Theoretical and experimental studies on molybdenum and stainless steel mirrors cleaning by high repetition rate laser beam

• Published in: Fusion engineering and design 2011-10, Vol.86 (9), p.1728-1731
• Main Authors: Leontyev, A., Semerok, A., Farcage, D., Thro, P.-Y., Grisolia, C., Widdowson, A., Coad, P., Rubel, M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cleaning; Controled nuclear fusion plants; Damage; Damage thresholds; Diagnostic mirror; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Installations for energy generation and conversion: thermal and electrical energy; Laser cleaning; Molybdenum; Plastic deformation; Repetition; Stainless steel; Stainless steels; Thresholds; Ytterbium
• ISSN: 0920-3796; 1873-7196; 1873-7196
• DOI: 10.1016/j.fusengdes.2010.12.068

Our studies were aimed to determine the damage threshold of molybdenum (Mo) and stainless steel (SS) mirrors to provide the maximum fluence which the mirror surfaces could withstand without affecting their reflectivity properties. A high repetition rate ytterbium fiber laser (20 kHz, 1.06 μm, 120 ns) was applied. The experimental single-pulse and multiple-pulse damage thresholds were obtained. To calculate damage thresholds, a 1D analytical model which takes into account the temperature dependent absorptance and multiple-pulse damage based on plastic deformations accumulation was applied. The experimental damage thresholds and the theoretical ones are in a good agreement. Cleaning tests with the contaminated mirrors exposed in JET have been performed.