Research on the wetted first wall concept for future laser fusion reactors. Final report No. 2, February 1, 1976--August 31, 1977

The possible application of thin, falling liquid lithium films to protect the inner walls of future laser fusion reactors is discussed. It has been proposed that the relatively smooth initial region of a falling liquid film can provide the nearly uniform liquid thickness on the order of a few hundred micrometers required to prevent radiation and plasma ions from the fusion micro-explosion from seriously damaging the solid first wall. In order to extend the existing results on liquid films to the higher surface tension numbers characteristic of alkali metals, experiments using hot water on a vertical plate were run primarily in the wavy laminar flow regime. Results show that very low minimum flow rates can fully wet the surface provided that the surface is carefully cleaned and preconditioned. It is also shown that both the wave inception distance and the equilibrium wave amplitude decrease as the surface tension number increases for a given flow Reynolds number. Based on these results, the scaling laws for the minimum wetting rate, the wave inception distance and the saturated or equilibrium wave amplitude can now be extended up to surface tension numbers of about 10,000