Speaker
Description
Neon (Ne) is considered to be used in magnetic confinement fusion devices for radiative plasma edge cooling and reduction of divertor heat loads. However, uncontrolled release of medium-Z impurities such as Ne will degrade plasma performance and lead to erosion of plasma-facing materials (PFM) by sputtering of high-Z elements. It is thus important to understand the Ne-retention behaviour in wall materials. Furthermore, for devices with tungsten (W) as PFM, wall conditioning techniques such as boronization will be unavoidable for startup. As a consequence, the presence of boron (B) and W:B mixtures can be expected: their formation has been previously observed in WEST [1].
The retention of neon was investigated by an isotopic tracer technique using ion beam analysis (IBA) to atomic concentration depth profiles of thin-films of mixed W and B as well as for pure W and B layers, grown both on silicon- (Si) and W-substrates by means of magnetron sputter deposition. Two Ne-isotopes, $^{20}$Ne and $^{22}$Ne, were implanted to a fluence of 3×10$^{16}$ at./cm$^2$ at different energies (35-190 keV) in order to achieve well-separated implantation profiles at specific depths in the thin-films (close to the surface and a deeper region). Thermal annealing in combination with time-of-flight elastic recoil detection analysis (ToF-ERDA) was employed to investigate the retention and depth distribution of the Ne-isotopes in each composition for a range of temperatures between room temperature and 1000°C.
This first-of-its-kind study has shown that both isotopes remain at their original implantation depth for the full range of temperatures and for all studied compositions, thus suggesting that no diffusion, intermixing nor desorption occurred. Substrate type did not play any significant role in the retention properties of the grown films. The research program is being extended to examine the impact of plasma impurities on the stability of the Ne-containing layers.
- A. Marin et al., J. Nucl. Mater. 604 (2025) 155525, doi: 10.1016/j.jnucmat.2024.155525.