Ion Beam Radiation Effects in Monazite.

International audienceMonazite is a potential matrix for conditioning minor actinides arising from spent fuel reprocessing. The matrix behavior under irradiation must be investigated to ensure long-term containment performance. Monazite compounds were irradiated by gold and helium ions to simulate the consequences of alpha decay. This article describes the effects of such irradiation on the structural and macroscopic properties (density, hardness) of monazites LaPO4 and La0.73Ce0.27PO4. Irradiation by gold ions results in major changes in the material properties. At a damage level of 6.7 dpa, monazite exhibits volume expansion of about 8.1%, a 59% drop in hardness, and structure amorphization, although Raman spectroscopy analysis shows that the phosphate-oxygen bond is unaffected. Conversely, no change in the properties of these compounds was observed after He ion implantation. These results indicate that ballistic effects predominate in the studied dose range

Le commerce de l’estampe ancienne

Lauren Laz : Nous ouvrons cet après-midi le volet du commerce de l’estampe ancienne. Pour traiter cette très vaste question, nous recevons cinq personnalités dont les cœurs de métier ou d’activité, assez différents les uns des autres, nous permettront d’illustrer différents jalons de la vie d’une estampe : Annie Martinez-Prouté, marchande d’estampes et de dessins pour la maison Paul Prouté installée rue de Seine ; Xavier Seydoux, marchand d’estampes installé rue Jacob ; Sylvie Collignon, expe..

Effets d'une impulsion laser Infra-rouge femtoseconde sur les micro-nanostructures des minéraux (implications pour les analyses in-situ par LA-ICP-MS)

TOULOUSE3-SCD-Bib. electronique (315559904) / SudocSudocFranceF

Near Infra Red femtosecond Laser Ablation: the influence of energy and pulse width on the LA-ICP-MS analysis of monazite

International audienceWe studied the influence of pulse energy (E 0) and pulse width (s) of Near Infra Red femtosecond Laser Ablation coupled to Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). A particular emphasis was put on the 206 Pb/ 238 U and 208 Pb/ 232 Th repeatability from Moacyr monazite (Itambe, Brazil). Synthetic glass (Standard Reference Material) NIST610 was used as a reference material, as well as a monazite from Manangotry (Madagascar). Pulse energy was investigated in the range E 0 ¼ 0.03 to 0.8 mJ/pulse (s ¼ 60 fs) while pulse width has been studied from s ¼ 60 fs to 300 fs (E 0 ¼ 0.1 mJ/pulse). Data suggest that pulse width has no detectable influence on the accuracy and repeatability of measured elemental ratios in the range of 60-300 fs. Observed measurements repeatabilities are 2.5%RSD and 1.8%RSD for 206 Pb/ 238 U and 208 Pb/ 232 Th, respectively. At 60 fs, the 0.03-0.8 mJ/pulse energy range studied does not induce any detectable change in data accuracy and repeatability. Uncertainties of 1.1-2.8%RSD were obtained for 206 Pb/ 238 U. In the range of E 0 ¼ 0.1-0.8 mJ/pulse, matrix matched calibration using Manangotry monazite gives a similar good repeatability of 2.4%RSD for 206 Pb/ 238 U. No clear matrix effect could be highlighted

Study of near infra red femtosecond laser induced particles using transmission electron microscopy and low pressure impaction: Implications for laser ablation–inductively coupled plasma-mass spectrometry analysis of natural monazite

