AbstractCarbon impurities create carbon films saturated by tritium and deuterium onto the gas box liner. The reference gas box liner (GBL) formed by chevron shaped tungsten tiles is capable of depositing and/or recombining only 5% of the carbon impurities. The innovative solution presented here increases within the range 102–103 the surface interacting with the pumped gas by using an array of filaments, either disordered (felt) or ordered (spiral). This paper describes the experiments carried out to prepare felt/spiral samples and indicates possible ways of fabricating a representative gas box liner mock-up.