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Cryogenics for Fusion Laboratory (LCF)

Published on 8 October 2021
For more than forty years, the Laboratory of Cryogenics for Fusion (LCF) has been developing hydrogen cryo-technologies for large scientific instruments and CEA missions. The LCF's activities are focused on research towards thermonuclear fusion by magnetic confinement, fusion by inertial confinement and high-power lasers.

Fusion by Magnetic Confinement
The LCF has a long expertise in the field of hydrogen pellet injectors used in tokamaks to feed and control thermonuclear fusion reactions. This work is done in the framework of national or international partnerships for the Tore Supra, JET, JT-60SA, ITER, DEMO tokamaks... For this research, the laboratory develops in-situ condensation cells and extrusion sources for the formation of hydrogen pellets at -255°C. Once the pellets are made at cryogenic temperature, they are accelerated by means of gas or centrifugal launchers. Fast optical diagnostics are used to characterize these pellets shots. The laboratory holds to date the record of injection speed of deuterium pellets for a tokamak with repetitive shots at 4.5 km/s.
The pumping of fusion "ashes" is also studied in the laboratory with the development of cryo-mechanical pumping of He from the fusion reaction.

Fusion By Inertial Confinement
The LCF is involved in the Laser MegaJoule (LMJ) project implemented by the CEA in the framework of the "Simulation" program. A characteristic experiment of the LMJ will be the implosion by this powerful laser of a microbead filled with hydrogen, thus making it possible to reach the pressure and temperature conditions necessary to trigger thermonuclear fusion reactions. For these experiments to be feasible, the hydrogen, which is gaseous in its natural state, must be solidified at -255°C inside the cryogenic target and maintained at this temperature to within a thousandth of a degree until the lasers are fired. For this program, the LCF brings its cryogenic expertise to CEA/DAM for all the components of the cryogenic chain necessary for the realization and the regulation of cryogenic targets for inertial fusion.
In parallel, the LCF conducts research in hydrodynamics on inertial confinement through the analysis of bubble explosions of a hydrogen-oxygen mixture.

High-power lasers
The LCF develops solid hydrogen targets at -255°C for plasma acceleration (proton and neutron generation). For this purpose, the laboratory provides cryostats producing micrometric solid hydrogen films by thermomechanical extrusion. These cryostats are used for plasma acceleration experiments on high power lasers such as PALS and ELI Beamlines in Czech Republic, Vulcan in England and ELFIE in France.
In addition to the production of cryogenic targets for high power lasers, the LCF is studying the cryogenic cooling of the amplifiers (Ti_Sa, Yb_YAG) of these high power lasers to improve their performance.