Lithium Vapor Shielding: Experiment and Modeling

Li has been shown to help mitigate the high incident plasma fluxes by a behavior known as Li vapor shielding (LVS) successfully protecting W targets for heat fluxes up to 29 MW/m2. The exact mechanics and limitations with LVS are still not well understood. Experiments have been conducted on Magnum-PSI to help understand the LVS phenomenon. Another experimental campaign on HIDRA was undertaken with the specific aim of measuring Li redeposition and recreating vapor shielding regimes in a toroidal environment. The measured redeposition rates lower than the expected > 0.999 from literature. A plasma chemistry model was developed to compute the power loss per Li particle due to electron impact excitation, ionization and recombination. A global plasma reaction solver named CRANE was used to solve for the steady-state content of a 0-D vapor cloud. Calculations also show that redeposition rates below 0.99 are needed to justify LVS from a plasma chemistry description and is in agreement with experimentally measured rates on HIDRA. CRANE was then coupled to Zapdos, a plasma transport solver to expand to a 1-D model. The Zapdos-CRANE implementation was tuned to reproduce similar Li clouds to the ones observed during the Magnum experiments and successfully demonstrated the ability of the vapor cloud to radiate enough power away.