Guiding hard X-rays by means of a periodic multilayer waveguide with an air clearance: a numerical study

A periodic multilayer waveguide for X-rays with an air gap serving as a guiding layer is considered. The propagation of hard X-ray guided modes through such a waveguide has been investigated with the help of numerical modeling. The propagation lengths of the guided modes are analyzed thoroughly with respect to their dependence on the reflectivity of the periodic multilayers forming the waveguide. It is shown that the guided modes can be generated even in a waveguide composed of low-reflectivity multilayers. The influence of a standing wave inside the reflecting multilayers on the transmission of the guided waves by the waveguide is demonstrated. Conditions which are favorable for the excitation of the guided modes are discussed.