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Observation of Medium-Induced Yield Enhancement and Acoplanarity Broadening of Low- p T Jets from Measurements in pp and Central Pb-Pb Collisions at sNN =5.02 TeV
Get PDFThe ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high pT) hadron trigger in proton-proton and central Pb-Pb collisions at sNN=5.02 TeV. A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb-Pb collisions. Recoil jet distributions are reported for jet resolution parameter R=0.2, 0.4, and 0.5 in the range 7<140 GeV/c and trigger-recoil jet azimuthal separation π/2<Δφ<π. The measurements exhibit a marked medium-induced jet yield enhancement at low pT and at large azimuthal deviation from Δφ∼π. The enhancement is characterized by its dependence on Δφ, which has a slope that differs from zero by 4.7σ. Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation
RELAP5-based thermal-hydraulic assessment of the STEAM facility for DEMO WCLL balance of plant analysis
Get PDFDEMO power station aims to demonstrate the generation of hundred MWs of electrical power from fusion reactions, then transmitted from the Tokamak reactor to the grid through the Balance of Plant (BoP). The design approach for the Water Cooled Lithium Lead (WCLL) Breeding Blanket (BB) Primary Heat Transfer Systems (PHTSs) leverages nuclear industry expertise but faces challenges due to DEMO pulsed operation and low-load periods. To assess the feasibility of these components, ENEA Experimental Engineering Division at Brasimone R.C. is designing STEAM, a facility investigating water technologies applied to the DEMO BB and BoP systems and components. STEAM is mainly composed of a primary system reproducing the DEMO WCLL BB PHTS thermodynamic conditions (15.5 MPa, 328–295 °C) and a secondary two-phase (liquid/steam) loop reproducing the DEMO power conversion system conditions (6.4 MPa, 238–300 °C). Experimental validation will reproduce steady-state and transient operation under DEMO-relevant conditions, including dedicated tests on the DEMO once through steam generator mock-up. STEAM objectives and description are presented in this paper, together with the RELAP5/Mod3.3 nodalization of the facility. The latter is used to, thermal-hydraulically characterize the facility behaviour. The outcomes of the steady-state qualification supported the optimization of the system layout appraising the performances of key components under the specified operating conditions
Detection of fluorescent low-energy proton tracks in lithium fluoride crystals
Get PDFThe exploitation of visible radiophotoluminescence in lithium fluoride (LiF) crystals, due to local aggregate point defects produced by ionizing radiation in the crystal lattice, is demonstrated for fluorescent imaging of single tracks of protons at low energies. LiF crystals were irradiated perpendicularly with respect to nearly monochromatic, collimated proton beams at the energies of about 1 MeV in a fluence range from ∼5.8 × 105 p/cm2 up to ∼3.4 × 107 p/cm2 and of about 2.6 MeV in a fluence range from ∼9.6 × 105 p/cm2 up to ∼4.7 × 106 p/cm2. The fluence values were estimated by detecting and automatically counting the tracks on the images acquired with a fluorescence microscope at high magnification; they were found to be in agreement with those obtained using CR39 plastic detectors irradiated under the same experimental conditions. Despite the very short range in matter of these charged particles, by focusing the excitation blue light at discrete depths in the irradiated LiF crystals, an estimate of the proton energies was also obtained. These first results are encouraging for the utilization of LiF crystals as fluorescent nuclear track detectors under typical conditions employed in ion radiobiology
Geometrical Aspects of the Optics of Linear Fresnel Concentrators: A Review
Get PDFLinear Fresnel concentrators (LFR) are widely seen by the scientific community as one of the most promising systems for the production of solar energy via thermal plants or concentrated photovoltaics. The produced energy depends on the optical efficiency of the LFR, which is mainly dictated by the geometry of the plant. For this reason, the analysis of LFR geometry and its effects on optical behavior is a crucial step in the design and optimization of a Fresnel plant. The theoretical and computational tools used to model the optics of a LFR are fundamental in research on energy production. In this review, geometrical aspects of the optics of linear Fresnel concentrators are presented, with a detailed discussion of the parameters required to define the geometry of a plant and of the main optical concepts. After an overview of the literature on the subject, the main part of the review is dedicated to summarising useful formulas and outlining general procedures for optical simulations. These include (i) a ray-tracing procedure to simulate a mirror field, and (ii) a fast quasi-analytical method useful for optimizations and on-the-fly computations
High Current Measurement of Commercial REBCO Tapes in Liquid Helium: Experimental Challenges and Solutions
Get PDFRecent advances in high-temperature superconductors (HTS) have made them extremely attractive for low-temperature, high-magnetic-field-power applications such as in fusion technology, where the advantages over traditional low-temperature superconductors (LTS) allow for the design of fusion reactors operating in different and more convenient regimes. However, the performance enhancement exhibited by novel conductors poses several challenges for the measurement of their superconducting properties. The high critical currents coupled with the relatively low thermal stability of the conductors and their mechanical fragility render this task a challenge, as the angular anisotropies complicate the experimental setup. In this work, we describe the development of our novel high-current measurement facility, focusing on the solutions introduced regarding critical aspects such as the superconducting leads and the sample holder design. We show how simple but effectively designed solutions can be adopted to combat the complexity of the measurement. The results reported in this work guide the development of a measurement system able to withstand high critical currents (I > 1500 A) at high magnetic fields (μ0H > 12 T) by evaluating the angular response of 4 mm wide short samples (L ~ 7.5 cm) in a robust and reproducible manner
Novel Applications of State-of-the-Art Gamma-Ray Imaging Technique: From Nuclear Decommissioning and Radioprotection to Radiological Characterization and Safeguards
