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The effect of He+ ion irradiation on a distribution of Cr atoms in model (EFDA) Fe(100-x)Cr(x) (x=5.8, 10.75, 15.15) was studied by means of conversion electrons Mossbauer spectroscopy. The alloys were irradiated to the dose of 1.2E16 ions per cm2 (7.5 dpa) with He+ of 0.25 and 2.0 MeV. The distribution of Cr atoms within the first two coordination shells around the probe Fe atoms was expressed in terms of the Warren-Cowley short-range order parameters alpha1 (first-neighbour shell, 1NN), alpha2 (second-neighbour shell, 2NN) and alpha12 (1NN+2NN. In non-irradiated alloys alpha1 was positive and alpha2 was negative for all three samples which indicates an ordering of Cr atoms. Yet, the value of alpha12 were close to zero, i.e. the distribution of Cr atoms averaged over the first two coordination shells around the probe Fe atoms, was random. The effect of the irradiation of the Fe5Cr sample is similar for the two energies of the He+ projectiles viz. increase of number of Cr atoms in the 1NN and decrease in the 2NN shell. Consequently, the degree of the ordering increased. For the other two samples, the effect of the irradiation depends on the composition, and it is stronger for the less energetic ions where, in the case of Fe10Cr, the disordering disappeared and some traces of Cr clustering (alpha12 weakly positive) can be seen. In the Fe15Cr sample the clustering is clear. In the samples irradiated with 2.0 MeV ions the ordering also survived in the samples with x=10.75 and 15.15, although its degree became smaller than in the Fe5Cr sample. Small changes in the magnetic texture were revealed., 19 pages, 11 figures, 41 references. arXiv admin note: text overlap with arXiv:1402.5612

International audience; Oxide nanoceramics combine the enhanced radiation tolerance of nanocrystalline materials with the chemical inertness of oxides, and are promising materials for highly corrosive and intense radiation environments. In this work, nanocrystalline Al2O3 thin films are irradiated at 600 °C with either 12 MeV Au5þþ18 MeV W8þ or 4 MeV Ni2þ ions. The radiation damage exposure exceeds 450 displacements per atom. A comprehensive analysis of the irradiated samples is accomplished by X-Ray Diffractometry (XRD), Transmission Electron Microscopy (TEM) and Scanning-TEM (STEM). Results are compared in an effort to establish correlations between the irradiation spectrum and the response of this class of materials to radiation environments. The results show that grain growth is the main microstructural change induced by ion irradiation in the material, regardless of the ion utilized in this work. The phase evolution may be depth-dependent, and depends strongly on the ion utilized and on the irradiation spectrum.12 MeV Au5þþ18 MeV W8þ irradiations favor the formation of g-Al2O3 and a-Al2O3, while 4 MeV Ni2þ irradiations yield mainly d-Al2O3, accompanied by small a-Al2O3 centers. Molecular dynamics simulations of displacement cascades are used to support discussions on the mass effect brought about by the different ions.

490 keV Fe + ion irradiation of 200 nm thick Fe films was found to induce both structural and magnetic changes. Both, the lattice constant and the grain size increase as a function of dose and both properties follow the same power law. Irradiation induces a depth dependent magnetic profile consisting of two sublayers. The top Fe sublayer has a magnetic moment higher than that of the Fe before the irradiation whereas the bottom sublayer lower. The two sublayers are connected with the effects of Fe + irradiation, i.e. the top sublayer with the depth in which mainly radiation damage occurs whereas the bottom one with the implantation of impinging Fe + ions. The magnetic moments of the two sublayers have a non-monotonous variation with irradiation dose depicting a maximum for the top sublayer and a minimum for the bottom one at 96.2 dpa (‘displacements per atom’). The magnetic moment enhancement/reduction is discussed in relation with the atomic volume variation in the case of atom displacements and/or implantation effects.

International audience; In irradiated material, cavities result from the condensation of vacancies induced by collision cascades. The study of their formation is a relevant topic since a high density of cavities may alter significantly the material performance. In this work, a simplified version of in line holography was successfully applied for imaging cavities in ion-irradiated 6061 aluminium alloy. In transmission electron microscopy, the incoming electrons experience a phase shift owing to the potential variation induced by the cavities. The retrieval of this phase shift provides a convenient map to observe and highlight the cavities. Information on density of cavities can be easily obtained. In addition, interstitial clusters may also be detected.

Raman spectroscopy is an efficient technique for studying the evolution of microstructure of materials under irradiation. For that purpose, a Raman spectrometer has been recently installed at the JANNUS-Saclay platform. In this paper, we describe the new setup for in situ experiments. These in situ experiments allowed following the microstructural evolution of different materials (SiC, ZrO2 and B4C) as a function of ion fluence on a single sample (either single crystal or polycrystalline ceramics) under the same irradiation conditions. Our results show that Raman spectroscopy is a versatile non-contact technique for studying on-line crystalline phase changes or amorphization of irradiated iono-covalent solids. A detailed analysis of Raman spectra is provided for the three materials (SiC, ZrO2 and B4C) investigated in this study, revealing quite different behaviors upon irradiation. Basically, Raman spectroscopy gives insight on these evolutions at the level of bonds given by specific phonon modes, in good agreement with Rutherford backscattering channeling (RBS/C), X-ray diffraction (XRD) or transmission electron microscopy (TEM) data, which provide information at a long-range scale. Copyright © 2015 John Wiley & Sons, Ltd.

