D-depth profiling in as-implanted and annealed Li-based breeder blanket ceramics

In future power plants (i.e. DEMO), the nuclear fusion of hydrogen isotopes will be used for energy production. The behaviour of hydrogen isotopes in lithium-enriched ceramics for breeder blankets (BBs) is one of the most important items to be understood. In this paper we present the chemical, microstructural and morphological features of Li4SiO4, Li2TiO3 and a third ceramic candidate with a higher Li:Si proportion (3:1), implanted with D at an energy of 100 keV and at room temperature at a fluence of 1 × 1017 cm−2. The D depth-profile in as-implanted and annealed ceramics (at T ⩽ 200 °C) was characterised by Resonance Nuclear Reaction Analysis (RNRA). The RNRA data indicate that the total amount of D is retained at room temperature, while annealing at 100 °C promotes D release and annealing at T ⩾ 150 °C drives D to completely desorb from all the studied ceramics. D release will be discussed as a function of the microstructurural and morphological features of each material

Thermal diffusion profile by NRA of Deuterium implanted in solid breeder blanket materials

This paper studies the relationship between aging, physical changes and the results of non-destructive testing of plywood. 176 pieces of plywood were tested to analyze their actual and estimated density using non-destructive methods (screw withdrawal force and ultrasound wave velocity) during a laboratory aging test. From the results of statistical analysis it can be concluded that there is a strong relationship between the non-destructive measurements carried out, and the decline in the physical properties of the panels due to aging. The authors propose several models to estimate board density. The best results are obtained with ultrasound. A reliable prediction of the degree of deterioration (aging) of board is presented. Breeder blanket materials have to produce tritium from lithium while fulfilling several strict conditions. In particular, when dealing with materials to be applied in fusion reactors, one of the key questions is the study of light ions retention, which can be produced by transmutation reactions and/or introduced by interaction with the plasma. In ceramic breeders the understanding of the hydrogen isotopes behaviour and specially the diffusion of tritium to the surface is crucial. Moreover the evolution of the microstructure during irradiation with energetic ions, neutrons and electrons is complex because of the interaction of a high number of processes

ジャンル確立と閉塞の力学 -創成期寶塚の「少女文化」化-

The lattice order degree and the strain in as-grown, Mn-implanted and post-implantedannealedInAsthinfilms were investigated with depth resolution by means of Rutherford backscattering spectrometry in channeling conditions (RBS/C). Three main crystallographic axes were analyzed for both In and As sublattices. The behaviour of the induced defects was evaluated in two regions with different native defects: the interface and the surface. The results show that Mn implantation and post-implantation annealing are anisotropic processes, affecting in a different way the In and As sublattices. The mechanisms influencing the enhancement and deterioration of the crystal quality during the implantation are discussed in relation to the as-grown defects and the segregation of the element

Caracterización de especies ligeras en cerámicas de Li

Desarrollar cerámicas de Li con propiedades adecuadas para ser utilizadas en el manto reproductor de reactores de fusión. Estudiar el comportamiento de especies ligeras, en particular D, en cerámicas de Li en función de: Composición, Microestructura, Temperatura

Microstructure and high temperature mechanical properties of hard TaSiN coatings

Hard nitride coatings are widely used in the cutting tool industry, where coatings are commonly exposed to high temperature under service conditions. The addition of Si into nitride coatings, such as the TaSiN system, has been shown to enhance their oxidation resistance [1], which coupled with its high hardness, make this system of great interest for many engineering applications involving high temperatures. In this study, the room and high temperature mechanical properties of magnetron sputtered TaSiN coatings were measured using nanoindentation (between 25°C and 500°C). Fracture toughness was also evaluated at a similar temperature range using the micro-pillar splitting method (see Figure 1). The effects of N2 flow ratios on the composition, evolving phases and microstructure of the obtained nanocrystalline TaSiN coatings before and after the high temperature testing were examined by RBS, XRD and TEM analysis. Hardness was observed to increase with N content as we approach stoichiometries that allow higher degrees of crystallization of the TaN hard phases, which are embedded in an amorphous matrix. Coatings with an optimal composition of Ta55Si10N35 retain a hardness value of up to 30 GPa at 500°C, being also the toughest. Please click Additional Files below to see the full abstract

Comparative study regarding the sputtering yield of nanocolumnar tungsten surfaces under Ar+ irradiation

Nanostructured tungsten has been proposed as a promising option for plasma facing materials in future fusion reactors, because compared to conventional tungsten it shows advantages such as a better radiation resistance and, in particular, a retardation of tungsten-fuzz growth. Besides these aspects, the sputtering yield of nanostructured tungsten under ion bombardment is of interest, since it would affect the atomic density of tungsten emitted into the fusion plasma, which leads to radiative heat losses. In this work, we present a multiscale approach for investigating the sputtering yield of nanocolumnar tungsten surfaces under 1 keV and 2 keV Ar irradiation. Our results cover experiments and also computational simulations, which operate either on the basis of the binary collision approximation and ray tracing or use a full molecular dynamics implementation. In our studied case, both computational approaches can predict the sputtering yield of nanocolumnar tungsten surfaces very well. In comparison to flat W, we observe a much reduced dependence on the ion incidence angle, similar as reported for conventional rough surfaces in literature. However, an additional global reduction of the sputtering yield was identified, which can be attributed to geometrical redeposition effects between the separated nanocolumns. These results support the applicability of nanocolumnar tungsten as a first wall coating.Peer reviewe

