Search Results (349)

Different polyurethanes (PURs) and silicone for potential use in particle accelerators and detectors have been characterized in the uncured state, after curing, and after exposure to ionizing irradiation in ambient air and in liquid helium. The viscosity evolution during processing was measured with a rheometer. Dynamic mechanical analysis (DMA) and Shore A hardness measurements were applied to detect irradiation-induced crosslinking and chain scission effects. Uniaxial tensile and flexural tests under ambient and cryogenic conditions have been performed to assess changes in mechanical strength, elongation at break, and elastic properties. The initial viscosity of 550 cP at 25 °C of the uncured PUR RE700-4 polyol and RE106 isocyanate system for protective encapsulation is sufficiently low for impregnation of small magnet coils, but the pot life of about 30 min is too short for impregnation of large magnet coils. The cured RE700-4 system has outstanding mechanical properties at 77 K (flexural strength, impact strength, and fracture toughness). When RE700-4 is exposed to ionizing radiation, chain scission and cross-linking occur at a similar rate. In the other casting systems, irradiation-induced changes are cross-linking dominated, as manifested by an increase of the rubbery shear modulus (G’_rubbery), the ambient temperature Young’s modulus (E_RT), and the Shore A hardness. Cross-linking rates are strongly reduced when irradiation occurs in liquid helium. The irradiation effect on mechanical properties can be strongly dependent on the testing temperature. The RT mechanical strength and strain at fracture of the cross-linking silicone is drastically decreased after 1.6 MGy, whereas its 77 K strain at fracture has almost doubled. In addition, 77 K elastic moduli are similar for all pure resins and only slightly affected by irradiation. Full article

This contribution aims to honour Guido Barbiellini’s profound interest in the interpretation and impact of quantum mechanics by examining the implications of the so-called before–before Experiment on quantum entanglement. This experiment was inspired by talks and discussions with John Bell at CERN. This was during the years when John and Guido co-worked, promoting the mission of the laboratory: “to advance the boundaries of human knowledge”. As the experiment uses measuring devices in motion, it can be considered a complement to entanglement experiments using stationary measuring devices, which have meanwhile been awarded the 2022 Nobel Prize in Physics. The before–before Experiment supports the idea that the quantum realm exists beyond space and time and that the quantum state is a real mental entity concerning choices. As it also leads us to a better understanding of the ‘quantum collapse’ and the measurement process, we pay homage to Guido’s work on detectors, such as his collaborations on the DELPHI experiment at CERN, on cosmic ray detection at the International Space Station, and gamma-ray astrophysics during a large NASA space mission. Full article

This mini-review traces the evolution of axion searches at the CERN Super Proton Synchrotron (SPS), beginning with the early proposal by Guido Barbiellini in 1982 and culminating in the recent advances of the NA62 and NA64 experiments. We discuss the experimental strategies employed in early beam dump searches, the current status of axion and axion-like particle (ALP) searches at the CERN SPS and future directions. This review serves as a tribute to Guido Barbiellini’s scientific legacy and his visionary contributions to this field. Full article

The Standard Model (SM) fails to explain many problems (neutrino masses, dark matter, and matter–antimatter asymmetry, among others) that may be resolved with new particles beyond the SM. No observation of such new particles may be explained either by their exceptionally high mass or by considerably small coupling to SM particles. The latter case implies relatively long lifetimes. Such long-lived particles (LLPs) then to have signatures different from those of SM particles. Searches in the “central region” are covered by the LHC general purpose experiments. The forward small angle region far from the interaction point (IP) is unexplored. Such particles are expected to have the energy as large as E = $\mathcal{O}$(1 TeV) and Lorentz time dilation factor $\gamma =E/m\approx {10}^2$–${10}^3$ (with m the particle mass) hence long enough decay distances. A new class of specialized LHC detectors dedicated to LLP searches has been proposed for the forward regions. Among these experiments, FASER is already operational, and FACET is under consideration at a location 100 m from the LHC IP5 (the CMS detector intersection). However, some features of FACET require a specially enlarged beam pipe, which cannot be implemented for LHC Run 4. In this study, we explore a simplified version of the proposed detector PREFACE compatible with the standard LHC beam pipe in the HL-LHC Run 4. Realistic Geant4 simulations are performed and the background is evaluated. An initial analysis of the physics potential with the PREFACE geometry indicates that several significant channels could be accessible with sensitivities comparable to FACET and other LLP searches. Full article

