Physics and Technology Research for Liquid-Metal Divertor Development, Focused on a Tin-Capillary Porous System Solution, at the OLMAT High Heat-Flux Facility

The operation of the Optimization of Liquid Metal Advanced Targets (OLMAT) facility began in April 2021 with the scientific objective of exposing liquid-metal plasma facing components (PFCs) to the particle and power fluxes provided by one of the hydrogen neutral beam injectors of the TJ-II stellarator. The system can deliver heat fluxes from 5 to 58 MW m−2 of high energy hydrogen neutral particles (≤ 33 keV) with fluxes up to 1022m2s−1 (containing an ion fraction ≤ 33% in some instances), pulsed operation of 30–150 ms duration and repetition rates up to 2 min−1. These characteristics enable OLMAT as a high heat flux (HHF) facility for PFC evaluation in terms of power exhaust capabilities, thermal fatigue and resilience to material damage. Additionally, the facility is equipped with a wide range of diagnostics that includes tools for analyzing the thermal response of the targets as well as for monitoring atomic/plasma physics phenomena. These include spectroscopy, pyrometry, electrical probing and visualization (fast and IR cameras) units. Such particularities make OLMAT a unique installation that can combine pure technological PFC research with the investigation of physical phenomena such as vapor shielding, thermal sputtering, the formation/characterization of plasma plumes with significant content of evaporated metal and the detection of impurities in front of the studied targets. Additionally, a myriad of surface characterization techniques as SEM/EDX for material characterization of the exposed PFC prototypes are available at CIEMAT. In this article, first we provide an overview of the current facility upgrade in which a high-power CW laser, that can be operated in continuous and pulsed modes (0.2–10 ms), dump and electrical (single Langmuir) probe embedded on the target surface have been installed. This laser operation will allow simulating more relevant heat loading scenarios such as nominal steady-state divertor heat fluxes (10–20 MW m−2 in continuous mode) and transients including ELM loading and disruption-like events (ms time scales and power densities up to GW m−2 range). The work later focuses on the more recent experimentation (2022 fall campaign) where a 3D printed Tungsten (W) Capillary Porous System (CPS) target, with approximated 30 μm pore size and a 37% porosity and filled with liquid tin. This porous surface was a mock-up of the PFC investigated in the ASDEX Upgrade divertor manipulator. The target composed with this element was eventually exposed to a sequence of shots with the maximum heat flux that OLMAT provides (58 ± 14 MWm−2). Key questions as resilience to dry-out and particle ejection of the liquid metal layer, its refilling, the induced damage/modification of the porous W matrix and the global performance of the component are addressed, attempting to shed light on the issues encountered with the PFC at tokamak scale testing.</p

Overview of recent TJ-II stellarator results

The main results obtained in the TJ-II stellarator in the last two years are reported. The most important topics investigated have been modelling and validation of impurity transport, validation of gyrokinetic simulations, turbulence characterisation, effect of magnetic configuration on transport, fuelling with pellet injection, fast particles and liquid metal plasma facing components. As regards impurity transport research, a number of working lines exploring several recently discovered effects have been developed: the effect of tangential drifts on stellarator neoclassical transport, the impurity flux driven by electric fields tangent to magnetic surfaces and attempts of experimental validation with Doppler reflectometry of the variation of the radial electric field on the flux surface. Concerning gyrokinetic simulations, two validation activities have been performed, the comparison with measurements of zonal flow relaxation in pellet-induced fast transients and the comparison with experimental poloidal variation of fluctuations amplitude. The impact of radial electric fields on turbulence spreading in the edge and scrape-off layer has been also experimentally characterized using a 2D Langmuir probe array. Another remarkable piece of work has been the investigation of the radial propagation of small temperature perturbations using transfer entropy. Research on the physics and modelling of plasma core fuelling with pellet and tracer-encapsulated solid-pellet injection has produced also relevant results. Neutral beam injection driven Alfvénic activity and its possible control by electron cyclotron current drive has been examined as well in TJ-II. Finally, recent results on alternative plasma facing components based on liquid metals are also presented. ISSN:0029-5515 ISSN:1741-432

