Improvement of Bake-Out Prediction thanks to Realistic Species Separation

Abstract

A new approach to material outgassing modelling based on chemical species separation was applied to Bake-Out modelling. The outgassing of the Scotchweld EC-9323-2 epoxy glue was first characterized experimentally, both before and after Bake-Out. Based on the former, the latter was modelled, following the classical approach on the one hand and the new approach on the other hand. The MS-based species separation of this new approach allowed measuring the emitted flux of each species individually, even during the outgassing phase. The evolution of these fluxes all along the outgassing tests, during the five classical 24 h plateaus was successfully modelled by diffusion-limited outgassing laws, while it proved inconsistent with a desorption-limited outgassing. Their modelling by diffusion laws allowed a very consistent modelling of the total mass measurements in TML and CVCMs, with a small number of chemical species of different volatilities. The effect of a preliminary Bake-Out on this outgassing was finally modelled and compared to the experimental characterization of the baked material. The modelling accuracy still remains comparable to that of the traditional modelling based on mathematical species. Yet, the realistic species separation of the new approach allows simpler assumptions on water regain (its first species) than the traditional one, which needs to assess the amount of water contained in each mathematical species. Progress in the new method should come from an improved species separation and a direct characterisation of the water flux.