Get PDFGamma-ray imaging is a powerful technique subjected to important research efforts in nonmedical fields, providing information about the possible spatial distribution of radioactive materials emitting photons and potential contamination spots, in generic area survey or to specific component analyses. This capability opens up a range of possible applications in nuclear installations and radioactive waste management sites, where radiation survey protocols and radiological characterization of items may be highly and positively impacted by this technique. In this work, a new-generation 3-D pixelated CdZnTe gamma-ray imaging and spectrometry detector has been used in the context of the TRIGA RC-1 Research Reactor at the ENEA Casaccia Research Centre to test several applications where gamma-ray imaging can provide valuable information otherwise unknown (with equivalent level of accuracy and effort). Experiments carried out range from radiological survey, where hotspots are identified and radioactive items are sorted from conventional waste to improvements in the quantification of gamma emitters via gamma-spectrometry analysis, and from safeguards and nonproliferation purposes (e.g., providing methods to assess the amount of special nuclear material (SNM), which remains fixed and unchanged in time) up to radiation protection issues (e.g., identification of unexpected contributions to personnel total exposure). The results obtained in this experimental campaign, as well as the validations provided by comparison with 'traditional' methods, demonstrate the applicability of state-of-the-art gamma-ray imaging systems to the presented tasks, with consequences that could positively impact the current radiation survey routines and radiological characterization protocols followed at ENEA TRIGA RC-1 as well as other installations
Shedding light on the cellular mechanisms involved in the combined adverse effects of fine particulate matter and SARS-CoV-2 on human lung cells
Get PDFAirborne pathogens represent a topic of scientific relevance, especially considering the recent COVID-19 pandemic. Air pollution, and particulate matter (PM) in particular, has been proposed as a possible risk factor for the onset and spread of pathogen-driven respiratory diseases. Regarding SARS-CoV-2 infection, exposure to fine PM (PM2.5, particles with an aerodynamic diameter < 2.5 μm) has been associated with increased incidence of the COVID-19 disease. To provide useful insights into the mechanisms through which PM might be involved in infection, we exposed human lung cells (A549) to PM2.5 and SARS-CoV-2, to evaluate the toxicological properties and the molecular pathways activated when airborne particles are combined with viral particles. Winter PM2.5 was collected in a metropolitan urban area and its physico-chemical composition was analyzed. A549 cells were exposed to SARS-CoV-2 concomitantly or after pre-treatment with PM2.5. Inflammation, oxidative stress and xenobiotic metabolism were the main pathways investigated. Results showed that after 72 h of exposure PM2.5 significantly increased the expression of the angiotensin-converting enzyme 2 (ACE2) receptor, which is one of the keys used by the virus to infect host cells. We also analyzed the endosomal route in the process of internalization, by studying the expression of RAB5 and RAB7. The results show that in cells pre-activated with PM and then exposed to SARS-CoV-2, RAB5 expression is significantly increased. The activation of the inflammatory process was then studied. Our findings show an increase of pro-inflammatory markers (NF-kB and IL-8) in cells pre-activated with PM for 72 h and subsequently exposed to the virus for a further 24 h, further demonstrating that the interaction between PM and SARS-CoV-2 determines the severity of the inflammatory responses in lung epithelial cells. In conclusion, the study provides mechanistic biological evidence of PM contribution to the onset and progression of viral respiratory diseases in exposed populations
Safety analysis for the Divertor Tokamak Test (DTT)
No full textThe Divertor Tokamak Test (DTT) facility will emit ionizing radiation during its operation, both due to D-D (deuterium-deuterium) reactions and to accelerating electrons and other particles within the plasma. Therefore, the plant shall be designed and operate according to the Italian legislation and regulations applicable to facilities using ionizing radiations. The licensing process involves the execution of safety analyses dedicated to demonstrating compliance with the legal limits in the various operational phases and in the incidental/accidental conditions that could occur. Accordingly, safety analyses begin at an early stage of the project development. A functional failure mode and effect analysis (FFMEA) was performed when the DTT design was at conceptual level. The output of this first assessment was the identification of a set of safety concerns and a set of hazards (e.g. possible source terms). Preliminary reference accident sequences have also been outlined for the transient deterministic analyses to be performed in order to demonstrate that safety requirements are met and that structural containment is not challenged. Evaluations of source terms such as tritium, activated dust in the plasma chamber and activated corrosion products (ACPs) in cooling circuits have started and are still ongoing. In parallel, as the design has progressed significantly, component-level failure mode and effects analyses (FMEA) have been initiated, as well as deterministic assessments. FMEAs allow the confirmation/identification of the complete set of hazards, the possible initiating events and the selection of reference accident sequences. Deterministic assessments will evaluate the possible consequences related to the reference accidents and demonstrate compliance with safety limits. In this work, the following studies are presented: • functional analysis, which defines the process and safety functions provided by the systems, structures and components (SSC) in the DTT; • the functional FMEA in terms of methodology used and results obtained when the design was only in a pre-conceptual phase; • the analysis of ACPs related to the primary heat transfer system (PHTS) of the vacuum vessel (VV); • the FMEA at component level both in terms of results obtained and design improvements necessary to reduce safety risks
Determination of 226Ra in urine and water samples and sequential separation of 228Ra and 90Sr in drinking water
No full textAmong natural radionuclides, 226Ra and 228Ra intake can contribute considerably to radiological dose. Liquid scintillation counting offers a reliable and sensitive method for measurement in environmental (water) and biological (urine) matrices. While the determination of 226Ra in water is quite simple, its determination in urine requires a suitable radiochemical procedure. In both cases an indirect measurement of daughter 222Rn (with 218Po and 214Po) in secular equilibrium allows to determine 226Ra activity. Moreover, in presence of anthropogenic radionuclides, a sequential separation of 228Ra and 90Sr in water has been developed, isolating daughters 228Ac and 90Y in secular equilibrium in the same vial
