Speaker
Description
Based on the interaction of negative muons with matter and the following emission of X-ray radiation (specific to the atom which absorbed the muon), Muonic atom X-ray Emission Spectroscopy (µXES) is a very powerful method for elemental characterisation. Compared to common methods, which employ X-ray and electron beams, a significant advantage of using negative muons is their remarkable penetration depth. Moreover, thanks to their high energy (0.01-6 MeV), muonic X-rays are emitted from the bulk of the samples without significant photon self-absorption, thus enabling depth profiling. These characteristics, with the addition of a wide multi-elemental range (from Lithium to Uranium) and no residual activity left in the sample after irradiation, make µXES a unique tool for elemental analysis, with many different research projects published in the last few years [1, 2].
Over the last decade, the CHNet group at the INFN Milano-Bicocca section has actively collaborated with the ISIS Neutron and Muon Source to develop and apply μXES for Heritage Science studies. With two CSNV-founded projects and two PhD projects, the Milano-Bicocca section has built a unique knowledge and experience about negative muon spectroscopy. Within this framework, the CHNet-MAXI project, which concluded at the end of last year, focused on the development and validation of a non-destructive approach for the determination of lead isotopic ratios, a key tool for provenance studies of archaeological and historical artefacts. The project investigated isotopic shifts in high-energy muonic X-ray lines and associated γ-ray emissions following muon nuclear capture, through systematic measurements on certified Pb standards irradiated with negative muons, along with the development of a new digital acquisition system.
Besides development projects, the group continues the activities in support of users, including an ongoing collaboration with the Opificio delle Pietre Dure for the study of gilded surfaces and enamels. In the past years, experimental campaigns have been carried out at the ISIS facility to further contribute to the consolidation of the technique and the strengthening of the collaboration. In this context, Monte Carlo simulation software is routinely employed to support data interpretation. Simulation tools are used to optimise experimental configurations, reproduce experimental setup and correlate measured spectral features with sample composition and depth, highlighting the role of digital tools in the advancement of non-invasive cultural heritage analysis [3].
References
[1] Hillier, A.D., Blundell, S.J., McKenzie, I. et al. Nat Rev Methods Primers 2, 4, 2022.
[2] K. Ninomiya, Journal of Nuclear and Radiochemical Sciences 19, 2019, 8-13.
[3] M. Cataldo, A.D. Hillier et Al, Spectrochimica Acta Part B: Atomic Spectroscopy, 2025