E. de Juan Pardo

Bio: E. de Juan Pardo is an academic researcher from Max Planck Society. The author has contributed to research in topics: Yield (engineering) & Carbon. The author has an hindex of 7, co-authored 7 publications receiving 111 citations.

Metal-doped carbon films obtained by magnetron sputtering

Abstract: Carbon films doped with Ti, V, W, Zr, Cr, and Cu were produced by magnetron sputtering. To predict the film composition, the deposition rates were systematically studied as a function of discharge power and working pressure. The achieved dopant concentrations range from 20 down to 1 at.%. The films are laterally homogeneously doped and show columnar growth. The dopant distribution is not thermally stable. After heating at 1100 K, the carbides TiC, VC, WC, ZrC, and Cr 3 C 2 are definitely present and their grain size is on the nanometre scale. Cu segregates out. There are strong indications of the formation of carbides already during deposition.

Erosion Processes of Carbon Materials under Hydrogen Bombardment and their Mitigation by Doping

Abstract: Two regimes of the chemical erosion of carbon materials under hydrogen bombardment have been separated: (i) the thermally activated regime, Ytherm, with the maximal erosion yield in the temperature range between 550 and 850 K, and (ii) the so-called "surface" regime, Ysurf, at low temperatures (~300 K) and low impact energies ( 1025 D/m2), a reduction of the erosion yield by one order of magnitude is observed for fine-grain carbide-doped graphites. Scanning electron microscopy (SEM) allows to associate these fluence dependencies with the evolution of a rough surface morphology of several µm in the erosion area. For Ytherm an almost complete suppression of the CD4-production yield is observed for Ti-doped C layers. This reduction due to the doping on atomic scale exceeds all previously observed reductions of materials with a coarser dopant distribution. For all investigated carbon materials, the yield below RT does not depend on temperature.

Deuterium Retention by Implantation in Carbide-Doped Graphites

Abstract: For fine-grain graphites with different final heat treatment, the influences of the porosity, degree of graphitization, and dopant (TiC, VC, WC, and ZrC) on the fluence dependence of the retention of 1 keV deuterium were investigated using thermal desorption spectroscopy. A strong decrease of the D retention for fluences higher than 1021 D/m2 was observed for the undoped graphites graphitized at temperatures above 2000 K compared to material only calcined at 1270 K. Due to the identical manufacturing processes for the carbide-doped graphites used in this study, the structure is comparable for all of them. The choice of dopant as well as the ratio of open to closed porosity show no influence on the D retention. Therefore, these properties of the graphites can be neglected for hydrogen retention estimations.

Chapter 4: Power and particle control

Abstract: Progress, since the ITER Physics Basis publication (ITER Physics Basis Editors et al 1999 Nucl. Fusion 39 2137–2664), in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are energy transport in the scrape-off layer (SOL) in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main-chamber material elements, edge localized mode (ELM) energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low- and high-Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma–materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas: refinement in the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral–neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma–materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed.

Plasma-surface interaction, scrape-off layer and divertor physics:Implications for ITER

Abstract: Recent research in scrape-off layer (SOL) and divertor physics is reviewed; new and existing data from a variety of experiments have been used to make cross-experiment comparisons with implications for further research and ITER. Studies of the region near the separatrix have addressed the relationship of profiles to turbulence as well as the scaling of the parallel power flow. Enhanced low-field side radial transport is implicated as driving parallel flows to the inboard side. The medium-n nature of edge localized modes (ELMs) has been elucidated and new measurements have determined that they carry ~10?20% of the ELM energy to the far SOL with implications for ITER limiters and the upper divertor. The predicted divertor power loads for ITER disruptions are reduced while those to main chamber plasma facing components (PFCs) increase. Disruption mitigation through massive gas puffing is successful at reducing PFC heat loads. New estimates of ITER tritium retention have shown tile sides to play a significant role; tritium cleanup may be necessary every few days to weeks. ITER's use of mixed materials gives rise to a reduction of surface melting temperatures and chemical sputtering. Advances in modelling of the ITER divertor and flows have enhanced the capability to match experimental data and predict ITER performance.

Recent advances on hydrogen retention in ITER's plasma-facing materials: Beryllium, carbon and tungsten

Abstract: Management of tritium inventory remains one of the grand challenges in the development of fusion energy, and the choice of plasma-facing materials is a key factor for in-vessel tritium retention. The Atomic and Molecular Data Unit of the International Atomic Energy Agency organized a Coordinated Research Project (CRP) on the overall topic of tritium inventory in fusion reactors during the period 2001-2006. This dealt with hydrogenic retention in ITER’s plasma-facing materials – Be, C, and W – and in compounds (mixed materials) of these elements as well as tritium removal techniques. The results of the CRP are summarized in this paper together with recommendations for ITER. Basic parameters of diffusivity, solubility, and trapping in Be, C, and W are reviewed. For Be, the development of open porosity can account for transient hydrogenic pumping, but long-term retention will be dominated by codeposition. Codeposition is also the dominant retention mechanism for carbon and remains a serious concern f...

Chemical sputtering of Be due to D bombardment

Abstract: While covalently bonded materials such as carbon are well known to be eroded by chemical sputtering when exposed to plasmas or low-energy ion irradiation, pure metals have been believed to sputter only physically. The erosion of Be when subject to D bombardment was in this work measured at the PISCES-B facility and modelled with molecular dynamics simulations. During the experiments, a chemical effect was observed, since a fraction of the eroded Be was in the form of BeD molecules. This fraction decreased with increasing ion energy. The same trend was seen in the simulations and was explained by the swift chemical sputtering mechanism, showing that pure metals can, indeed, be sputtered chemically. D ions of only 7eV can erode Be through this mechanism.

Deposition and characterization of reactive magnetron sputtered zirconium carbide films

Abstract: Zirconium carbide films have been deposited on silicon (100) substrates using direct current magnetron reactive sputtering using CH4 as a carbon source. The films exhibit a typical nanocomposite st ...