Managing obsolescence of alignment control system on the Laser Megajoule facility

The Laser MegaJoule, a 176-beam laser facility developed by CEA, is located near Bordeaux. It is part of the French Simulation Program, which combines improvement of theoretical models used in various domains of physics and high performance numerical simulation. It is designed to deliver about 1.4 MJ of energy on targets, for high energy density physics experiments, including fusion experiments. The LMJ technological choices were validated on the LIL, a scale-1 prototype composed of 1 bundle of 4-beams. The first bundle of 8-beams was commissioned in October 2014 with the implementation of the first experiment on the LMJ facility. The operational capabilities are increasing gradually every year until the full completion by 2026. By the end of 2025, 22 bundles of 8-beams will be assembled (full scale) and 19 bundles are expected to be fully operational. The alignment control system is an essential part of the LMJ facility that allows the alignment of all the beams through the bundles to the target. It is built to control several hundred of devices, mainly drives, but also cameras and lasers. The architecture of the alignment control system is based on physical and software PLC that were chosen 15 years ago. These PLC are now obsolete and we have to replace them. This article discusses our strategy to manage the obsolescence of alignment control system by minimizing the impact on the operation of the LMJ. Key words: Laser facility, LMJ, IT, Obsolescence, PLC, Control System