timing Layer subdetectors of CMS are approaching series production of electronic boards, including voltage conditioning PCBs: LVRs and PCCs respectively. 2448 LVRs and 864 PCCs will be installed during LS3 of the LHC. These boards are hosting radiation-tolerant bPOL12V ASICs which convert a broad input voltage range into required voltage levels for microelectronics between 1.2–2.5 V. Each card must be tested multiple times at various production stages to ensure its conformity. This contribution describes a methodology of testing bPOL12V conversion quality including the detection of instability regions at certain load levels.

NAPA-p1 is a prototype Monolithic Active Pixel Sensor 'MAPS' developed as a first iteration towards meeting the detectors general requirements for future e⁺e^- colliders. Long-term objective is to develop a wafer-scale sensor in MAPS with an area ∼ 10 cm × 10 cm. This article presents the motivations for the design choices of NAPA-p1, translating the physics requirement into circuit specifications. Simulations show a pixel jitter of < 400 ps-rms and an equivalent noise charge of 13 e^-rms with an average power consumption of 1.15 mW/cm² assuming a 1% duty cycle, meeting the target specifications. The prototype is designed in 65 nm CMOS imaging technology, with dimensions of 1.5 mm × 1.5 mm and a pixel pitch of 25 μm. The prototype chip has been fabricated and characterization results will be available soon.

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 Phase-2 Upgrade [1] of the CMS Outer Tracker [2] requires the production of 7608 Strip-Strip (2S) and 5592 Pixel-Strip (PS) modules, altogether incorporating 45 192 hybrid circuits of 15 design variants. The module design makes the potential repairs impractical; therefore, performing production-scale testing of the hybrids is essential. Accordingly, a scalable, crate-based test system was designed and manufactured, allowing for parallel, high-throughput testing. To reproduce the operating conditions, the system was integrated within a climate chamber, which required the development of a remote control interface and the calibration of thermal cycles. The results and lessons learned from the test system integration and commissioning will be presented.

Fast simulation of the energy depositions in high-granular detectors is needed for future collider experiments at ever-increasing luminosities. Generative machine learning (ML) models have been shown to speed up and augment the traditional simulation chain in physics analysis. However, the majority of previous efforts were limited to models relying on fixed, regular detector readout geometries. A major advancement is the recently introduced CaloClouds model, a geometry-independent diffusion model, which generates calorimeter showers as point clouds for the electromagnetic calorimeter of the envisioned International Large Detector (ILD). In this work, we introduce CaloClouds II which features a number of key improvements. This includes continuous time score-based modelling, which allows for a 25-step sampling with comparable fidelity to CaloClouds while yielding a 6× speed-up over Geant4 on a single CPU (5× over CaloClouds). We further distill the diffusion model into a consistency model allowing for accurate sampling in a single step and resulting in a 46× speed-up over Geant4(37× over CaloClouds). This constitutes the first application of consistency distillation for the generation of calorimeter showers.

The ECAL Barrel and MTD Barrel Timing Layer subdetectors of CMS are approaching series production of electronic boards, including voltage conditioning PCBs: LVRs and PCCs respectively. 2448 LVRs and 864 PCCs will be installed during LS3 of the LHC. These boards are hosting radiation-tolerant bPOL12V ASICs which convert a broad input voltage range into required voltage levels for microelectronics between 1.2–2.5 V. Each card must be tested multiple times at various production stages to ensure its conformity. This contribution describes a methodology of testing bPOL12V conversion quality including the detection of instability regions at certain load levels.

Transverse instability growth rates in the CERN Proton Synchrotron (PS) are studied thanks to the recently updated impedance model of the machine. Using this model, macroparticle tracking simulations were performed with a new method well-suited for the slicing of short wakes, which achieves comparable performance to the originally implemented method while reducing the required number of slices by a factor of 5 to 10. Furthermore, dedicated beam-based measurement campaigns were carried out to benchmark the impedance model. Until now, beam dynamics simulations based on this model underestimated instability growth rates at injection energy. Thanks to a recent addition to the impedance model, namely the kicker magnets' connecting cables and their external circuits, the simulated instability growth rates are now comparable to the measured ones even when neglecting the impact of the space charge force. Finally, the space charge force is included in simulations and its impact on the instability growth rate and intra-bunch motion is studied.

The ALICE collaboration is proposing a completely new detector, ALICE 3, for operation during the LHC Runs 5 and 6. One of the ALICE 3 subsystems is the Muon IDentifier detector (MID), which has to be optimised to be efficient for the reconstruction of  J/ψ at rest (muons down to p_T ≈ 1.5 GeV/c) for |η| < 1.3. Given the modest particle flux expected in the MID of a few Hz/cm², technologies like plastic scintillator bars (≈ 1 m length) equipped with wavelength-shifting fibers and silicon photomultiplier readout, and lightweight Multi-Wire Proportional Chambers (MWPCs) are under investigation. To this end, different plastic scintillator paddles and MWPCs were studied at the CERN T10 test beam facility. This paper reports on the performance of the scintillator prototypes tested at different beam momenta (from 0.5 GeV/c up to 6 GeV/c) and positions (horizontal, vertical, and angular scans). The MWPCs were tested at different momenta (from 0.5 GeV/c to 10 GeV/c) and beam intensities, their efficiency and position resolutions were verified beyond the particle rates expected with the MID in ALICE 3.

