1,721,081 research outputs found
Metodologie per la rivelazione e il riconoscimento di impurezze solide mediante sorgenti X : caratterizzazione di materiali complessi con applicazione al caso della matrice solida dell'acqua
Full text linkI ghiacciai sono un naturale sistema di immagazinamento di dati climatologici, che consente attraverso le precipitazioni di raccogliere in serie temporalmente ordinate le particelle provenienti dalla circolazione atmosferica. A questo proposito, l'identificazione di polvere mineralogia svolge un ruolo chiave. In questa tesi, partecipo ad un esperimento preliminare di spettroscopia di assorbimento X (XAS) di minerali di polvere estratte da carote di ghiaccio antartico e alpino sulla soglia del Fe. Nella tesi viene descritta una camera sperimentale da alto vuoto, progettata e realizzata per lo studio della fluorescenza e assorbimento X anche ad incidenza radente. Presso lo Stanford Synchrotron Radiation Lightsource (SSRL), sono state effettuate misure di fluorescenza e assorbimento X di materiali a bassissime concentrazioni. I risultati mostrano che questa tecnica sperimentale permette il riconoscendo di inclusioni di ferro (dell'ordine di 1-10 ug) nel particolato insolubile .
Inoltre, presso i Laboratori Nazionali di Frascati dell'INFN, con il mio contributo è stato progettato, sviluppato e realizzato, un sistema di micro-spettroscopia, discusso nella tesi, al fine di raggiungere una mappatura di micro-fluorescente X (uXRF) con una risoluzione spaziale di chi 100x100 um. Questo apparecchio permette anche di effettuare "Imaging" (con radiazione non coerente), per mezzo di un ingrandimento del settore in analisi mediante lenti rifrazione (CRL).Aeolian mineral dust archived in polar and mid latitude ice cores represents a precious proxy for assessing
environmental and climatic variations at different timescales. In this respect, the identification of dust
mineralogy plays a key role. In this thesis, I partecipate in preliminary X-ray absorption spectroscopy
(XAS) experiments on mineral dust particles extracted from Antarctic and from Alpine firn cores at the Fe K-edge. A dedicated high vacuum experimental chamber was set up for
normal-incidence and X-Ray Fluorescence (normal and total-reflection configuration) and Absorption Spectroscopy analyses on minor
amounts of mineral materials at the Stanford Synchrotron Radiation Lightsource. Results show that this experimental technique and protocol allows recognizing iron inclusion mineral fraction on insoluble dust in the 1-10 ug range.
Moreover, at the "Laboratori Nazionali di Frascati" of INFN, with my contribution has been designed, developed and done, a system of micro-spectroscopy, discussed in the thesis, in order to achieve a mapping in micro-fluorescent X (uXRF) with a spatial resolution of about 100x100 um. This apparatus allows also to carry "imaging" (with radiation not coherent), by means of a magnification of the area in analysis by means of lenses refractive (CRL)
CTS—A new X-ray facility for imaging and tomography @ XlabF
No full textX-ray based techniques are widely used in the world. However, high interactions between radiation and
matter causes a not so easy radiation handling by optical devices. In the last 30 years, the studies concerning
novel advanced material have fostered the development of several solutions for more efficient X-ray setup,
necessary to perform high spatial resolution analysis in spectroscopy as well as for imaging techniques applied
in Medicine/Pharmacology, Cultural Heritage, Geology and Environment, Electronics, Aerospace, etc.
Recent results (principally in three main fields, such as high resolution X-ray Imaging, micro X-Spectroscopy
and micro Tomography) obtained at XLab-Frascati (XlabF) were previously discussed while very recently, a
new experimental setup, dedicated for High Resolution X-ray Imaging and micron-Tomography, was developed as
a part of Italian Premiale project, called "Computed Tomography Station" (CTS). This apparatus is equipped
with a micro-focusing source (5 μm on the anode), high precision mechanics and high-resolution CCD detector
(10.4 μm per pixel), so as through the phase retrieval technique, we can reach the estimated resolution of less
than 1 μm. The CTS experimental setup was commissioned ad the beginning of 2023 and it is already ready
to be opened for internal and external users.
In this work, we will show the last results concerning our new experimental setup, related to the analysis
of a glass capillary, with different geometrical distances, and two organic samples entrapped in matrix amber.
