Reduction in benefits of total flux expansion on divertor detachment due to parallel flows

The Super-X divertor (SXD) is an alternative divertor configuration leveraging total flux expansion at the outer strike point (OSP). Key features for the attractiveness of the SXD are facilitated detachment access and control, as predicted by the extended 2-point model (2PM). However, parallel flows are not consistently included in the 2PM. In this work, the 2PM is refined to overcome this limitation: the role of total flux expansion on the pressure balance is made explicit, by including the effect of parallel flows. In consequence, the effect of total flux expansion on detachment access and control is weakened, compared to predictions of the 2PM. This new model partially explains discrepancies between the 2PM and experiments performed on TCV, in ohmic L-mode scenarios, where in core density ramps in lower single-null (SN) configuration, the impact of the OSP major radius Rt on the CIII emission front movement in the divertor outer leg - used as a proxy for the plasma temperature - is substantially weaker than 2PM predictions; and in OSP sweeps in lower and upper SN configurations, with a constant core density, the peak parallel particle flux density at the OSP is almost independent of Rt, while the 2PM predicts a linear dependence. Finally, analytical and numerical modelling of parallel flows in the divertor is presented, to support the argument. It is shown that an increase in total flux expansion can favour supersonic flows at the OSP. Parallel flows are also shown to be relevant by analysing SOLPS-ITER simulations of TCV

Late glacial and Holocene landscape change and rapid climate and coastal impacts in the Canal Beagle, southernmost Patagonia

Palaeoenvironmental data for the Late Glacial and Holocene periods are provided from Caleta Eugenia, in the eastern sector of Canal Beagle, southernmost Patagonia. The record commences at c. 16 200 cal a bp following glacier retreat in response to climatic warming. However, cooler conditions persisted during the Late Glacial period. The onset of more temperate conditions after c. 12 390 cal a bp is indicated by the arrival of southern beech forest and later establishment at c. 10 640 cal a bp, but the woodland growth was restricted by lower levels of effective moisture. The climate signal is then truncated by a rapid marine incursion at c. 8640 cal a bp which lasted until a more gradual emergence of the coast at c. 6600 cal a bp. During this period the pollen record appears to be dominated by the southern beech woodland. A punctuated hydroseral succession follows the isolation of the site from the sea leading to the re‐establishment of a peat bog. Between c. 5770 cal a bp and the present there were several periods of short rapid climatic change leading to drier conditions, probably as a result of late Holocene periods of climatic warming

Late glacial and Holocene landscape change and rapid climate and coastal impacts in the Canal Beagle, southernmost Patagonia

Palaeoenvironmental data for the Late Glacial and Holocene periods are provided from Caleta Eugenia, in the eastern sector of Canal Beagle, southernmost Patagonia. The record commences at c. 16 200 cal a bp following glacier retreat in response to climatic warming. However, cooler conditions persisted during the Late Glacial period. The onset of more temperate conditions after c. 12 390 cal a bp is indicated by the arrival of southern beech forest and later establishment at c. 10 640 cal a bp, but the woodland growth was restricted by lower levels of effective moisture. The climate signal is then truncated by a rapid marine incursion at c. 8640 cal a bp which lasted until a more gradual emergence of the coast at c. 6600 cal a bp. During this period the pollen record appears to be dominated by the southern beech woodland. A punctuated hydroseral succession follows the isolation of the site from the sea leading to the re‐establishment of a peat bog. Between c. 5770 cal a bp and the present there were several periods of short rapid climatic change leading to drier conditions, probably as a result of late Holocene periods of climatic warming