Future experiments at high energy e⁺e^- colliders will focus on extremely precise Standard Model measurements. Among the most important physics benchmarks, there is the capability to resolve the Higgs decays into W or Z pairs, in their completely hadronic decay modes (4 jets in the final state), only based on the invariant mass of the jet pair coming from decay of the on-shell boson. This translates into a relative energy resolution target of 30%/√E, well beyond current detector performances. Dual-readout calorimetry is a technique which aims to improve the energy resolution, for single hadrons and hadronic jets, exploiting the information produced by two different physical processes, namely scintillation and Čerenkov light emission. The IDEA detector, whose concept has been included in both the FCC and CEPC Conceptual Design Reports, is based on a dual-readout fibre calorimeter with independent fibre readout exploiting Silicon PhotoMultipliers (SiPMs). The individual SiPM information will be beneficial for a highly granular calorimeter design, opening up to advanced reconstruction techniques such as Particle Flow and a variety of neural network algorithms. In this paper the status of calorimeter prototypes that have been developed to demonstrate the feasibility of the dual-readout method in association with the high granularity feature is illustrated. The specific choice for the design of each prototype is presented, together with the performances achieved at high-energy test beams or through simulations.

This work presents the analog circuitry of the FastRICH ASIC, a 16-channel ASIC, developed in a 65 nm CMOS technology specifically designed for the RICH detector at LHCb to readout detectors like Photomultiplier Tubes to be used at the LHC Run 4 and Silicon Photomultipliers candidates for Run 5. The front-end (FE) stage has an input impedance below 50 Ω and an input dynamic range from 5 μA to 5 mA with a power consumption of ∼5 mW/channel. The chip includes a Leading Edge Comparator (LED) and a Constant Fraction Discriminator (CFD) for time pick-off and a Time-to-Digital Converter (TDC) for digitization.

This paper describes the experience with the calibration, reconstruction and evaluation of the timing capabilities of the CMS HGCAL prototype in the beam tests in 2018. The calibration procedure includes multiple steps and corrections ranging from tens of nanoseconds to a few hundred picoseconds. The timing performance is studied using signals from positron beam particles with energies between 20 GeV and 300 GeV. The performance is studied as a function of particle energy against an external timing reference as well as standalone by comparing the two different halves of the prototype. The timing resolution is found to be 60 ps for single-channel measurements and better than 20 ps for full showers at the highest energies, setting excellent perspectives for the HGCAL calorimeter performance at the HL-LHC.

The quasistellar neutron spectrum produced via ⁷Li (p, n)⁷Be reaction at a proton energy of 1.912 MeV has been extensively studied and employed reaction for neutron-induced reaction studies. We are working towards using this reaction at various proton energies from 1.9 MeV to 3.6 MeV to produce a neutron field at a temperature range of ∼ 1.5–3.5 GK to conduct measurements of neutron-induced charge particle reaction cross sections on various unstable nuclei at explosive stellar temperatures. In this paper, we are reporting our design and simulation study with regards to experimental set-up and a gaseous detector with a segmented Micromegas detector for conducting neutron-induced charge particle reactions studies for nuclei of astrophysics importance, for example, ²⁶Al(p, n)²⁶Mg,  ²⁶Al(n, α)²³Na and ⁴⁰K(p, n)⁴⁰Ar,  ⁴⁰K(n, α)³⁷Cl reactions. We plan to perform our experiments with a 10-μA proton beam at the Physikalisch Technische Bundesanstalt facility (PTB, Germany), with a Micromegas-based gaseous detector under construction as discussed in the paper.

At injection into the Large Hadron Collider (LHC), the radio frequency (RF) system is perturbed by beam-induced voltage resulting in strong RF power transients and the instant detuning of the cavities. The automatic tuning system, however, needs time for the mechanical compensation of the resonance frequency to take place. Acting back on the beam, the transients in RF power are expected to limit the maximum injected intensity by generating unacceptable beam loss. Reducing them is therefore essential to reach the target intensity during the High Luminosity (HL) LHC era. At LHC flat bottom, the cavities are operated using the half-detuning beam-loading compensation scheme. As implemented today, the tuner control algorithm starts acting only after the injection of the first longer bunch train which causes the bunches for this injection to experience the largest power spikes. This contribution presents an adapted detuning scheme for the RF cavities before injection. It was proposed as a path to decrease the transients, hence increasing the available intensity margin for the available RF power. The expected gain is evaluated in particle tracking simulations and measurements acquired during operation.