Study of fast-ion-driven toroidal Alfvén eigenmodes impacting on the global confinement in TCV L-mode plasmas

Following recent observations of unstable Toroidal Alfvén Eigenmodes (TAEs) in a counter-current Neutral Beam Injection (NBI) scenario developed in TCV, an in-depth analysis of the impact of such modes on the global confinement and performance is carried out. The study shows experimental evidence of non-degradation of ion thermal confinement despite the increasing of auxiliary power. During such an improved confinement period, Toroidal Alfvén Eigenmodes (TAEs) driven by fast ions generated through Neutral Beam Injection (NBI) are found unstable. Together with the TAEs, various instabilities associated with the injection of the fast neutrals are observed by multiple diagnostics, and a first characterization is given. Nonlinear wave-wave couplings are also detected through multi-mode analysis, revealing a complex picture of the stability dynamics of the TCV scenario at hand. The measurements provided by a short-pulse reflectometer corroborate the identification and radial localization of the instabilities. A preliminary, but not conclusive, analysis of the impact of TAEs on the amplitude of the electron density fluctuations is carried out. Local flux-tube gyrokinetic simulations show that the dominant underlying instabilities in the absence of fast ions are Trapped Electron Modes (TEM), and that these modes are effectively suppressed by zonal flows. Attempts to simulate the simultaneous presence of fast-ion driven TAEs and TEM turbulence show that elongated streamers develop up to the full radial extent of the flux-tube domain, thereby invalidating the local assumption and indicating that a global approach is mandatory in these TCV plasmas

An EBSD study of the deformation of service-aged 316 austenitic steel

Electron backscatter diffraction (EBSD) has been used to examine the plastic deformation of an ex-service 316 austenitic stainless steel at 297K and 823K (24 °C and 550 °C)at strain rates 3.5x10-3 to 4 x 10-7 s-1. The distribution of local misorientations was found to depend on the imposed plastic strain following a lognormal distribution at true strains 0.1. At 823 K (550 °C), the distribution of misorientations depended on the applied strain rate. The evolution of lattice misorientations with increasing plastic strain up to 0.23 was quantified using the metrics kernel average misorientation, average intragrain misorientation, and low angle misorientation fraction. For strain rate down to 10-5 s-1 all metrics were insensitive to deformation temperature, mode (tension vs. compression) and orientation of the measurement plane. The strain sensitivity of the different metrics was found to depend on the misorientation ranges considered in their calculation. A simple new metric, proportion of undeformed grains, is proposed for assessing strain in both aged and unaged material. Lattice misorientations build up with strain faster in aged steel than in un-aged material and most of the metrics were sensitive to the effects of thermal aging. Ignoring aging effects leads to significant overestimation of the strains around welds. The EBSD results were compared with nanohardness measurements and good agreement established between the two techniques of assessing plastic strain in aged 316 steel

Numerical tools for burning plasmas

The software stack under development within a European coordinated effort on tools for burning plasma modelling is presented. The project is organised as a Task (TSVV Task 10) under the new E-TASC initiative (Litaudon et al 2022 Plasma Phys. Control. Fusion 64 034005). This is a continued effort within the EUROfusion inheriting from the earlier European coordination projects as well as research projects based at various European laboratories. The ongoing work of the TSVV Tasks is supported by the Advanced Computing Hubs. Major projects requiring the high performance computing (HPC) resources are global gyrokinetic codes and global hybrid particle-magnetohydrodynamics (MHD) codes. Also applications using the integrated modelling tools, such as the Energetic-Particle Workflow, based on the ITER Integrated Modelling & Analysis Suite (IMAS), or the code package for modelling radio-frequency heating and fast-ion generation may require intensive computation and a substantial memory footprint. The continual development of these codes both on the physics side and on the HPC side allows us to tackle frontier problems, such as the interaction of turbulence with MHD-type modes in the presence of fast particles. One of the important mandated outcomes of the E-TASC project is the IMAS-enabling of EUROfusion codes and release of the software stack to the EUROfusion community

El fenómeno de la concentración y centralización espacial en América Latina: elementos para una discusión

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Economías regionales extrapampeanas y exclusión social en el marco del ajuste

<abstract language="eng">This paper summarizes the progresses of a research being carried out by the author at the Centro de Estudios Urbanos y Regionales - Center of Urban and Regional Studies (CEUR), University of Buenos Aires. The purpose of the research is to make a diagnosis of regional development evolution in Argentina considering the impacts of the current process of Structural Adjustment or Plan de Convertibilidad. Rofman and its team of assistant researchers are expecting to conclude this work by the end of 1997 and its results will be published by Amorrort

La dimensión ambiental en la planificación del desarrollo del área de influencia del aprovechamiento múltiple de Salto Grande

Incluye BibliografíaEvalua el nivel actual de los programas de desarrollo ambiental y regional en el Aprovechamiento Multiple de Salto Grande. Analiza las politicas nacionales de planificacion en Argentina y Uruguay y cada uno de los programas mencionados. Formula recomendaciones acerca de los ajustes y pasos futuros a adoptar por dichos programas a fin de satisfacer los propositos enunciados en el acuerdo firmado por ambos paises en relacion al uso del agua del rio Uruguay

À propos de la décentralisation et de la démocratie en Amérique Latine

Les politiques de décentralisation spatiale, planifiées ou non, que certains pays d'Amérique Latine ont récemment mises en œuvre coexistent de façon significative avec deux processus liés à un contexte spécifique : le retour à un système constitutionnel de gouvernement après de longues périodes de régime militaire et une conjoncture peu favorable à un processus de reconstruction démocratique -qui n'est encore qu'une étape de transition vers l'établissement d'une démocratie stable-, une conjon..

Una interpretacion historica de la estructura urbano-regional de America Latina; version preliminar

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