Experimental research on the TCV tokamak

Tokamak à configuration variable (TCV), recently celebrating 30 years of near-continual operation, continues in its missions to advance outstanding key physics and operational scenario issues for ITER and the design of future power plants such as DEMO. The main machine heating systems and operational changes are first described. Then follow five sections: plasma scenarios. ITER Base-Line (IBL) discharges, triangularity studies together with X3 heating and N2 seeding. Edge localised mode suppression, with a high radiation region near the X-point is reported with N2 injection with and without divertor baffles in a snowflake configuration. Negative triangularity (NT) discharges attained record, albeit transient, βN ∼ 3 with lower turbulence, higher low-Z impurity transport, vertical stability and density limits and core transport better than the IBL. Positive triangularity L-Mode linear and saturated ohmic confinement confinement saturation, often-correlated with intrinsic toroidal rotation reversals, was probed for D, H and He working gases. H-mode confinement and pedestal studies were extended to low collisionality with electron cyclotron heating obtaining steady state electron iternal transport barrier with neutral beam heating (NBH), and NBH driven H-mode configurations with off-axis co-electron cyclotron current drive. Fast particle physics. The physics of disruptions, runaway electrons and fast ions (FIs) was developed using near-full current conversion at disruption with recombination thresholds characterised for impurity species (Ne, Ar, Kr). Different flushing gases (D2, H2) and pathways to trigger a benign disruption were explored. The 55 kV NBH II generated a rich Alfvénic spectrum modulating the FI fas ion loss detector signal. NT configurations showed less toroidal Alfvén excitation activity preferentially affecting higher FI pitch angles. Scrape-off layer and edge physics. gas puff imaging systems characterised turbulent plasma ejection for several advanced divertor configurations, including NT. Combined diagnostic array divertor state analysis in detachment conditions was compared to modelling revealing an importance for molecular processes. Divertor physics. Internal gas baffles diversified to include shorter/longer structures on the high and/or low field side to probe compressive efficiency. Divertor studies concentrated upon mitigating target power, facilitating detachment and increasing the radiated power fraction employing alternative divertor geometries, optimised X-point radiator regimes and long-legged configurations. Smaller-than-expected improvements with total flux expansion were better modelled when including parallel flows. Peak outer target heat flux reduction was achieved (>50%) for high flux-expansion geometries, maintaining core performance (H98 > 1). A reduction in target heat loads and facilitated detachment access at lower core densities is reported. Real-time control. TCV’s real-time control upgrades employed MIMO gas injector control of stable, robust, partial detachment and plasma β feedback control avoiding neoclassical tearing modes with plasma confinement changes. Machine-learning enhancements include trajectory tracking disruption proximity and avoidance as well as a first-of-its-kind reinforcement learning-based controller for the plasma equilibrium trained entirely on a free-boundary simulator. Finally, a short description of TCV’s immediate future plans will be given

LA OCUPACIÓN DEL ALERO DE CERRO CASTILLO: UN SITIO RESIDENCIAL EN UN MIRADOR PANORÁMICO CERRO CASTILLO ROCKSHELTER OCCUPATION: A RESIDENTIAL SITE IN A PANORAMIC VIEWING-POINT

