236 research outputs found
Experimental investigation of the radial structure of energetic particle driven modes
Alfv\'en eigenmodes (AEs) and energetic particle modes (EPMs) are often
excited by energetic particles (EPs) in tokamak plasmas. One of the main open
questions concerning EP driven instabilities is the non-linear evolution of the
mode structure. The aim of the present paper is to investigate the properties
of beta-induced AEs (BAEs) and EP driven geodesic acoustic modes (EGAMs)
observed in the ramp-up phase of off-axis NBI heated ASDEX Upgrade (AUG)
discharges. This paper focuses on the changes in the mode structure of
BAEs/EGAMs during the non-linear chirping phase. Our investigation has shown
that in case of the observed down-chirping BAEs the changes in the radial
structure are smaller than the uncertainty of our measurement. This behaviour
is most probably the consequence of that BAEs are normal modes, thus their
radial structure strongly depends on the background plasma parameters rather
than on the EP distribution. In the case of rapidly upward chirping EGAMs the
analysis consistently shows shrinkage of the mode structure. The proposed
explanation is that the resonance in the velocity space moves towards more
passing particles which have narrower orbit widths.Comment: submitted to Nuclear Fusio
Validity of models for Dreicer generation of runaway electrons in dynamic scenarios
Runaway electron modelling efforts are motivated by the risk these energetic
particles pose to large fusion devices. The sophisticated kinetic models can
capture most features of the runaway electron generation but have high
computational costs which can be avoided by using computationally cheaper
reduced kinetic codes. In this paper, we compare the reduced kinetic and
kinetic models to determine when the former solvers, based on analytical
calculations assuming quasi-stationarity, can be used. The Dreicer generation
rate is calculated by two different solvers in parallel in a workflow developed
in the European Integrated Modelling framework, and this is complemented by
calculations of a third code that is not yet integrated into the framework.
Runaway Fluid, a reduced kinetic code, NORSE, a kinetic code using non-linear
collision operator, and DREAM, a linearized Fokker-Planck solver, are used to
investigate the effect of a dynamic change in the electric field for different
plasma scenarios spanning across the whole tokamak-relevant range. We find that
on time scales shorter than or comparable to the electron collision time at the
critical velocity for runaway electron generation kinetic effects not captured
by reduced kinetic models play an important role. This characteristic time
scale is easy to calculate and can reliably be used to determine whether there
is a need for kinetic modelling, or cheaper reduced kinetic codes are expected
to deliver sufficiently accurate results. This criterion can be automated, and
thus it can be of great benefit for the comprehensive self-consistent modelling
frameworks that are attempting to simulate complex events such as tokamak
start-up or disruptions
Anais do I Congresso Mineiro de Diagnóstico por Imagem
Anais do I Congresso Mineiro de Diagnóstico por Imagem O I Congresso Mineiro de diagnóstico por Imagem, aconteceu no formato online, em Belo Horizonte, Minas Gerais, no Campus do Centro Universitário de Belo Horizonte- UniBH, no período de 03 a 05 de dezembro de 2020
Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption
Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25-50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density
Conveni regulador de la subvenció concedida per l'Ajuntament de Barcelona a l'entitat Asociación por la paz y los derechos humanos Taula per Mèxic per a l'execució del projecte "Barcelona protegeix periodistes de Mèxic”
Aprovat per les institucions signants el 10-05-202
Adherence to and appropriateness of anti-osteoporotic treatments in patients aged 50 and over in the Valencia Region (Spain). The ESOSVAL-AD Study
<p>Summary</p> <p>Background</p> <p>A study to evaluate the adherence to and appropriateness of anti-osteoporotic treatments in a cohort of men and women aged 50 and over participating in the ESOSVAL-R study.</p> <p>Methods/Design</p> <p><it>Design</it>: An observational, longitudinal, prospective cohort study; Study subjects: Men and women aged 50 and over living in the Valencia Region (Spain) who initiated treatment between June 15, 2009, and June 15, 2011, in primary healthcare centers with electronic medical records; <it>Data sources</it>: The main data source will be electronic medical records. <it>Measurement of results: </it>Degree of compliance with and persistence of anti-osteoporotic treatments, and the proportion of patients with appropriate anti-osteoporotic treatment in accordance with the most relevant and high impact recommendations with clearly defined treatment algorithms in Spain (the Spanish National Health System guide (2010), the General Practitioners' Society (2007) and the General Directorate for Pharmacy and Medical Products of Madrid (2007)), and with the National Osteoporosis Foundation (NOF, 2010), and the International Osteoporosis Foundation guidelines (IOF, 2008); <it>Analysis</it>: 1.) Descriptive analysis of patients undergoing treatment and the treatments prescribed; 2.) Descriptive analysis of compliance with and persistence of anti-osteoporotic treatments; 3.) Analysis of factors associated with compliance with and persistence of treatments by Cox proportional hazard regression models, 4.) Descriptive analysis of appropriateness of treatment; 5.) Analysis of factors associated with the appropriateness of treatment by multilevel models (4 levels: patient, doctor, Basic Healthcare Zone/Primary Healthcare Center, and Health Area variables).</p> <p>Discussion</p> <p>ESOSVAL-AD will provide information regarding adherence to osteoporosis treatments and the factors associated with a higher or lower adherence (including the appropriateness of the treatment) in the Spanish context. A better understanding of this phenomenon and the interventions needed to address it would contribute to the increased effectiveness of therapeutic measures, a reduction in morbidity and mortality, and a corresponding reduction in healthcare costs.</p
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