XRF

A combined experimental approach to the study of ancient coins and its application: the Venetian “sesino”

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Sesino Doge Priuli rettoThe material study of ancient coins is very often rendered particularly challenging by several factors: the presence of surface alteration products; the occasional or deliberate, e.g., forgery, changes in the composition of the base alloy; the misleading information deriving from historical and literature sources.

We present herewith a multi-analytical approach to the study of ancient coins. The selected test samples are coins widely used in the Venetian Republic over a time span ranging from the second half of the 16th until the early years of the 17th century: the so-called “sesino”. The rationale of the study was to establish a model, taking into account the layered structure of the surface region of the coins, that once validated could be used for a fully non-destructive characterization of similar items. The specific interest of the results obtained from this investigation is twofold. First, the actual composition of the copper based alloy used for these specific type of Venetian coin, has been measured for the first time with direct measurements on the coin cross-section. Second, the detailed characterization of the coins provides an essential background knowledge for a fully non-destructive characterization of the same kind of coins.

Link to the complete text: https://doi.org/10.1016/j.nimb.2019.06.010

Combined XRD-XRF cluster analysis for automatic chemical and crystallographic surface mappings

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X-ray diffraction-X-ray fluorescence (XRD-XRF) data sets obtained from surface scans of synthetic samples have been analysed by means of different data clustering algorithms, with the aim to propose a methodology for automatic crystallographic and chemical classification of surfaces.

Three data clustering strategies have been evaluated, namely hierarchical, k-means, and density-based clustering; all of them have been applied to the distance matrix calculated from the single XRD and XRF data sets as well as the combined distance matrix. Classification performance is reported for each strategy both in numerical form as the corrected Rand index and as a visual reconstruction of the surface maps. Hierarchical and k-means clustering offered comparable results, depending on both sample complexity and data quality.

When applied to XRF data collected on a two-phases test sample, both algorithms allowed to obtain Rand index values above 0.8, whereas XRD data collected on the same sample gave values around 0.5; application to the combined distance matrix improved the correlation to about 0.9. In the case of a more complex multi-phase sample, it has also been found that classification performance strongly depends on both data quality and signal contrast between different regions; again, the adoption of the combined dissimilarity matrix offered improved classification performance.

Link to the complete text: https://doi.org/10.1017/S0885715619000216

EXSA Quant 2017 Workshop – Berlino

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EXSA Martorelli DamianoDall’11 al 13 Ottobre abbiamo preso parte all’EXSA Quant 2017, un workshop congiunto alla riunione della Fundamental Parameter Initiative.

Circa 75 colleghi, tra cui 25 studenti, hanno partecipato a una settimana di intenso dibattito e scambio scientifico sul tema “Metodi quantitativi nella spettrometria a raggi X”. Due giorni di lezioni preliminari hanno introdotto gli studenti sull’argomento, mentre il seminario comprendeva discussioni sulla ricerca in corso e due vivaci discussioni, una sui Parametri fondamentali e l’altra sull’imaging micro-XRF.

Inoltre, l’area dedicata alla presentazione dei poster ha riscontrato un grande successo e ha fornito una piattaforma eccellente per i partecipanti per mostrare la ricerca scientifica che ha completato le sessioni in corso durante il workshop.

EXSA Quant 2017 Foto di Gruppo - Copyright M.Waehmer, PTB 2017
EXSA Quant 2017 – Foto di Gruppo al’EXSA Workshop di fronte alla sede del PTB di Berlino (D) – Copyright M. Waehmer, PTB 2017

Poster Martorelli Damiano EXSA Quant 2017Da parte nostra, abbiamo presentato il poster “Characterization of Venetian coins sesini (XVI century) through a combined XRF/XRD quantitative approach” D. Martorelli(1,2), M. Bortolotti(1), L. Lutterotti(1), G. Pepponi(2), B. Marcinik (collaborazione tra (1) Università di Trento, Department of Industrial Engineering, Via Sommarive 9, 38123 Trento, (2) Center for Materials and Microsystems, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Trento). Il poster ha riguardata l’analisi non distruttiva ai raggi X (in tecnica combinata XRF/XRD) di antiche monete veneziane del XVI secolo, chiamate sesini, di prorpietà del Comune di Ala (TN) e oggetto di analisi quantitativa ai fine della ricostruzione del contenuto in lega argento-rame e dei contaminanti e fasi di corrosione presenti sulla superficie delle monete, autenticate dalla numismatica dr.ssa Beate Marcinik.

Un premio poster è stato organizzato per riconoscere ad un dottorando che ha dimostrato una ricerca di alta qualità presentata in formato poster e ha evidenziato le prospettive scientifiche del lavoro.

Il premio per il miglior poster è stato assegnato a Malte L. Wansleben per il suo lavoro su “A compact and calibratable von-Hamos X-Ray Spectrometer based on full-cylindrical HAPG mosaic crystals“.