El fondo de la antigua cuenca glaciar del lago Toro, localizada en la entrada del Parque Nacional Torres del Paine, es un área rica en sitios arqueológicos erosionados, en particular en el borde de los ríos. Éstos testimonian una expansión demográfica importante en la zona, si bien ésta es poco conocida y está mal datada. Nuevas excavaciones de un sitio arqueológico descubierto en un alero rocoso en Cerro Castillo podían documentar el desarrollo de estos grupos a partir del V° milenio AP. (San Román y Morello 2003). Con este fin, la misión arqueológica francesa realizó un segundo sondeo en el sitio durante el año 2006. Este sondeo permitió un estudio paleoambiental del sitio (Bertrán 2009, Solari 2009, ambos en este volumen). El estudio de más de 10.000 vestigios líticos (Langlais y Morello 2009, en este volumen), y la realización de un primer análisis arqueozoológico (San Román y Morello 2003; Prieto en Legoupil y Bertrán 2006). El conjunto de estos datos confirma el fuerte potencial informativo de este alero que, al ofrecer un control visual del inmenso valle representa un paradero excepcional para cazadores. Los testimonios de actividades cinegéticas son escasos (pocas puntas de proyectil y ninguna bola), mas el sitio presenta las características de un campamento habitacional en el que ocurrieron importantes actividades domésticas; así lo atestiguan la producción de lascas (a menudo utilizadas) y la abundancia de raederas, raspadores y cuchillos, próximas a áreas de combustión. A pesar de las perturbaciones postdeposicionales típicas en tales contextos, y de la riqueza del palimpsesto de ocupaciones registradas, es posible distinguir grandes etapas de ocupación humana en el sitio. El Hombre se instaló hace 4500 años, en los primeros momentos de formación de la capa sedimentaria IV, un período húmedo que favoreció el desarrollo de una cubierta vegetal que también es registrada a continuación en la capa III antes de desaparecer en la etapa final del depósito: la estepa actual. En un contexto caracterizado por una tecnología común, se observan diversas modificaciones técnicas (quizás de origen funcional): por ejemplo, el abandono del uso de la obsidiana en favor de la calcedonia, o el reemplazo de las raederas por lascas retocadas y raspadores como herramientas dominantes. La distribución de los restos, la presencia de fogones y el uso de bloques rocosos, estos últimos tal vez dispuestos intencionalmente, ponen de manifiesto el potencial paleoetnográfico del sitio. Cerro Castillo podría contribuir a aclarar las características de los modos de vida de los cazadores terrestres de la región y ofrecer una columna estratigráfica bien controlada para la segunda mitad del Holoceno.The end of the former Lago Toro glacier basin, at the entry of Torres del Paine park, is a rich area with eroded archaeological sites, especially at the edge of rivers. These bear witness to an important demographic expansion in the zone, which, however, little known and poorly dated. An archaeological site discovered in a rock shelter at Cerro Castillo (San Roman and Morello 2003) might document these groups, from the 5° millenium AP. With this purpose, a second test pit was done in year 2006 by the archaeological French mission, allowing a palaeoenvironmental study of the site (Bertrán 2009, Solari 2009, both in this volume). More than 10.000 lithic materials were studied (Langlais and Morello 2009), and a first archaeozoological analysis was done (San Roman and Morello 2003; Prieto in Legoupil and Bertran 2006). These studies confirm the strong informative potential of this rock shelter which, by offering visual control of the immense valley, represents an exceptional where about for hunters. Nevertheless evidence of hunting activities is scanty (few projectile points and no bolas), instead the site shows characteristics of a habitation camp, with important domestic activities that testify the production of stone flakes (often used) and the abundance of sidescrapers, end-scrapers and knives in the proximity of combustion areas. In spite of postdepositional disturbances, common in such contexts, and of the rich palimpsest of occupations observed, it is possible to distinguish broad stages of human occupation in the site. Man installed himself 4500 years ago, in the first moments of sedimentary unit IV, a humid period that favored the development of woodland cover, which is also recorded in unit III before disappearing in the final stage; where the current steppe predominates. Within a common technological environment, different technical modifications are noted (probably of functional origin): for example, abandon sent of the use of obsidian in favour of chalcedony, and the replacement of side-scrapers for retouched flakes anwd end-scrapers, as dominant tools. The distribution of remains, the presence of fireplaces and the use of blocks, the latter possibly arranged intentionally, highlight the palaeoethnographic potential of this site. It might clarify the lifeways of terrestrial hunters in the region and offer a well controlled stratigraphic column coverig the second half of the Holocene

L’Amérique du Sud préhistorique

"Si l'on conserve au mot « préhistoire » son sens le plus courant : « histoire de l'humanité depuis les temps les plus reculés jusqu'à l'apparition des premiers témoignages écrits » (M. Brézillon, 1969), la préhistoire sud-américaine ne prend fin qu'au début du xvie siècle avec l'arrivée des premiers navigateurs et des conquistadores européens ; en effet, aucun témoignage indubitable d'un système d'écriture quelconque n'a jusqu'ici été retrouvé en Amérique du Sud, et notre connaissance des civilisations précolombiennes se fonde essentiellement sur l'interprétation des vestiges matériels. Il est donc nécessaire de choisir ici un autre critère, qui sera l'apparition des premières sociétés dites complexes, sédentaires, à l'organisation sociale élaborée et hiérarchisée, à l'économie fondée sur l'agriculture et/ou l'élevage et utilisant, pour la plupart d'entre elles, la poterie." (source auteur

Les datations 14C

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