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Raman microscopy is one of the methods that could be used for future post-mortem analyses of samples extracted from ITER plasma facing. This study shows that this technique is useful for studying tungsten-based materials containing impurities including oxides and nitrides. Here, we apply pulsed laser deposition and DC argon glow discharges to produce tungsten-containing synthetic films (compact, porous) and nanoparticles and investigate the influence of their morphology on the measured Raman spectra. The amounts of oxygen and/or nitrogen in the films are also investigated. Comparative data are obtained by X-ray Photoelectrons Spectroscopy, Atomic Force Microscopy, Electron Microscopies (Scanning and Transmission), Energy Dispersive X-ray spectroscopy, Time-of-Flight Elastic Recoil Detection Analysis. The power density of the laser beam used to perform Raman microscopy is varied by up to 4 orders of magnitude (0.01-20 mW/$\mu$m 2) to investigate thermal stability of films and nanoparticles. As a first result, we give evidence that Raman microscopy is sensitive enough to detect surface native oxides. Secondly, more tungsten oxides are detected in porous materials and nanoparticles than in compact films, and the intensities of the Raman band correlate to their oxygen content. Thirdly, thermal stability of these films (i.e. structural and chemical modification under laser heating) is poor when compact films contain a sufficiently large amount of nitrogen. This finding suggests that nitrogen can be substituted by oxygen during Raman laser induced heating occurring in ambient air. Finally, our methodology can be used to rapidly characterize morphology and chemistry of the samples analyzed, and also to create oxides at the micrometer scale. keywords: PLD, Raman spectroscopy, tungsten oxide, tungsten nitride, plasma wall interaction, laser heating, post-mortem analysis 2, Comment: Nuclear Fusion, IOP Publishing, 2020

International audience; Nanocrystalline tungsten oxide (WO 3) thin films synthesized by thermal oxidation of tungsten substrates were exposed to low energy helium ions (energy: 80 eV; flux: 1.4-1.7×10 20 m-2 s-1) at room temperature and at 673 K. The structure and morphology changes of the oxide were studied using Raman spectroscopy and electron microscopy. Due to the low ion energy, no erosion is observed at room temperature. On the contrary, at 673 K, a colour change is observed and a significant erosion is measured (~ 70 nm for a fluence of ~ 4×10 21 m-2) due to a synergetic effect between ion bombardment and heating. We show that erosion processes and structural changes strongly depend on the ion fluence and in particular the higher the fluence, the lower the erosion yield, most likely due to oxygen depletion in the oxide near-surface layers.

International audience; This study demonstrates that Raman microscopy is a suitable technique for future $post\ mortem$ analyses of JET and ITER plasma facing components. We focus here on laboratory deposited and bombarded samples of beryllium and beryllium carbides and start to build a reference spectral databases for fusion relevant beryllium-based materials. We identified the beryllium phonon density of states, its second harmonic and E$_{2G}$ and B$_{2G}$ second harmonic and combination modes for defective beryllium in the spectral range 300-700 and 700-1300 cm$^{-1}$ , lying close to BeD modes of beryllium hydrides. We also identified beryllium carbide signature, Be$_2$C, combining Raman microscopy and DFT calculation. We have shown that, depending on the optical constants of the material probed, in depth sensitivity at the nanometer scale can be performed using different wavelengths. This way, we demonstrate that multi-wavelength Raman microscopy is sensitive to in-depth stress caused by ion implantation (down to ≈30 nm under the surface for Be) and Be/C concentration (down to 400 nm or more under the surface for Be+C), which is a main contribution of this work. The depth resolution reached can then be adapted for studying the supersaturated surface layer found on tokamak deposits.

