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Institution

CERN

FacilityGeneva, Switzerland
About: CERN is a(n) facility organization based out in Geneva, Switzerland. It is known for research contribution in the topic(s): Large Hadron Collider & Higgs boson. The organization has 33977 authors who have published 47112 publication(s) receiving 1738924 citation(s). The organization is also known as: European Organization for Nuclear Research.
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Journal ArticleDOI
Abstract: The forming limit diagram of high-purity niobium sheets used for the manufacturing of superconducting radiofrequency (SRF) cavities is presented. The Marciniak (in-plane) test was used with niobium blanks with a thickness of 1 mm and blank carriers of annealed oxygen-free electronic copper. A high formability was measured, with an approximate true major strain at necking for plane-strain of 0.441. The high formability of high-purity niobium is likely caused by its high strain rate sensitivity of 0.112. Plastic strain anisotropies (r-values) of 1.66, 1.00, and 2.30 were measured in the 0°, 45°, and 90° directions. However, stress–strain curves at a nominal strain rate of ~10−3 s−1 showed similar mechanical properties in the three directions. Theoretical calculations of the forming limit curves (FLCs) were conducted using an analytical two-zone model. The obtained results indicate that the anisotropy and strain rate sensitivity of niobium affect its formability. The model was used to investigate the influence of strain rate on strains at necking. The obtained results suggest that the use of high-speed sheet forming should further increase the formability of niobium.

Journal ArticleDOI
A. Onufrena1, A. Onufrena2, A. Onufrena3, T. Koettig3  +5 moreInstitutions (3)
Abstract: Compact high-effectiveness Counter Flow Heat EXchangers (CFHEX) are crucial components of recuperative coolers, such as Joule-Thomson and Turbo-Brayton coolers and of remote cooling systems realised by a convective loop. This paper presents a design and analysis of a cryocooler-based remote cooling system that extends the cooling capabilities of a two-stage cryocooler. Increased heat exchange between high- and low-pressure channels is established by adding copper mesh material. A compact effective mesh-based CFHEX design covering the 4.5-290 K temperature and 1–10 bar pressure operation ranges is presented. The discretised numerical model of the CFHEX is also presented and covers a wide field of parameters, including axial conduction, variable material and fluid properties based on experimental and theoretical data and wall-mesh thermal contact conductance. In our design the latter has shown to have a significant influence on the effectiveness of the CFHEX based on the analysis of a range of inner tube materials. The sizing of a high-performance CFHEX with a predicted effectiveness of 96.5 % (number of transfer units ( N T U )=27.6) and an accumulated pressure drop of 15 mbar using the model is demonstrated. The outlook for future work and experimental measurements of the parameters to complete the numerical model is presented.

Journal ArticleDOI
Robert Appleby1, Robert Appleby2, Roger Barlow3, Dirk Krucker  +7 moreInstitutions (5)
Abstract: Merlin++ is a C++ charged-particle tracking library developed for the simulation and analysis of complex beam dynamics within high energy particle accelerators . Accurate simulation and analysis of particle dynamics is an essential part of the design of new particle accelerators, and for the optimization of existing ones. Merlin++ is a feature-full library with focus on long-term tracking studies . A user may simulate distributions of protons or electrons in either single particle or sliced macro-particle bunches. The tracking code includes both straight and curvilinear coordinate systems allowing for the simulation of either linear or circular accelerator lattice designs, and uses a fast and accurate explicit symplectic integrator . Physics processes for common design studies have been implemented, including RF cavity acceleration, synchrotron radiation damping, on-line physical aperture checks and collimation , proton scattering , wakefield simulation, and spin-tracking. Merlin++ was written using C++ object orientated design practices and has been optimized for speed using multicore processors . This article presents an account of the program, including its functionality and guidance for use. Program summary Program Title: Merlin++ CPC Library link to program files: https://doi.org/10.17632/4x4nsbhz37.1 Developer's repository link: 10.5281/zenodo.3700155 Licensing provisions: GPLv2+ Programming language: C++ Nature of problem: Complexity of particle accelerators beam dynamics over extensive tracking distances. Solution method: Long-term particle accelerator and tracking simulations utilizing explicit symplectic integrators. Additional comments including restrictions and unusual features: For further information see github.com/Merlin-Collaboration

