Hydrogen isotope retention and impact in materials containing crystal lattice defects

Understanding the interaction of hydrogen with the host lattice of plasma-facing as well as structural materials is crucial since low hydrogen isotope (HI) retention is a stringent prerequisite in thermonuclear fusion. In a future fusion power plant, the largest fraction of the released energy is carried by high-energy neutrons produced by the deuterium-tritium fusion reaction (D + T → He (3.5 MeV) + neutron (14 MeV)). For the expected operational reactor duty cycles the irradiation by 14 MeV neutrons will create defects in the material lattice, the so-called displacement damage, which is anticipated to be few displacements per atom per year. Created defects will importantly influence on HI retention and transport, since lattice defects act as trapping sites for HIs with high de-trapping energy as compared to the energy of HI diffusion. This PhD work will be focused on the development of a new characterization technique to explore the influence of structural defects on HI retention and vice versa. We want to develop and use a novel ion channelling method at the tandem accelerator laboratory in Ljubljana to characterize the produced structural defects and HI retention. As an upgrade to existing channelling procedures applying Rutherford backscattering spectroscopy in channeling configuration (RBS-C), we want to combine it with the absolute quantitative deuterium detection method and perform it in the channelling mode, so-called channeling-nuclear reaction analysis (NRA-C). Such an approach will enable the direct correlation of the HI retention with the structural defects (from small structural defects, such as vacancies, to large defects such as voids) and determination of the lattice positions of hydrogen atoms around studied structures.

PhD candidate would study the defects in the crystal lattice of the material caused by high-energy particle bombardment and consequently impact of these defects on the retention of hydrogen isotopes in the materials. As part of the doctoral topic, the candidate would develop analytical techniques in channeling mode (RBS-C and NRA-C) in the existing experimental setup that will allow the detection of defects in the crystal lattice and the amount of hydrogen trapped in the defects. This newly developed techniques will allow us to upgrade our current knowledge in the interaction of HI with defects with the goal of better extrapolation for future fusion reactors. The proposed project will also bring a new analysis method for material development for laboratories working on hydrogen technology (hydrogen storage) and for characterization of materials for laboratories studying hydrogen embrittlement. PhD work will be internationally involved and will be part of European EUROfusion projects.  

 The work would take place at a Department for low and medium energy physics (F2) in an experimental station on 2 MV tandem accelerator, in a dynamic and relaxed environment. It would mainly include experimental work in Laboratory for fusion research on a beam line intended for the study of hydrogen retention and modelling of physical processes that will help to understand the experimental results.

References related to the work:

Markelj et al. Acta Materialia 263 (2024) 119499

Markelj S. et al., Phys. Scr. 97 (2022) 024006

Pečovnik M. et al. Nucl. Fusion 60 (2020) 036024. 

Markelj S. et al.  Nucl. Fusion 59 (2019) 086050.