Speaker
Description
The performance, operational safety, and long-term viability of ITER’s magnetic confinement are determined by the interaction of hydrogen isotopes with plasma-facing components. As a full-tungsten reactor environment is now desired, boronization is essential for reducing impurity levels. Boron high affinity for residual gases such as oxygen and nitrogen, lead to improved plasma purity and stability. Nevertheless, under continuous plasma exposure, boronized surfaces are modified by sputtering, erosion, and redeposition processes involving boron, tungsten, and hydrogen isotopes. These dynamic interactions result in the formation of boron-tungsten and boron-deuterium co-deposited layers, which is an important parameter regarding the in impurity retention, hydrogen storage, and long-term wall conditioning in fusion devices. As a result, there is a significant interest in studying these materials with respect to relevant ITER deposition parameters and methods, as well as their retention and release behavior. Therefore, a systematic investigation of boron–tungsten systems under ITER-relevant deposition conditions is necessar to study the mechanisms governing hydrogen isotope retention and release in these materials.
In this study, PVD deposition techniques such as Thermionic Vacuum Arc (TVA), RF magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS) are used to synthesize boron and boron-tungsten-based coatings under controlled conditions. These techniques are selected in order to access different plasma regimes and particle energy distributions relevant to fusion environments. During the magnetron-based deposition processes, plasma conditions are systematically investigated, with particular emphasis on ion flux and ion energy as functions of the applied power and the Ar/D₂ gas ratio. This approach will enable a controlled adjustment of the energetic conditions experienced by the growing films. The resulting boron and boron–deuterium co-deposited layers are characterized with respect to their structural and morphological properties, compound formation, and hydrogen isotope retention behavior. The influence of the deposition conditions on deuterium trapping and release mechanisms within the films is studied. In addition, deuterium release behavior is investigated by thermal desorption spectroscopy, allowing both the determination of release temperatures and the quantification of the total retained deuterium. The study aims to establish correlations between deposition parameters, plasma conditions, and film properties, providing insight into the mechanisms governing hydrogen isotope retention and release in boron-based structures relevant for ITER applications.
Acknowledgement: This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-IV-P2-2.1-TE-2023-1140, within PNCDI IV.