Determination of activation yield curves for fusion escaping particle diagnostics

Conference (2013, June)

Relationship between the Synthesis of Prussian Blue Pigments, Their Color, Physical Properties, and Their Behavior in Paint Layers

in Journal of Physical Chemistry C (2013), 117(19), 96939712

Prussian blue pigments, highly insoluble mixed-valence iron(III) hexacyanoferrate(II) complexes of typical stoichiometry Fe4III[FeII(CN)6]3·xH2O or KFeIII[FeII(CN)6]·xH2O, have been used as pigments in ... [more ▼]

Prussian blue pigments, highly insoluble mixed-valence iron(III) hexacyanoferrate(II) complexes of typical stoichiometry Fe4III[FeII(CN)6]3·xH2O or KFeIII[FeII(CN)6]·xH2O, have been used as pigments in oil paintings and watercolors for 300 years. For poorly understood reasons, these pigments often fade with time. Although the preparation methods have been recognized since the mid-eighteenth century as a contributory factor in the fading of the pigment, the spectral and physical properties of Prussian blue that vary with the type of synthesis were not precisely identified. Several Prussian blue pigments have been prepared by different methods and characterized by thermogravimetric analyses, high-energy powder X-ray diffraction, atomic absorption and flame emission, UV–visible, iron-57 Mössbauer, iron K-edge X-ray absorption, and Raman spectroscopy. The type of synthesis influences the hue, tinting strength, and hiding power properties of the Prussian blue pigments. Two major features appear to be strongly dependent on the preparative methods, the particle size and the local disorder. Both a nitrogen atmosphere and an intermediate aging step of the Berlin white, Fe2II[FeII(CN)6], during the synthesis are required to obtain a highly colored pigment through the optimization of particle size, minimization in the perturbations to the FeII–CN–FeIII intervalence electron transfer pathway, and the minimization of disordered vacancies. The potassium containing Prussian blue structure has been revisited. It can be described with the Pm3m space group, where approximately one-quarter of the [FeII(CN)6]4– sites are vacant and where the potassium cation is located at a zeolitic-like position inside the lattice cavities. The degree of ordering of the [FeII(CN)6]4– vacancies in all Prussian blues was quantified using atomic pair distribution analysis, an ordering that is consistent with the iron K-edge X-ray absorption spectra. The presence of strain in the crystals is observed by both powder X-ray diffraction and Mössbauer spectroscopy. The structural similarity between the alkali-free, improperly referred to as “insoluble”, and the alkali containing, “soluble”, Prussian blues may explain why the two varieties are almost undistinguishable by spectroscopic techniques. [less ▲]

X-ray production cross-sections measurements for high-energy alpha particle beam for Si, Fe and Cu

Conference (2013, March)

Investigation of advanced materials for fusion alpha particle diagnostics

in Fusion Engineering & Design (2013)

Fusion alpha particle diagnostics for ITER remain a challenging task. Standard escaping alpha particle detectors in present tokamaks are not applicable to ITER and techniques suitable for fusion reactor ... [more ▼]

Fusion alpha particle diagnostics for ITER remain a challenging task. Standard escaping alpha particle detectors in present tokamaks are not applicable to ITER and techniques suitable for fusion reactor conditions need further research and development [1,2]. The activation technique is widely used for the characterization of high fluence rates inside neutron reactors. Tokamak applications of the neutron activation technique are already well developed [3] whereas measuring escaping ions using this technique is a novel fusion plasma diagnostic development. Despite low alpha particle fluence levels in present tokamaks, promising results using activation technique combined with ultra-low level gamma-ray spectrometry [4] were achieved before in JET [5,6]. In this research work, we use new advanced detector materials. The material properties beneficial for alpha induced activation are (i) moderate neutron cross-sections (ii) ultra-high purity which reduces neutron-induced background activation and (iii) isotopic tailoring which increases the activation yield of the measured activation product. Two samples were obtained from GERDA[7], an experiment aimed at measuring the neutrinoless double beta decay in 76Ge. These samples, made of highly pure (9 N) germanium highly enriched to 87% in isotope Ge-76, were irradiated in real D-D fusion plasma conditions inside the TEXTOR tokamak. Comparison of the calculated and the experimentally measured activity shows good agreement. Compared to previously investigated high temperature ceramic material [8], this candidate detector offers better prospects for signal to background S/B ratio, energy resolution and particle selectivity due to a unique alpha particle signature. Applicability to ITER is discussed. Finally, research needs for further development of this diagnostic technique are outlined. © 2013. [less ▲]

