Thin liquid layers have been proposed for heat extraction and protection of the solid surfaces of divertors in magnetic fusion reactors. A number of conceptual designs for plasma-facing components (PFC) use stationary and flowing liquid layers as a renewable first wall for reactor chambers to remove heat and shield solid surfaces from damaging radiation while maintaining acceptable plasma purity levels. Such liquid-protected PFC have the potential to make fusion more commercially attractive by increasing reactor lifetimes and decreasing failure rates. The results of this research will help identify the parameter ranges for successful operation of such protection schemes. This thesis investigates the thermocapillary behavior of axisymmetric horizontal liquid layers with initial heights from 0.27 to 3.0 mm. A negative radial temperature gradient is imposed at the bottom of the liquid layer. Experimental, numerical and asymptotic analyses were carried out for thin layers where buoyancy forces are negligible. A novel asymptotic solution for this axisymmetric geometry was derived from the previous two-dimensional long-wave analysis by Sen et al. (1982). A numerical simulation using the level contour reconstruction method was used to follow the evolution of the liquid-gas interface above an axisymmetric non-isothermal solid surface. Experimental validation of the theoretical and numerical studies was performed using silicone oils of various viscosities (μ = 0.48 × 10-2 9.6 × 10-2 N s/m2). Two measurement techniques, a needle contact method and laser-confocal displacement method, were employed to obtain height profiles for applied temperature differences up to 65°C. Finally, reflectance shadowgraphy was used to visualize free-surface deformation and classify flow regimes in thick layers, where the assumptions of negligible buoyancy and axisymmetric flow are no longer valid. The results of this investigation will allow designers to determine operating windows for successful implementation of liquid-protected PFC.

The chamber walls in inertial fusion reactors must be protected from the photons and ions resulting from the target explosions. One way this can be accomplished is through a sacrificial liquid wall composed of either liquid jets or thin liquid films. The x-rays produced by the exploding targets deposit their energy in a thin liquid layer on the wall surface or in the surface of liquid jets arrayed to protect the wall. The partially vaporized liquid film/jet forms a protective cloud that expands toward the incoming ionic debris which arrives shortly (a few s) thereafter. The charged particles deposit their energy in the vapor shield and the unvaporized liquid, thereby leading to further evaporation. Re-condensation of the vapor cloud and radiative cooling of the expanding plasma allow the energy deposited in the liquid to be recovered prior to the next target explosion (100ms). Chamber clearing prior to the next explosion represents a major challenge for all liquid protection systems, inasmuch as any remaining liquid droplets may interfere with beam propagation and/or target injection. Therefore, the primary objective of this research is to experimentally examine the interaction between liquid droplets and low- temperature, low-pressure plasmas under conditions similar to those expected following inertial fusion target explosions and the subsequent expansion. The data obtained in this research will be useful in validating mechanistic chamber-clearing models to assure successful beam propagation and target injection for the subsequent explosion.