|Thermal Behaviour of Electrical Multilayer Insulation Permeable to Superfluid Helium|
|B. Baudouy, A. Boucheffa, M.X. Francois, C. Meuris|
Abstract: ========= Electrical multilayer insulations made of Kapton tapes and prepreg or adhesive Kapton tapes, used in dipole magnets, may offer a complicated arrangement of thin helium channels which cannot be easily predicted and modelled. Several insulation systems have been tested in order to characterize their helium channels pattern. Heat transfer data analysis shows clearly the contribution of superfluid channels inside the insulation. Appearance of the vortex-free regime for very small temperature differences (10-5 to 10-3 K) and of the Gorter-Mellink regime for higher temperature differences allows to establish the mean value of the channels diameter. We present in this paper the thermal behaviour of several combinations of insulating materials with different geometrical arrangements and porosities.