Patent Number: 
Section: claims

1. An X-ray beam device for X-ray analytical applications, comprising:an X-ray source designed such as to emit a divergent beam of X-rays; andan optical assembly designed such as to focus said beam onto a focal spot,wherein said optical assembly comprises a first reflecting optical element, a monochromator device and a second reflecting optical element sequentially arranged between said source and said focal spot, wherein said first optical element is designed such as to collimate said beam in two dimensions towards said monochromator device, and wherein said second optical element is designed such as to focus the beam coming from said monochromator device in two dimensions onto said focal spot;wherein the X-ray source has a source size S of 100 microns or less; andwherein the said first optical element has a focal length F1 given by ΔθM≦S/F1≦5*ΔθM in order to produce a focal spot size which is only slightly asymmetric, wherein F1 is also the distance between said X-ray source and said first optical element, and wherein ΔθM is the angular acceptance of said monochromator device. 2. An X-ray beam device according to claim 1, characterized in that said monochromator device comprises at least one crystal monochromator. 3. An X-ray beam device according to claim 1, characterized in that at least one of said first optical element and said second optical element comprises a multilayer. 4. An X-ray beam device according to claim 1, characterized in that at least one of said first optical element and said second optical element has a reflecting surface shaped as a surface of revolution. 5. An X-ray beam device according to claim 4, characterized in that the reflecting surfaces of said first optical element and of said second optical element have the same radius of curvature. 6. An X-ray beam device according to claim 1, characterized in that said distance F1 is equal to a distance F2 between said second optical element and said focal spot. 7. An X-ray beam device according to claim 1, characterized in that it furthermore comprises a plurality of slits, which are positioned between said second optical element and said focal spot and/or in front of said second optical element. 8. An X-ray beam device according to claim 7, characterized in that said slits are designed such as to cause an asymmetric convergence of said beam, wherein the smallest convergence is at least two times the angular acceptance ΔθM of the monochromator, and the largest convergence is larger than 0.25°. 9. An X-ray beam device according to claim 7, characterized in that said slits are adjustable in such a way as to select one among two modes of operation, one mode where the X-ray beam device is adapted for high-resolution X-ray diffraction measurements and the other mode where the X-ray beam device is adapted for refiectometry measurements or low resolution x-ray diffraction measurements. 10. An X-ray beam device according to claim 1 characterized in that at least one of said first optical element and said second optical element has an opening angle in a range between 40° and 180°. 11. An X-ray beam device according to claim 1, characterized in that a distance between said X-ray source and said focal spot is in a range between 50 cm and 1.50 m. 12. An X-ray beam device according to claim 1, characterized in that at least one of said first optical element and said second optical element comprises a plurality of reflecting mirrors positioned in a VVolter arrangement. 13. An X-ray beam device according to claim 1, characterized in that the monochromator device is made removable in such a way that it can be moved out of the X-ray beam. 14. An X-ray beam device according to claim 1, characterized in that the optical assembly comprises a monolithic holding support wherein the reflective surface of each optical element is directly disposed on the holding support and the monochromator device is fixed directly on the holding support on a goniometer stage located on an intermediate zone between the upstream and downstream optical elements. 15. An X-ray beam device according to claim 1, characterized in that the optical assembly comprises a monolithic holding support wherein the reflective surface of each optical element is directly disposed on the holding support and the monochromator device is fixed on a goniometer stage on a cover of the optical assembly which is disposed on top of the optical assembly and attached to the holding support.