Journal
OPTICS AND LASER TECHNOLOGY
Volume 150, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.optlastec.2022.107913
Keywords
LIBS; Laser-Induced Breakdown Spectroscopy; Tungsten; Ablation; Plasma Facing Components
Categories
Funding
- Euratom Research and Training Programme [754586, 633053]
- Agence Nationale de la Recherche (ANR) [ANR-10-LABX-09-01]
- Region Normandie, France
- European Regional Development Fund (ERDF) of the European Union, ZEOMETHYL project
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The Laser-Induced Breakdown Spectroscopy (LIBS) technique was used to control the ablation of a tungsten layer on plasma facing components. The study found that the ablation rate of the tungsten layer obtained by physical vapor deposition (PVD) was lower compared to bulk tungsten, and the ablation process could lead to the formation of secondary craters. Additionally, spectroscopic monitoring allowed for real-time measurement of the deposited layer thickness, and using a defocused laser beam reduced the ablation rate.
The Laser-Induced Breakdown Spectroscopy (LIBS) technique is tested to control the ablation of a tungsten layer having a dozen micrometers thickness obtained by physical vapor deposition (PVD) on a CuCrZr substrate figuring plasma facing components used in the WEST tokamak. In the conditions of a Gaussian laser source with a wavelength of 532 nm, 30 ps as laser time duration and irradiance of ti 10(17) W m(- 2) in air at atmospheric pressure, the mean ablation rate of the PVD tungsten is 90 nm per pulse, which is much lower than the one of bulk tungsten measured at 500 nm per pulse. The ablation process can lead to the formation of secondary craters not directly driven by the laser irradiance distribution. The ablation rate on CuCrZr is measured at 600 nm per pulse. Measuring the deposited layer thickness requires to spectroscopically monitor the CuCrZr components to avoid any damage of the substrate. We show that this can be performed in real time. A more secure process based on the use of a defocused laser beam is tested and leads to significantly lower ablation rate with the same precision for the thickness measurement. The increase in the ablation radius may be used to clean substrates polluted by tungsten layers.
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