Abstract
A compact electron cyclotron resonance plasma source has been utilized at Sandia National Laboratory to expose heated W samples (1270 K) to 50-75 eV He ions at fluxes on the order of 1019 m-2 s-1 and fluences on the order of 1024 m-2. Scanning electron microscopy (SEM) analysis of the surface has indicated bubbles up to 150 nm in diameter that exhibit signs of bursting near the surface. Comparisons have been made between W samples prepared from warm-rolled W sheet stock and ITER-Grade W rod stock. Focused ion beam (FIB) cross sectioning has been used with SEM and transmission electron microscopy (TEM) to identify large sub surface bubbles (100 nm diameter) at depths up to one micron as well as a dense layer of smaller bubbles (<10 nm diameter) within the first 100 nm of the surface, similar to bubble layers observed on higher flux experiments. SEM-Electron Backscatter Diffraction (EBSD) analysis has identified a unique surface morphology feature associated with the exposed ITER-Grade W as well as features similar to previous EBSD studies of rolled W stock. Thermal desorption spectroscopy (TDS) analysis has identified that pre-existing He bubbles found in the Sandia He-ion exposed samples do alter the D trapping and desorbing behavior in W. The findings from these preliminary characterization studies are presented and discussed in context with results from similar plasma exposure stages at other facilities around the world.
| Original language | English |
|---|---|
| Pages (from-to) | 337-346 |
| Number of pages | 10 |
| Journal | Fusion Science and Technology |
| Volume | 72 |
| Issue number | 3 |
| DOIs | |
| State | Published - Oct 2017 |
Funding
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000, SAND Number: 2013–3918 C. This work was also supported by US Department of Energy under DE-AC03-89ER51114, DE-FC02-04ER54698, DE-AC52-07NA27344, and 44500007360. CMP supported by an Early Career Award, US Department of Energy, Office of Science, Fusion Energy Sciences. FEI Talos F200X S/TEM tool provided by US DOE, Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. Samples exposed at the Sandia plasma exposure stage were examined at the Plasma Science and Fusion Center (PSFC) at the Massachusetts Institute of Technology (MIT) using high resolution SEM and FIB cross sectioning. This collaboration was made possible in part by the Plasma Surface Interaction (PSI) Science Center supported by the Department of Energy (DOE) Office of Fusion Energy Science (OFES). SEM images of a Plansee warm-rolled W sample, referred to in this work as sample P-1, exposed at 1270 K to 50 eV He-ions to a total fluence of 3.5 × 1024 m−2 at a flux of 2.3 × 1019 m−2 s−1 are shown in Figs. 1 and 2 (note that all SEM images were taken
Keywords
- Fusion
- Helium ion damage
- Ion source
- Plasma
- Plasma-facing components
- Plasma-material interactions
- Tungsten
