Fundamental hydrogen interactions with beryllium: a magnetic fusion perspective

Technical Report · Thu Mar 01 00:00:00 EST 2012

DOI:https://doi.org/10.2172/1039401· OSTI ID:1039401

Kolasinski, Robert D. ^[1]; Bartelt, Norman Charles ^[1]; Whaley, Josh A. ^[1]; Felter, Thomas E. ^[1]; Wampler, William R. ^[2]

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1. Sandia National Laboratories (SNL-CA), Livermore, CA (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Increasingly, basic models such as density functional theory and molecular dynamics are being used to simulate different aspects of hydrogen recycling from plasma facing materials. These models provide valuable insight into hydrogen diffusion, trapping, and recombination from surfaces, but their validation relies on knowledge of the detailed behavior of hydrogen at an atomic scale. Despite being the first wall material for ITER, basic single crystal beryllium surfaces have been studied only sparsely from an experimental standpoint. In prior cases researchers used electron spectroscopy to examine surface reconstruction or adsorption kinetics during exposure to a hydrogen atmosphere. While valuable, these approaches lack the ability to directly detect the positioning of hydrogen on the surface. Ion beam techniques, such as low energy ion scattering (LEIS) and direct recoil spectroscopy (DRS), are two of the only experimental approaches capable of providing this information. In this study, we applied both LEIS and DRS to examine how hydrogen binds to the Be(0001) surface. Our measurements were performed using an angle-resolved ion energy spectrometer (ARIES) to probe the surface with low energy ions (500 eV - 3 keV He⁺ and Ne⁺). We were able to obtain a 'scattering maps' of the crystal surface, providing insight on how low energy ions are focused along open surface channels. Once we completed a characterization of the clean surface, we dosed the sample with atomic hydrogen using a heated tungsten capillary. A distinct signal associated with adsorbed hydrogen emerged that was consistent with hydrogen residing between atom rows. To aid in the interpretation of the experimental results, we developed a computational model to simulate ion scattering at grazing incidence. For this purpose, we incorporated a simplified surface model into the Kalypso molecular dynamics code. This approach allowed us to understand how the incident ions interacted with the surface hydrogen, providing confirmation of the preferred binding site.

• Research Organization: Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 1039401
• Report Number(s): SAND--2012-2323
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ADSORPTION
ATOMS
BERYLLIUM
DIFFUSION
ELECTRON SPECTROSCOPY
FIRST WALL
FUNCTIONALS
HYDROGEN
ION BEAMS
KINETICS
MONOCRYSTALS
POSITIONING
PROBES
RECOMBINATION
RECYCLING
SCATTERING
SPECTROMETERS
SPECTROSCOPY
TRAPPING
TUNGSTEN
VALIDATION