How Fast Ions Damage Crystalline Materials
When a radioactive atom fissions inside a mineral, its fast-moving fragments wreak nanometer-scale trails of damage known as fission tracks. Researchers study their formation by pelting high-energy ions at materials in accelerators to create similar trails, known as ion tracks. In principle, these trails can be used to characterize new materials or to investigate the melt history of rocks in Earth’s crust, as their shapes depend on the microscopic structure of the damaged material. However, linking the tracks to a material’s crystal structure has been difficult because previous methods lacked sufficient resolution. Now Jessica Wierbik at the Australian National University (ANU) and collaborators have adapted a small-angle x-ray scattering (SAXS) setup to study ion tracks produced along crystallographic directions in various single crystals [1]. The SAXS images revealed that an ion track’s cross-sectional shape depends on its alignment with respect to the crystal’s axes.
The team tested its method on three different materials: lab-grown alpha-quartz and two natural gemstones, fluorapatite and tourmaline. To create ion tracks, the researchers pelted these materials with gold ions at the 14UD accelerator at ANU. By rotating the crystalline samples 360 degrees around the ion-track axis, they captured the entire cross-sectional shape for each sample. An ion track’s size and whether its cross-sectional shape was circular or not turned out to depend on how the track aligned with the two crystallographic directions studied. The tracks from the three materials differed depending on each crystal’s elasticity, where higher elasticity along a particular crystallographic direction corresponded to a wider track radius in that direction. Wierbik says that her team’s technique could lead to the design of better materials for encapsulating nuclear waste.
Correction (28 January 2026): The second paragraph has been changed to clarify that the sample was rotated around the ion track axis and not the SAXS detector as stated in the original version.
–Sophia Chen
Sophia Chen is a freelance science writer based in Columbus, Ohio.
References
- J. Wierbik et al., “Anisotropic fine structure of ion tracks in single crystals,” Phys. Rev. B 113, 035306 (2026).