Evolution and Progress of the Cryogenic Target Shroud Remover Prototypes Developed for the LMJ Facility

The Laser Megajoule (LMJ) cryogenic target is protected from ambient thermal radiation by a thermal shroud. When the cryotarget, held by the cryotarget positioner, is at the LMJ chamber center, the thermal shroud has to be removed just before the shot to allow the laser beams to reach the laser entrance hole of the cavity.The shroud remover, PET, will have to disconnect the thermal shroud from the cryogenic target base without disturbing the target base temperature regulation (˜18 K ± 2 mK), which guarantees the needed cryogenic target conditions to reach the ignition.The shroud withdrawal is divided into two successive phases: a slow withdrawal for the thermal disconnection between shroud and target base and a fast withdrawal for a quick extraction of the shroud out of the laser beamways pointing onto the cavity. The slow shroud withdrawal must be handled within 30 min to respect laser pointing stability. After the final target alignment at the chamber center, the shroud must be ejected 0.5 m awa...