Fusion Science and Technology / Volume 51 / Number 4 / May 2007 / Pages 764-768
The Laser Megajoule (LMJ) Cryotarget Positioner (PCC) will be used to set cryogenic targets in the vacuum chamber centre of this experimental facility for fusion by inertial confinement. In the French concept, only the targets will be transferred at cryogenic temperature to the PCC, using a Cryotarget Transfer Unit (UTCC). Some of the specifications are very ambitious. Indeed, the targets must be transferred automatically between those cryorobots, at a temperature between 20 K and 29 K. Then, they have to be cooled carefully by the PCC to the triple point (TP) of deuterium-tritium mixture at a rate of 0.5 mK/min. Just below the TP they have to be regulated with an accuracy of +/- 2 mK. Eventually, the DT mixture has to be set 1.5 K below the TP.
Scale one prototypes of the cryostats have been built at the Low Temperature Laboratory (SBT) in CEA-Grenoble, France, to deal with specific issues: cryogenic contact resistances, fine cryogenic temperature regulation, test of the feasibility of various thermodynamic paths, 6 degrees of freedom robot positioner, vision control of the transfer and automation. This paper presents the results obtained with these prototypes regarding topics specific to cryogenic transfers, followed by very fine regulation of temperature around 20 K and by dynamic quenching just before the laser shot.