Jiandong Zhang oral presentation (SN1-Mon1-3-3)
Annealing Behavior of Hydrogen in Polycrystalline Tungsten Using In-Situ Time-of-Fight Secondary Ion Mass Spectrometry
1 Lanzhou University, Tianshui South Road 222, 730000 Lanzhou, China
2 Pacific Northwest National Laboratory, , WA 99354 Richland, United States
3 Pacific Northwest National Laboratory - Energy and Environment Directorate, 902 Battelle Boulevard, WA 99352 Richland, United States
4 Pacific Northwest National Laboratory - Environmental Molecular Sciences Laboratory, 902 Battelle Boulevard, WA 99352 Richland, United States
5 Texas A&M University - Department of Nuclear Engineering, 3133 TAMU, TX 77843 College Station, United States
Due to its outstanding physical properties, tungsten (W) has been proposed as a plasma-facing material in fusion reactors. Degradation of the material properties is expected to occur as a result of tritium permeation and trapping in W. Investigation of its retention and release from W is needed to develop an understanding of the associated processes. This study uses 1H as a surrogate for 3H. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) provides both high mass resolution and high depth resolution, and is well suited for study H behavior in W. Two polycrystalline tungsten plates were implanted with 80 keV H2+ ions to a fluence of 2×1021 H+/m2 at nominally room temperature. After periods of 10 and 130 days, H depth profiles were measured in situ as a function of annealing temperature using ToF-SIMS. Focused ion beam (FIB) and scanning electron microscopy (SEM) were also used to observe the surface topography. The results show that the implanted H atoms diffused well beyond the projected range. During isothermal annealing, a rapid release of H from W occurred at temperatures below 150˚C, followed by a more gradual release at higher temperatures. Moreover, two possible release stages from 200 to 300 ˚C and from 400 to 500 ˚C are observed, likely corresponding to the reported trapping energies of 1.4 eV and 2.1 eV. Observations also indicate that the retained H atoms continue to release over the next 60 days and become stable at room temperature after another 60 days. In addition, FIB-SEM results show that two types of blisters are formed on the surface of the implanted specimen, with mean sizes of ~0.5 and 1.5 μm, respectively. After thermal annealing at 600 ˚C, no changes are observed in the surface topography.