A Novel Non-Destructive Technique for Cultural Heritage: Depth Profiling and Elemental Analysis Underneath the Surface with Negative Muons

Abstract

Scientists, curators, historians and archaeologists are always looking for new techniques for the study of archaeological artefacts, especially if they are non-destructive. With most non-destructive investigations, it is challenging to measure beneath the surface. Among the vast board of techniques used for cultural heritage studies, it is difficult to find one able to give information about the bulk and the compositional variations, along with the depth. In addition, most other techniques have self-absorption issues (i.e., only surface sensitive) and limited sensitivity to low Z atoms. In recent years, more and more interest has been growing around large-scale facility-based techniques, thanks to the possibility of adding new and different insights to the study of material in a non-destructive way. Among them, muonic X-ray spectroscopy is a very powerful technique for material characterization. By using negative muons, scientists are able to perform elemental characterization and depth profile studies. In this work, we give an overview of the technique and review the latest applications in the field of cultural heritage.

A Vision for the Future of Neutron Scattering and Muon Spectroscopy in the 2050s

“…Beams coming from pions decaying in flight are called “decay muons”, allowing for higher and lower momenta and also negative muons. Decay muons can be used in pressure cells, in situations where a negative muon has a clearer interaction with the sample, or to use the X-rays emitted by nuclear capture of negative muons to determine the elements the sample contains, this has particular advantages for studies of cultural heritage objects . All of these techniques work with bulk samples but beams of positive muons can also be moderated to far lower energies, “slow muons” with keV rather than MeV energies, which are used to study thin film materials with thicknesses in the range 10–200 nm …”

Neutron and muon characterisation techniques for battery materials

“…This technique is called muonic atom X-ray emission spectroscopy (μ-XES) and has two main advantages over its X-ray counterpart due to the intrinsic properties of the muon: it is non destructive, and the emitted signal is much more energetic making it possible to detect light elements such as lithium. 147 So far, this technique has been mainly applied to cultural heritage studies due to the non-destructiveness of the technique, 145 however, Umegaki et al used μ-XES to detect metallic lithium deposited on a graphite anode. 146 They found that the intensity of muonic X-rays from metallic lithium was about 50 times higher than that of lithium ions, which allowed them to clearly distinguish between both.…”

The Implementation of MuDirac in Geant4: A Preliminary Approach to the Improvement of the Simulation of the Muonic Atom Cascade Process

“…The process, after initial muon-induced Auger emission, becomes radiative, with the emission of high-energy X-rays (an extensive description of muon capture and muonic atoms can be found here [13]). With a particular interest in Cultural Heritage studies, the technique has many fields of applications, from the characterization of lithium batteries to meteorites to material engineering [14][15][16][17][18][19][20][21][22]. Given its novelty, the technique has room for improvement, especially as it is now performed at the ISIS facility in terms of detector, electronics and data interpretation.…”