Starting from these results, the next step is to use modern polycapillary optics as a grating interferometric
hexagonal matrix for a better phase-contrast resolution
Time resolved IR and X-ray simultaneous spectroscopy: new opportunities for the analysis of fast chemical-physical phenomena in materials science
No full textShaped X-ray beams by channeling in polycapillary optics
No full textPolycapillary optics (polyCO) is an x-ray optical unit used in different instruments in a wide variety of scientific and industrial applications. The optics works utilising the phenomenon of x-ray total external reflection at radiation transmission through the optics micro-channels. The polyCO devices, according to their geometries, are capable to focus x-ray beam, manipulate divergent or quasi parallel beams. Their use may reduce both size and weight of the device resulting in low power compact x-ray instruments. However, matching polyCO parameters is crucial for developing portable, remote or in-line, industrial sensors and novel instruments for materials science, chemical-environmental and bio-medical applications.In this work we present the analyses of x-ray beam formed behind polyCO devices paying attention to the parameters such as the radiation flux, focal spot-size and divergence. X-ray techniques will be also discussed to outline state of the art of world-wide polyCO-based research
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Desktop X-ray tomography for low contrast samples
No full textBased on the experience in the use of polycapillary optical systems, recently XLab Frascati LNF and IM CNR have been strongly involved in studying the techniques for high resolution X-ray Imaging and micro-tomography that intends in the development of a new imaging instrument to examine low con-trast samples complicated by fast developing processes. In order to get the reliable signal to noise ratio, typically available via synchrotron radiation (SR) dedicated X-ray optical devices, for the desktop solu- tions we have to increase the radiation fluxes from conventional sources. As known, manipulated through polycapillary optics beams result in getting higher fluxes with respect to a pin-hole (with a gain factor of
102–103). Moreover, polycapillary semi lenses can provide low divergent beams comparable by the divergence with synchrotron radiation beams (mrad order). These features make possible the realization of high resolution imaging of low contrast samples in the transmission mode without various algorithmic processes as typically done, for instance, for phase contrast imaging.
This work presents the results on X-ray micro tomography for both static biological and fast dynamic samples as well as a possible future development of a polycapillary-based experimental layout for bio-medical imaging diagnostics, for the studies in material and environmental sciences, for diagnostics ofhi-tech samples, etc
X-ray applications and recent advances @ XLab Frascati
Full text linkXLab Frascati is a facility open to external users for different X-ray analyses, ranging from structural studies through X-ray diffraction to elemental mapping by means of μX-ray Fluorescence, colour tomography and X-ray imaging studies. This is possible thanks to our experimental layouts XENA (X-ray Experimental station for Non-destructive Analysis) and RXR (Rainbow X-Ray) along with our facility for the production of polycapillary optic
Colour characterisation for the restoration of a japanese handscroll
No full textIn the restoration of painted artworks, the colour characterisation is a fundamental analysis to address the choice of suitable materials for the recovery and the consolidation of the painting layers. In this paper, we present a diagnostic study on a unique Japanese painted paper handscroll (emakimono), dated back between the late Edo (1603-1867) and the early Meiji (18681912) periods, preserved at the Museum of the Civilisation-Prehistoric Ethnographic Museum "Luigi Pigorini" in Rome (Italy). The artwork required an urgent restoration and the consolidation of the entire structure. In order to define specific interventions, non-destructive measurements by means of Fiber Optics Reflectance Spectroscopy (FORS) X-Rays Fluorescence Spectroscopy (XRF) were carried out on the artefact. The results allowed the identification of the colour palette used for tests on the chromaticity and the efficacy of the proper consolidants to employ in the restoration
Application of polycapillary optics to x-ray fluorescence for advanced spectroscopy and microscopy studies
No full textAdvances in x-ray techniques, including x-ray optics, have paved the way to obtain challenging results in several research fields thanks to the improvement in terms of spatial resolution. This is particularly true for x-ray fluorescence (XRF), where the combination of conventional x-ray sources with polycapillary optics has permitted to have high flux and high focused beams. However, XRF spectroscopy applied to archeological samples at a lab scale is mainly dedicated to qualitative studies. At the same time, quantitative analysis still remains a strong hurdle mainly due to important matrix effects that affect the signal related to the chemical components under evaluation. In this respect the adoption of x-ray optics on both the source and the detector represents a way to improve the signal to noise ratio, necessary for quantitative analysis. At LNF XLab Frascati the expertise, gained on x-ray techniques and on polycapillary lenses, has allowed researchers to carry out advanced μXRF studies. RXR (Rainbow X-ray), is the experimental station dedicated to 2D/3D XRF micro-imaging and TXRF analysis, being equipped with 2 detectors of different energy efficiency (covering a full spectrum from 800 eV to 25 keV) and working in confocal mode with the source coupled with a full-lens and both the detectors combined with dedicated half-lenses. This report aims in depicting the RXR potentialities through the results obtained in 2 case studies dedicated to carry out a semi-quantitative analysis of 2 different artifacts (an ancient book, a Buddhist scroll) by μXRF characterization
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