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The effectiveness of a dome-shaped wall covered by a thin gold foil (hollow wall) [M. Vandenboomgaerde et al., Phys. Plasmas 25, 012713 (2018)PHPAEN1070-664X10.1063/1.5008669] in holding back the high-Z plasma expansion in a gas-filled hohlraum is demonstrated for the first time in experiments reproducing the irradiation conditions of indirect drive at the ignition scale. The setup exploits a 1D geometry enabling record of the complete history of the gold expansion for 8 ns by imaging its emission in multiple x-ray energy ranges featuring either the absorption zones or the thermal emission regions. The measured expansion dynamics is well reproduced by numerical simulations. This novel wall design could now be tailored for the megajoule scale to enable the propagation of the inner beams up to the equator in low gas-filled hohlraum thus allowing the fine-tuning of the irradiation symmetry on the timescale required for ignition.

The effectiveness of a dome-shaped wall covered by a thin gold foil (hollow wall) [M. Vandenboomgaerde et al., Phys. Plasmas 25, 012713 (2018)PHPAEN1070-664X10.1063/1.5008669] in holding back the high-Z plasma expansion in a gas-filled hohlraum is demonstrated for the first time in experiments reproducing the irradiation conditions of indirect drive at the ignition scale. The setup exploits a 1D geometry enabling record of the complete history of the gold expansion for 8 ns by imaging its emission in multiple x-ray energy ranges featuring either the absorption zones or the thermal emission regions. The measured expansion dynamics is well reproduced by numerical simulations. This novel wall design could now be tailored for the megajoule scale to enable the propagation of the inner beams up to the equator in low gas-filled hohlraum thus allowing the fine-tuning of the irradiation symmetry on the timescale required for ignition.

High-Z metallic foils including rare-earth (RE) elements are required for some experiments implemented on the Laser Megajoule. A specific process based on physical vapor deposition and laser machining was developed to produce high-Z material foils meeting strict specifications. This process allows pure metallic ultrathin foil fabrication from a few hundred nanometers to several microns of thickness of any high-Z materials. In the case of RE metals sensitive to oxidation, thin foils are buried under aluminum protective layers of about a few hundred nanometers. These metallic thin foils are flat, show thickness uniformity over 95%/cm2, and have roughness of about 10 nm. The foils are opaque to light, have a density similar to bulk material, present an oxygen content of about 1 at. %, and are stable over months under atmospheric conditions.

Hydrodynamics growth experiments involve rippled ablator samples (CHx, Ge:CH, or Si:CH). The rippled surface features a microscale mathematical shape (sinusoidal functions are widely used). Neverth...

Targets dedicated to high power lasers experiments require accurate and reliable manufacturing technologies. In that frame, laser micro-welding represents a potential powerful tool for targets assembly. The feasibility of joining highly reflective and thin materials has been studied. Demanding requirements have to be fulfilled (gas tightness and target's geometry).

In this work, samples of ultrapure aluminum (content 99.999%) and AA 5083 aluminum alloy (Al-Mg) have been welded under conduction regime, with a pulsed Nd:YAG laser. Due to the very specific final application (use of aluminum assemblies in cryogenic conditions), stringent specifications are imposed for the weld in terms of thermal conductivity and gas tightness at a temperature of 18°K. Process conditions were refined and were validated according to our cryogenic criteria

The cryogenic target assemblies (CTAs) designed for Laser Megajoule (LMJ) experiments have many functions and have to meet severe specifications imposed by implosion physics, the CTA thermal environment, and the CTA interfaces with the Megajoule laser cryogenic target positioner. Therefore, CTA fabrication uses many challenging materials and requires several technological studies. During the last 2 years, many developments have enabled better collection of comprehensive data on target constitutive materials and improvements in the fabrication of the CTA base, hohlraum, and aluminum turret.Studies have been carried out (a) to better characterize thermal properties of materials allowing optimization of the thermal simulation of the hohlraum, (b) to improve the CTA base fabrication process in order to optimize thermal studies of the LMJ experimental filling station (EFS), and (c) to determine coatings on the polyimide membrane that may limit the 300 K thermal effect on the microshell and increase the...