Sections efficaces de production de rayonnement gamma sur Li et F

Poster (2012, December 11)

Automatic X-ray fluorescence scanning mobile system for 2D chemical analysis

Conference (2012, December)

Fusion alpha and proton diagnostics by thin layer activation

Conference (2012, September)

Crystal Structure and Local Disorder in Modern and Ancient Prussian Blue Pigments

Poster (2012, June 06)

The necessity of understanding degradation and alteration processes in a painting's materials is well established for preservation and art history issues. The task is however complex because of the highly ... [more ▼]

The necessity of understanding degradation and alteration processes in a painting's materials is well established for preservation and art history issues. The task is however complex because of the highly heterogeneous character of a paint layer, which consists of a mixture of pigments and a binder on a support. In this context we focus on a particular pigment, Prussian blue. Prussian blue is a hydrated ferric ferrocyanide complex, first synthesized in 1704 in Berlin. It has been widely used by artists until the 1970's. However reports of discoloration had already appeared in eighteenth and nineteenth century books. To date, little attention has been devoted to the understanding of the degradation processes of Prussian blue in paint layers. The preparation methods of Prussian blue were rapidly recognized as a contributory factor in the fading of the pigment because they lead to the introduction of impurities in its structure. The crystal structure of Prussian blue is notoriously complex because of the presence of vacancies and local disorder. Unresolved questions about the crystal structure of the soluble variety of Prussian blue, i.e., Prussian blue containing alkali cations, are still found in the literature. We reproduced modern and ancient preparation methods of Prussian blue and analyzed the obtained pigments by high-energy powder diffraction at the beamline ID11, ESRF, Grenoble and at the beamline CRISTAL, Soleil, Paris. The crystal structure of soluble Prussian blue was reviewed by Rietveld refinement and appears to contain approximately a quart of iron(II) sites vacant, similarly to the well-known insoluble crystal structure. The refinement of the pair distribution function extracted from the total scattering signal revealed a local structure different from the average one. The local arrangements are best described by combining three different substructures with different numbers of vacancies and vary upon the type of synthesis. The PDF analysis also evidenced the formation of nanocrystalline ferrihydrite and alumina hydrate in Prussian blue pigments synthesized according to eighteenth-century recipes. The local disorder and the presence of an undesirable iron compound in Prussian blue can help to better understand the degradation mechanisms in paint layers containing this pigment. [less ▲]

Comparison of sediment core analysis by mobile scanning XRF system and by PIXE

Conference (2012, June)

New external beam and particle detection set-up of Liège cyclotron – First applications of high energy beams to cultural heritage

in Nuclear Instruments & Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (2012), 273

Improvements on the Liége cyclotron have yielded an energy resolution comparable to that of classic electrostatic accelerators. The latest upgrades of the High-Energy High-Resolution beam line (HE-HR) are ... [more ▼]

Improvements on the Liége cyclotron have yielded an energy resolution comparable to that of classic electrostatic accelerators. The latest upgrades of the High-Energy High-Resolution beam line (HE-HR) are presented which consist of the addition of both a new extraction nozzle for non-invasive in-air measurements and a new particle-detection setup developed to take full advantage of the increased probed thickness with depth sensitive analytical methods. The suitability of the new setup and the advantages provided by the larger flexibility in choosing both the proper particle with an extended energy available will be illustrated by discussing latest results of studies recently led on Roman gilding techniques on cultural heritage artifacts by means of “High-Energy” alpha backscattering spectrometry combined with PIXE. [less ▲]