Journal ArticleDOI
Abstract: Leptoquarks (LQs) have attracted increasing attention within recent years, mainly since they can explain the flavor anomalies found in R ( D ( ⁎ ) ) , b → s l + l − transitions and the anomalous magnetic moment of the muon. In this article, we lay the groundwork for further automated analyses by presenting the complete Lagrangian and the corresponding set of Feynman rules for scalar leptoquarks. This means we consider the five representations Φ 1 , Φ 1 ˜ , Φ 2 , Φ 2 ˜ and Φ 3 and include the triple and quartic self-interactions, as well as couplings to the Standard Model (SM) fermions, gauge bosons and the Higgs. The calculations are performed using FeynRules and all model files are publicly available online at https://gitlab.com/lucschnell/SLQrules . Program summary Program Title: SLQrules CPC Library link to program files: https://doi.org/10.17632/sf8s89rhmv.1 Developer's repository link: https://gitlab.com/lucschnell/SLQrules Licensing provisions: CC By 4.0 Programming language: Mathematica, FeynRules Nature of problem: In order to explain the deviations from SM predictions in R ( D ( ⁎ ) ) , b → l + l − transitions and the muon AMM jointly, models involving multiple LQ representations are necessary. This significantly increases the number of possible interactions and creates the need for computational tools that allow for studying the phenomenology of these LQ models in an automated manner. While model files exist for each LQ representation individually [1], we are not aware of any publicly available model files that combine all scalar LQ representations as well as their self-interactions. Solution method: We implemented the complete scalar LQ Lagrangian in a FeynRules [2] model file and provide the corresponding MOD and UFO model files. These can be imported directly in FeynArts [3] and MadGraph [4] to obtain a versatile toolbox for the study of scalar LQs. References [1] I. Dorsner, A. Greljo, J. High Energy Phys. 05 (2018) 1-21. [2] A. Alloul, et al. Comput. Phys. Commun. 185 (2014) 2250-2300. [3] T. Hahn, Comput. Phys. Commun. 140 (2001) 418-431. [4] J. Alwall, et al., J. High Energy Phys. 07 (2014) 079.

1 citations


Journal ArticleDOI
David Schmid1, David Schmid2, B. Verlaat1, Paolo Petagna1  +2 moreInstitutions (3)
Abstract: A test facility to investigate flow pattern transitions of vertical two-phase flow of CO2 has been built within the scope of the high-luminosity detector upgrades at the European Organization for Nuclear Research (CERN). Adiabatic flow pattern observations for both vertical up- and downflow are recorded with high-speed imaging in tubes of 8 mm inner diameter, with saturation temperatures in the range of − 25 ° C to + 5 ° C and mass velocities ranging from 100 kg m − 2 s − 1 to 450 kg m − 2 s − 1 . A database of 431 flow pattern observations in upward and 123 in downward direction has been compiled. The recorded data have been analyzed with machine learning techniques and a previously trained Frame- and Flow-Regime-Classifier is used for the flow regime classification. The observed two-phase flow pattern transitions did not match the transition lines of existing flow pattern maps. As a consequence, new transition lines for the bubbly-to-slug, slug-to-churn and churn-to-annular transitions have been developed for both vertical upflow and downflow respectively and condensed into new flow pattern maps. It is concluded, that the flow regime transitions are strongly depended on vapour quality, mass velocity, the flow direction and the fluid properties. Compared to horizontal flow, a dryout region is not observed and the liquid film of the annular flow regime dries out symmetrically at vapour qualities close to x = 1 .

Authors

Showing all 33977 results

NameH-indexPapersCitations
Yi Chen2174342293080
David Miller2032573204840
Edward Witten202602204199
Martin White1962038232387
Michael A. Strauss1851688208506
Jing Wang1844046202769
H. S. Chen1792401178529
Chris Sander178713233287
Jie Zhang1784857221720
Jasvinder A. Singh1762382223370
D. M. Strom1763167194314
Hyun-Chul Kim1764076183227
J. N. Butler1722525175561
Andrea Bocci1722402176461
Sophie Henrot-Versille171957157040
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202211
20211,273
20201,721
20191,713
20181,534
20171,589