International audienceThe characteristics of infra red femtosecond laser-induced aerosols are studied for monazite (LREE, Th (PO 4)) ablation and correlations are established with inductively coupled plasma-mass spectrometry (ICP-MS) signals. Critical parameters are tested within wide ranges of values in order to cover the usual laser ablation-ICP-MS analysis conditions: pulse energy (0.15 b E 0 b 1 mJ/pulse), pulse width (60 b τ b 3000 fs), ablation time (t ≤ 10 min) and transport length (l ≤ 6.3 m). Transmission electron mi-croscopy reveals that aerosols are made of agglomerates of ~ 10 nm particles and 20-300 nm phosphorus depleted condensed spherical particles. These structures are not affected by any laser ablation parameter. Particle counting is performed using electronic low pressure impaction. Small changes on particle size distribution are noticed. They may be induced either by a peak of ablation rate in the first 15 s at high fluence (larger particles) or the loss of small particles during transport. We found a positive correlation between I (ICP-MS mean signal intensity in cps) and N (particle density in cm − 3) when varying E 0 and t, suggesting that N is controlled by the irradiance (P 0 in W·cm − 2). Elemental ratio measurements show a steady state signal after the initial high ablation rate (mass load effect in the plasma torch) and before a late chemical fractionation, induced by poor extraction of bigger, early condensed spherical particles from the deepening crater. Such chemical fractionation effects remain within uncertainties, however. These effects can be limited by monitoring E 0 to shorten the initial transient state and delay the attainment of an unfavorable crater aspect ratio. Most adopted settings are for the first time deduced from aerosol characteristics, for infra red femtosecond laser ablation. A short transport (l b 4.0 m) limits the agglomeration of particles by collision process along the tube. Short τ is preferred because of higher P 0 , yet no benefit is found on ICP-MS signal intensity under 200 fs. Under such pulse widths the increased particle production induces more agglomeration during transport, thereby resulting in higher mass load effects that reduce the ionization efficiency of the plasma torch. Thus, pulse energy must be set to get an optimal balance between the need for a high signal/background ratio and limitation of mass load effects in the plasma torch

Performances of 800 nm femtosecond laser ablation on natural and synthetic quartz

International audienceA commercial femtosecond laser system operating at its fundamental wavelength (l ¼ 800 nm, near Infra-Red) was used to ablate both synthetic and natural quartz on polished and unpolished surfaces. Ablation rates and maximum depths were determined using two distinct optical setups: a 25 mm focal length Cassegrain reflecting objective, and a 50 mm focal length convergent coated lens. All samples were ablated with the same laser beam at E 0 ¼ 1 mJ, t ¼ 60 fs, f ¼ 5 Hz and N ¼ 10-8000 shots. The depth of ablation craters obtained with the lens shows a linear increase with shot number N up to N ¼ 2000 shots. Then the depth increases much less with N and reaches a plateau above N ¼ 3000 shots. Maximum depth was close to 1300 mm for N ¼ 3000 shots. Using the reflecting objective, ablation rate starts from 0.42 mm/shot and decreases rapidly to 0.02 mm/shot at a maximum depth of 350 mm for N ¼ 1500 shots. Ablation thresholds (F th) were calculated for 1 and 10 consecutive shots with energy increasing from E 0 ¼ 0.1-2 mJ/ pulse. Threshold values varies from F th ¼0.1 J.cm À2 (unpolished, 10 shots) to F th ¼ 2.9 J.cm À2 (polished, single shot). The energy penetration of IR-femtosecond laser pulses in quartz has been calculated at l ¼ 271 nm. The low absorption of IR wavelengths in quartz affects the ablation efficiency in the first shots. The associated non-linear effects are visible on a crater FIB foil observed with TEM as progressive high-pressure photomechanical damage developing under the ablation pit. The present study emphasizes the potential of IR-femtosecond laser for ablation of highly transparent material, and provides reliable data for LA-ICP-MS applications in earth sciences

In situ characterization of infra red femtosecond laser ablation in geological samples. Part B: the laser induced particles

