Redesign of the image processing techniques used for the alignment of the LMJ amplifier section

The laser Megajoule (LMJ) project was launched in 1995 by the French Atomic Energy Commission and is aimed at developing a facility to achieve inertial confinement fusion. The LMJ architecture is based on 176 laser beamlines. To provide these 176 high-powered beams when required for subsequent operations, one of the main issues consists in reliably aligning the laser amplifier sections. This paper provides an overview of the image processing techniques developed to identify and measure the beam centering and pointing directions. These techniques have been developed and tested thoroughly against sets of up to 450 images representing both nominal and extreme conditions acquired during the initiation and power rising of the Laser Integration Line (LIL). This facility is fully consistent with the LMJ requirements, a complete laser chain with 4 beamlines. After presenting the basic design principles, we focus on the demonstrated performances measured.