Desing an Performance Characteristics of a Windowless Argon Excimer Source

Emission from rare gas excimers such as , and exhibiting photon energies of 7.2, 8.5 and 9.85 eV, respectively, can be used to induce strong surface modifications of polymers. In particular, argon excimer shows a number of interesting features: the 9.85 eV photons are absorbed within less than 100 nm from the polymer surface giving rise to electronic excitation and even ionization. Excited states and ions formed by the primary interaction of argon excimer photons with molecular polymer units are capable of generating radicals. Because the reactive radicals are contained in a very thin surface layer, strong surface modification effects are initiated. In argon an RF-powered dielectric barrier discharge can be used to generate argon excimer emission. Sealed quartz vessels of planar or cylindrical geometries have been designed as emission sources. In addition, the quartz vessel forms the dielectric which is covered by the RE electrodes 1-3]. For argon excimer emission of 126 nm. optical window materials such as fused silica, calcium or magnesium fluoride show insufficient transmission. As a result, the photon flux penetrating the window is strongly decreased by wall absorption. To provide a high power photon flux for technical applications, an "open" argon excimer source was designed. No sealed vessel is needed. The dielectric discharge is generated in flowing argon. Outside the discharge the argon flow is conducted in such a way that air penetration into the irradiation zone is avoided. Argon is also used as an inert gas as it is known from nitrogen inerting systems. Thus web materials such as films or paper which pass the irradiation zone are subjected to an unattenuated flux of high energy photons.