This work introduces an innovative approach for estimating the Single-Event Upset (SEU) cross-sections in Static Random-Access Memory (SRAM) devices, addressing challenges related to limited technological information and the complexity of Technology Computer-Aided Design (TCAD) simulations. The proposed methodology is designed to be accessible even to users without in-depth TCAD expertise, enabling a streamlined yet accurate SEU cross-section estimation. Using simplified mixed-modeling (TCAD-based 2D modeling with circuit-level SPICE simulations), this approach significantly reduces computational efforts while maintaining good correlation with experimental data. Furthermore, this study identifies key parameters that influence TCAD modeling accuracy and proposes strategies for approximating unknown parameters, enhancing the reliability of SEU cross-section predictions. Full article

Future $e^{+}{e}^{-}$ colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected correlation structures in these distributions is considered to be a hint for new physics perturbing the QCD partonic cascade and thereby modifying azimuthal and (pseudo)rapidity correlations. Using Pythia8 Monte Carlo generator and fast simulation, including selection cuts and detector effects, we study potential structures in the two-particle angular correlation function. We adopt the QCD-like Hidden Valley (HV) scenario as implemented in Pythia8 generator, with relatively light HV v-quarks (below about 100 GeV), to illustrate the potential of this method. Full article

The dynamic aperture is an essential concept in circular particle accelerators, providing the extent of the phase space region where particle motion remains stable over multiple turns. The accurate prediction of the dynamic aperture is key to optimising performance in accelerators such as the CERN Large Hadron Collider and is crucial for designing future accelerators like the CERN Future Circular Hadron Collider. Traditional methods for computing the dynamic aperture are computationally demanding and involve extensive numerical simulations with numerous initial phase space conditions. In our recent work, we have devised surrogate models to predict the dynamic aperture boundary both efficiently and accurately. These models have been further refined by incorporating them into a novel active learning framework. This framework enhances performance through continual retraining and intelligent data generation based on informed sampling driven by error estimation. A critical attribute of this framework is the precise estimation of uncertainty in dynamic aperture predictions. In this study, we investigate various machine learning techniques for uncertainty estimation, including Monte Carlo dropout, bootstrap methods, and aleatory uncertainty quantification. We evaluated these approaches to determine the most effective method for reliable uncertainty estimation in dynamic aperture predictions using machine learning techniques. Full article

In particle physics experiments, fragment separators utilize dipole magnets to distinguish and isolate specific isotopes based on their mass-to-charge ratio as particles traverse the dipole’s magnetic field. Accurate fragment selection relies on precise knowledge of the magnetic field generated by the dipole magnets, necessitating dedicated measurement instrumentation to characterize the field in the constructed magnets. This study presents measurements of the two first-of-series dipole magnets (Type II—11 degrees bending angle—and Type III—9.5 degrees bending angle) for the Superconducting Fragment Separator that is being built in Darmstadt, Germany. Stringent field quality requirements necessitated a novel measurement system—the so-called translating fluxmeter. It is based on a PCB coil array installed on a moving trolley that scans the field while passing through the magnet aperture. While previous publications have discussed the design of the moving fluxmeter and the characterization of its components, this article presents the results of a measurement campaign conducted using the new system. The testing campaign was supplemented with conventional methods, including integral field measurements using a single stretched wire system and three-dimensional field mapping with a Hall probe. We provide an overview of the working principle of the translating fluxmeter system and validate its performance by comparing the results with those obtained using conventional magnetic measurement methods. Full article