Oxide Dispersion Strengthened (ODS) steels are considered as promising materials for structural components of advanced fusion and fission reactors. Its performance is largely determined by particle size and stability of the dispersed oxide nano-particles which forms during high temperature extrusion after dissolution of yttria in Fe during mechanical alloying. As the reactor structural materials are exposed to high neutron flux, study of irradiation stability of these particles is very important. In order to study irradiation stability of oxide particles in ODS alloy, two different ODS alloys of composition Fe-0.2Ti-0.3Y2O3, Fe–14Cr-0.2Ti-0.3Y2O3 were irradiated using 5 MeV Ni2+ ion beam to 150 dpa at 700 °C and 600 °C at JANNUS irradiation facility giving a dose of 40 dpa at the surface. In order to study the evolution of the nano oxide particles, the irradiated samples were examined using transmission electron microscopy (TEM). A drastic reduction in particle size along with an increase in particle density was observed in the Fe–14Cr-0.2Ti-0.3Y2O3 alloy irradiated up to 40 dpa at 700 °C as compared to 600 °C. The average size reduced from 4 nm (in as-prepared alloy) to 1 nm size. In Fe-0.2Ti-0.3Y2O3 alloy too, particle size reduction was observed upon irradiation at 700 °C, 40 dpa. The observations indicate that the nucleation of oxide particles in Fe matrix occurs along with inverse Oswald ripening.

The Oxide Dispersion Strengthened (ODS) materials are potential candidates as cladding tubes for Sodium-cooled Fast Reactors. The nano-oxides are finely dispersed within the grains and confer excellent mechanical properties to these alloys. Hence, assessing nano-particle stability under irradiation remains crucial to guarantee safe use of these materials. Although neutron irradiation remains a binding and challenging experimental study to conduct, difficulties can be overcome by ion beam processing. Ion beam processing of the ODS material allows to identify the radiation-induced Ostwald ripening as the mechanism governing the nano-particle response under irradiation. The result is the increase in size and a decrease in density of the finely dispersed Y2Ti2O7 nano-particles. Under neutron irradiation, radiation-induced Ostwald ripening appears to be less effective since a slight growth of nano-particles is observed. Further, our approach shows that nanoparticle growth kinetics should scale as φ1/3, φ being the radiation flux. This suggests that the low irradiation flux is at the origin of the slower growth kinetics of the neutron irradiated particles. Both neutron and ion irradiation induce a modification of the nanoparticles/matrix interfaces which are generally flat and sharp prior to irradiation and present steps after irradiation. This could alter the nano-particle coarsening during irradiation.

JANNUS (Joint Accelerators for Nanosciences and Nuclear Simulation), the unique triple beam facility in Europe, offers the possibility to produce three ion beams simultaneously for nuclear recoil damage and implantation of a large array of ions for well-controlled modeling-oriented experiments. The first triple beam irradiation was performed in March 2010. Along with irradiation developments, continuous efforts have been made to implement ex situ and in situ characterization tools. In this study, we set out the present status of the JANNUS facility of the Saclay site. We focus on the instrumentation used for conducting multi-ion beam irradiations and implantations as well as for characterizing bombarded samples. On-line control of irradiation parameters, in situ modification monitoring using Raman spectroscopy or ion beam induced luminescence, and ex situ characterization by ion beam surface analysis [Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA), and elastic recoil detection analysis (ERDA)] of implanted samples are detailed. Some examples of single, dual, and triple beam irradiation configurations are presented. Access to the facility is provided by the French network EMIR for national and international users ( http://emir.in2p3.fr/ ).

Mesoporous sol-gel silica thin films were irradiated with gold ions of medium energies from 0.5 MeV to 12 MeV. In all cases these porous materials are compacted as a result of mesopore collapse and deformation. X-ray reflectivity and SEM measurement show that the total compaction (densification) is achieved for a fluence of about 2 × 10 14 cm −2 (∼5 × 10 21 keV cm −3 ). The process of mesoporosity collapse seems different according to the irradiation regime (nuclear versus electronic). This effect results in a U-shaped evolution of the curve of the damage cross section as a function of the energy of ions Au. Infrared measurement of Au 0.5 MeV irradiated samples show a shift of TO 3 band towards lower wavenumber, related to Si-O-Si bond angle and Si-O bond length change. The sol-gel mesoporous and nonporous samples exhibit a delayed shift compared to thermal nonporous ones, which indicates that sol-gel materials are more radiation tolerant from this point of view. The sensitivity of these mesoporous structures to the damage caused by irradiation opens interesting prospects for obtaining self-conditioning materials.

