Four Years of Experimental Results on the Prototypes of the Cryogenic Holders of the Laser Mégajoule Facility

AbstractThe Laser Megajoule cryotarget positioner, PCC, will be used to set cryogenic targets in appropriate conditions for the laser shot in order to reach ignition. These conditions can be summarized as a few parameters of the deuterium-tritium (DT) solid layer: sphericity, roughness, and density of DT gas. The DT mixture is confined and held in a target assembly that is handled and cooled by the PCC. Thus, the parameters of the DT solid layer are controlled by the PCC. In particular, roughness depends on the control of the target base temperature (±1 mK), on the temperature slope while crossing the DT triple point (0.5 mK/min), and on the thermodynamic way followed to reach gas density conditions expected at the laser shot [slow cooling (0.5 mK/min), quenching (several kelvins per second), or rapid cooling (several kelvins per minute)]. Moreover, the required gas density needs high cryogenic power performances of the PCC to be fulfilled. As the target is gripped at cryogenic temperature by the PCC, the...