314 research outputs found
Study of electron acceleration and X-ray radiation as a function of plasma density in capillary-guided laser wakefield accelerators
Laser wakefield electron acceleration in the blow-out regime and the associated betatron X-rayradiation were investigated experimentally as a function of the plasma density in a configuration where the laser is guided. Dielectric capillary tubes were employed to assist the laser keeping self-focused over a long distance by collecting the laser energy around its central focal spot. With a 40 fs, 16 TW pulsed laser, electron bunches with tens of pC charge were measured to be accelerated to an energy up to 300 MeV, accompanied by X-ray emission with a peak brightness of the order of 10 21 ph/s/mm 2 / mrad 2 /0.1%BW. Electron trapping and acceleration were studied using the emitted X-ray beamdistribution to map the acceleration process; the number of betatron oscillations performed by theelectrons was inferred from the correlation between measured X-ray fluence and beam charge. A studyof the stability of electron and X-ray generation suggests that the fluctuation of X-ray emission can be reduced by stabilizing the beam charge. The experimental results are in good agreement with 3D particle-in-cell (PIC) simulation.Fil: Ju, L.. Universite de Paris Xi; Francia;Fil: Svensson, K.. Lund University; SueciaFil: Ferrari, Hugo Emilio. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Döpp, A.. Universite de Paris Xi; Francia;Fil: Cassou, K.. Universite de Paris Xi; Francia;Fil: Genoud, G.. Lund University; Suecia;Fil: Wojda, F.. Lund University; Suecia;Fil: Burza, M.. Lund University; Suecia;Fil: Persson, A.. Lund University; Suecia;Fil: Lundh, O.. Lund University; Suecia;Fil: Wahlström, C. G.. Lund University; Suecia;Fil: Cros, B.. Universite de Paris Xi; Francia
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
Early mobilisation in critically ill COVID-19 patients: a subanalysis of the ESICM-initiated UNITE-COVID observational study
Background
Early mobilisation (EM) is an intervention that may improve the outcome of critically ill patients. There is limited data on EM in COVID-19 patients and its use during the first pandemic wave.
Methods
This is a pre-planned subanalysis of the ESICM UNITE-COVID, an international multicenter observational study involving critically ill COVID-19 patients in the ICU between February 15th and May 15th, 2020. We analysed variables associated with the initiation of EM (within 72 h of ICU admission) and explored the impact of EM on mortality, ICU and hospital length of stay, as well as discharge location. Statistical analyses were done using (generalised) linear mixed-effect models and ANOVAs.
Results
Mobilisation data from 4190 patients from 280 ICUs in 45 countries were analysed. 1114 (26.6%) of these patients received mobilisation within 72 h after ICU admission; 3076 (73.4%) did not. In our analysis of factors associated with EM, mechanical ventilation at admission (OR 0.29; 95% CI 0.25, 0.35; p = 0.001), higher age (OR 0.99; 95% CI 0.98, 1.00; p ≤ 0.001), pre-existing asthma (OR 0.84; 95% CI 0.73, 0.98; p = 0.028), and pre-existing kidney disease (OR 0.84; 95% CI 0.71, 0.99; p = 0.036) were negatively associated with the initiation of EM. EM was associated with a higher chance of being discharged home (OR 1.31; 95% CI 1.08, 1.58; p = 0.007) but was not associated with length of stay in ICU (adj. difference 0.91 days; 95% CI − 0.47, 1.37, p = 0.34) and hospital (adj. difference 1.4 days; 95% CI − 0.62, 2.35, p = 0.24) or mortality (OR 0.88; 95% CI 0.7, 1.09, p = 0.24) when adjusted for covariates.
Conclusions
Our findings demonstrate that a quarter of COVID-19 patients received EM. There was no association found between EM in COVID-19 patients' ICU and hospital length of stay or mortality. However, EM in COVID-19 patients was associated with increased odds of being discharged home rather than to a care facility.
