ABSTRACT
The maximized reflectivity for different wavelength of x-ray laser is calculated by using the above method, and the result is summarized in the table I. In the calculations the interfaces between the two materials were assumed to be smooth, abrupt, and without inter-diffusion across the interface. The optical constants for various materials were derived from the atomic scattering factors, and were obtained from the Center of X-ray Optics worldwide web server at Lawrence Berkeley National laboratory [7]. The variation of the reflectivity for Sc/Si multilayer used for 46.9nm x-ray laser with wavelength is shown in Fig.l, and the one for CoCr/C multilayer used for 4.48nm x-ray
laser in Fig.2. For the Sc/Si multiplayer, the rms roughness influence the reflectivity slightly, while for the CoCr/C multiplayer, the reflectivity decrease greatly with the increase of the rms roughness. This mainly resulted from the fact that the rms roughness is much less than the wavelength and the thickness of period at 46.9nm, but for the shorter wavelength, the situation is much different. Therefore, the fabrication of the multilayer mirrors for the x-ray laser with a shorter wavelength should make the roughness as small as possible. Selecting suitable material and controlling the parameter of film deposition can resolve the problem.
