Abstract Details
Abstracts
Author: Shahinul Islam
Requested Type: Poster
Submitted: 2025-03-14 14:38:33
Co-authors:
Contact Info:
Lawrence Livermore National Laboratory
7000 East Ave
Livermore, CA 94550
United States
Abstract Text:
NSTX-U is a spherical tokamak designed to deliver significant heat flux to the divertor target plates, and liquid lithium (Li) is a promising candidate for plasma-facing components due to its low atomic number and self-healing properties. To investigate the operational window for the NSTX-U Li divertor, particularly regarding the core contamination through fuel dilution and radiation, a self-consistent coupling has been developed between the plasma boundary transport code, UEDGE, and a separate wall code modeling heat transport in the material walls and Li flux off the wall. The coupled model is currently applied to NSTX as a test bed; it will be extended
to NSTX-U simulations in future studies.
In the coupled model, Li fluxes from plasma-facing surfaces (PFC), including contributions from physical sputtering (D+
ions on Li), ad-atom processes, and evaporation, are determined in the wall code based on the calculated surface temperature (Tsurf) and the incident main ion flux. These Li fluxes enter the boundary plasma in UEDGE as Li neutral atoms originating from the divertor plates, and UEDGE computes plasma and neutral transport, providing the surface heat flux with account for Li evaporation heat as a boundary condition to the wall code.
In these simulations, the input heating power is varied over a wide range to assess the sensitivity of Li erosion to the incident heat
flux which is 5-25 MW/m2 at the peak. The coupled model accounts for the evaporative cooling which provides a vapor shielding effect, limiting the heat flux to the surface and maintaining constant Li surface temperature under 800℃ even as the power from the core increases. Detailed results and insights from the model will be presented at the conference.
Characterization: 2.0
Comments: