European Particle Physics Laboratory Research Articles

A year of celebration of 70 years of CERN

On 30 January CERN, the European Laboratory for Particle Physics, kicked off a yearlong programme to celebrate its 70th anniversary in 2024.

고온초전도 자석 개발을 위한 진공에서의 절연파괴 특성 분석

The high-temperature superconducting (HTS) magnet used in particle accelerators for cancer treatment exhibits a large current change for a short period of time due to its fast ramp-up characteristics, which results in high voltage and instant vulnerability to electrical insulation. This research introduces the saddle-coil, which, due to its complex shape and small bending radius, allows for the local concentration of electric field intensity. Reports from the European particle physics laboratory, CERN have revealed dielectric breakdown due to 1000V between layers during low-temperature superconducting (LTS) magnet experiments for accelerators, yet no research has been conducted to solve this problem. HTS magnets operating in vacuum may be susceptible to electrical breakdown due to high induced voltage and local quench due to rapid-ramp characteristics. Therefore, this paper deals with the dielectric characteristics of vacuum to develop an electrically stable HTS magnet. Specifically, dielectric experiments on penetration and creepage discharge were conducted under various vacuum conditions, and empirical formulae for calculating the electric field intensity at sparkover for the insulation design of HTS magnets was derived.

Experimental characterization of cyclic behaviour of pure lead: Temperature sensitivity and strain-rate effects

Proton beam pulses with an energy of 20 GeV/c collide with a pure-lead based target installed in the neutron Time-Of-Flight facility (n_TOF) at the European Laboratory for Particle Physics (CERN). The interaction between the proton beam and lead produces neutrons via spallation mechanism and results in a rapid temperature increase and propagation of stress waves. To evaluate the material response in such challenging conditions, a reliable thermo-mechanical characterization is necessary for the calibration of an appropriate constitutive model for pure lead that is valid under cyclic plasticity and high temperature. In this work, the experimental bases for the development of such constitutive material description are lied. Starting with metallurgical characterization, the typical grain size of the material was initially investigated as well as any variations in the metallurgical features. The grains appeared to have an equivalent size ranging from 2 to 6 mm. Then, static tensile tests were conducted at room temperature and different strain-rates from 10−1 to 10−4 s−1. The obtained results were crucial for optimizing the specimen geometry and test setup for the subsequent cyclic tests. Tension-compression cyclic tests were performed at different strain amplitudes from 0.1 to 1.5%, and at three different temperatures (room temperature, 90 °C and 150 °C). The strain amplitudes were controlled by an extensometer and the strain field evolution during the test was recorded by means of 2D DIC.

Design, testing, commissioning, and early operation of the third-generation n_TOF neutron spallation target at CERN

The n_TOF facility at the European Laboratory for Particle Physics (CERN) is a top-class, high-brightness neutron spallation source dedicated to high-resolution neutron time-of-flight experiments. During CERN’s Long Shutdown 2 (LS2, 2019-2021), the facility’s neutron spallation target was upgraded and is now operating with its third-generation target. The target is based on a pure-Pb core cooled by gaseous nitrogen and has been designed to withstand the impact of a 20-GeV/c proton beam in bunches of 1013 protons with a bunch duration of 6-8 ns RMS. The produced neutrons span 11 orders of magnitude in kinetic energy (from thermal to GeV) and are delivered to two experimental areas and a neutron irradiation station near the target. This contribution includes a description of the physics and engineering design processes that brought the facility from its second-generation target to its current third-generation target, the planned autopsy of the second-generation target in 2023 to investigate its status after 10 years of operation, tests under beam irradiation carried out on target prototypes at CERN’s HiRadMat facility, and the commissioning with beam of the new target, as well as the challenges encountered during the first year of its operation.

Selection of radiation tolerant commercial greases for high-radiation areas at CERN: Methodology and applications

At the European Laboratory for Particle Physics (CERN), commercial greases and oils are extensively used to lubricate moving devices operating in high-radiation areas, absorbing doses up to the MGy range. Due to their sensitivity to radiation, lubricants can become fluid or solid in operation, potentially causing component failures and compromising the operation of the accelerator complex. CERN is therefore developing methodologies to select radiation tolerant commercial lubricants for critical Beam Intercepting Devices (BIDs) such as high-power targets, dumps and collimators. A careful selection of greases is fundamental to reduce the risk of failure, to optimize equipment lifetime and to minimize maintenance and unwanted radiation exposure of personnel in high radiation areas. Three different parameters are considered to select commercial lubricants: the expected total dose absorbed in operation, the maintenance feasibility and the failure impact in terms of accelerator downtime and of personnel involvement in replacement procedures. Based on these criteria, an example of relevant application is presented: the lubrication of the new internal beam dump of the Super Proton Synchrotron (SPS). Experimental radiation damage data allowed the identification of two radiation tolerant commercial greases to lubricate the dump support jack assembly.

