[en] Time-resolved fluorescence spectroscopy (TRFS) was applied to an aluminate glass sample doped with Eu³⁺ cation as a fluorescent probe of the chemical environment and local symmetry. Conventional far-field experiments revealed the presence of two different phases: an amorphous phase featured by a highly disordered environment surrounding the Eu³⁺ cation and a more ordered polycrystalline phase that exhibits a significant increase in the Eu³⁺ fluorescence decay time compared to that of the amorphous phase. Near-field fluorescence spectra and decay kinetics were recorded in the frontier region between the two phases using a home-built scanning near-field optical microscope. SNOM-TRFS experiments confirmed the presence of local heterogeneities in this part of the glass at a sub-micrometric spatial scale. Polycrystalline sites featured an important shear-force interaction with the probing fiber optic tip, a longer fluorescence decay time, and a higher Stark splitting of the ⁵D₀ → ⁷F_J (J = 1-4) electronic transitions of the Eu³⁺ cations. (authors)

[en] This paper presents the design and characteristics of a mixed-signal 64-channel front-end readout ASIC called IMOTEPAD dedicated to multi-channel plate (MCP) photodetector coupled to LYSO scintillating crystals for small-animal PET imaging. In our configuration, the crystals are oriented in the axial direction readout on both sides by individual photodetector channels allowing the spatial resolution and the detection efficiency to be independent of each other. As a result, both energy signals and timing triggers from the photodetectors are required to be read out by the front-end ASIC. This dedicated ASIC IMOTEPAD comprises two parts: the analog part IMOTEPA and the digital part IMOTEPD. The IMOTEPA is dedicated to energy measurement. And the timing information is digitized by the IMOTEPD in which the key principal element is a time-to-digital converter (TDC) based on a delay-locked loop (DLL) with 32 delay cells. The chip is designed and fabricated in 0.35 μm CMOS process. The measurements show that for the analog part IMOTEPA, the energy gain is 13.1 mV/pC while the peak time of a CR-RC pulse shaper is 280 ns. The SNR is 39 dB and the RMS noise is 300 μV. The nonlinearity is less than 3%. The crosstalk is less than 0.2%. For the IMOTEPD, the bin size of the TDC is 625 ps with a reference clock of 50 MHz. The RMS jitter of the DLL is less than 42 ps. The DNL of the TDC is equal to about 0.17 LSB and the INL is equal to 0.31 LSB. The power dissipation of each channel is less than 16.8 mW. The design of the ASIC, especially for TDC and the measurement results of the IMOTEPAD will be presented and discussed in this paper.

[en] Recent developments in micro-CT have revolutionized the ability to examine in vivo living experimental animal models such as mouse with a spatial resolution less than 50 μm. The main requirements of in vivo imaging for biological researchers are a good spatial resolution, a low dose induced to the animal during the full examination and a reduced acquisition and reconstruction time for screening purposes. We introduce inline acquisition and reconstruction architecture to obtain in real time the 3D attenuation map of the animal fulfilling the three previous requirements. The micro-CT system is based on commercially available x-ray detector and micro-focus x-ray source. The reconstruction architecture is based on a cluster of PCs where a dedicated communication scheme combining serial and parallel treatments is implemented. In order to obtain high performance transmission rate between the detector and the reconstruction architecture, a dedicated data acquisition system is also developed. With the proposed solution, the time required to filter and backproject a projection of 2048 x 2048 pixels inside a volume of 140 mega voxels using the Feldkamp algorithm is similar to 500 ms, the time needed to acquire the same projection

[en] Highlights: • A spectral separation method is proposed for Infrared and XPS spectra. • It assesses the advancement for in situ evolution under UV illumination. • This method was carried out to characterize hybrid thin films based on sol-gel. Under in situ UV illumination, some materials present evolution of their opto-electronic properties that can be monitored by spectroscopy. We present here a mathematical method which can be applied to spectroscopic measurements when an evolving set of data is recorded: the vectorial method. The investigations and quantifications are performed by Infrared spectroscopy and XPS on organic-inorganic thin films prepared by sol-gel. The inorganic part of these hybrid thin films contains Ti oxide-network based whereas the organic part is composed of N,N-dimethylformamide and its hydrolysis products. Under UV illumination, those films exhibit intermediate bandgap behavior due to the photoreduction of Ti(IV) in Ti(III). The role of the solvent in the thin film is underlined during the process of photoreduction together with an understanding of the condensation of the Ti oxide-based network, as these evolutions are critical for the opto-electronic properties of those thin films.