This work reviews the current research directions pursued by collaborations at CERN’s Antiproton Decelerator (AD), with an outlook on future perspectives and challenges in the field. The advancement of precision studies on antimatter builds upon foundational contributions by pioneering researchers, such as Guido Barbiellini Amidei, whose early work on antimatter detection and instrumentation has profoundly influenced the design and methodologies of contemporary experiments at the AD and beyond. This review underscores the lasting impact of these early innovations on ongoing investigations into fundamental symmetries and interactions involving antimatter. Full article

The proliferation of sensors brings an immense volume of spatio-temporal (ST) data in many domains, including monitoring, diagnostics, and prognostics applications. Data curation is a time-consuming process for a large volume of data, making it challenging and expensive to deploy data analytics platforms in new environments. Transfer learning (TL) mechanisms promise to mitigate data sparsity and model complexity by utilizing pre-trained models for a new task. Despite the triumph of TL in fields like computer vision and natural language processing, efforts on complex ST models for anomaly detection (AD) applications are limited. In this study, we present the potential of TL within the context of high-dimensional ST AD with a hybrid autoencoder architecture, incorporating convolutional, graph, and recurrent neural networks. Motivated by the need for improved model accuracy and robustness, particularly in scenarios with limited training data on systems with thousands of sensors, this research investigates the transferability of models trained on different sections of the Hadron Calorimeter of the Compact Muon Solenoid experiment at CERN. The key contributions of the study include exploring TL’s potential and limitations within the context of encoder and decoder networks, revealing insights into model initialization and training configurations that enhance performance while substantially reducing trainable parameters and mitigating data contamination effects. Full article

(1) Background: As the demand for ²¹²Pb for clinical theranostics rises, empirical studies that examine the radiation safety implications of different ²²⁴Ra sources are needed to facilitate discussions with local authorities for the translation of ^203/212Pb theranostics routine clinical practice. (2) Methods: Environmental ²²⁰Rn (Thoron) emanation was detected by a RAD7 detector in the vicinity of respective ²¹²Pb sources and additional alpha-dosimeters to detect ²²⁰Rn during generator elution, radiosynthesis, and quality control. Personnel gamma exposure was measured using whole-body and ring dosimeters. Generators included those based on wet-chemical-process- and emanation-based technology. (3) Results: During generator handling, varying levels of ²²⁰Rn were observed in the vicinity of generators. An additional monthly whole-body dose must be considered when handling different sources of ²¹²Pb generators, and this depends upon local shielding and the handling approaches toward use of the technology. (4) Conclusions: ²²⁴Ra in any form (including radionuclide generators) should always be handled within a fume hood to keep potential contamination and exposure to personnel as low as reasonably achievable. Following standard practices of radiation safety, generators of ²¹²Pb can be used safely for theranostic applications. Full article

With the evolution of synchrotron light sources to fourth generation (diffraction-limited storage rings), the brilliance is increased by several orders of magnitude compared to third generation facilities. For example, the Swiss Light Source (SLS) has been upgraded to SLS 2.0, promising a horizontal emittance reduced by a factor of 40, and a brilliance up to two orders of magnitude (three at higher energies). A key challenge arising from the increased flux is the heightened accumulated dose in silicon sensors, which leads to a significant increase in radiation damage. This translates into an increase of both noise and dark current, as well as a reduction in the dynamic range for long exposure times, thus affecting the performance of the detector, in particular, for charge-integrating detectors. We have designed sensors with a 4 × 4 mm² pixel array featuring 16 design variations of 25 µm pitch pixels with different implant and metal sizes and tested them bump-bonded to MÖNCH 0.3, a charge integrating hybrid pixel detector readout ASIC. Following a first assessment of the functionality and performance of the different pixel designs, the assembly has been irradiated with X-rays. The variation in the tested parameters was characterized at different accumulated doses up to 100 kGy at the sensor entrance window side. The annealing dynamics at room temperature have also been measured. The results show that the default pixel design is currently not optimal and can benefit from layout changes (reduction in the inter-pixel gap area with full metal coverage of the implant). Further studies on the metal coverage over large implants could be conducted. The layout changes are, however, not sufficient for future full-sized sensors, requiring improved radiation hardness and long-term stability, and additional strategies such as focusing on detector cooling and changes in sensor technologies would be required. Full article