Biodiversity Literature Repository: Building the customized FAIR repository by using custom metadata

In the landscape of general-purpose repositories, Zenodo was built at the European Laboratory for Particle Physics' (CERN) data center to facilitate the sharing and preservation of the long tail of research across all disciplines and scientific domains. Given Zenodo’s long tradition of making research artifacts FAIR (Findable, Accessible, Interoperable, and Reusable), there are still challenges in applying these principles effectively when serving the needs of specific research domains. Plazi’s biodiversity taxonomic literature processing pipeline liberates data from publications, making it FAIR via extensive metadata, the minting of a DataCite Digital Object Identifier (DOI), a licence and both human- and machine-readable output provided by Zenodo, and accessible via the Biodiversity Literature Repository community at Zenodo. The deposits (e.g., taxonomic treatments, figures) are an example of how local networks of information can be formally linked to explicit resources in a broader context of other platforms like GBIF (Global Biodiversity Information Facility). In the context of biodiversity taxonomic literature data workflows, a general-purpose repository’s traditional submission approach is not enough to preserve rich metadata and to capture highly interlinked objects, such as taxonomic treatments and digital specimens. As a prerequisite to serve these use cases and ensure that the artifacts remain FAIR, Zenodo introduced the concept of custom metadata, which allows enhancing submissions such as figures or taxonomic treatments (see as an example the treatment of Eurygyrus peloponnesius) with custom keywords, based on terms from common biodiversity vocabularies like Darwin Core and Audubon Core and with an explicit link to the respective vocabulary term. The aforementioned pipelines and features are designed to be served first and foremost using public Representational State Transfer Application Programming Interfaces (REST APIs) and open web technologies like webhooks. This approach allows researchers and platforms to integrate existing and new automated workflows into Zenodo and thus empowers research communities to create self-sustained cross-platform ecosystems. The BiCIKL project (Biodiversity Community Integrated Knowledge Library) exemplifies how repositories and tools can become building blocks for broader adoption of the FAIR principles. Starting with the above literature processing pipeline, the concepts of and resulting FAIR data, with a focus on the custom metadata used to enhance the deposits, will be explained.

Design of the third-generation lead-based neutron spallation target for the neutron time-of-flight facility at CERN

The neutron time-of-flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a pulsed white-spectrum neutron spallation source producing neutrons for two experimental areas: the Experimental Area 1 (EAR1), located 185 m horizontally from the target, and the Experimental Area 2 (EAR2), located 20 m above the target. The target, based on pure lead, is impacted by a high-intensity 20-GeV/c pulsed proton beam. The facility was conceived to study neutron-nucleus interactions for neutron kinetic energies between a few meV to several GeV, with applications of interest for nuclear astrophysics, nuclear technology, and medical research. After the second-generation target reached the end of its lifetime, the facility underwent a major upgrade during CERN's Long Shutdown 2 (LS2, 2019-2021), which included the installation of the new third-generation neutron target. The first and second-generation targets were based on water-cooled massive lead blocks and were designed focusing on EAR1, since EAR2 was built later. The new target is cooled by nitrogen gas to avoid erosion-corrosion and contamination of cooling water with radioactive lead spallation products. Moreover, the new design is optimized also for the vertical flight path and EAR2. This paper presents an overview of the target design focused on both physics and thermo-mechanical performance, and includes a description of the nitrogen cooling circuit and radiation protection studies.