International audience; In high energy physics point-to-point resolution is a key prerequisite for particle detector pixel arrays. Current and future experiments require the development of inner-detectors able to resolve the tracks of particles down to the micron range. Present-day technologies, although not fully implemented in actual detectors, can reach a 5-μm limit, this limit being based on statistical measurements, with a pixel-pitch in the 10 μm range. This paper is devoted to the evaluation of the building blocks for use in pixel arrays enabling accurate tracking of charged particles. Basing us on simulations we will make here a quantitative evaluation of the physical and technological limits in pixel size. Attempts to design small pixels based on SOI technology will be briefly recalled here. A design based on CMOS compatible technologies that allow a reduction of the pixel size below the micrometer is introduced here. Its physical principle relies on a buried carrier-localizing collecting gate. The fabrication process needed by this pixel design can be based on existing process steps used in silicon microelectronics. The pixel characteristics will be discussed as well as the design of pixel arrays. The existing bottlenecks and how to overcome them will be discussed in the light of recent ion implantation and material characterization experiments.

International audience; The deep trapping gate device concept for charged particle detection was recently introduced in Saclay/IRFU. It is based on an n-MOS structure in which a buried gate, located below the n-channel, collects carriers which are generated by ionizing particles. They deposit their energy in a volume which extends in the bulk, below the buried gate. The n-channel device is based on holes in-buried gate localization. Source–drain current modulation occurs, measurable during readout. The buried gate (Deep Trapping Gate or DTG) contains deep level centers which can be introduced during process or may be made with a Quantum Well. The device can be scaled down providing a micron range resolution. The proof of principle for such a device was verified using 2D device and process simulations. Work under way focusses on the study of building blocks. In this contribution, the pixel proof of design, using existing fabrication techniques will be discussed first. The use of this pixel for photon imaging will be discussed.

International audience; The microstructure of a 6061-T6 Al alloy subjected to ion irradiation at 95 and 165 displacements per atom (dpa) has been evaluated by transmission electron microscopy and atom-probe tomography. The initial microstructure of the alloy is dominated by needle-shaped β″ precipitates. After 95 dpa irradiation, the β″ precipitates display a slight lattice distortion and are partially dissolved, together with the formation of a new phase. After 165 dpa irradiation, the β″ precipitates are completely dissolved, the new phase has grown and a high density of clusters rich in Mg, Si, Cu and Cr is observed. The determination of ballistic versus radiation enhanced diffusion coefficients shows that enhanced diffusion is predominant for β” dissolution. The formation and growth of the new particles may be caused by radiation induced segregation. Solute drag by vacancies or mixed dumbbell interstitials migration could explain the diffusion of some elements as Si or Cr towards the new particles.

International audience; Bare and Al2O3-coated austenitic steel samples are exposed to lead-fast-reactor relevant corrosive conditions.Selective leaching of Ni, Mn and Cr is observed in bare samples exposed to high temperature stagnant lead(550 DC, 10et8722;8 wt.percent oxygen, 1000 and 4000 h). By contrast, corrosion is not observed in either pristine (4000 h)or irradiated (1000 h) coated samples. Further characterization and testing methods include SEM, TEM, STEM,EDS, cyclic nanoimpact, microindentation, scratch, and thermal cycling. Overall, the results show that thecoatings retain structural integrity under the conditions investigated, which is a crucial prerogative for corrosionprotection with ceramic coatings.

6H–SiC single crystals and two types of SiC fibers, Hi-Nicalon type S and Tyranno SA3, have been irradiated with 4-MeV Au3+ up to 2 × 1015 cm−2 (4 dpa) at room temperature, 100°C and 200°C. These fibers are composed of highly faulted 3C–SiC grains and free intergranular C. Stacking fault linear density and grain size estimations yield, respectively, 0.29 nm−1 and 26–36 nm for the Hi-Nicalon type S fibers and 0.18 nm−1 and 141–210 nm for the Tyranno SA3 fibers. Both transmission electron microscopy and surface micro-Raman spectroscopy reveal the complete amorphization of all the samples when irradiated at room temperature and 100°C and a remaining crystallinity when irradiated at 200°C. The latter observations reveal a multi-band irradiated layer consisting in a partially amorphized band near the surface and an in-depth amorphous band. Also, nanocrystalline SiC grains with high stacking fault densities can be found embedded in amorphous SiC at the maximum damage zone of the Hi-Nicalon type S fibers irradiated at 200°C.

Hi Nicalon type S (HNS) SiC fiber and 6H-SiC single crystals have been irradiated with 4 MeV Au3+ at room temperature (RT) and to a fluence of 2 × 1015 cm−2. These irradiation conditions lead to the complete amorphization of the irradiated layer in both samples. Post-irradiation thermal annealing effect on the amorphized samples has been characterized in situ with both Environmental Scanning (E-SEM) and Transmission (TEM) Electron Microscopes. E-SEM observations reveal cracking and exfoliation of the amorphous layer in both samples for temperatures between 850 and 1000 °C. In parallel, TEM observations reveal recrystallization of the amorphous layer in both samples. Even though TEM thin foil specimens did not suffer mechanical failure during the tests, the good agreement between the recrystallization temperatures – 870 °C for the single crystal and 900 °C for the HNS fiber – place the recrystallization process as the stress source for the cracking and exfoliation phenomena. Crack detail of a Hi Nicalon type S SiC fiber triggered by the post-irradiation thermal annealing.

