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In Memoriam: Carlo Guaraldo (1938–2024)
No full textInternational audienceIt is with profound sadness that we announce the passing of Professor Carlo Guaraldo from Istituto Nazionale di Fisica Nucleare (INFN), Frascati National Laboratories, on 19 May 2024, in Rome
Le LIBD, pour une quantification hautement sensible de nanoparticules en milieux aquatiques
No full textInternational audienceAll natural aquatic systems contain nanoparticles which can be inorganic, organic or even include microorganisms. The quantification of these nanoparticles presents considerable difficulties as they are often present at very low concentrations and with a predominance of the size distribution over small diameters (< 100 nm). The methods traditionally used for their characterization are based on separation and/or fractionation (Ultrafiltration, Ultracentrifugation, Size-Exclusion Chromatography, Flow Field Fractionation…) but also on Static and Dynamic Light Scattering methods. However, these techniques have important limitations: separation and fractionation interfere with the colloidal system and easily lead to changes in the colloidal population (coagulation, sorption and precipitation) while Light Scattering has relatively high detection limits for particles with an average diameter of less than about 100 nm.Alongside these techniques, LIBD (originally invented to monitor ultrapure water in the semiconductor industry) was rapidly used and improved for the detection and characterization of synthetic or natural aquatic nano-colloids.Tous les systèmes aquatiques naturels contiennent des nanoparticules qui peuvent être inorganiques, organiques et même inclure des micro-organismes. Leur quantification présente des difficultés considérables car elles sont souvent présentes à de très faibles concentrations et avec une prédominance de la distribution de taille sur les petits diamètres (< 100 nm). Les méthodes, traditionnellement utilisées pour leur caractérisation, sont basées sur la séparation et/ou le fractionnement (ultrafiltration, ultracentrifugation, chromatographie d'exclusion de taille, fractionnement en champ libre...) mais aussi sur des méthodes de diffusion statique et dynamique de la lumière.Cependant, ces techniques présentent des limitations importantes : la séparation et le fractionnement interfèrent avec le système colloïdal et conduisent facilement à des changements dans la population colloïdale (coagulation, sorption et précipitation) tandis que la diffusion de la lumière a des limites de détection relativement élevées pour les particules dont le diamètre moyen est inférieur à 100 nm.Parallèlement à ces techniques, le « Laser Induced Breakdown Detection » ou LIBD (inventé à l'origine pour le contrôle de l'eau ultrapure dans l'industrie des semi-conducteurs) a rapidement servi et été perfectionné pour la détection et la caractérisation des nano-colloïdes synthétiques ou naturels en milieu aquatique
Production cross section measurements of the natNi(d,x)61Cu reaction
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Proton-induced reactions for Sc (and Sc) production: new nuclear cross section measurements on enriched titanium targets
No full textInternational audienceSc is a theranostic radionuclide under the spotlight of the scientific community thanks to its potential for SPECT imaging and therapeutic applications. This work presents the recent measurements of proton-induced nuclear reaction cross-sections aimed at Sc production using enriched Ti, Ti and Ti targets from 23 up to 70 MeV. Since the co-production of contaminant isotopes is a key issue, and Sc is the main one having a longer half-life than Sc, the Ti(p,x)Sc and Sc cross sections are presented and compared with the scarce literature data and TALYS estimations
Unveiling the origins and transport processes of radioactive pollutants downstream from a former U-mine site using isotopic tracers and U-238 series disequilibrium
No full textInternational audienceHigh U concentrations (reaching up to 14,850 mg ⋅ kg−1), were determined in soils and sediments of a wetland downstream of a former U mine in France. This study aims to identify the origin of radioactive contaminants in the wetland by employing Pb isotope fingerprinting, (234U/238U) disequilibrium, SEM, and SIMS observations. Additionally, information about U and 226Ra transport processes was studied using U-238 series disequilibrium. The results of Pb fingerprinting highlighted inherited material inputs of different U-mines with mainly two types of U-ores: i) pitchblende (UO2), and ii) parsonsite (Pb2(UO2)(PO4)2). Moreover, significant disequilibrium of (230Th/238U) and (226Ra/230Th) activity ratios highlighted the mobility of 238U and 226Ra in the wetland, primarily driven by the water table fluctuations. Finally, this work uncovered a limitation of Pb isotope fingerprinting in the case of parsonsite materials, as the high natural Pb content of this mineral may hide the uranogenic Pb signature in the samples
The CCube reconstruction algorithm for the SoLid experiment
