Rafael Ferragut | Scientific.Net

Advances in Medical Imaging: Will Positron Annihilation Spectroscopy Be the Promise of Preventive Diagnostics

Authors: Matteo Vicini, Paola Folegati, Rafael Ferragut, Claudio Conci

Abstract: Positron annihilation spectroscopy (PAS) offers a transformative approach to medical imaging, providing detailed insights into molecular structures. Although PAS has been extensively applied in studying defects in semiconductors and synthetic materials—yielding quantitative data on their microscopic properties—its potential in medical imaging could significantly enhance diagnostic methodologies. The application of positrons and other forms of radiation in analyzing living tissues necessitates careful consideration of potential damage. In this work, a model method designed to determine the optimal dose for experimental measurements is introduced. While Positron Emission Tomography (PET) has been instrumental in clinical diagnostics using radiopharmaceuticals to visualize metabolic processes, PAS presents a cutting-edge tool for improving the specificity and accuracy of biological imaging. Its capability to non-destructively explore structural transformations and micro-environmental changes in biological samples positions it as a promising innovation in diagnostics, paving the way for enhanced healthcare outcomes globally.

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Coincidence Doppler Broadening to Study the Chemical Environment at Positron Annihilation Sites

Authors: Rafael Ferragut

Abstract: This paper introduces a Coincidence Doppler Broadening (CDB) analysis method, as presented during the Alfredo Dupasquier [1] Summer School held in Brunate preceding the 2024 International Workshop on Positron Studies of Defects (PSD-24) in Como. CDB spectroscopy provides quantitative information on the chemical environment surrounding defects in various materials, including metal alloys, oxides, and polymers. Reference materials were analyzed to estimate the average chemical environment around defects, voids and porosities. The methodology is applied not only to homogeneous materials, such as metallic alloys, but also to investigate depth profiles in thin films of various materials. The statistical accuracy of element separation is also examined, along with the necessity to refine the method’s calibration through theoretical calculations and the integration of direct observation techniques.

27

Positron Manipulation and Positronium Laser Excitation in AEgIS

Authors: Sebastiano Mariazzi, Ruggero Caravita, Stefano Aghion, Claude Amsler, Akitaka Ariga, Tomoko Ariga, Germano Bonomi, Philippe Bräunig, Johan Bremer, Roberto S. Brusa, Luis Cabaret, Massimo Caccia, Fabrizio Castelli, G. Cerchiari, Karl Chlouba, Simone Cialdi, Daniel Comparat, Giovanni Consolati, Andrea Demetrio, Lea di Noto, Michael Doser, Alexey Dudarev, Antonio Ereditato, Craig Evans, Rafael Ferragut, Julian Fesel, Andrea Fontana, Ola K. Forslund, Sebastian Gerber, Marco Giammarchi, Angela Gligorova, Sergei Gninenko, Francesco Guatieri, Stefan Haider, Helga Holmestad, Torkjell Huse, Ine L. Jernelv, Elena Jordan, Thomas Kaltenbacher, Alban Kellerbauer, Mitsuhiro Kimura, Torsten Koetting, Daniel Krasnicky, Vittorio Lagomarsino, Pierre Lansonneur, Patrice Lebrun, Sebastian Lehner, Joanna Liberadzka, Chloe Malbrunot, Lisa Marx, Viktor Matveev, Zeudi Mazzotta, Giancarlo Nebbia, Patrick Nedelec, Markus Oberthaler, Nicola Pacifico, Davide Pagano, Luca Penasa, Vojtech Petracek, Ciro Pistillo, Francesco Prelz, Marco Prevedelli, Luca Ravelli, Laura Resch, Benjamin Rienäcker, Ole M. Røhne, Stefan Rosenberger, Alberto Rotondi, Michele Sacerdoti, Heidi Sandaker, Romualdo Santoro, Paola Scampoli, Fiodor Sorrentino, Michal Spacek, James Storey, Izabela M. Strojek, Gemma Testera, Ingmari Tietje, Stefan Vamosi, Eberhard Widmann, Pauline Yzombard, Sandra Zavatarelli, Johann Zmeskal

Abstract: Production of antihydrogen by using the charge exchange reaction, as proposed by AEgIS (Antimatter Experiment: gravity, Interferometry, Spectroscopy), requires the formation of a dense cloud of positronium atoms excited to Rydberg states. In this work, the recent advances in AEgIS towards this result are described. Namely, the manipulation of positrons to produce bunches containing more than 10⁸ particles and the laser excitation of positronium to Rydberg states, using n=3 as intermediate level, are presented.

