Ignition targets for LMJ experiments require a very constant DT ice layer t
hickness (1%) in order to improve the implosion process. This implies that
the temperature must be uniform over the shell containing the DT layer (to
some tens of microkelvin).
In this paper, thermal studies, two or three dimensional, accounting for fr
ee convection or not, carried out in order to meet this requirement, are re
viewed and the corresponding simulation results are discussed.