Experimental facility for high cycle thermal fatigue tests using laser shocks

International audienceno abstrac

Characterization of temperature and strain fields during cyclic laser shocks

International audienceno abstrac

Essai de fatigue thermique par chocs laser

National audienceA new experimental setting is used to study thermal fatigue phenomenon occurring in structures ofnuclear power plants. The cyclic thermal shocks are performed by a laser. A thermal fatigue test ispresented on an A316L(N) stainless steel. The initial temperature is 380°C and the thermal loading isof 200°C imposed at a frequency of 1.5 Hz. The thermal fatigue test is performed till a crack is formed(of 800µm). The thermal and kinematic fields are measured owing to an infrared and a visiblecamera. Thanks to the synchronization of both cameras and to the digital image correlation methodused, the initiation and propagation of the crack can be approximated.Un nouveau dispositif expérimental est utilisé pour étudier les phénomènes de fatigue thermique dansles matériaux de structures de centrales nucléaires au travers de chocs thermiques cycliques par unlaser de puissance. Un essai de fatigue, sur un acier AISI 316 L(N), est mené jusqu’à apparition defissure (800µm) avec une température initiale de l’échantillon de 380°C et une variation cyclique detempérature de 200°C à une fréquence de 1.5 Hz. Les champs de température et de déformation dansla zone d’impact sont mesurés expérimentalement sans contact. Grâce à la synchronisation descaméras et à la méthode de corrélation d’image numérique, les premiers stades d’amorçage et depropagation peuvent être estimés

Theoretical and Experimental Studies on Molybdenum and Stainless Steel Mirrors Cleaning by High Repetition Rate Laser Beam Theoretical and Experimental Studies on Molybdenum and Stainless Steel Mirrors Cleaning by High Repetition Rate Laser Beam

AbstrAct 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 (20kHz, 1.06µm, 120ns) 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

Removal of beryllium-containing films deposited in JET from mirror surfaces by laser cleaning

A set of stainless steel (SS) and molybdenum mirror samples located in the divertor and at the outer mid-plane of the vessel were exposed in JET from 2005 to 2007. A selection of these mirror samples with well adhered deposits (i.e. not flaking) of up to a few hundred nanometers in thickness and with Be/C ratios ranging from 0 to similar to 1 have been cleaned using a laser system developed at CEA, Saclay. Following laser cleaning the recovered reflectivity was generally better in the infrared than the visible spectrum, with recovery of up to 90% of the initial reflectivity being obtained at 1600 nm for both Mo and SS mirrors falling as low as 20-30% of initial reflectivity at a wavelength of 400 nm for some SS mirrors, rising to similar to 80% for Mo mirrors. Some deposit remained on the mirrors after the cleaning trials. (C) 2010 EURATOM. Published by Elsevier B.V. All rights reserved

Removal of beryllium-containing films deposited in JET from mirror surfaces by laser cleaning

A set of stainless steel (SS) and molybdenum mirror samples located in the divertor and at the outer mid-plane of the vessel were exposed in JET from 2005 to 2007. A selection of these mirror samples with well adhered deposits (i.e. not flaking) of up to a few hundred nanometers in thickness and with Be/C ratios ranging from 0 to similar to 1 have been cleaned using a laser system developed at CEA, Saclay. Following laser cleaning the recovered reflectivity was generally better in the infrared than the visible spectrum, with recovery of up to 90% of the initial reflectivity being obtained at 1600 nm for both Mo and SS mirrors falling as low as 20-30% of initial reflectivity at a wavelength of 400 nm for some SS mirrors, rising to similar to 80% for Mo mirrors. Some deposit remained on the mirrors after the cleaning trials. (C) 2010 EURATOM. Published by Elsevier B.V. All rights reserved

Modular EUV Source for the Next Generation Lithography

International audienceThe present work, performed in the frame of the EXULITE project, was dedicated to the design and characterization of a laser-plasma-produced extreme ultraviolet (EUV) source prototype at 13.5 nm for the next generation lithography. It was conducted in cooperation with two laboratories from CEA, ALCATEL and THALES. One of our approach originalities was the laser scheme modularity. Six Nd:YAG laser beams were focused at the same time on a xenon filament jet to generate the EUV emitting plasma. Multiplexing has important industrial advantages and led to interesting source performances in terms of in-band power, stability and angular emission properties with the filament jet target. A maximum conversion efficiency (CE) value of 0.44% in 2π sr and 2% band-width was measured, which corresponds to a maximum in band EUV mean power of 7.7 W at a repetition rate of 6 kHz. The EUV emission was found to be stable and isotropic in these conditions