The Laser MegaJoule (LMJ) is a 176-beam laser facility, located at the CEA CESTA Laboratory near Bordeaux (France). It is designed to deliver about 1.4 MJ of energy to targets, for high energy density physics experiments, including fusion experiments. The commissioning of the two first bundles of 8 beams was achieved in December 2016 and commissioning of next bundles is on the way. <p> </p>A computational system, PARC has been developed and is under deployment to automate the laser setup process, and accurately predict laser energy and temporal shape. PARC is based on the computer simulation code MIRO. For each shot on LMJ, PARC determines the characteristics of the injection laser system required to achieve the desired main laser output and supplies post-shot data analysis and reporting. <p> </p>The presentation compares energy end temporal shapes measured after amplification and after frequency conversion with results computed with PARC. For most of the LASER shots, both measurement and computed results agree within five percent accuracy.
The Laser MegaJoule (LMJ) is a 176-beam laser facility, located at the CEA CESTA near Bordeaux (France). It is designed to deliver about 1.4 MJ of energy to targets, for high energy density physics experiments, including fusion experiments. <p> </p>A computational system, PARC has been developed and is under deployment to automate the laser setup process, and accurately predict laser energy, spatial and temporal shapes. PARC is based on MIRO computer simulation code. For each shot on LMJ, PARC determines the characteristics of the injection laser system required to achieve the desired main laser output and supplies post-shot data analysis and reporting.<p> </p> The presentation compares all characteristics (energy, spatial and temporal shapes, spot size, synchronism, wavefront correction and alignment on target) after amplification and after frequency conversion with predicted results or results computed with PARC.
The Laser Mégajoule (LMJ) facility has about 40 large optics per beam. For 22 bundles with 8 beams per bundle, it will contain about 7.000 optical components. First experiments are scheduled at the end of 2014. LMJ components are now being delivered. Therefore, a set of acceptance criteria is needed when the optical components are exceeding the specifications. This set of rules is critical even for a small non-conformance ratio. This paper emphasizes the methodology applied to check or re-evaluate the wavefront requirements of LMJ large optics. First we remind how LMJ large component optical specifications are expressed and we describe their corresponding impacts on the laser chain. Depending on the location of the component in the laser chain, we explain the criteria on the laser performance considered in our impact analyses. Then, we give a review of the studied propagation issues. The performance analyses are mainly based on numerical simulations with Miró propagation simulation software. Analytical representations for the wavefront allow to study the propagation downstream local surface or bulk defects and also the propagation of a residual periodic aberration along the laser chain. Generation of random phase maps is also used a lot to study the propagation of component wavefront/surface errors, either with uniform distribution and controlled rms value on specific spatial bands, or following a specific wavefront/surface Power Spectral Distribution (PSD).
This paper describes the alignment system developed on the Laser Mégajoule facility, allowing to focus the laser beams
and to point the plasma diagnostics on the target. After an overview of the main laser components and alignment
architecture, we detail some major equipments as the 6 tele-microscopes used to align the target, the continuous phase
plate within the final optics assembly, the plasma diagnostic green pointer and the common reference which is the
cornerstone of the chamber center alignment. Finally we present some results obtained on the telemicroscope prototype
and a photometric prototype of the common reference. The expected performance of the alignment system will also be
This paper presents a statistical method for determining the dimensions, tolerance and specifications of components
for the Laser MegaJoule (LMJ).
Numerous constraints inherent to a large facility require specific tolerances:
the huge number of optical components;
the interdependence of these components between the beams of same bundle;
angular multiplexing for the amplifier section;
distinct operating modes between the alignment and firing phases;
the definition and use of alignment software in the place of classic optimization.
This method provides greater flexibility to determine the positioning and manufacturing specifications of the optical
Given the enormous power of the Laser MegaJoule (over 18 kJ in the infrared and 9 kJ in the ultraviolet), one of the
major risks is damage the optical mounts and pollution of the installation by mechanical ablation. This method enables
estimation of the beam occultation probabilities and quantification of the risks for the facility. All the simulations were run using the ZEMAX-EE optical design software.