TY - JOUR

T1 - In-situ study of the processes of damage to the tungsten surface under transient heat loads possible in ITER

AU - Vyacheslavov, Leonid N.

AU - Vasilyev, Alexander A.

AU - Arakcheev, Alexey S.

AU - Cherepanov, Dimitrii E.

AU - Kandaurov, Igor V.

AU - Kasatov, Alexander A.

AU - Popov, Vladimir A.

AU - Ruktuev, Alexey A.

AU - Burdakov, Alexander V.

AU - Lazareva, Galina G.

AU - Maksimova, Anastasia G.

AU - Shoshin, Andrey A.

N1 - Funding Information: Measurements of the bending of a sample were financially supported by Russian Science Foundation (project No. 19-19-00272 ). Measurements of the dynamics of cracking were financially supported by Russian Science Foundation (project No. 17-79-20203 ). Publisher Copyright: © 2020 Elsevier B.V. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2021/2

Y1 - 2021/2

N2 - Experiments on the effect of fast heat loads on the surface of tungsten were carried out on the BETA facility at the Budker Institute. Tungsten samples were uniformly heated by an electron beam with a heat flux factor below the melting threshold. During and shortly after exposure, the 2D surface temperature distribution was measured, as well as the temperature history on selected surface areas. Active diagnostics using the scattering of CW laser light on a surface exposed by the electron beam allowed us to monitor the damage dynamics. At the heating stage, an increase in the surface roughness occurred, caused by inhomogeneous elastic and plastic deformations of the heated layer. As the cooling progressed, the residual plastic deformations remained. Simultaneously with the modification of the surface, bending of samples with a thickness of 3-4 mm occurred. The bending dynamics of the sample was measured by the intensity of a converging laser beam reflected from the back surface of the sample, polished to a mirror state. The residual sag due to bending increases with the heat load similarly as residual roughness of the front surface of the sample. These data, together with simultaneously measured temperature dynamics and the spatial heating profile, can provide an experimental basis for the numerical calculation of the residual stresses in the sample. The data obtained in situ were compared with those measured outside the vacuum chamber with X-ray diffraction, optical profiler, and optical interferometer. At the stage of cooling, after a sufficient intensity of heating, the second stage of damage took place — the cracking of the surface layer. The time before the start of this relatively fast process usually exceeded the time to achieve a DBTT by 1–4 orders of magnitude.

AB - Experiments on the effect of fast heat loads on the surface of tungsten were carried out on the BETA facility at the Budker Institute. Tungsten samples were uniformly heated by an electron beam with a heat flux factor below the melting threshold. During and shortly after exposure, the 2D surface temperature distribution was measured, as well as the temperature history on selected surface areas. Active diagnostics using the scattering of CW laser light on a surface exposed by the electron beam allowed us to monitor the damage dynamics. At the heating stage, an increase in the surface roughness occurred, caused by inhomogeneous elastic and plastic deformations of the heated layer. As the cooling progressed, the residual plastic deformations remained. Simultaneously with the modification of the surface, bending of samples with a thickness of 3-4 mm occurred. The bending dynamics of the sample was measured by the intensity of a converging laser beam reflected from the back surface of the sample, polished to a mirror state. The residual sag due to bending increases with the heat load similarly as residual roughness of the front surface of the sample. These data, together with simultaneously measured temperature dynamics and the spatial heating profile, can provide an experimental basis for the numerical calculation of the residual stresses in the sample. The data obtained in situ were compared with those measured outside the vacuum chamber with X-ray diffraction, optical profiler, and optical interferometer. At the stage of cooling, after a sufficient intensity of heating, the second stage of damage took place — the cracking of the surface layer. The time before the start of this relatively fast process usually exceeded the time to achieve a DBTT by 1–4 orders of magnitude.

KW - cracking

KW - in-situ diagnostics

KW - residual stress

KW - thermal shock

KW - Tungsten

KW - HYDROGEN

KW - BEHAVIOR

KW - FLUX

UR - http://www.scopus.com/inward/record.url?scp=85097572353&partnerID=8YFLogxK

U2 - 10.1016/j.jnucmat.2020.152669

DO - 10.1016/j.jnucmat.2020.152669

M3 - Article

AN - SCOPUS:85097572353

VL - 544

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

SN - 0022-3115

M1 - 152669

ER -