Implantation of He+ in candidate fusion first wall materials

The effect of high temperature (700–1200 °C) implantation of helium in candidate fusion first wall materials was studied in the University of Wisconsin Inertial Electrostatic Confinement device. Powder metallurgy tungsten, single crystal tungsten, and a W–25% Re alloy were irradiated with 30–50 keV He+ ions. Scanning electron microscopy was used to evaluate changes in surface morphology for various ion fluences at temperature ranges comparable to first wall temperatures. Helium fluences in excess of 1 × 1018 He+/cm2 produce extensive pore formation at 1150 °C. These changes will have an impact on the lifetime of thin tungsten coatings on the first walls and divertors of inertial and magnetic confinement fusion reactors.