Patent Number: 
Section: claims

1. A X-ray waveguide comprising:a core configured to guide X-rays having a wavelength band in which the real part of refractive index of material is smaller than 1; anda cladding configured to confine the X-rays in the core,wherein the core has a one-dimensional periodic structure in which a plurality of layers respectively formed of inorganic materials having different real parts of refractive indices are periodically laminated,the core and the cladding are configured so that a critical angle for total reflection for the X-rays at an interface between the core and the cladding is larger than a Bragg angle due to a periodicity of the one-dimensional periodic structure, anda critical angle for total reflection for the X-rays at an interface between layers in the one-dimensional periodic structure is smaller than the Bragg angle due to the periodicity of the one-dimensional periodic structure. 2. The X-ray waveguide according to claim 1, wherein the number of periods in the periodic structure is greater than or equal to 20. 3. The X-ray waveguide according to claim 1, wherein the inorganic materials, which form the core and have different real parts of refractive index, are at least two types of materials selected from the group consisting of Be, B, C, B4C, BN, SiC, Si3N4, SiN, Al2O3, MgO, TiO2, SiO2, and P. 4. The X-ray waveguide according to claim 1, wherein a material forming the cladding are at least one type of material selected from the group consisting of Au, W, Ta, Pt, Ir, and Os.