11

Study of the Nanostructures Formed in 2024 Alloy during Thermomechanical Treatments

Authors: Alfredo Tolley, Rafael Ferragut, Alberto Somoza

Abstract: A study on the microstructures developed during artificial aging of the 2024 alloy in nondeformed and 8% pre-deformed specimens is presented. The microstructural characterization was carried out using transmission electron microscopy (TEM), specifically, diffraction contrast and highresolution imaging. The S phase was found to precipitate heterogeneously on dislocations in both nondeformed and pre-deformed alloys. After the same artificial aging time, a larger density of S phase precipitates was obtained in the pre-deformed specimens. In non-deformed specimens, a high density of small nanometer-sized aggregates was found, that was absent in the pre-deformed specimens, that were identified as GP zones. To further analyze the small sized aggregates, artificially aged specimens with no previous deformation were also studied with Coincidence Doppler Broadening (CDB) of positron annihilation radiation. With this technique, information on the chemical environment around vacancy sites contained in the GP zones was obtained. Specifically, a composition close to (AlCu)2Mg was derived.

489

Vacancy-Solute Aggregates in Al-Zn-Mg-(Cu, Ag)

Authors: Rafael Ferragut, A. Dupasquier, M.M. Iglesias, C.E. Macchi, Alberto Somoza, Ian J. Polmear

Abstract: Positron annihilation spectroscopy in two versions (lifetime and coincidence Doppler broadening) has been applied to investigate solute/vacancy interactions when minor amounts (<1wt.%) of Ag or Cu are added to the alloy Al-4Zn-3Mg (wt.%) during ageing at 150°C. The results show early clustering of vacancies with Zn (and with Cu, if present). Ag displays a strong interaction with vacancies in competition with Mg and forms clusters that may help further aggregation of the other alloying elements during artificial ageing. High Mg concentration is observed at the misfit interfaces of semi-coherent or incoherent precipitates.

309

Vacancy-Solute Interactions in Al-Cu-Mg

Authors: R.K.W. Marceau, Rafael Ferragut, A. Dupasquier, M.M. Iglesias, Simon P. Ringer

Abstract: This is an initial report of a multi-technique study on the effect of Mg alloying on solute-vacancy interactions during the early stages of ageing of dilute 2xxx Al-Cu-Mg alloys so as to better understand the early rapid hardening (RH) that occurs in certain compositions of these alloys and the more general phenomena of secondary hardening (SH) at ambient temperatures. Therefore, RH at 150 °C and SH at room temperature from the as-quenched condition and after 60 sec ageing at 150 °C were studied in Al-1.1Cu and Al-1.1Cu-0.5Mg (at. %) variously by positron annihilation lifetime spectroscopy (PALS), coincidence Doppler broadening (CDB) spectroscopy and atom probe tomography (APT) and monitored by Vickers hardness measurements. The present results indicate that Cu-Cu, Mg-Mg and Cu-Mg clusters are formed in the ternary alloy already in the asquenched state and that they persist during ageing at 150 °C. The fraction of the solutes Cu and Mg that were associated with vacancies after ageing was increased 10-fold and double, respectively and the strength of the Cu clustering is enhanced greatly after 60 sec at 150 °C.

197

Positron Spectroscopy Analysis of Vacancy-Solute Nanoaggregates in Al-Cu

Authors: Rafael Ferragut, Gabriel Ferro, M. Biasini, A. Dupasquier, Alberto Somoza

75

Early Solute Clustering in an AlZnMg Alloy

Authors: A. Dupasquier, Rafael Ferragut, M.M. Iglesias, C.E. Macchi, Mario Massazza, P. Mengucci, G. Riontino, Alberto Somoza

16

Secondary Ageing in an Al-Cu-Mg Alloy with High Cu/Mg Ratio

Authors: A. Dupasquier, Rafael Ferragut, P. Folegati, Mario Massazza, G. Riontino, Alberto Somoza

783

Mechanisms of Age-Hardening in two Al-Cu-Mg Alloys Studied by Positron Annihilation Spectroscopy

Authors: Rafael Ferragut, Alberto Somoza, A. Dupasquier, Ian J. Polmear

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Papers by Author: Rafael Ferragut