Authors: E.A. Hodille | B. Pavec | J. Denis | A. Dunand | Y. Ferro | Marco Minissale | T. Angot | C. Grisolia | R. Bisson
Source: Nuclear Fusion (article, 2024-02-16)
Field: Materials Science — Materials Chemistry

Deuterium uptake, desorption and sputtering from W(110) surface covered with oxygen Abstract Rate equation modelling is performed to simulate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">D</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">D</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> <mml:mo>+</mml:mo> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">D</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> exposure of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">W</mml:mi> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mn>110</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> surface with varying coverage of oxygen atoms (O) from the clean surface up to 0.75 monolayer of O. Density Functional Theory (DFT) calculated energetics are used as inputs for the surface processes and desorption energies are optimized to best reproduce the Thermal Desorption Spectrometry (TDS) experiments obtained for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">D</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> exposure. For the clean surface, the optimized desorption energies (1.10 eV–1.40 eV) are below the DFT ones (1.30 eV–1.50 eV). For the O covered surface, the main desorption peak is reproduced with desorption energies of 1.10 eV and 1.00 eV for 0.50 and 0.75 monolayer of O respectively. This is slightly higher than the DFT predicted desorption energies. In order to simulate satisfactorily the total retention obtained experimentally for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">D</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:mrow> <mml:mo>+</mml:mo> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">D</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> exposure, a sputtering process needs to be added to the model, describing the sputtering of adsorbed species (D atoms) by the incident D ions. The impact of the sputtering process on the shape of the TDS spectra, on the total retention and on the recycling of D from the wall is discussed. In order to better characterize the sputtering process, especially its products and yields, atomistic calculations such as molecular dynamics are suggested as a next step for this study. Deuterium ; Sputtering ; Desorption ; Oxygen ; Materials science ; Atomic physics ; Analytical Chemistry (journal) ; Physics ; Adsorption ; Chemistry ; Environmental chemistry ; Thin film ; Nanotechnology ; Physical chemistry Fusion materials and technologies ; Advanced Chemical Physics Studies ; Atomic and Molecular Physics