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The dynamic retention of deuterium in a full-tungsten JET-like tokamak is investigated thanks to the Dynamics of Wall Elements (DWE) code. DWE is a wall model coupled to the SolEdge-EIRENE edge-plasma transport code. It is composed of two internal codes: (i) WE-temp, which determines the wall temperature, and (ii) MHIMS, which determines the transport, trapping and desorption of hydrogen isotopes in the wall material. In this work, four consecutive discharges are modeled and analysed with DWE. These discharges are identical and present a transition from a H-mode phase to a L-mode phase, which induces strongly different plasma-wall interactions. The main results are as follows. (i) A release of deuterium is observed at the vicinity of both strike-points at the end of the H-mode phase. This dynamics is explained by an increase of the wall temperature at both strike-points due to the strong plasma heat flux received there, leading to detrapping from trap with low detrapping energy. On the contrary, during the subsequent L-mode phase, the wall temperature at the strike-points decreases, leading to retention by filling the trap emptied during the H-mode. (ii) A release of deuterium from the first-wall is unexpectedly observed at the transition between the H-mode and the L-mode. This release is a consequence of a decrease in implantation energy between the two phases, as it entails a shallower implantation of deuterium. Despite the different material considered in the simulation, the latter result offers a possible explanation of the strong transient release of deuterium experimentally observed in the JET-ILW at the NBI cutoff during high density H-mode discharges.

International audience; Hydrogen isotopes transport in tokamaks is a crucial issue for several reasons, especially in the divertor exposed to the highest heat and particles fluxes. First, the total inventory of radioactive material trapped in the reactor must be limited to a certain amount (in ITER, the limit of tritium in the vacuum vessel is 1 kg). Secondly, outgassing of hydrogen from the monoblocks composing the divertor and from the tokamak first wall can reduce the plasma performances. Finally, the lifespan of plasma facing components can be reduced due to hydrogen-induceddamage.A new method coupling 2D Finite Element monoblock simulations of H transport [3] to plasma codes such as SOLPS [4] is presented. This work investigates the influence of the divertor neutral pressure on the full divertor hydrogenic inventory. It is shown that the peak heat flux (and therefore the peak temperature) decreases with the neutral pressure. The H inventory is maximum in the strike points neighbourhood and a local minimum is observed at the strike points. Even considering very conservative assumptions (eg. s of continuous exposure), the total divertor inventory of hydrogen isotopes is around 14 g which is much lower than the ITER safety limit. Moreover, this divertor inventory only varies slightly with the divertor neutral pressure (from 12 g to 14 g)

International audience; Understanding hydrogen isotopes transport in plasma facing components is crucial for tokamak operation and for safety issues. Numerical modelling is often required and can be complex when applied to multi-material environments with complex interfaces and geometries (2D/3D). This is the case for many plasma facing components such as the monoblocks that will be used in the divertor of present and future fusion reactors like WEST and ITER. To this day, few studies have simulated hydrogen transport and retention in these components with relevant physics and geometries. To simulate these processes, a finite element modelling code called FESTIM has been developed [1]. FESTIM can perform complex multidimensional simulations with several materials. The code also simulates heat transfer in solids to take into account the non-homogeneous temperature field induced by the non-homogeneous heat flux and by the cooling system. FESTIM has been used to estimate the hydrogen inventory in the ITER divertor with different exposure conditions such as surface temperature and surface hydrogen concentration using machine learning algorithm. The aim of this study is to apply the same methodology to the WEST tokamak using SOLEDGE3X-EIRENE plasma backgrounds in various divertor operational regimes (density scan, power scan). In addition, several ITER operation cases are examined.