A Vertex-Aligned Model for Packing 4-Hexagonal Clusters in a Regular Hexagonal Container

This paper deals with a problem the packing polyhex clusters in a regular hexagonal container. It is a common problem in many applications with various cluster shapes used, but symmetric polyhex is the most useful in engineering due to its geometrical properties. Hence, we concentrate on mathematical modeling in such an application, where using the “bee” tetrahex is chosen for the new Compact Muon Solenoid (CMS) design upgrade, which is one of four detectors used in Large Hadron Collider (LHC) experiment at European Laboratory for Particle Physics (CERN). We start from the existing hexagonal containers with hexagonal cells packed inside, and uniform clustering applied. We compare the center-aligned (CA) and vertex-aligned (VA) models, analyzing cluster rotations providing the increased packing efficiency. We formally describe the geometrical properties of clustering approaches and show that cluster sharing is inevitable at the container border with uniform clustering. In addition, we propose a new vertex-aligned model decreasing the number of shared clusters in the uniform scenario, but with a smaller number of clusters contained inside the container. Also, we describe a non-uniform tetrahex cluster packing scheme in the proposed container model. With the proposed cluster packing solution, it is accomplished that all clusters are contained inside the container region. Since cluster-sharing is completely avoided at the container border, the maximal packing efficiency is obtained compared to the existing models.

Design of the third-generation neutron spallation target for the CERN’s n_TOF facility

The neutron Time-Of-Flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a pulsed white-spectrum neutron spallation source producing neutrons for two experimental areas: EAR1, located 185 m downstream of the spallation target, and EAR2, located 20 m above the target. The facility is based on a lead target impacted by a high-intensity 20 GeV/c proton beam. It is designed to study neutron-nucleus interactions for neutron kinetic energies from a few meV to several GeV, with applications in nuclear astrophysics, nuclear technology, and medical research. The facility is undergoing a major upgrade in 2019–2020, which will include the installation of the new third-generation target. The second-generation target consists in a water-cooled lead cylinder, while the new target will be cooled by nitrogen to avoid erosion-corrosion phenomena and contamination of the cooling water with radioactive lead spallation products. The new design will be optimized also for the vertical flight path. The operation of the new spallation target will start in 2021. This paper presents an overview on the evolution of the design and on the related R&D activities (including beam irradiation tests) carried out to ensure the best performance for both experimental areas and avoid the contamination issues of the previous targets.

Flexible graphite as beam dumping material in the TDE blocks of the Large Hadron Collider

The Large Hadron Collider (LHC) is a high energy particle collider at the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland. The LHC Beam Dumping System (LBDS) is composed by different equipment employed to extract and absorb the LHC circulating beam in case of need. At the end of the LBDS resides the LHC main dump (so called TDE, which stands for Target Dump External). The TDE block is constituted by several graphite blocks with different densities enclosed in a 318L stainless steel jacket. Among the different type of carbon-based materials, the flexible graphite is the one owning the lowest density (1-1.2 g/cm3). It differs from typical graphite forms such as polycrystalline and pyrolytic graphite in that no binder is added during the production process. The bonding frictional forces due to particle asperities give the typical flexibility to the material and contribute to the deformation mechanism. In order to predict the thermo-mechanical response to the proton beam-induced sudden energy deposition, the material behavior needs to be investigated in-depth in a wide range of temperature and strain-rates. In this preliminary work, the static properties of a commercial flexible graphite (Sigraflex® from SGL Carbon) have been observed at room temperature in the in-plane direction. Two sides DIC technique has been employed in order to get a reliable measurement of the strain on both front and edge specimen surfaces; the crosshead displacement-rate was varied between 0.01-10 mm/min. Finally, a discussion about the stress-strain behavior and the deformation mechanism has been given.

Application of hot isostatic pressing (HIP) technology to diffusion bond refractory metals for proton beam targets and absorbers at CERN

A target assembly, composed of several collinear molybdenum (Mo)-based and tungsten (W)-based cylindrical blocks, will reside in the core of the new beam dump facility (BDF) being designed at the European Laboratory for Particle Physics (CERN). The target blocks will be protected from the cooling water erosion-corrosion by a tantalum (Ta)-based cladding. In order to obtain intimate and reliable bonding between the several cylinders composing each target block and with the cladding, hot isostatic pressing (HIP) assisted diffusion bonding technique was explored. Several down-scaled target block prototypes were conceived to investigate the bondings. Starting from the previously gained experience in Ta cladding on W from neutron spallation targets, here, we present results on Ta cladding on TZM (Mo alloy), Ta2.5W (Ta alloy) cladding on TZM and W, and on TZM to TZM and W to W self-bondings. The resulting interfaces were systematically characterized with electron microscopy, tensile testing, and thermal conductivity measurements. Successful diffusion bonding was achieved for all the studied material combinations, resulting in homogeneous and defect-free interfaces, strong interfacial bondings, and limited interfacial thermal contact resistance. The HIP parameters and diffusion interfacial aids were of great importance to optimize the interface and bulk material properties.