The Jannus multi-ion beam facility at Saclay allows performing as well single, dual or triple beam irradiation, ion implantation and ion beam analysis. This versatility is due on one hand to the large range of ion beams available from the three coupled accelerators and on the other hand to the possibility to use several dedicated or multi-purpose vacuum chambers. It is thus possible to investigate the radiation tolerance of inorganic or organic materials and the specific effect of an atomic species of nuclear interest like hydrogen, helium, fission or transmutation products under thermal treatment or ion irradiation. This paper discusses the capabilities offered by the Jannus facility to study helium mobility in advanced nuclear materials.

Third generation silicon carbide fibers, mainly Hi-Nicalon Type S and Tyranno SA3, have improved the irradiation resistance of silicon carbide composites. In this work the microstructural evolution of these fibers due to ion irradiation is investigated in terms of Raman micro-spectrometry. In comparison with a 6H–SiC single crystal, similar amorphization kinetics have been found for increasing fluences of 4-MeV Au3+ ions. Also, in situ tensile tests have been performed to these micrometric fibers that allow real time tracking of their strain behavior under different in-core-like conditions. Tyranno SA3 fibers have been irradiated with 12-MeV C4+ at 300 MPa at RT and 1000 °C revealing a high influence of the irradiation temperature on the fiber residual strain.

International audience; Synergistic effects of nuclear (Sn) and electronic (Se) energy losses are investigated by comparing the damage accumulated in selected oxide (c-ZrO2, MgO, Gd2Ti2O7) and carbide (SiC) single crystals irradiated with single and dual low and high energy ion beams. Channeling results show that the Sn/Se synergy induces a strong decrease of the damage in MgO and SiC (where amorphization is prevented) and almost no effects in c-ZrO2 and Gd2Ti2O7. Raman and TEM results confirm this statement. The healing of defects generated by nuclear collisions in MgO and SiC is due to the electronic excitation produced in the wake of swift ions. These results present a strong interest for technological applications in the nuclear industry where expected cooperative Sn/Se effects may preserve the integrity of nuclear materials.

β–SiC nanoprecipitates can be patterned in crystalline silicon with an almost monomodal size distribution by simultaneous-dual-beam of C+ and Si+ ion implantations at 550 °C. Their shape appears as spherical (average diameter ~4–5 nm) ,and they are in epitaxial relationship with the crystalline silicon matrix. The narrow size distribution follows the left wing of the carbon distribution where the nuclear ion stopping, and thus the point defect generation rate is largest. This observation allows us to conclude that the induced damage act as sinks for C atoms leading to the SiC nanoprecipitates formation centered at the maximum of the simulated damage distribution. The nuclear reaction analysis, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy techniques were used to characterize the samples.

For the first time, Raman spectroscopy is used to study hydrogen implanted in steels. A Fe–12 wt.%Cr–0.4 wt.%Y2O3 oxide-dispersion strengthened (ODS) steel was irradiated at room temperature in triple-ion-beam conditions (24 MeV Fe8+, 1.9 He+ and 600 keV H+ ions). Using Raman spectroscopy, we successfully measure the hydrogen distribution and the vibration frequency of the H2 molecule in the irradiated ODS steel.

The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C –namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films.

Silicon carbide fiber-reinforced SiC matrix composites are promising candidates as fuel cladding for several concepts of Generation IV reactors and as structural materials for fusion reactors. The composites used in this study were composed of a SiC matrix obtained by chemical vapor infiltration associated with various fiber types (Tyranno Type-S, Tyranno SA Grade-3 and Hi-Nicalon Type-S) and with a PyC layer as the interphase. 12 MeV Au ions were used for irradiation up to 0.05 and 1 displacement per atom (dpa) fluences at room temperature and 800 °C. Analysis of both microstructure and composition of composites were performed by scanning electron microscopy (SEM), electron probe microanalysis and Raman spectroscopy. At room temperature and low fluence, Raman spectroscopy results showed that irradiation induces a disordered/distorted state into fibers and matrix. With increasing fluence, a total amorphization of these constituents occurs. The increase in the irradiation temperature leads to a damage recovery and partial recrystallization of samples. Image analysis performed from SEM micrographs highlights no significant change in fiber diameter and shape. However, SEM analysis suggests a longitudinal shrinkage of Tyranno Type-S fibers for the composite irradiated at 1 dpa at room temperature and 800 °C. These results are in complete agreement with conclusions from neutron irradiations suggesting an appropriate relevance of irradiations with 12 MeV Au.

This work clearly demonstrates that the X Ray Reflectometry technique (XRR), extensively used to assess the quality of microelectronic devices can be a useful tool to study the first stages of ion beam mixing. This technique allows measuring the evolution of the Si concentration profile in irradiated Cr/Si layers. From the analysis of the XRR profiles, it clearly appears that the Si profile cannot be described by a simple error function.

A number of studies have suggested that the irradiation behavior and damage processes occurring during sequential and simultaneous particle irradiations can significantly differ. Currently, there is no definite answer as to why and when such differences are seen. Additionally, the conventional multi-particle irradiation facilities cannot correctly reproduce the complex irradiation scenarios experienced in a number of environments like space and nuclear reactors. Therefore, a better understanding of multi-particle irradiation problems and possible alternatives are needed. This study shows ionization induced thermal spike and defect recovery during sequential and simultaneous ion irradiation of amorphous silica. The simultaneous irradiation scenario is shown to be equivalent to multiple small sequential irradiation scenarios containing latent damage formation and recovery mechanisms. The results highlight the absence of any new damage mechanism and time-space correlation between various damage events during simultaneous irradiation of amorphous silica. This offers a new and convenient way to simulate and understand complex multi-particle irradiation problems.

