Retention behavior in tungsten and molybdenum exposed to high fluences of deuterium ions in TPE

The Tritium Plasma Experiment (TPE) has been used to investigate deuterium fuel retention behavior in tungsten and molybdenum-materials utilized for plasma-facing surfaces in some existing tokamak plasma devices and under consideration for future devices. Although several studies have been performed over the past several years on these metals, many issues remain unresolved, including for example blister formation mechanisms and correlation to surface conditions. In this study, we expose several metal samples to deuterium ion fluences up to 1026 ions/m2 and measure retention behavior with thermal desorption spectroscopy. Fractional retention of up to 2.0 x 10-5 is found for W at 600 K, and Mo similarly retains deuterium at a fraction of 1.5 x 10-5 at 600 K. Blistering was found for W samples exposed at temperatures above 453 K, whereas blistering was not observed for Mo samples at any experiment temperature.