Review of Particle Physics

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,873 new measurements from 758 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 118 reviews are many that are new or heavily revised, including a new review on Neutrinos in Cosmology. Starting with this edition, the Review is divided into two volumes. Volume 1 includes the Summary Tables and all review articles. Volume 2 consists of the Particle Listings. Review articles that were previously part of the Listings are now included in volume 1. The complete Review (both volumes) is published online on the website of the Particle Data Group (http://pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is also available. The 2018 edition of the Review of Particle Physics should be cited as: M. Tanabashi et al. (Particle Data Group), Phys. Rev. D 98, 030001 (2018).Received 31 July 2018DOI:https://doi.org/10.1103/PhysRevD.98.030001© 2018 Regents of the University of California*The publication of the Review of Particle Physics is supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, the Division of High Energy Physics of the U.S. Department of Energy under Contract No. DE–AC02–05CH11231; by the U.S. National Science Foundation under Agreement No. PHY-0652989; by the European Laboratory for Particle Physics (CERN); by an implementing arrangement between the governments of Japan (MEXT: Ministry of Education, Culture, Sports, Science and Technology) and the United States (DOE) on cooperative research and development; and by the Italian National Institute of Nuclear Physics (INFN).Physics Subject Headings (PhySH)Research AreasParticle phenomenaPhysical SystemsBaryonsHypothetical particlesLeptonsMesonsPropertiesParticle propertiesTechniquesParticle data analysisParticles & Fields

Antiproton physics in the ELENA era.

The programme of physics with low-energy antiprotons at CERN, the European Particle Physics Laboratory, has a long history, beginning with the inauguration of the Low Energy Antiproton Ring (LEAR) in 1982 [1]. That machine produced antiprotons decelerated to kinetic energies of a few MeV, an achievement made possible due to advances in techniques that enabled cooling of charged particles held in storage rings [2,3]. Pioneering experiments to trap and cool antiprotons to meV energies were carried out at LEAR [4,5] and a landmark achievement was reached in 1995, when the first nine atoms of antihydrogen were observed by the PS210 experiment [6]. A short lapse in the availability of low-energy antiprotons followed this success, as LEAR …

EL CERN CUMPLE 60 AÑOS

In 2014 they have reached 60 years of the creation of CERN (European Organization for Nuclear Research or European Laboratory for Particle Physics in Geneva, Switzerland), the largest research center in the world in fundamental physics.

Radiation protection challenges in the management of radioactive waste from high-energy accelerators.

The European Laboratory for Particle Physics (CERN) has operated high-energy accelerators for fundamental physics research for nearly 60 y. The side-product of this activity is the radioactive waste, which is mainly generated as a result of preventive and corrective maintenance, upgrading activities and the dismantling of experiments or accelerator facilities. Prior to treatment and disposal, it is common practice to temporarily store radioactive waste on CERN's premises and it is a legal requirement that these storage facilities are safe and secure. Waste treatment typically includes sorting, segregation, volume and size reduction and packaging, which will depend on the type of component, its chemical composition, residual activity and possible surface contamination. At CERN, these activities are performed in a dedicated waste treatment centre under the supervision of the Radiation Protection Group. This paper gives an overview of the radiation protection challenges in the conception of a temporary storage and treatment centre for radioactive waste in an accelerator facility, based on the experience gained at CERN. The CERN approach consists of the classification of waste items into 'families' with similar radiological and physical-chemical properties. This classification allows the use of specific, family-dependent techniques for radiological characterisation and treatment, which are simultaneously efficient and compliant with best practices in radiation protection. The storage was planned on the basis of radiological and other possible hazards such as toxicity, pollution and fire load. Examples are given of technical choices for the treatment and radiological characterisation of selected waste families, which could be of interest to other accelerator facilities.

