The traditional Debye-Scherrer method for crystallite size determination faces fundamental limitations when analyzing nanosized objects due to peak broadening effects. This research explores parametric X-ray radiation (PXR) as a promising alternative approach, where radiation is excited directly from the beam of relativistic electrons passing inside a material, enabling a nanostructure characterization. We present systematic research of PXR from diamond powders across a wide particle size range (4 nm through 42 μm). Experiments conducted at the Röntgen-1 facility using a 7 MeV microtron revealed identifiable PXR reflections from the (111) and (220) crystallographic planes. The key finding demonstrates significant PXR peak broadening for nanopowders (4 nm), which exceeds the instrumental resolution by a factor of up to five at a 150° observation angle.
Particle Induced X-ray Emission (PIXE) is widely used for the elemental analysis of cultural heritage materials; however, irradiation by MeV protons can induce physical and chemical modifications that may compromise the integrity of sensitive samples. In this work, we investigate radiation-induced colour changes in proxy rock art paints subjected to proton irradiation with fluences in the range relevant to PIXE analysis, and higher. Samples consisting of natural colouring materials combined with representative binders and substrates were irradiated using two different accelerator systems: ELISA (at CERN), a compact radio-frequency quadrupole (RFQ) linac delivering a pulsed proton beam; and a conventional tandem accelerator (Tandetron, at the Surrey Ion Beam Centre, SIBC) providing a continuous (DC) beam. Colour changes were quantified using image-based analysis of high-resolution scans acquired before and after irradiation. The dependence of colour change on fluence was characterised; for both of the accelerator systems used, the degree of colour change increased with fluence, saturating at some level. However, the samples tested showed a greater sensitivity to irradiation at ELISA than at SIBC. Although the facilities differ in several respects, one of the main differences is in the beam time structure (DC at SIBC, pulsed at ELISA), raising the possibility that dose rate or temporal structure may play a role in colour modification processes. These findings have implications for the optimisation of PIXE measurements for studies of cultural heritage objects, including in the development of portable systems operating with pulsed beams. Further work is required to establish quantitative damage thresholds and to disentangle the contributions of dose rate, beam profile and material composition.