[en] X-ray photoelectron and Raman spectroscopies were used to investigate the chemical and the structural properties of thin diamond films synthesised by Plasma Assisted Chemical Vapour Deposition (PACVD). Continuous polycrystalline diamond films were grown under different plasma conditions and based on the combination of detailed XPS and Raman spectroscopic analysis two main topics are highlighted (i) the stress measurements were discussed by distinguishing clearly the chemical effects from the mechanical effects; (ii) an electronic gap at 2.7 eV probed by Raman resonance that corresponds to an energy loss peak on the XPS carbon signal, was related to the surface hydrogenation

[en] This paper is devoted to the iron corrosion phenomena induced by the α (⁴He²⁺) water radiolysis species studied in conjunction with the production/consumption of H₂ at the solid/solution interface. On one hand, the solid surface is characterized during the ⁴He²⁺ ions irradiation by in situ Raman spectroscopy; on another hand, the H₂ gas produced by the water radiolysis is monitored by ex situ gas measurements. The ⁴He²⁺ ions irradiation experiments are provided either by the CEMHTI (E = 5.0 MeV) either by the ARRONAX (E = 64.7 MeV) cyclotron facilities. The iron corrosion occurs only under irradiation and can be slowed down by H₂ reductive atmosphere. Pure iron and carbon steel solids are studied in order to show two distinct behaviors of these surfaces vs. the ⁴He²⁺ ions water irradiation: the corrosion products identified are the magnetite phase (Fe(II)Fe(III)₂O₄) correlated to an H₂ consumption for pure iron and the lepidocrocite phase (γ-Fe(III)OOH) correlated to an H₂ production for carbon steel sample. This paper underlined the correlation between the iron corrosion products formation onto the solid surface and the H₂ production/consumption mechanisms. H₂O₂ species is considered as the single water radiolytic species involved into the corrosion reaction at the solid surface with an essential role in the oxidation reaction of the iron surface. We propose to bring some light to these mechanisms, in particular the H₂ and H₂O₂ roles, by the in situ Raman spectroscopy during and after the ⁴He²⁺ ions beam irradiation. This in situ experiment avoids the evolution of the solid surface, in particular phases which are reactive to the oxidation processing

[en] With the widespread use of batteries, their increased performance is of growing in importance. One avenue for this is the enhancement of ion diffusion, particularly for solid-state electrolytes, for different ions such as lithium (Li${}^{+}$) and magnesium (Mg${}^{2+}$). Unraveling the origin of better cation diffusion in confined ionic liquids (ILs) in a polymer matrix (ionogels) is compared to that of the IL itself. Ionic conductivity measured by electrochemical impedance spectroscopy for ionogels (7.0 mS cm${}^{-<!--\; ???\; -->1}$ at 30 °C) is very close to the conductivity of the non-confined IL (8.9 mS cm${}^{-<!--\; ???\; -->1}$ at 30 °C), that is, 1-ethyl-3-methyimidazolium bis(trifluorosulfonyl)imide (EMIM TFSI). An even better ionic conductivity is observed for confined EMIM TFSI with high concentrations (1 m) of lithium or magnesium salt added. The improved macroscopic transport properties can be explained by the higher self-diffusion of each ion at the liquid-to-solid interface induced by the confinement in a poly-vinylidenedifluoride (PVDF) polymer matrix. Upon confinement, the strong breaking down of ion aggregates enables a better diffusion, especially for TFSI anion and strongly polarizing cations (e.g., Li${}^{+}$, Mg${}^{2+}$). The coordination number of these cations in the liquid phase confirmed that Li${}^{+}$ and Mg${}^{2+}$ interact with the polymer matrix. Moreover, it is a major result that the activation energy for diffusion is lowered. (© 2024 Wiley‐VCH GmbH)

[en] The short-range (few μm in water) of the α-emitting from the spent fuel involves that the radiolytic corrosion of this kind of sample occurs at the solid/solution interface. In order to establish the role of localization of H_2O_2 species produced by the He"2"+ particle beam in water from the surface, we perform UO_2 radiolytic corrosion experiment with different distance between H_2O_2 production area and UO_2 surface. Then, in this work, the radiolytic corrosion of UO_2 particles by oxidative species produced by "4He"2"+ radiolysis of water was investigated in open to air atmosphere. The dose rate, the localization of H_2O_2 produced by water radiolysis and the grain boundaries present on the surface of the particles were investigated. UO_2 corrosion was investigated by in situ (during irradiation) characterization of the solid surface, analysis of H_2O_2 produced by water radiolysis and quantification of the uranium species released into the solution during irradiation. Characterization of the UO_2 particles, surface and volume, was realized by Raman spectroscopy. UV–vis spectrophotometry was used to monitor H_2O_2 produced by water radiolysis and in parallel the soluble uranium species released into the solution were quantified by inductively coupled plasma mass spectrometry. During the He"2"+ irradiation of ultra-pure water in contact with the UO_2 particles, metastudtite phase was formed on the solid surface indicating an oxidation process of the particles by the oxidative species produced by water radiolysis. This oxidation occurred essentially on the grain boundaries and was accompanied by migration of soluble uranium species (U(VI)) into the irradiated solution. Closer to the surface the localization of H_2O_2 formation, higher the UO_2 oxidation process occurs, whereas the dose rate had no effect on it. Simultaneously, closer to the surface the localization of H_2O_2 formation lower the H_2O_2 concentration measured in solution. Moreover, the metastudtite was the only secondary phase formed whatever the irradiation conditions. One hypothesis proposed in this work is the H_2O_2 may undergo a dismutation reaction leading to the formation of OH at the UO_2 surface.