Measuring the Temperature Dependence of the Vapor Pressure and Evaporate Composition of Eutectic Lead-Lithium

The interest in using liquid lithium as a plasma facing component (PFC) in fusion reactors has grown in recent years due to the PFC’s self-healing surface, and low hydrogen recycling. However, the liquid PFC can be hindered by its relatively high vapor pressure (about 1Pa at 800K). This hinderance introduces relatively high Z material into the bulk plasma, thereby decreasing the reactor’s efficiency. However, alloying lithium with lead may substantially lower the vapor pressure (expected to be about: 1mPa at 800K) while also increasing the ability for tritium breeding.

Measurement of the vapor pressure is done using Knudsen effusion and a quartz crystal microbalance. The technique relies on: the cell maintaining a constant supply of evaporated material, uniform temperature across the cell, measurement of evaporated mass flux and the composition of the evaporate. The composition is measured by capturing some of the evaporated material on a silicon witness plate and running the plate through compositional techniques such as TOF SIMS. Preliminary evaporate composition was done to look for the presence of lead in the evaporate. This presentation will discuss the experimental techniques and findings of the work.