International audience

In all plasma devices, a constant exchange of particle develops between the plasma and the wall. This phenomenon, referred to as recycling, is of critical interest for those reactors as, once the plasma is established, particle recycling represents the main particle source for the plasma. A complete understanding of the recycling phenomenon is therefore essential to ensure a reliable plasma density control and optimum performance. However, the in-situ experimental study of recycling remains challenging. Modelling can assist in the understanding of this phenomenon.The edge-plasma transport codes present the most-advanced description of the plasma-wall interaction. However, the description of recycling remains partial: atomic reflection is already handled while molecular desorption is set ad-hoc by the code user. This PhD focuses on the development of an extension of the SolEdge2D-EIRENE transport code, named D-WEE, whose goal is to model the dynamics of desorption.To initialise D-WEE, a sequence of plasma discharges is simulated with D-WEE to model a tokamak operation. The simulated wall dynamics during those discharges is studied, reveling some interesting behaviours that could impact the reactor operation. To assess the relevance of the simulated wall dynamics, a confrontation to post-pulse experimental pressure measurement is performed which reveals a qualitative agreement between the temporal pressure drop obtained in the simulation (with a $t^{-0.8}$ trend) and the one observed experimentally under ILW configuration. The retention rate during the discharge is also studied and reproduces qualitatively the experimental trends., Dans les réacteurs à fusion nucléaire, un échange constant de particules se développe entre le plasma et la paroi. Ce phénomène, appelé recyclage, présente un intérêt crucial pour ces réacteurs car, une fois le plasma établi, le recyclage représente la principale source de particules pour le plasma. Une connaissance complète du recyclage est donc essentielle pour assurer un contrôle fiable de la densité plasma ainsi qu'une performance optimale du réacteur. Cependant, les études in-situ du recyclage demeurent complexes. La modélisation numérique peut assister dans la compréhension de ce phénomène.Les codes de transport de plasma de bord présentent la description la plus avancée de l’interaction plasma-paroi. La description du recyclage reste néanmoins partielle : la réflexion atomique est déjà traitée tandis que la désorption moléculaire est fixée ad-hoc par l’utilisateur. Cette thèse de doctorat se concentre sur le développement d’une extension au code de transport SolEdge2D-EIRENE, dénommée D-WEE, dont l’objectif est de modéliser la dynamique de la désorption.Afin d’initialiser D-WEE, une séquence de décharges plasma est simulée pour modéliser l’opération d’un tokamak. La dynamique simulée pendant ces décharges est étudiée, révélant des comportements intéressants qui pourraient impacter l’opération du réacteur. Pour évaluer la pertinence de la simulation, une confrontation avec l'expérience est effectuée et révèle un accord qualitatif entre la chute de pression post-décharge simulée (avec une tendance en $t^{-0.8}$) et celle observée expérimentalement. Le taux de rétention simulé pendant la décharge est étudié et présente un accord qualitatif avec l'expérience.

International audience; In order to improve cross-field transport description, drifts and currents have been implemented in SOLEDGE2D-EIRENE. The derivation of an equation for the electric potential is recalled. The resolution of current equation is tested in a simple slab case. WEST divertor simulations in forward-B and reverse-B fields are also discussed. A significant increase of ExB shear is observed in the forward-B configuration that could explain a favorable L-H transition in this case.

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Rapports

Endothelial cells play a central role in chronic inflammation: for example, they express adhesion molecules and present chemokines leading to enhanced leukocyte recruitment into tissues. Numerous markers of endothelial cells have been reported but there has been a lack of comparative data on their specificity. The present study compared the specificity of seven endothelial cell markers in the rheumatoid synovium and the colon of patients with Crohn's disease. These markers were: the sulphated epitope MECA-79, the Duffy antigen receptor for chemokines (DARC), von Willebrand factor, CD31 (PECAM-1), CD34, CD105 (endoglin) and CD146. MECA-79, DARC and von Willebrand factor showed a specific endothelial cell distribution. MECA-79, which recognizes sulphated ligands for leukocyte adhesion receptor L-selectin (CD62L), was selective for a subset of venules in highly inflamed tissue and was present in rheumatoid but not control osteoarthritic synovia. DARC was also specific for venules but had a more widespread distribution than MECA-79, and was present in rheumatoid and control synovia. The other markers all labelled endothelial cells in venules, arterioles and capillaries. However, they also localized to other cell types. For example, CD34 stained fibroblasts, CD146 was expressed by the pericytes and smooth muscle cells of vessel walls and CD31 and CD105 labelled a broad range of cell types.