Trial registration ClinicalTrials.gov: NCT04836065 (retrospectively registered April 8th 2021)
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
The effect of a saturated kink on the dynamics of tungsten impurities in the plasma core
We studied the effect of saturated kink like instabilities on the redistribution of W impurities. A numerical code that follows the exact trajectories of the impurity ions in the total fields and includes collisions was employed. The code is written in CUDA C and runs in graphical processing units, allowing simulations with a large number of particles with modest resources.The total electric and magnetic fields are calculated as the sum of a simple analytical equilibrium (large aspect ratio, circular cross section) plus the fields of the kink mode. Our simulations show that when the W ions have a thermal velocity distribution, with zero mean velocity, the kink hasno effect on the W density. However, when we include the plasma rotation and the drag on the impurities, the kink can affect the W density. When the average passing frequency of the W ions is similar to the frequency of the kink mode, the expulsion of W ions from the plasma core is maximum and the W density profile shows a hollow structure. This could have implications for the mitigation of W accumulation.Fil: Ferrari, Hugo Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Farengo, Ricardo. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Universidad Nacional de Cuyo. Instituto Balseiro; ArgentinaFil: Clauser, Cesar Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Universidad Nacional de Cuyo. Instituto Balseiro; Argentin
FOCUS: A full-orbit CUDA solver for particle simulations in magnetized plasmas
A Full-Orbit CUDA Solver for particle simulations in plasmas, FOCUS, has been developed. The code follows exact particle trajectories by solving Newton’s equations with the Lorentz force. The code can use fields calculated analytically or numerically and it is also possible to use the information provided by equilibrium reconstruction and transport codes. FOCUS has an elastic collisions module which covers the whole particle energy range in magnetic fusion devices. Moreover, an atomic collision module was also included to simulate the interaction of the test particles with neutral or partially ionized species. Regarding performance, the main feature is that the code runs on GPUs, allowing the simulation of a large number of particles using moderate computational resources. Different versions of the code have been used in several papers. Here we present a complete description of its capabilities, the basis physics included and detailed information about the numerical algorithms employed. Finally, some examples are presented.Fil: Clauser, Cesar Fernando. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Farengo, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Ferrari, Hugo Emilio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentin
Trapped particle resonance effects on the NTM driven losses of energetic particles
The m = 2, n = 1 (where m and n are the poloidal and toroidal mode numbers, respectively) neoclassical tearing mode (NTM) has been proposed as a candidate to explain the larger than expected losses of high energy ions produced by neutral beam injection observed in several experiments. Although the numerical simulations performed so far to study the effect of NTMs on energetic ions have reproduced several features observed in experiments, the agreement is not completely satisfactory. In particular, it has been difficult to reproduce the total amount of losses, which are affected by the details of the perturbation in the edge region. In this work, we study the effect of NTMs on the confinement of energetic ions produced by NBI injection using FOCUS, a full orbit code that runs in graphical processing units. This allows us to follow the evolution of a large number of ions with modest resources. A reconstruction technique that includes the experimental information available is employed to calculate the perturbed magnetic field. The main result of this study is that when the frequency of the NTM matches the toroidal precession frequency ω tp of the trapped ions ( ω t p ∼ E , where E is the energy of the ion), the losses increase significantly.Fil: Ferrari, Hugo Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Farengo, R.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; ArgentinaFil: Garcia Martinez, P. M.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Universidad Nacional de Rosario; ArgentinaFil: Clauser, C. F.. Lehigh University; Estados Unido
Redistribution of high energy alpha particles due to sawteeth with partial reconnection
The redistribution of high energy alpha particles due to internal kink modes is studied in plasmas with ITER-like parameters. The exact particle trajectories in the total fields, equilibrium plus perturbation, are calculated. The equilibrium magnetic field is obtained by analytically solving the Grad–Shafranov equation and the perturbed electric and magnetic fields are reconstructed using ideal MHD and the experimental information about the displacement eigenfunction. The (1, 1), (2, 2) and (2, 1) modes are included and the effect of changing their amplitude and frequency is determined. The results show that if the conditions are similar to those reported in Igochine et al (2007 Nucl. Fusion 47 23), the peak density of counter-passing particles decreases between 25% and 40% (depending on the energy); the peak of the trapped particles density shifts outwards by approximately 10% of the minor radius and the total on axis density decreases by more than 25%. This redistribution occurs inside the q = 1 surface. The addition of a (2, 1) mode, which can produce the stochastization of the magnetic field, significantly increases particle redistribution and allows particles to spread beyond the q = 1 surface. Different groups of particles (co-passing, counter-passing, trapped) respond differently to the perturbations.Fil: Farengo, Ricardo. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Ferrari, Hugo Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Garcia Martinez, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Firpo, M. C.. Centre National de la Recherche Scientifique; FranciaFil: Ettoumi, W.. Centre National de la Recherche Scientifique; FranciaFil: Lifschitz, A. F.. Centre National de la Recherche Scientifique; Franci
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