Kevin Ambrogioni

In the field of cultural heritage, there is an urgent need to enhance our understanding of the composition of plastic materials and their degradation processes, especially given their susceptibility to relatively rapid deterioration. Among these materials, acrylonitrile–butadiene–styrene (ABS), commonly found in museum collections, is particularly vulnerable to photoaging, primarily affecting the polybutadiene (PB) phase through oxidation and cross-linking, significantly compromising its mechanical properties. While noninvasive techniques have been successfully applied to characterize surfaces of ABS-based objects, a major limitation exists in terms of assessing the depth and spatial distribution of degradation without invasive sampling. This study introduces microspatially offset Raman spectroscopy (micro-SORS) as a noninvasive method to investigate artificially aged turbid ABS-based objects at both the surface and the subsurface level. First, micro-SORS spectra were collected using both a benchtop and an in-house-developed micro-SORS portable prototype, demonstrating the potential of the method for in situ diagnostics. Then, a simplified physical model based on light transport in turbid material is developed to describe the UV–vis photo-oxidation process. Lastly, a protocol is proposed for estimating the degradation depth in turbid ABS-based materials by interpreting micro-SORS measurements through the UV–vis degradation model. The model is initially calibrated through a few sacrificial samples to estimate the physical parameters. Then, the approach operates fully noninvasively, providing quantitative insights into subsurface aging phenomena. By providing a new strategy for depth-resolved aging assessment, this work bridges a key methodological gap in polymer conservation and paves the way for more informed treatment strategies and future noninvasive diagnostic applications.

Low-density near-critical materials in laser-plasma interaction (LPI) stand out for their capability in enhancing the coupling between the laser radiation and the target. Indeed, they can be exploited for fundamental physics studies, optimised particle acceleration for practical applications, and inertial confinement fusion. However, the modelling of complex non-linear phenomena occurring during the interaction of these materials and high-intensity lasers, together with the accurate control and characterisation of their physical properties, are still object of intense research. In this context, near-critical nanofoams produced via pulsed laser deposition represent a promising option owing to the versatility and controllability of their deposition technique. In this paper, we report on our modelling and experimental activities related to laser-nanofoam interaction. In particular, we first present the deposition methodology, focusing on the production of nanofoams with controlled composition and morphology. Then, we show our numerical strategy to model the foam aggregation. We also discuss how the nanofoam morphology affects the LPI by integrating the realistic nanostructure in particle-in-cell simulations, focusing on various regimes of interaction. Lastly, we present examples of applications of nanofoam-based targets via numerical simulations and experiments, focusing also on the open issues for reaching the requirements for full-fledged applications. Our work demonstrates nanofoam-based targets as a versatile tool to effectively optimise and advance LPI physics.

A source of high-energy photons, ions, and positrons can be attained with the interaction of ultra-intense femtosecond laser pulses with advanced nanostructured targets. We present and characterise a numerical model that mimics the foam deposition process on solid substrates, as it occurs in Double-Layer Target (DLT) manufacturing. The model is integrated into Particle-In-Cell (PIC) simulations in full three-dimensional geometry to study electron acceleration, consequent high-energy photon emission, proton acceleration, and pair production with realistic target and laser parameters, focusing on Strong-Field Quantum Electrodynamics (SFQED) processes. We highlight the importance of realistic foam morphology modelling even at high-laser intensity and the need for specific optimisation of target parameters with realistic PIC simulations to improve radiation production efficiency. Our study shows that the DLT could be a compact multi-purpose scheme to achieve high-brightness photons and high-energy protons and to observe and optimise non-linear Breit-Wheeler pair production.

Contemporary murals are highly susceptible to rapid color fading due to outdoor urban exposure. This study investigates the photodegradation mechanisms affecting synthetic organic pigments (SOPs) and commercial acrylic–vinyl paints under simulated visible light exposure. Artificial aging experiments were conducted on two types of systems: (a) pigment pellets, composed of pre-fixed pigments on mineral bases, as supplied by the manufacturer, and (b) commercial paints applied on glass substrates. Both systems were aged under controlled and uncontrolled relative humidity (RH) conditions. Colorimetric analyses revealed significant color fading, particularly in pigments PR112, PO5, and PV23. Vibrational spectroscopies highlighted the reduction in pigment-related bands after aging, indicating SOPs’ vulnerability to photodegradation. In paint mock-ups, FTIR-ATR measurements indicated binder degradation and an increase in signals from inorganic fillers. A superficial layer enriched in inorganic components was investigated non-invasively by Micro Spatially Offset Raman spectroscopy (Micro-SORS) in the beamsteer modality. It highlighted a gradient of calcite to pigment with depth. These findings indicate that color fading in mural paints results from the combined degradation of both pigments and binders.

A source of high-energy photons, ions, and positrons can be attained with the interaction of ultra-intense femtosecond laser pulses with advanced nanostructured targets. We present and characterise a numerical model that mimics the foam deposition process on solid substrates, as it occurs in Double-Layer Target (DLT) manufacturing. The model is integrated into Particle-In-Cell (PIC) simulations in full 3D geometry to study electron acceleration, consequent high-energy photon emission, proton acceleration, and pair production with realistic target and laser parameters. We highlight the importance of realistic foam morphology modelling even at high-laser intensity and the need for specific optimisation of target parameters with realistic PIC simulations to improve radiation production efficiency. Our study shows that the DLT could be a compact multi-purpose scheme to achieve high-brightness photons and high-energy protons and to observe and optimise non-linear Breit-Wheeler pair production.