Implantation of D and He in W-Coated Refractory Carbides

The effect of high temperature (700-1200°C) implantation of deuterium and helium in candidate fusion first wall materials was studied in the University of Wisconsin Inertial Electrostatic Confinement (IEC) device. Tungsten coated TaC and HfC ''foam'', single crystal tungsten, and high-emissivity tungsten coated ''foam'' were compared to previous tungsten powder metallurgy samples studied in the IEC device for the High Average Power Laser (HAPL) program. Scanning electron microscopy was performed to evaluate changes in surface morphology for various ion fluences at temperatures comparable to first wall temperatures. Single crystal tungsten was shown to exhibit less damage than polycrystalline samples at a fluence of 4×10¹⁶ He⁺/cm². It was found that no significant deformations occur with deuterium implantation up to ~10¹⁸ D⁺/cm² at 800°C on W-coated TaC and HfC foam samples. However, helium fluences in excess of 6×10¹⁷ He⁺/cm² show extensive pore formation at 800°C and higher. These changes may have an impact on the lifetime of tungsten coatings on the first walls of inertial and magnetic confinement fusion reactors.