International audience; In this work, recrystallization of ion-amorphized Hi Nicalon Type S and Tyranno SA3 SiC fibers (4 MeV Au3+, 2 × 1015 cm−2) has been studied via in situ TEM annealing. Both fibers show a two-step recovery process of the radiation damage. First recovery stage starts at temperatures as low as 250 °C and implies recovery of the radiation swelling. Eventually the amorphous layer recrystallizes with no signs of polytype change (3C-SiC). Recrystallization temperatures yield 900–920 °C and 930 °C for the HNS and the TSA3 respectively. HNS fiber shows columnar recrystallization perpendicular to the amorphous–crystalline interphase with a grain growth rate of ∼20 nm min−1. On the other hand, recrystallization of TSA3 fiber is rather “spontaneous” with no preferential growth direction. The different recrystallization is attributed to the different microstructure of the fibers.

Iron magnetic moment enhancement is observed following the irradiation of iron films with 490 keV Fe+ at room temperature. The iron magnetic moment enhancement increases to saturation with irradiation dose. The enhanced magnetic moment decays exponentially to its value before the irradiation with a time constant of 5.2 months. The iron magnetic moment enhancement is attributed to the creation of vacancy clusters having a concentration of about 20%, whereas the relaxation effects is attributed to the dissociation of these clusters. © 2016 American Physical Society.

This paper is an experimental investigation of high temperature-dose stability of yttria particle dispersions in pure Fe matrix. Irradiation experiments were performed using single Fe and dual Fe and He ion beams, up to 100 dpa/360 appm He at 600 °C. Irradiation-induced evolutions are investigated by means of TEM observations, in combination with nano-indentation measurements. Particle stability at 600 °C is directly confirmed, up to 25 dpa/40 ppm He, while pronounced evolution of particle size distribution is evidenced at 80 dpa/360 ppm He. Diminution of particle density and particle coarsening is reflected in a significant evolution of the nano-indentation response. The change in the micro-mechanical evolution is ascribed to enhanced strain localization, associated with irradiation-induced particle size changes. Radiation-induced defect cluster and void formation are not detectable using TEM observations, in the whole investigated temperature/dose domain. Specific effect of implanted He is the augmentation of the micro-mechanical yields stress.

The third accelerator of the multi-ion irradiation platform JANNUS (Joint Accelerators for Nanosciences and NUclear Simulation), a 6SDH-2 Pelletron from National Electrostatic Corporation, Middleton was installed at Saclay in October 2009. The first triple beam irradiation combining Fe, He and H ion beams has been performed in March 2010. In the first part of this paper, we give a technical description of the triple beam facility, its performances and experimental capabilities. Typically, damage dose up to 100 dpa can be reached in 10 h irradiation with heavy ion beams, with or without simultaneous bombardment by protons, helium-4 ions or any other heavy ion beam. In the second part of this paper, we illustrate some IBA results obtained after irradiation and implantation experiments.

ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe–Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

Crystal and interfacial structures of oxide nanoparticles and radiation damage in 16Cr–4.5Al–0.3Ti–2W–0.37 Y2O3 ODS ferritic steel have been examined using high-resolution transmission electron microscopy (HRTEM) techniques. Oxide nanoparticles with a complex-oxide core and an amorphous shell were frequently observed. The crystal structure of complex-oxide core is identified to be mainly monoclinic Y4Al2O9 (YAM) oxide compound. Orientation relationships between the oxide and the matrix are found to be dependent on the particle size. Large particles (>20 nm) tend to be incoherent and have a spherical shape, whereas small particles (

The purpose is to investigate the secondary defects distribution to test the influence of the irradiation mode on the microstructure in Eurofer97 and a model alloy (Fe–9 wt% Cr). Two modes are experimented at the same damage (3 dpa) at 350 and 550 °C. The first is a long-time continuous irradiation and the second is a short-time irradiation. The materials studied are irradiated by krypton ions. The first step consists in qualitative characterization of the secondary defects. Post irradiation in situ annealing experiments show that accumulated defects condense at temperature higher than 550 °C in Eurofer. In the investigated conditions, the irradiation mode does not induce a major difference: the morphologies, sizes and densities of loops are quite similar.

Multiple ion beam facilities have been used for nearly 30 years to simulate the irradiation effects of neutrons on relevant nuclear materials. Simultaneous ion beam irradiation allow the study of structural damage and foreign atoms accumulation in a broad range of parameters (projected range, temperature, dose rate, fluence, nuclear over electronic stopping power ratio) coupled with characterization of the investigated material. First, a review is given on the multi-irradiation facilities in operation worldwide. Then, the progress report of the Joint Accelerators for Nanosciences and NUclear Simulation project (JANNUS) is presented. In the third part of this paper, the main planned activity fields using JANNUS will be discussed i.e. the study of irradiation behaviour of nuclear materials, the controlled modification of materials properties by ion beam irradiation/implantation and the teaching of ion beam interactions with solids, ion beam physics and ion beam analysis.