No full textInternational audienceThe SoLid experiment is a very-short-baseline experiment aimed at searching for nuclear reactor-produced active to sterile antineutrino oscillations. The detection principle is based on the pairing of two types of solid scintillators: polyvinyl toluene and LiF:ZnS(Ag), which is a new technology used in this field of Physics. In addition to good neutron-gamma discrimination, this setup allows the detector to be highly segmented (the basic detection unit is a 5 cm side cube). High segmentation provides numerous advantages, including the precise location of Inverse Beta Decay (IBD) products, the derivation of the considerate antineutrino energy estimator, and a powerful background reduction tool based on the topological signature of the signal. Finally, the system is read out by a network of wavelength-shifting fibres coupled to a photodetector (MPPC). This paper describes the design of the reconstruction algorithm that allows maximum use of the granularity of the detector. The goal of the algorithm is to convert the output of the optical-fibre readout to the list of the detection units from which it originated. This paper provides a performance comparison for three methods and concludes with a choice of the baseline approach for the experiment
Simulant molten core–concrete interaction experiments in view of understanding Fukushima Daiichi Nuclear Power Station Cs-bearing particles generation mechanism
No full textInternational audienceThe Fukushima Daiichi accident resulted in the release of a novel form of radioactive Cs contamination into the environment, called Cs-bearing microparticles (CsMP). CsMPs constitute a substantial portion of the radioactive pollution near the nuclear power station and traveled beyond several hundred kilometers. Extensive characterization of the CsMPs revealed an amorphous silica matrix, along with Cs and other minor or trace elements such as Fe and Zn. This study explores the unclear generation mechanism of CsMPs by conducting experimental molten core concrete interactions (MCCI) as a source of Si and analyzing the resultant aerosols. The findings demonstrate that MCCI is in capacity to produce spherical submicronic and micronic particles, primarily composed of amorphous silica and incorporating elements akin to CsMPs. A humid atmosphere is found to favour an even closer chemical composition. Examination of the internal structure of the synthesized particles unveils pores and numerous crystalline nanoinclusions possibly serving as nucleation sites for CsMP formation through the condensation of Si-rich vapors
Measurement of beauty-quark production in pp collisions at TeV via non-prompt D mesons
No full textInternational audienceThe -differential production cross sections of non-prompt , , and mesons originating from beauty-hadron decays are measured in protonproton collisions at a centre-of-mass energy of 13 TeV. The measurements are performed at midrapidity, , with the data sample collected by ALICE from 2016 to 2018. The results are in agreement with predictions from several perturbative QCD calculations. The fragmentation fraction of beauty quarks to strange mesons divided by the one to non-strange mesons, , is found to be . This value is compatible with previous measurements at lower centre-of-mass energies and in different collision systems in agreement with the assumption of universality of fragmentation functions. In addition, the dependence of the non-prompt D meson production on the centre-of-mass energy is investigated by comparing the results obtained at and 13 TeV, showing a hardening of the non-prompt D-meson -differential production cross section at higher . Finally, the production cross section per unit of rapidity at midrapidity is calculated from the non-prompt , , , and hadron measurements, obtaining ${\rm d}\sigma/{\rm d}y = 75.2\pm 3.2~(\mathrm{stat.}) \pm 5.2~(\mathrm{syst.})^{+12.3}_{-3.2} ~(\mathrm{extrap.})\text{ } \rm \mu b \;.
Is the protactinium(V) mono-oxo bond weaker than what we thought?
No full textInternational audienceThe bond distance is the simplest and most obvious indicator of the nature of a given chemical bond. However, for rare chemistry, it may happen that it is not yet firmly established. In this communication, we will show that the formally-triple protactinium(V) mono-oxo bond is predicted longer than what was previously reported in the solid state and in solution, based on robust quantum mechanical calculations, supported by an extensive methodological study. Furthermore, additional calculations are used to demonstrate that the Pa-Ooxo bond of interest is more sensitive to complexation than the supposedly analogous U-Oyl ones, not only in terms of bond distance but also of finer bond descriptors associated with the effective bond multiplicity
Observation of Gravitational Waves from the Coalescence of a Compact Object and a Neutron Star
No full textInternational audienceWe report the observation of a coalescing compact binary with component masses and (all measurements quoted at the 90% credible level). The gravitational-wave signal GW230529_181500 was observed during the fourth observing run of the LIGO-Virgo-KAGRA detector network on 2023 May 29 by the LIGO Livingston Observatory. The primary component of the source has a mass less than at 99% credibility. We cannot definitively determine from gravitational-wave data alone whether either component of the source is a neutron star or a black hole. However, given existing estimates of the maximum neutron star mass, we find the most probable interpretation of the source to be the coalescence of a neutron star with a black hole that has a mass between the most massive neutron stars and the least massive black holes observed in the Galaxy. We estimate a merger rate density of for compact binary coalescences with properties similar to the source of GW230529_181500; assuming that the source is a neutron star-black hole merger, GW230529_181500-like sources constitute about 60% of the total merger rate inferred for neutron star-black hole coalescences. The discovery of this system implies an increase in the expected rate of neutron star-black hole mergers with electromagnetic counterparts and provides further evidence for compact objects existing within the purported lower mass gap