Preliminary Results of He Implantation in Tungsten at Angled Incidence in DAISIE

A new experimental facility at the University of Wisconsin-Madison, the Dual-Advanced Ion Simultaneous Implantation Experiment (DAISIE), has been designed and constructed to examine tungsten surface damage phenomena. These include microstructure formation and erosion due to helium bombardment as well as the retention of hydrogen gas while under the simultaneous bombardment of helium and deuterium ion beams, as would occur in ITER or other deuterium-burning fusion devices. DAISIE features two ion guns angled at 55 degrees to the sample normal. These guns are independent with respect to beam current, allowing for a high degree of control over the separate D and He beams fluxes and fluences and the composition ratio of these ions impinging upon the tungsten sample surface. Preliminary results are available for helium-only implantations at energies of 30 keV to average fluences of 3 x 10(18) He/cm(2) in tungsten samples at temperatures of 900 degrees C. As in prior experiments, surface damage appears to be highly-dependent on the crystallography of the individual grains. although a distinct set of helium-induced microstructures from past experiments is observed. Erosion yield is consistent with prior, similar helium irradiation experiments at the University of Wisconsin, but exceeds that predicted by physical sputtering yields and other past sputtering experiments.