A possible biomedical facility at the European Organization for Nuclear Research (CERN)

A well-attended meeting, called "Brainstorming discussion for a possible biomedical facility at CERN", was held by the European Organization for Nuclear Research (CERN) at the European Laboratory for Particle Physics on 25 June 2012. This was concerned with adapting an existing, but little used, 78-m circumference CERN synchrotron to deliver a wide range of ion species, preferably from protons to at least neon ions, with beam specifications that match existing clinical facilities. The potential extensive research portfolio discussed included beam ballistics in humanoid phantoms, advanced dosimetry, remote imaging techniques and technical developments in beam delivery, including gantry design. In addition, a modern laboratory for biomedical characterisation of these beams would allow important radiobiological studies, such as relative biological effectiveness, in a dedicated facility with standardisation of experimental conditions and biological end points. A control photon and electron beam would be required nearby for relative biological effectiveness comparisons. Research beam time availability would far exceed that at other facilities throughout the world. This would allow more rapid progress in several biomedical areas, such as in charged hadron therapy of cancer, radioisotope production and radioprotection. The ethos of CERN, in terms of open access, peer-reviewed projects and governance has been so successful for High Energy Physics that application of the same to biomedicine would attract high-quality research, with possible contributions from Europe and beyond, along with potential new funding streams.

Review of Particle Physics

This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2658 new measurements from 644 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 112 reviews are many that are new or heavily revised including those on Heavy-Quark and Soft-Collinear Effective Theory, Neutrino Cross Section Measurements, Monte Carlo Event Generators, Lattice QCD, Heavy Quarkonium Spectroscopy, Top Quark, Dark Matter, Vcb & Vub, Quantum Chromodynamics, High-Energy Collider Parameters, Astrophysical Constants, Cosmological Parameters, and Dark Matter. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov/. The 2012 edition of Review of Particle Physics is published for the Particle Data Group as article 010001 in volume 86 of Physical Review D. This edition should be cited as: J. Beringer et al. (Particle Data Group), Phys. Rev. D 86, 010001 (2012).Received 18 July 2012DOI:https://doi.org/10.1103/PhysRevD.86.010001© 2012 Regents of the University of California*The publication of the Review of Particle Physics is supported by the Director, Office of Science, Office of High Energy and Nuclear Physics, the Division of High Energy Physics of the U.S. Department of Energy under Contract No. DE–AC02–05CH11231; by the U.S. National Science Foundation under Agreement No. PHY-0652989; by the European Laboratory for Particle Physics (CERN); by an implementing arrangement between the governments of Japan (MEXT: Ministry of Education, Culture, Sports, Science and Technology) and the United States (DOE) on cooperative research and development; and by the Italian National Institute of Nuclear Physics (INFN).

Higgs Boson Makes Its Debut After Decades-Long Search

Last week's announcement that physicists at the European particle physics laboratory, CERN, had discovered the Higgs boson could mark the end of the road for particle physics.

The Large Hadron Collider project: organizational and financial matters (of physics at the terascale)

In this paper, I present a view of organizational and financial matters relevant for the successful construction and operation of the experimental set-ups at the Large Hadron Collider of CERN, the European Laboratory for Particle Physics in Geneva. Construction of these experiments was particularly challenging: new detector technologies had to be developed; experimental set-ups that are larger and more complex than ever before had to be constructed; and larger collaborations than ever before had to be organized. Fundamental to the success were: the 'reference' provided by CERN, peer review, signed memoranda of understanding, well-organized resources review boards as an interface to the national funding agencies and collegial, but solidly organized, experimental collaborations.

Measurement system for evaluation of the muon chambers for the LHCb experiment

Abstract In a detector with the complexity of the LHCb, where only for the muon system more than 1300 chambers, divided into 20 different types, will be used, resulting on more than 120 k channels to be readout, it is of crucial importance to study the many types of chambers to create a complete knowledge of the detector operation and to guarantee a high-quality performance during the experiment. To make it possible, a complete setup was built and a C++ based software was developed to carry out a set of measurements on the full-equipped chambers of the LHCb muon detector. The setup is made of front-end control electronics, high-voltage supply and acquisition circuitry while the software, running on a PC, remotely controls each element of the system and implements a number of automatized procedures to assess the main characteristics of the chambers. The main advantages of this system are its versatility and speed of measurement which are crucial to the experiment since there is the need to characterize every single chamber before final installation. Moreover, in this work it was proposed to measure the starting knee of the high-voltage operational plateau without the use of an external trigger by making use of the internal structure of the chambers. Two laboratories were prepared at CERN (European Laboratory for Particle Physics) to receive this system; one used to test chambers arrived from the CERN itself and the PNPI (Petersburg Nuclear Physics Institute) production sites, and one to test the chambers arrived from the INFN (National Institute of Nuclear Physics) production sites. In this document, the hardware and software setup will be presented together with the measurement-oriented implementations.