Cold plasma studies on the influence of surface microstructured thickness in the secondary electron emission from tungsten coatings

The Secondary Electron Emission (SEE) from the Plasma Facing Components, (PFCs) affects the plasma sheath and edge structure of magnetically confined toroidal plasmas with effects on the Scrappe Off Layer (SOL), heat transport and incident plasma heat flux to the divertor targets. It is also behind the performance degradation in aerospace devices as Hall thrusters. In future reactor prototypes using tungsten (W) components, much more demanding and longer term conditions for the exposed PFCs are expected. These scenarios will exacerbate the material degradation of the exposed surfaces that will change its morphology, thus modifying its plasma material interaction behavior. In such scenario, specific studies on the influence of the microstructure in the tungsten SEE yields become necessary. In these laboratory experiments, the SEE emission of different microstructured tungsten coatings exposed to helium Glow Discharge (GD) plasmas has been analyzed by using a previously developed laboratory technique. It enables the characterization of the I-V characteristics of the biased sample and, at the same time, the acquisition of the electron incident flux by using a gridded probe adjacent to the exposed sample. Different microstructured W coated samples differing in coating thickness (2500 nm and 500 nm) and primal substrate surface finishing (translated in final differences within the W coating topologies) were analyzed, also including cold rolled tungsten and original stainless steel (SS) substrate (material in which the microstructured tungsten film was deposited) as benchmarks for comparison. The overall results have shown that the presence of a 2500 nm thick microstructured W coating decreases the SEE yield of tungsten (cold rolled) up to a factor 40 % at electron mean energies of 100–175 eV. Conversely, 500 nm coatings did not reduce the SEE yield even showing an increase at 25–100 eV. The final increase/decrease in the obtained SEE yields seems to be more influenced by the microstructured coating thickness (where the role of intrinsic differences in oxygen content of the surfaces is discussed) rather than other questions possibly derived by the differences in surface topology (ordering, directionality and/or roughness of the microstructure features)

Generation and transport of atomic lithium during the exposure of liquid metals to hot plasmas in TJ-II

A full campaign of comparative Li/LiSn/Sn testing has been initiated in TJ-II stellarator plasmas. Solid and liquid samples of the three candidates, in a Capillary Porous System (CPS) arrangement, have been exposed to the edge plasma and the associated perturbation on the plasma has been recorded.In this work, only studies on Li and LiSn alloys are reported. The surface temperature of the liquid metal/CPS samples (a tungsten mesh impregnated with SnLi or Li) has been measured during plasma pulses with milliseconds resolution by pyrometry and radial profiles of Li, Li+, and Balmer Hα were recorded together with the electron edge parameters. A simple 1D model, based on the density decay, was applied to the data, allowing for the evaluation of the kinetic energy (Ek) of ejected atomic species while their residence time at the edge was determined by monitoring the ratio of first ion/neutral emission light intensities. Some evolution of Ek with sample temperature was seen for Li atoms, this being likely associated to the different relative contributions of sputtered/evaporated atoms, although values below 0.25 eV were found for sample temperatures above 500 K. The recorded Li+/Li ratios were analyzed through a simple model accounting for several mechanisms for the dispersal of the injected impurity away from the injection location. The same model was applied to injected He atoms (high recycling impurity) in order to check for prompt redeposition of Li.A transition from sputtering driven to evaporation of Li is observed with increasing temperature. Furthermore, no evidence of prompt redeposition is observed in our conditions. Keywords: Plasma facing materials, Liquid metals, LiSn alloys, Capillary porous system, Impurity screening, Reactor material

First thermal fatigue studies of tungsten armor for DEMO and ITER at the OLMAT High Heat Flux facility

