Deuterium Retention in a Nanostructured Tungsten Surface Layer Formed during High-Temperature Irradiation with Helium Plasma

Abstract

The preliminary irradiation of a tungsten sample with low-energy helium ions (80 eV, flux of 10²¹ m⁻² s⁻¹) at a temperature of 1200–1250 K in a facility with an inductive RF discharge leads to the formation of a nanostructured tungsten surface layer, which is referred to as fuzz. After that, the sample is subjected to a set of annealing procedures and irradiations with ${\text{D}}_{3}^{ + }$ ions with an energy of 2 keV (0.67 keV per D) at low fluences of 10¹⁹–10²⁰ m⁻². Deuterium retention at each stage is analyzed by in-situ thermal desorption spectroscopy. An increase in the helium concentration in the sample leads to a significant change of deuterium retention. At high helium concentrations, deuterium retention becomes low. Annealing in the temperature range of 1000–1400 K leads to helium desorption, modification of the surface layer and defects, and, as a consequence, an increase in the amplitude of the main deuterium desorption peak and a shift of the peak to higher temperatures. Annealing at a temperature of 1600 K leads to removal of the nanostructured fuzz from the tungsten surface and a decrease in the deuterium retention on account of an increase in the reflection coefficient from a smoother surface.