Graphite samples exposed to H, D and He plasma at fluencies from 10(16) to 10(18)cm(-2) have been investigated by means of atomic force and Raman microscopies. The ion energy was varied between 40 and 800eV, and the ion incidence was either perpendicular (Highly Oriented Pyrolitic Graphite) or parallel (carbon/carbon composite) to the basal plane. When increasing the impinging ion energy, the growth of nanometric domes at the surface has been observed by atomic force microscopy and the incident kinetic energy has been found as the parameter determining their height. Two different Raman signatures related to (1) a graphitic nano-crystalline component similar to that of a 10(14)cm(-2) bombarded 1-, 2- and 3-layer graphene, and to (2) an amorphous component, have been evidenced. Polarization studies have revealed that these components are related to regions with either in-plane or out-of-plane disorder, coexisting in the material. These Raman studies have also revealed that both the defect-defect distance in the first case and the aromatic domain size in the second case are typically 1nm. When the number of vacancies created in the material increases, the number of in-plane defects decreases to the benefit of the out-of-plane defects. Copyright (c) 2014 John Wiley & Sons, Ltd.

Analyses of erosion and deposition over the toroidal pump limiter of Tore Supra were performed combining scanning electron microscopy, confocal microscopy and lock-in thermography. The consistency between the different methods allows a complete mapping of the eroded and deposited mass of carbon to be performed. ∼920 g of eroded carbon and ∼520 g of deposited carbon are found, showing that more than half of the eroded carbon is redeposited on the limiter. The highest deposition zones are close to the eroded zones. The gap deposition contribution is estimated at ∼23%, mostly from the erosion zones and with a main contribution from the low field side of the tile toroidal gap surfaces. Raman microscopy and transmission electron microscopy in-depth analyses show that the structure of deposits is non-homogeneous, in agreement with a deuterium impoverishment of the deep layers.

International audience; We revisit here how Raman spectroscopy can be used to estimate the H content in hard hydrogenated amorphous carbon layers. The H content was varied from 2 at.% to 30 at.%, using heat treatments of a a-C:H, from room temperature to 1300 K and was determined independently using ion beam analysis. We examine the correlation of various Raman parameters and the consistency of their thermal evolution with thermo-desorption results. We identify a weak band at 860 cm-1 attributed to H bonded to C(sp2). We show that the HD/HG parameter (Height ratio between the D and G bands) is quasi-linear in the full range of H content and can thus be used to estimate the H content. Conversely, we show that the m/HG parameter (ratio between the photoluminescence background, m, and the height of the G band), often used to estimate the H content, should be used with care, first because it is sensitive to various photoluminescence quenching processes and second because it is not sensitive to H bonded to C(sp2).

International audience; This paper presents an extensive set of measurements from complementary surface analysis techniques performed for characterizing deuterium retention in carbon fiber composite Sepcarb®NB31 subsequently to a deuterium beam exposition: adsorption isotherm measurements and Hg porosimetry to characterize the porous network, coupled deuterium beam exposure and in situ µ-NRA analysis to follow the dynamics of the penetration of the retained deuterium in the material, TEM and Raman microscopy to investigate the change in the material structure induced by ion irradiation, and finally TPD to estimate the respective proportion of deuterium retained in the surface layer and in the bulk material. The parameters extracted from this set of characterizations are introduced in a 2D Monte Carlo model which couples the propagation of deuterium and eroded carbon atoms in a network of rectilinear pores and plasma–surface interaction parameters from the SRIM code. The simulations reproduce satisfactorily the main features of the measured deuterium concentration profile and behavior of the retained deuterium amount with incident fluence, validating the physical picture of deuterium retention in CFC as due to the simultaneous implantation of the incident ions in the few 10-nm-depth layer the closest to the surface and penetration of atoms deeper in the material (several tens of microns) through the pore network

The thermal stability of 200 nm thick plasma enhanced chemical vapor deposited a-C:H and a-C:D layers ranging from soft to hard layers has been studied and compared to that of deposits collected on the Tore Supra tokamak plasma facing components by means of in-situ Raman spectroscopy. Linear ramp heating and long term isotherms (from several minutes to 21 days) have been performed and correlations between spectrometric parameters have been found. The information obtained on the sp 2 clustering has been investigated by comparing the G band shift and the 514 nm photon absorption evolution due to the thermal treatment of the layer. The effects of isotopic substitution have also been investigated., Comment: appears in Thin Solid Films, Elsevier, 2014