JANNuS (Joint Accelerators for Nano-Science and Nuclear Simulation) will be a unique user facility in Europe dedicated to material modification by ion beam implantation and irradiation. The main originality of the project is that it will be possible to perform implantation and irradiation with simultaneous multiple ions beams and in situ characterization by transmission electron microscopy (TEM) observation or ion beam analysis. This facility will be composed of two experimental platforms located in two sites: the CEA-SRMP in Saclay and the CNRS-CSNSM in Orsay. This paper will focus on the design of two new transport beam lines for the Orsay site. One of the most challenging parts of the JANNuS project (Orsay site) is to design two new beam lines in order to inject, into a 200 kV TEM, two different ion beams (low and medium energy) coming from two existing pieces of equipment: a 2 MV Tandem accelerator and a 190 kV ion implanter. For these new beam lines, first order beam calculations have been done using transfer matrix formalism. A genetic algorithm has been written and adapted to perform the optimization of the beam line parameters. Then, using the SIMION code, field maps of the electrostatic elements (quadrupoles, spherical sectors) have been calculated and ion trajectories have been simulated. We studied specifically the optical aberrations induced by the electrostatic spherical deflectors. Finally, the results of the first order calculations and the field map simulations show a good agreement.

International audience; Quantitative depth profiling measurements of implanted light elements is an important issue for electronics and nuclear applications. Conventional elastic recoil detection analysis (ERDA) has been improved by using heavy ions as incident particles for quantitatively profiling helium in materials.A new system has been implemented on the triple beam irradiation platform JANNUS at Saclay devoted to carry out HI-ERDA measurements. This device is dedicated to helium depth profiling using a 15 MeV 16O5+ incident ion beam. Capabilities of the technique (quantitative analysis, resolution and limit of detection) were tested on samples of known composition.For the first time, 4He depth profiles in pure α-iron, as-implanted and annealed, are obtained. HI-ERDA measurements have shown that helium release in pure α-iron can be described by a succession of two steps, the first having a slow kinetics below 700C and the second with a fast kinetics above 700C.

Simple alkali-borosilicate glasses containing SiO2–B2O3–Li2O–Na2O and only one or two transition metal oxides (CeO2 and/or ThO2) have been synthesized by melting the stoichiometric powder mixture at 1100 °C in a platinum crucible. Thorium and cerium were used as chemical analogs of minor actinides (Pu and Am). Th is a purely tetravalent element, although Ce can be tetravalent or trivalent. Glass samples were submitted to aqueous leaching tests at 90 °C in deionised water for one week, with or without having previously been ion-irradiated. The irradiation experiments were conducted in the nuclear energy loss regime. Kr ions supplied by a 1 MV electrostatic Van de Graaff accelerator, were used to produce displacement cascades in the first hundreds of nanometers beneath the sample’s surfaces. The leached samples were then characterized by scanning electron microscopy (SEM), electron microprobe analysis (EMA) and ion beam analytical (IBA) methods: Rutherford backscattering spectrometry and elastic recoil detection analysis (RBS and ERDA), proton-induced X-ray or gamma ray emission (PIXE and PIGE). Th and Ce are shown to be enriched in the near surface region of leached glasses due to the extremely low solubility of their hydroxides. The effect of surface damage on the chemical behaviour of Th and Ce is then detailed. The possibility for Ce(IV) to be reduced as Ce(III) during ion-irradiation just before leaching and its consequences on the relative solubility of corresponding chemical species is discussed in terms of hydroxide solubility thermodynamical equilibria.

Safety assessment of a nuclear waste deposit is based on the chemical durability and irradiation resistance of the nuclear waste forms. It is well-known that the consequences of the impact of α, β and γ irradiation on glass integrity essentially affect the level of its recrystallized fraction and its initial dissolution rate. Complex alkali–borosilico-aluminate glasses were submitted to aqueous leaching tests at temperature ranging from 25 to 100 °C, from pH = 0 to pH = 12. Simple glasses containing one or two transition metal oxides have been synthesized. Some of them have been irradiated before being leached at 90 °C. Irradiation experiments have been performed with 150 keV Xe+ions mainly producing displacement cascades in the first hundreds of nanometers beneath the sample surfaces. The leached samples were then characterized by coupling performance techniques such as scanning electron microscopy (SEM), electron microprobe analysis (EMA), secondary ion mass spectrometry (SIMS) and ion beam analytical (IBA) methods: Rutherford backscattering and elastic recoil spectrometries (RBS and ERDA).

SiO2 layers were deposited by reactive d.c ion sputtering (using 1keV Ar+ ion gun) from a high purity silicon target in an oxygen ambient. The base pressure in the deposition chamber was 4.7·10-9mbar, and the substrate temperature was held at 550 °C. The argon partial pressure during ion gun operation was 1·10-3mbar. Structural characterization of the films was performed by Rutherford backscattering spectrometry (RBS analysis), electron microprobe analysis, X-ray diffraction (XRD analysis) and Raman spectroscopy. Reactive sputtering proved to be efficient for the deposition of silica at an oxygen partial pressure of 2·10-4mbar and an electrical current on the target of 5.5mA.