EURECA: European-Japanese microcalorimeter array

The EURECA project aims to demonstrate technological readiness of a micro-calorimeter array for application in future X-ray astronomy missions, like Constellation-X, EDGE, and XEUS. The prototype instrument consists of a 5 × 5 pixel array of TES-based micro-calorimeters read out by two SQUID-amplifier channels using frequency-domain-multiplexing (FDM) with digital base-band feedback. The detector array is cooled by a cryogen-free cryostat consisting of a pulse tube cooler and a two stage ADR. Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray energy resolution of 1.5 eV at 250 eV for read-out of one TES-pixel only. Next step is deployment of FDM to read-out the full array. Full performance demonstration is expected end 2008.This work was financially supported by the Dutch Organization for Scientific Research (NWO).Peer Reviewe

Coulomb explosion as a probe to understand the mechanism of electron stripping from ions interacting with crystalline solids

When an ion impinges on a solid, it rapidly undergoes a process in which its electrons are stripped away provided the velocity of the orbiting electrons is smaller than the projectile speed. Electron stripping determines any posterior behavior of the ions in the solid, and it is assumed that it takes place on the surface of the solid, but no information is available on the details of the process. Here we show, using the Coulomb explosion of C ions moving in Si as a tool, that electron stripping takes place in an orderly manner and that the number of electrons stripped, before charge equilibration, depends on a characteristic length. We also propose a relation capable of quantifying this dependence. We foresee these results as a starting point to a more general understanding of ion-solid interaction, with important consequences on ion beam analysis and modification techniques, and special significance in silicon technology.This work was financed by the Ministerio de Ciencia y Tecnología (MCYT) and Ministerio de Educación y Ciencia (MEC) of Spain under Grant No. MAT2005-03011, “Ramón y Cajal” (D.M.M.), “Juan de la Cierva” (R.G.-A.), and “Personal Técnico de Apoyo” (N.G.) Programmes; and by the Madrid Government and Universidad Autónoma de Madrid under Grant No. CCG07-UAM/MAT-1882/07. We thank V. A Khodyrev and D. O. Boerma for very helpful discussions and access to the simulation program UPIC.Peer reviewe

Free-carrier contribution to the optical response of N-rich Cu3N thin films

The influence of nitrogen excess on the optical response of N-rich Cu3N films is reported. The optical spectra measured in the wavelength range from 0.30 to 20.00 µm have been correlated with the elemental film composition which can be adjusted in the nitrogen atomic percentage (at%) range from 27 ± 2 up to 33 ± 2. The absorption spectra for the N-rich films are consistent with direct optical transitions corresponding to the stoichiometric semiconductor Cu3N plus a free-carrier contribution that can be tuned in accordance with the N-excess. The data are consistent with the incorporation of the excess N in the lattice as an electron acceptor that generates free holes.The authors thank Dr Olivares-Villegas for his invaluable help and Dr Wagner for helpful discussions. The authors acknowledge the M.E.C. and C.S.I.C. for the Juan de la Cierva (R.G.A) and M.C.Y.T (Grant MAT2005-03011) (N.G.G) for the financial support. NRA measurements were supported by the EU-Research Infrastructures Transnational Access Programme at the AIM Centre for Application of Ion Beams in Materials Research under EC contract No. 025646.Peer reviewe

Large current-induced broadening of the superconducting transition in Mo/Au transition edge sensors

The R(T, I) shape of the superconducting transition in transition edge sensors (TESs) is of crucial importance to determine their ultimate performance. This paper reports a study of the temperature and current dependences of the transition of Mo/Au TESs, focused on the low resistance region, where these devices preferentially operate. A large broadening of the transition is observed when increasing the applied current. An empirical analytic expression for R(T, I) is found, which describes the transition of devices with different critical temperatures, from R = 0 up to at least 30% Rn (in some cases nearly 80% Rn). Several mechanisms for this behaviour are considered; results show that a current assisted vortex pair unbinding mechanism (Berezinskii–Kosterlitz– Thouless transition) could be the possible origin for this behaviour. Finally, the consequences of the current-induced transition broadening for TES properties and operation are outlined.Work funded by the Spanish Ministerio de Economía y Competitividad (MINECO, project ESP2016-76683-C3-2-R) and the European Commission (H2020 project AHEAD: Integrated Activities for the high energy astrophysics domain’). Personnel from ICMAB acknowledge financial support from MINECO, through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-04969). We kindly thank Professor R Navarro for a critical reading of the manuscript.Peer reviewe