A PHYSICAL APPROACH TO THE RADIATION-DAMAGE MECHANISMS INDUCED BY X-RAYS IN X-RAY MICROSCOPY AND RELATED TECHNIQUES

A physical approach is used to analyse the various mechanisms induced by the absorption of X-ray photons of energies in the 0.2-20 keV range . At the atomic scale, besides the (Auger and photo) electron transpor t in the bulk or the ejection into the surrounding media, special atte ntion is devoted to the specific consequences of the initial Auger dec ay mechanism. At the macroscopic scale, the decisive role of the poor electronic conductivity of the radiation-sensitive materials is outlin ed and it is shown that the damaging effects occur in irradiated insul ators because the lack of conduction electrons prevents the initial ch arge of the excited atoms being quickly restored. Correlating irradiat ion conditions and physical properties of the specimen, various expres sions are proposed for the first time to quantify these effects. Some are neither dose-nor dose-rate-dependent and the influence of the surr ounding medium is also considered. The fundamental mechanisms investig ated here hold for a wide variety of specimens or components investiga ted in X-ray microscopy. Their consequences can be easily transposed t o other techniques using transmitted X-rays.