This contribution is devoted to the measurement of the thermal diffusion coefficient of 3He in crystalline nuclear ceramics. The experimental method is based on the observation of the 3He(d,p)α reaction. The detection of the high energy proton (12–14 MeV) is convenient for large implantation depths (5 μm

Direct observation of nuclear reactions leading to the emission of charged particles (p or α) allows to determine specifically the spatial distribution of isotopes of light elements from 1H to 23Na and despite low cross section values some heavier isotopes from 24Mg to 68Zn. After a brief overview of the analytical capabilities offered by μNRA, this contribution is focussed on the measurement of the thermal diffusion coefficient of 3He in crystalline ceramics. The experimental method is based on the observation of the 3He(d, p)α reaction. Due to the severe energy loss along the outgoing path, the choice of the detection of the high energy proton or recoil α nucleus depends on the average depth of the 3He distribution. For near surface distributions (

Host matrices for actinide immobilisation will undergo the formation of large helium quantities due to alpha decay. Helium diffusion rate has to be known in order to predict the long-term behaviour of the material, and particularly, the influence of helium accumulation on mechanical properties. A nuclear reaction analysis method, namely the 3He(d, p)4He reaction, has been used to analyse the evolution of 3He profiles after ion implantations at 1 and 3 MeV in two materials, monoclinic ZrO2 (as a test material) and Ca9Nd(PO4)5(SiO4)F1.5(OH)0.5 britholite (envisaged for Am and Pu long-term storage). Two data processing methods are used: the classical excitation curve (proton yields versus deuteron energy) and second, the proton energy spectrum for a given deuteron energy. The characteristics of the 3He profiles (depth, width) obtained by both methods are compared to SRIM estimations. Their evolution during subsequent annealings allows an estimation of the helium diffusion rate in the britholite: D ( cm 2 / s )=(2.5±1.5)×10 −4 exp (−(1.07±0.03 eV )/ kT ) in the temperature range 200–400 °C, in agreement with previous results on similar materials. Moreover, the shape of the proton energy spectra suggests channeling effects in britholite.

Oxide dispersion strengthened (ODS) ferritic steels are considered promising candidates as cladding tubes for Generation IV nuclear reactors. In such reactors, irradiation damage can reach more than 150 dpa at temperatures ranging from 400 to 650 degrees C. Thus nanopartide stability has to be guaranteed in order to ensure that these materials possess excellent creep properties. Using Fe ions, ODS steels were irradiated at 500 degrees C up to 150 dpa. At this temperature the nano-oxide population evolution under irradiation is similar to that observed after annealing at high temperature. It consists of a slight increase in the particle size and a slight decrease in the density, which can be both explained by an Ostwald ripening mechanism. Conversely, irradiations performed at room temperature using Au ions lead to a complete dissolution of the oxide particles, in agreement with the estimation of ballistic vs. radiation enhanced diffusion effects. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

While the current second and third generation nuclear plant designs provides an economically, technically, and publicly acceptable electricity supply in many markets, further advances in nuclear energy system design can broaden the opportunities for the use of nuclear energy. The fourth generation of nuclear reactors is under development. These new reactors are designed with the following objective in mind: sustainability, safety and reliability, economics, proliferation resistance. Out of six Generation IV systems namely, Gas-Cooled Fast Reactor (GFR), Lead-Cooled fast reactor (LFR), Molten Salt Reactor (MSR), Sodium-Cooled Fast Reactor (SFR), Supercritical-Water-Cooled Reactor (SCWR), Very-High-Temperature Reactor (VHTR), this work is dedicated to identify specific fuel type that is compatible with gas-Cooled fast reactor (GFR) in-Core service conditions and could be extended to diagnose potential cladding material for SFR. The French strategy is mainly oriented towards the development of sodium-Cooled fast reactors (SFR) and very slightly focused on GFR. This dissertation is focused on the study of transition metal ceramics which are candidates for fuel coatings in GFR and have been considered as potential cladding materials for SFR. The specific fuel type in GFR should consists of spherical fuel particle made up of UC or UN, surrounded by a ceramic coating which provides structural integrity and containment of fission products. The most promising candidates for ceramic coatings are ZrN, ZrC, TiN, TiC & SiC due to a combination of neutronic performance, thermal properties, chemical behavior, crystal structure, and physical properties. It is obvious that these ceramics would be exposed to energetic fission products from fuel such as heavy ions and neutrons. These high-Energy neutron will knock the atoms in the surrounding materials and can induce (n, α) reactions, thus producing high concentration of helium atoms during and after reactor operation. The helium atoms produced are energetic and can easily penetrate into the surrounding material. Helium atoms are considered to be highly insoluble in previously studied structural nuclear materials. The accumulation of helium into solid matrix, can lead to the formation of bubbles, cavity, swelling, embrittlement etc. Helium can strongly induce grain boundary cavitation that can produce formation of inter-Granular channels, which may serve as pathways for release of radioactive elements to the environment or lead to grain-Boundary weakening and de-Cohesion. Particularly in ceramics, large quantities of helium can also lead to dimensional changes and cracks due to over-Pressurized helium bubbles. Therefore, study of helium behavior in advanced nuclear ceramics under high operating temperatures and extreme radiation conditions predicted for GFRs is viewed as crucial. In this thesis, ion-Implantation technique and material characterization techniques are used to study diffusion of helium in transition metal ceramics under thermal and extreme irradiation environments. Our main aim during this thesis is: 1) To calculate diffusion and migration energies of helium under different experimental conditions by applying theoretical models on experimental data.2) To investigate the role of microstructure such as grain boundaries, native vacancies and porosity on helium accumulation and its evolution after helium accumulation.3) To know the role of helium introduction conditions on helium diffusion. 4) To establish and validate an approach to calculate pressure built by helium gas inside the bubbles and to verify if the pressure approaches mechanical stability limit.