The ALICE (A Large Ion Collider Experiment) detector at the Large Hadron Collider (LHC), operated by the European Organization for Nuclear Research (CERN), is dedicated to heavy-ion collisions. Within ALICE, the application logs of the online computing systems are consolidated through a logging system known as Infologger, which integrates data from various sources. To identify potential anomalies, shifters in the control room manually review logs for anomalies, which require significant expertise and pose challenges due to the frequent onboarding of new personnel. To address this issue, we propose a real-time semi-supervised log anomaly detection framework designed to automatically detect anomalies in ALICE operations. The framework leverages BERTopic, a topic modeling technique, to provide real-time insights for incoming log messages for shifters. This includes an analytical dashboard that represents the anomaly status in log messages, facilitating informative monitoring for shifters. Through evaluation, including Infologger and BGL (BlueGene/L supercomputer), we analyze the effects of word embeddings, clustering algorithms, and HDBSCAN hyperparameters on model performance. The result demonstrates that the BERTopic can enhance the log anomaly detection process over traditional topic models, achieving remarkable performance metrics and attaining F1-scores of 0.957 and 0.958 for the InfoLogger and BGL datasets, respectively, even without the preprocessing technique. Full article

Timing measurements are critical for the detectors at the future HL-LHC, to resolve reconstruction ambiguity when the number of simultaneous interactions reaches up to 200 per bunch crossing. The ATLAS collaboration therefore builds a new High-Granularity Timing detector for the forward region. A customized ASIC, called ALTIROC, has been developed, to read out fast signals from low-gain avalanche detectors (LGADs), which has 50 ps time-resolution for signals from minimum-ionizing particles. To meet these requirements, a custom-designed pre-amplifier, a discriminator, and TDC circuits with minimal jitter have been implemented in a series of prototype ASICs. The latest version, ALTIROC3, is designed to contain full functionality. Hybrid assemblies with ALTIROC3 ASICs and LGAD sensors have been characterized with charged-particle beams at CERN-SPS and with laser-light injection. The time-jitter contributions of the sensor, pre-amplifier, discriminator, TDC, and digital readout are evaluated. Full article

In CERN’s beam transfer lines, high-voltage generators have traditionally relied on thyratron switches; however, thyratrons present operational challenges and are also becoming increasingly hard to source. To address this issue, there is a growing interest in adopting compact pulse generators made from commercially available off-the-shelf (COTS) components. Recent research has demonstrated that thyristors designed for rectifier applications, which are not specifically designed for fast rise times, can be activated in overvoltage mode—also referred to as impact-ionization mode. These devices achieve substantial improvements in their dU/dt and dI/dt characteristics. This activation method involves applying a substantial overvoltage between the thyristor’s anode and cathode, along with a fast slew rate exceeding 1 kV/ns. The adoption of compact pulse generators built from COTS components opens up new opportunities for deploying this technology across multiple domains, including high-speed kicker generators in particle accelerators. In our methodology, we incorporated commercially available high-voltage components—SiC MOSFETs—that were triggered using a fast gate driver, which was custom-designed. The generated output pulse was then amplified and sharpened in a four-stage Marx generator composed of small, $1.2$ kV rated D2PAK thyristors. This configuration yielded an output pulse with an amplitude of 11 kV and a 10–90% dU/dt of $13.3$ kV/ns. The present study details the design of the Marx generator and the resulting pulses, along with the challenges faced in high-voltage measurements. Full article