The effects of tungsten's pre-irradiation surface condition on helium-irradiated morphology

Erosion is a serious concern associated with the use of tungsten as a plasma-facing component in fusion reactors. To compare the damage progression, polycrystalline tungsten (PCW) and (110) single crystal tungsten (SCW) samples were prepared with (1) a mechanical polish (MP) with roughness values in the range of 0.018-0.020 mu m and (2) an MP and electropolish (MPEP) resulting in roughness values of 0.010-0.020 mu m for PCW and 0.003-0.005 mu m for SCW samples. Samples were irradiated with 30 keV He+ at 1173 K to fluences between 3 x 10(21) and 6 x 10(22) He/m(2). The morphologies that developed after low-fluence bombardment were different for each type of sample-MP SCW, MPEP SCW, MP PCW, and MPEP PCW. At the highest fluence, the SCW MPEP sample lost significantly more mass and developed a different morphology than the MP SCW sample. The PCW samples developed a similar morphology and had similar mass loss at the highest fluence. Surface preparation can have a significant effect on postirradiation morphology that should be considered for the design of future fusion reactors such as ITER and DEMO. (C) 2015 Elsevier B.V. All rights reserved.