Quality of polyimide foils for nuclear applications in relation to a new preparation procedure

For more than 30 years thin polyimide foils have been produced at IRMM by in-situ polymerisation. The procedure consists of three steps, all performed under ambient atmosphere: preparation of a polycondensate solution used to form foil by spreading on a glass plate, removal of the solvent by thermal treatment for 4 h at 100 oC and final polymerisation at high temperature (350 oC). Recently modifications of this procedure including preparation in an argon atmosphere and elimination of the time-consuming solvent removal were applied. The influence of these modifications on the quality of the foils was studied by testing the mechanical and thermal properties and the lifetime of the foil under a charged projectile beam. The influence of the modifications on the characteristics and on the level of impurities in the foils is presented as well. Comparative studies of parameters were performed for foils with an areal density between 20 and 80 μg cm-2. This work showed that the foils prepared by the new fast preparation manner in a dry atmosphere have the best properties for nuclear physics applications.