First picosecond diagnostic of the Laser Megajoule timing system

The Laser MegaJoule (LMJ), a 176-beam laser facility developed by CEA, is located at the CEA CESTA site near Bordeaux. The LMJ facility is part of the French Simulation Program, which combines improvement of theoretical models and data used in various domains of physics, high performance numerical simulations and experimental validation. It is designed to deliver about 1.4 MJ of energy on targets, for high energy density physics experiments, including fusion experiments. With 19 bundles operational by the end of 2025, the operational capabilities are gradually increasing until full completion of the LMJ facility by 2027. At present, there is no global control and measurement of the synchronization system*. It's up to each individual subassembly to check that the trigger or fiducial signals are correct. To ensure that the LMJ synchronization system works perfectly, a new diagnostic was developed and tested on several 1w and 3w laser bundles in comparison with central chamber synchronization. In this paper, a review of the LMJ’s first synchronization measurement is given with a description of the prototype measurement diagnostic, the main values measured and a presentation of the future deployment of this diagnostic on all 22 bundles.