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Structure of Hydrocarbon Fluid and Couette Flows in Slit Pores with Pyrophyllite Walls
No full textInternational audienceThe process of Couette flow of a hydrocarbon liquid in the slit pores has been simulated and the dynamics of the liquid molecules ordering depending on the liquid density and the slit size has been investigated by means of molecular dynamics. Statistical analysis of the resulting regions of ordered molecules of the hydrocarbon fluid has indicates that the wall material and the liquid viscosity affect the size of such regions
Synthesis of Fukushima Daiichi Cs-bearing microparticles through molten core-concrete interaction in nitrogen atmosphere
No full textInternational audienceCs-bearing microparticles, released during the accident of Fukushima Daiichi, are a significant concern for health and environment due to their abundance on wide areas, associated with a low solubility. Since their discovery, efforts have been made to characterise these particles and use them as direct witnesses of the various events inside the reactors. This study reports the experimental synthesis of micrometric particles through molten core-concrete interaction. Primary chemical analyses on Al/Si, K/Si and Na/Si atomic ratios seem to confirm concrete as source of Si. Cs has also been identified in low concentrations
Exploring the NΛ–NΣ coupled system with high precision correlation techniques at the LHC
No full textInternational audienceThe interaction of Λ and Σ hyperons (Y) with nucleons (N) is strongly influenced by the coupled-channel dynamics. Due to the small mass difference of the NΛ and NΣ systems, the sizable coupling strength of the NΣ↔NΛ processes constitutes a crucial element in the determination of the NΛ interaction. In this letter we present the most precise measurements on the interaction of pΛ pairs, from zero relative momentum up to the opening of the NΣ channel. The correlation function in the relative momentum space for pΛ⊕p‾Λ‾ pairs measured in high-multiplicity triggered pp collisions at s=13 TeV at the LHC is reported. The opening of the inelastic NΣ channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum k⁎=289MeV/c. This represents the first direct experimental observation of the NΣ↔NΛ coupled channel in the pΛ system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the NΣ↔NΛ transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NNΛ interaction for a proper description of the Λ in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars
Long range plans to study the nuclear equation-of-state from sub- to supra-saturation densities with heavy-ion collisions
No full textInternational audienceWe cover here the present state-of-the-art in constraining the nuclear equation-of-state (EoS) and the symmetry energy using heavy-ion collisions (HIC), from sub- to supra-saturation densities, from Fermi to (ultra-) relativistic beam energies. We also discuss how HIC constraints on the EoS contribute to the knowledge of thermodynamical properties of neutron star matter. Necessary improvements and challenges are outlined, in particular in the perspective, for HICs, of staying competitive with future astrophysical multimessenger observations
Predictions for the sPHENIX physics program
No full textInternational audiencesPHENIX is a next-generation detector experiment at the Relativistic Heavy Ion Collider, designed for a broad set of jet and heavy-flavor probes of the Quark-Gluon Plasma created in heavy ion collisions. In anticipation of the commissioning and first data-taking of the detector in 2023, a RIKEN-BNL Research Center (RBRC) workshop was organized to collect theoretical input and identify compelling aspects of the physics program. This paper compiles theoretical predictions from the workshop participants for jet quenching, heavy flavor and quarkonia, cold QCD, and bulk physics measurements at sPHENIX
Hadronic Interactions Studies at the LHC
No full textInternational audienceThe deficit of muons in the simulation of extensive air showers is a long-standing problem and the origin of large uncertainties in the reconstruction of the mass of the high-energy primary cosmic rays. Hadronic interaction models re-tuned after early LHC data have a more consistent description of the muon content among them but still disagree with the data. Furthermore, some inconsistencies are also visible in the electromagnetic component. Ten years after the first LHC-tuned model release, much more detailed data are available both from LHC, SPS and hybrid air shower measurements, allowing for the understanding of some deficiencies in the model which could lead to a change in both Xmax and the muon production by air showers. A better treatment of the core-corona approach according to LHC data has important consequences on the muon production while an update of diffraction and nuclear fragmentation is changing the Xmax distribution. An updated version of EPOS LHC will be presented addressing the main issues of this model
Cryogenic bath-type heat exchangers for ultra-pure noble gas applications
No full textInternational audienceTwo cryogenic bath-type heat exchangers for ultra-pure noble gas applications were developed with particular emphasis on noble gas liquefaction in cryogenic distillation systems. The main objective was to construct heat exchangers for xenon from materials that do not emanate radon and that fulfill ultra-high vacuum standards. Therefore, only high-quality copper and stainless steel materials were used. Especially, large-area oxygen-free copper fins with high conductivity in a new design ensure efficient heat transfer. One bath-type Xe-Xe heat exchanger was designed with a diameter of 50 cm to achieve a xenon condensing capacity of at least 100 kg/h. In order to guarantee the necessary heat transfer between the two xenon reservoirs, this heat exchanger features a specially manufactured stainless steel flange with a copper plate welded inside. We first tested our concept on a dedicated bath-type heat exchanger with a reduced diameter of 30 cm using liquid nitrogen to liquefy the xenon. A model based on conservative assumptions such as film boiling on the nitrogen side and film condensation on the xenon side was developed and applied to caluclate the expected heat transfer for our design. We were able to demonstrate an adjustable xenon liquefaction rate of up to 113 kg/h limited only by our measurement procedure at a cooling efficiency of (0.98 ± 0.03) for the LN-Xe heat exchanger
Molecular-level understanding of metal ion retention in clay-rich materials
No full textInternational audienceClay minerals retain or adsorb metal ions in the Earth’s critical zone. Rocks, sediments and soils rich in clay minerals can concentrate rare earth elements (REEs) in ion adsorption-type deposits (IADs) and are similarly effective at metallic contaminant remediation. However, the molecular-scale chemical and physical mechanisms of metal ion retention remain only partly understood. In this Review, we describe the nature, location and energy requirements of metal retention at clay mineral surfaces. Retention originates mainly from electrostatic interactions during cation exchange at low pH and chemical bonding in surface complexation and precipitation at neutral and high pH. Surface complexation can induce surface redox reactions and precipitation mechanisms including neoformation of clay mineral layered structures. In IADs, outer-sphere adsorption is the major retention mechanism of REE ions. By contrast, the use of clay minerals in pollution control relies on various mechanisms that can coexist, including cation exchange, surface complexation and nucleation growth. To more effectively leverage clay mineral–metal interactions in resource recovery and contaminant remediation, complex mechanisms such as surface precipitation and redox reactions must be better understood; for instance, by utilizing advances in quantum mechanical calculations, close combination between synchrotron and simulation techniques, and upscaling of molecular-level information in macroscopic thermokinetic predictive models