International audience; Zirconolite and monazite matrices are potential ceramics for the containment of actinides (Np, Cm, Am, Pu) which are produced over the reprocessing of spent nuclear fuel. Actinides decay mainly through the emission of alpha particles, which in turn causes most ceramics to undergo structural and textural changes (amorphization and/or swelling). In order to study the effects of alpha decays on the above mentioned ceramics two parallel approaches were set up. The first involved the use of an external irradiation source, Au, which allowed the deposited recoil energy to be simulated. The second was based on short-lived actinide doping with 238Pu, (i.e. an internal source), via the incorporation of plutonium oxide into both the monazite and zirconolite structures during synthesis.In both types of irradiation experiments, the zirconolite samples became amorphous at room temperature with damage close to 0.3 dpa; corresponding to a critical dose of 4 × 1018 α g−1 (i.e. ∼1.3 × 1021 keV cm−3). Both zirconolite samples also showed the same degree of macroscopic swelling at saturation (∼6%), with ballistic processes being the predominant damaging effect. In the case of the monazite however, the macroscopic swelling and amorphization were dependent on the nature of the irradiation. Externally, (Au), irradiated samples became amorphous while also demonstrating a saturation swelling of up to 8%. In contrast to this, the swelling of the 238Pu doped samples was much smaller at ∼1%. Also, unlike the externally (Au) irradiated monazite these 238Pu doped samples remained crystalline up to 7.5 × 1018 α g−1 (0.8 dpa). XRD, TEM and swelling measurements were used to fully characterize and interpret this behavior. The low swelling and the conservation of the crystalline state of 238Pu doped monazite samples indicates that alpha annealing took place within this material.

The in situ strain behavior upon ion beam irradiation of a Tyranno SA3 SiC fiber was investigated in real time. For this purpose, a tensile test device suitable for micrometrical samples was developed to allow studies in various irradiation facilities. A 7.44 μm diameter SiC fiber was submitted to both low mechanical loading at 300 MPa and 92-MeV Xe ion beam irradiation at room temperature. The fiber exhibited a gradual increase of its longitudinal strain reaching a maximum value of 0.50% for a total fluence of 5 × 10 14 ions cm −2 . Raman spectroscopy analyses performed on fibers submitted to the same irradiation conditions have shown significant local structure modification but no evidence of amorphization.

Ceramic oxides and carbides are promising matrices for the immobilization and/or transmutation of nuclear wastes, cladding materials for gas-cooled fission reactors and structural components for fusion reactors. For these applications there is a need of fundamental data concerning the behavior of nuclear ceramics upon irradiation. This article is focused on the presentation of a few remarkable examples regarding ion-beam modifications of nuclear ceramics with an emphasis on the mechanisms leading to damage creation and phase transformations. Results obtained by combining advanced techniques (Rutherford backscattering spectrometry and channeling, X-ray diffraction, transmission electron microscopy, Raman spectroscopy) concern irradiations in a broad energy range (from key to GeV) with the aim of exploring both nuclear collision (S-n) and electronic excitation (S-e) regimes. Finally, the daunting challenge of the demonstration of the existence of synergistic effects between S-n and S-e is tackled by discussing the healing due to intense electronic energy deposition (SHIBIEC) and by reporting results recently obtained in dual-beam irradiation (DBI) experiments. (C) 2013 Elsevier B.V. All rights reserved.

Single and dual-beam irradiations of oxide (c-ZrO2, MgO, Gd2Ti2O7) and carbide (SiC) single crystals were performed to study combined effects of nuclear (S-n) and electronic (S-e) energy losses. Rutherford backscattering experiments in channeling conditions show that the S-n/S-e cooperation induces a strong decrease of the irradiation-induced damage in SiC and MgO and almost no effects in c-ZrO2 and Gd2Ti2O7. The healing process is ascribed to electronic excitations arising from the electronic energy loss of swift ions. These results present a strong interest for both fundamental understanding of the ion-solid interactions and technological applications in the nuclear industry where expected cooperative S-n/S-e effects may lead to the preservation of the integrity of nuclear devices. (C) 2013 AIP Publishing LLC.

Mesoporous silicas are highly potential materials for applications in the nuclear field like separation, recycling or nuclear wastes confinement. In this work, the effects of the radiation damage on the mesoporous network were investigated by XRR (X-Rays Reflectivity) and nitrogen adsorption isotherm on respectively mesoporous organized thin films (SBA) and disordered bulk mesoporous materials (Vycor glass). The article attempts to answer the question of the existence of a relationship between the rigidity of the mesoporous silica network, and the behavior of silica materials under irradiation.