We study the kinetics of the H release from plasma-deposited hydrogenated amorphous carbon films under isothermal heating at 450, 500 and 600 °C for long times up to several days using in situ Raman microscopy. Four Raman parameters are analyzed. They allow the identification of different processes such as the carbon network reorganization and the H release from sp 3 or sp 2 carbon atoms and the corresponding timescales. Carbon reorganization with aromatization and loss of sp 3 hybridization occurs first in 100 minutes at 500 °C. The final organization is similar at all investigated temperatures. Full H release from sp 3 carbon occurs on a longer timescale of about 10 hours while H release from sp 2 carbon atoms is only partial, even after several days. All these processes occur more rapidly with higher initial H content, in agreement with what is known about the stability of these types of films. A quantitative analysis of these kinetics studies gives valuable information about the microscopic processes at the origin of the H release through the determination of activation energies.

International audience; We performed electron microscopy analysis of carbon tiles dismantled from the toroidal limiter of the Tore Supra tokamak. The tile top surfaces are either eroded, or covered with deposits, depending on ion flux. On the contrary, the tile gap surfaces are covered with deposits whatever the region of the limiter. We analyzed both the topography and the microstructure of gap deposits. Deposits are tip-shaped and deposition is significant only down to ~1 mm, due to the limited penetration of ions. The direction of tips results from the combination of the ion speed along the magnetic lines and the drift associated to the local electric fields. The microstructure of deposits reveals the presence of graphitic species, such as onion-like nanoparticles, and our results therefore show that deposition results from local plasma chemistry similar to what is observed for cold plasmas.

International audience; The structure of six tiles extracted from the erosion and deposition zones (thin and thick deposition) of the Tore Supra toroidal pump limiter (TPL) have been analysed in the framework of the DITS campaign using micro-Raman spectroscopy. This post-mortem analysis gives information on both carbon structure and D content. We have found that the carbon structure is most often similar to that of plasma-deposited hard amorphous carbon layers. The role of the surface temperature during the discharge in the D content is investigated: in all locations where the temperature does not reach more than 500°C the D content seems to be roughly uniform with D/D+C ≈ 20%.

In this follow-up investigation, the authors studied all Swiss women in the canton of Zurich who developed anorexia nervosa between ages 12 and 25 years and who were hospitalized for the first time with this diagnosis between 1983 and 1985. Data were compared with those from an earlier study, which focused on the periods 1956-1958, 1963-1965, and 1973-1975. The incidence of anorexia nervosa did not increase significantly during 1983-1985 compared to 1973-1975, in contrast to the constant increase found between 1956 and 1975. However, the more frequent use of vomiting and abuse of laxatives in 1983-1985 may indicate an increase in cases with mixed features of anorexia nervosa and bulimia.

Recently, the surface of carbon fibre composite tiles of the toroidal pump limiter of Tore Supra has been analysed by scanning electron and atomic force microscopies. In regions where fibres are perpendicular to the surface, a specific erosion pattern has been observed. It is constituted of a striation oriented with an angle oblique with respect to the magnetic field. The characteristic wavelength of this structure is micrometric, and similar to the fibre size. Modelling has been undertaken to reproduce this micrometric pattern. It is shown to originate from the carbon composite structure, for which it has been found by measurement using laboratory plasma that the erosion rate of the fibres is different from that of the surrounding matrix. Modelling emphasizes the effect of the impinging flux angle distributions of deuterium ions and carbon impurities that are preliminarily determined from computation of the magnetic sheath. In the case of deuterium the sheath is shown to have little effect on the particle trajectories for the simulation parameters considered here, although when impurities are included the sheath deflection is significant. Furthermore this study shows how the fibre organization in the composite influences the striation direction and points out the importance of the angular dependence of the sputtering yield.

As part of the deuterium inventory in the Tore Supra project, a detailed structural analysis of the eroded tiles (carbon fiber composite tiles) of the main plasma-facing component of Tore Supra, the toroidal pump limiter, has been performed. It combines scanning electron microscopy, atomic force microscopy and Raman microscopy. A tile cross-section has been scanned, showing the eroded profile of the tile and allowing the net erosion rate to be determined. Ripples are observed on the surface of the eroded tiles and this pattern gives a clear indication of the ion flux direction. The height profile along the valleys indicates that the fibers are eroded faster than the matrix, the difference in the erosion rates probably originating from differences in microstructure.