The armor for future nuclear fusion reactors is one of the main areas of research due to the harsh conditions it will undergo. Thermal fatigue is one of the most serious damage, as it will cause any material to fail even if the heat and particle loads during the reactor operation are always maintained low. In this work we have compared the actual tungsten armor for ITER tokamak with a new advanced tungsten material: tungsten reinforced by tungsten fibers (Wf/W). ITER-like W has shown small intergranular cracking at heat loads similar to the ones found in other similar devices: heat flux factor of FHF = 5.2 ± 1.6 MW/m2s0.5. But at much lower number of pulses: 641 versus 105. H embrittlement by the high-energy ions of OLMAT has been postulated as one of the main reason of this relatively prompt cracking appearance. Opposed to this, the type of Wf/W studied here, Porous Matrix (PM-Wf/W), has shown no damage at the same conditions and up to 950 pulses. These results show the capabilities of OLMAT for fatigue studies in conditions relevant to a future nuclear fusion reactor. New upgrades of OLMAT will partially solve the issues found in this first phase. Future work to continue with fatigue studies will be addressed

Prudentia Iuris, 2004, n° 58 (número completo)

Contenido: Editorial – Derecho de familia : Garantías de la libertad y la internación de enfermos mentales / José Atilio Álvarez – Concubinato / Julio César Capparelli – Cooperación jurisdiccional contra el tráfico internacional de niños / María Susana Najurieta – El nombre y la protección de la identidad / Mario J. A. Oyarzábal – El proceso de adopción y el derecho a la identidad : reflexiones acerca de la aplicación de los artículos 321, inciso h, y 328 del Código Civil / María Cristina Diez – Topografía elemental de los procesos de familia / Hernán Pagés – Violencia familiar : la exclusión del hogar conyugal como medida cautelar autosatisfactiva en los procesos de familia / Maximiliano Camus – El régimen de comunicación de los hijos con el padre no conviviente : consecuencias y posibles soluciones de las denuncias por abuso sexual de uno de los padres contra el otro / Diego Iparraguirre – La anorexia : su relación con el art. 203 del Código Civil / María Elisa Petrelli ; María Egidia Galíndez – La lesión subjetiva y la ancianidad / María Elisa Petrelli de Aliano – Los tribunales de familia como operadores de crisis : entrevista con el Dr. Lucas C. Aón – Crecer persona / Enrique E. Fabbri SJ – In Memoriam -- Recensione

STATE AND SOCIETY AT TEOTIHUACAN, MEXICO

Between 100 BCE and 200 CE, the city of Teotihuacan grew rapidly, most of the Basin of Mexico population was relocated in the city, immense civic-religious structures were built, and symbolic and material evidence shows the early importance of war. Rulers were probably able and powerful. Subsequently the city did not grow, and government may have become more collective, with significant constraints on rulers\u27 powers. A state religion centered on war and fertility deities presumably served elite interests, but civic consciousness may also have been encouraged. A female goddess was important but probably not as pervasive as has been suggested. Political control probably did not extend beyond central Mexico, except perhaps for some outposts, and the scale and significance of commerce are unclear. Teotihuacan\u27s prestige, however, spread widely in Mesoamerica, manifested especially in symbols of sacred war, used for their own ends by local elites

Dual Targeting of G9a and DNA Methyltransferase-1 for the Treatment of Experimental Cholangiocarcinoma.

Cholangiocarcinoma (CCA) is a devastating disease often detected at advanced stages when surgery cannot be performed. Conventional and targeted systemic therapies perform poorly, and therefore effective drugs are urgently needed. Different epigenetic modifications occur in CCA and contribute to malignancy. Targeting epigenetic mechanisms may thus open therapeutic opportunities. However, modifications such as DNA and histone methylation often coexist and cooperate in carcinogenesis. We tested the therapeutic efficacy and mechanism of action of a class of dual G9a histone-methyltransferase and DNA-methyltransferase 1 (DNMT1) inhibitors