International audienceThe analytical study of infra red femtosecond laser induced particles has been performed using Transmission Electron Microscopy (TEM) and Low Pressure Impaction (ELPI). Various natural and synthetic matrices have been tested: monazite (phosphate), zircon (silicate), NIST610 (glass), spinel (oxide), quartz (silicate structure), silicon (semiconductor) and Nordic gold (metallic alloy). Three types of particles are systematically observed: very rare large round spherical particles (d p z 1 mm) whose composition is close to the initial sample, spherical particles of smaller size (d p # 250 nm) and agglomerates of d p z 10 nm particles. Chemical compositions of the latter two are complementary with respect to the ablated sample. Isolated occurrence of hydrodynamic sputtering may explain the creation of rare large droplets. Other particles are probably generated from the irradiated matter in the supercritical state during the cooling process and plasma expansion. A recent model provides a strong basis to describe vapour to particle conversion and further condensation/coalescence processes for simple systems (single component). Additional assumptions must be included to apply the model to our observations of complex multi-elemental systems. A qualitative interpretation may be proposed on the basis of fractionated condensation/coalescence and further agglomeration of particles, depending on plasma pressure and the ablated elements properties (mainly density and melting period) as well as the thermal evolution of the plume. This interpretation is discussed and validated for each sample type. Previous results concerning ablation mechanisms using the same system are included in our model. The generation of particles from a vapour phase confirms that vaporization is the main ablation mechanism in the femtosecond regime. Moreover, the possible presence of molecular sized clusters in the initial plasma, which can accelerate the nucleation process, strongly suggests that fragmentation is the secondary ablation mechanism. Finally, the present study is an experimental validation for recent femtosecond laser ablation simulation, and it brings new insights for interpreting particles generation processes for complex systems. Correlations between laser ablation ICP-MS measurements must now be made with the present results

In situ characterization of infrared femtosecond laser ablation in geological samples. Part A: the laser induced damage

International audienceInfrared femtosecond laser induced damage has been studied in order to determine, with analytical protocols, the processes involved in laser ablation in this regime. Transmission Electron Microscopy (TEM) coupled with Focused Ion Beam (FIB) milled cross-sections of natural ablated monazite were used. Craters were formed using N = 1 and 3 shots, E0 = 0.1 and 0.8 mJ per pulse and τ = 60 fs. Observations revealed that laser settings induce little changes in the nature and size of damaged structures. The crater bottom forms a ∼0.5 μm layer composed of melted and recrystallized monazite grains, and spherical ∼10 nm voids. The underlying sample shows lattice distortions, progressively attenuated with depth, typical of mechanical shocks (thermoelastic relaxation and plasma recoil pressure). No chemical difference appears between these two domains, excluding preferential vaporization and thus laser induced chemical fractionation. Correlations with existing molecular dynamics (MD) simulations indicate that the deep distorted lattice probably undergoes spallation whereas the upper layer rather goes through homogeneous nucleation. Nevertheless, these processes are not pushed forward enough to induce matter removal in the present conditions. In consequence, photomechanical fragmentation and vaporization, requiring higher energy density states, would rather be the main ablation mechanisms. This hypothesis was supported by an additional study focused on the laser produced aerosols. Further links to LA-ICP-MS measurements can then be developed

Dominance of mechanical over thermally induced damage during femtosecond laser ablation of monazite

International audienceEffects of infrared femtosecond laser ablation (800 nm, 60 fs, 5 Hz, 85 mJ/pulse, objective  15) of a well-characterized monazite on its micro-and nano-structure were investigated. Craters were produced by single and multiple pulses (N ¼ 10, 20, 50, 150 and 300) to follow the evolution of laser-induced damage in monazite using Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM) coupled with Focused Ion Beam (FIB) sample preparation, in order to characterize this damage. Voids are observed within craters from the first pulse and cracks appear already after 10 pulses, at the sample surface; radial cracks are well-defined for 50 pulses, and become conchoidal after 150 pulses, indicating high-strain fields in the vicinity of craters. After the first pulse, the monazite lattice is highly strained to depths greater than $1 mm with a spotty ring diffraction pattern demonstrating that the damaged monazite is a mosaic crystal. Under this area monazite is moderately strained over 6 mm in depth. Crack formation within the crystal is observed from the first pulse. Cracks formed at the surface and propagated over 2 mm into the crystal. Their number increased notably after 10 pulses, with some cracks propagating 8 mm into the crystal. Increasing lattice defects (mosaic crystal, twins) and fracture intensities demonstrate that a cumulative effect exists. Part of the energy carried by the laser is stored within the crystal and used in the formation of defects. This study highlights the intense damages that are created during a femtosecond laser ablation in monazite. Mechanical effects dominate thermal ones, limited to a thin layer (200 nm-1 pulse) of resolidified monazite, and are induced by high-pressure shock wave from plasma expansion