The theory of atomic hyperfine structures is re-formulated and the possibility of extracting information on the skin thickness of nuclear-charge distributions from the analysis of such structures is pointed out.

The intensity of the DF-ODMR spectrum has been derived when unlike triplets contribute to the annihilation process (heterofusion). Resonant microwave transitions that perturb the spin levels of the triplet pair and of the species diffusing separately (free species) were considered. In the latter case the DF-ODMR signals are negative at any orientation of the magnetic field. The spectra of single crystals of the Diphenylacetylene(DPA)-TCNB complex support the theoretical expectations

The photolysis and the fluorescence of C2F5COC2F5 have been studied at various temperatures, concentrations, and wavelengths. There is a strong dependence of the photochemical yield and to a lesser extent of the relative fluorescence yield on these factors. The reaction products are solely CO and C4F10. The fluorescence is excited by light of the wavelength region between 2537 Å and 3650 Å. The fluorescence band lies in almost the same wavelength region as that of CF3COCF3 and the relative fluorescence yield is slightly less in the higher concentration region. This behavior closely follows the pattern for CF3COCF3 and, hence, may be discussed by the same mechanism. A comparison is made of the primary photochemical reaction among fluorinated ketones.

The measurement of the fluorescence and photochemical yields of hexafluoroacetone previously made at 3130 angstrom and at room temperature is extended to various other wavelengths and temperatures. Relative fluorescence yields at room temperature increase with decrease of excitation energy. This wavelength dependence is smaller at higher concentrations. The yields increase with concentration eventually converging almost to a single value. On the other hand, the photochemical yields measured show the opposite trends with respect to variations in concentration and excitation energy. As concentration increases they also converge to a value almost identical with that at 3130 angstrom. The temperature effect on the fluorescence yield is also opposite to the one on the photolysis at 3130 angstrom. The fluorescence decreases with increase in temperature, the variation being much bigger at higher concentrations. The intensity distribution of the fluorescence band is independent of temperature. It seems difficult to interpret the observed temperature dependence for fluorescence quenching and for dissociation at infinite concentration on the basis of a single excited state. Two modes of dissociation are postulated arising respectively from low and from high vibrational levels of different electronic states.

Sono stati registrati gli spettri di risonanza paramagnetica elettronica degli ioni radicalici negativi del benzofenone e delle tre bezoilpiridine isomere ottenuti con il metodo elettrochimico. Le densita di spin determinate dalla struttura iperfine vengono discusse nel caso del benzofenone.

Vengono calcolati i primi livelli di energia degli elettronin e π per la molecola HFCO con il metodo LCAO, MO, SCF nella versione semiempirica di Pople-Pariser-Parr. Viene discussa principalmente la frequenza della transizionen → π prevista dal calcolo, confrontandola con il valore sperimentale recentemente trovato e con quello, gia noto da tempo, dell’analoga transizione della formaldeide.

The energy of the H2 molecule is calculated by using an « open shell » function analogous to the one used by Hylleraas for the He atom. In this way radial correlation is introduced without explicit inclusion of terms containing the interelectron distancer12. The calculated dissociation energy (4.17 eV) is one of the best values obtained in this approximation. A comparison with a similar wave function suggested by Muller and Eyring is made.

The rate constants and activation energies for the reactions of C3F7 radicals with methane and ethane have been measured by photolyzing mixtures of C3F7COC3F7 and hydrocarbon with 3130 Å light. Photolysis of mixtures of the ketone, methane, and deuterium has been used to check previous measurements on the reaction of C3F7 and deuterium.

Visible and ultra-violet absorption spectra have been taken for complexes of the type NiX2·2PR3 (X = NCS, Cl, Br; R = n-propyl, i-propyl, s-butyl, cyclohexyl). An assignment of the various transitions is suggested. Frequency shifts depending on alkyl substitution are shown to be due either to steric effects or to non-bonded group perturbations.