Evaporation and expansion of poly-tetra-fluoro-ethylene induced by irradiation of soft X-rays from a figure-8 undulator

The effects of soft X-ray irradiation of poly-tetra-fluoro-ethylene (PTFE) have been investigated using a figure-8 undulator. In the case of high-intensity irradiation, the surface temperature of the irradiated region increased and PTFE near the surface was evaporated effectively. In contrast, the PTFE surface swelled by the under low-intensity irradiation with the insertion of Al filters more than 9 mum thick. This reaction was found to be strongly dependent on the flux. The surface profile is largely determined by the relationship between fragment desorption and porous structure generation, and an increase in the surface temperature enhances the fragment desorption and has considerable influence on the surface profile. Al filter insertion decreases the flux and suppresses low-energy photons which are absorbed near the surface. Hence irradiated photons are composed of high-energy photons which penetrate deeply, and the surface temperature is difficult to increase by Al-filter-inserted irradiation.