Speaker
Description
The recent ITER re-baseline to an all-tungsten (W) reactor necessitates frequent boronizations, that will also lead to the production of intrinsic boron (B) dust whose transport and survivability should be well understood. Furthermore, it has been experimentally demonstrated that B powder injection can be utilized for real-time wall conditioning, pedestal control and turbulence suppression [1,2]. Thus, the intricate coupling between impurities from vaporization of injected B dust and edge plasmas needs to be elucidated. Surprisingly, in works that report simulations of B dust in fusion devices [3], there has been no discussion of the surface & material properties of B (light semi-conducting) that are fundamentally different from those of W (heavy refractory metal) or C/Be (light conducting).
The MIGRAINe dust dynamics code boasts a complete description of dust microphysical processes and mechanical impacts as well as a reactor relevant plasma collection model (that considers thin sheath and electron magnetization effects) [4]. We report the extension of MIGRAINe’s capabilities to B dust. MIGRAINe has been upgraded with state-of-the-art B models that describe all aspects of: (i) secondary electron emission and electron backscattering up to 5keV based on reliable experimental results and Monte Carlo simulations with Geant4, (ii) physical sputtering and ion reflection of H, D, T, He, B, Ne, W up to 5keV based on ERO SDTrimSP6 Monte Carlo simulations, (iii) thermal properties of thermodynamic nature (heat capacity, latent heat) and evaporative nature (vaporization, thermionic emission) based on reliable experimental results, (iv) optical properties (refractive index) based on measurements in an extended frequency range that are used to calculate the adhesive force via Lifshitz theory of van der Waals forces and the hemispherical emissivity via Mie scattering theory.
We report on MIGRAINe simulations of B dust survivability in plasma profiles relevant for Scrape-off-Layer and divertor plasmas. We focus on the cooling and heating contributions in different plasma scenarios and scan different sizes. The simulations of B dust are compared with those for W dust under identical conditions. Emphasis is put on the role of thermionic emission (dominant for W but insignificant for B dust) and secondary electron emission (important for B but insignificant for W dust).
[1] S. Ratynskaia et al., Rev. Mod. Plasma Phys. 6, 20 (2022).
[2] F. Nespoli et al., Nat. Phys. 18, 350 (2022).
[3] F. Nespoli et al., Nucl. Mater. Energy 42, 101837 (2025).
[4] S. Ratynskaia et al., Plasma Phys. Control. Fusion 64, 044004 (2022).