Patent Number: 048426652
Section: summary

This invention relates to a graphite monochromator for X-rays and neutrons which uses a graphitized product of polymer film. In recent years, X-rays are very widely used as a means of analysis including, for example, the structural analysis of materials. In such cases, usually characteristic X-rays obtained from copper, iron, molybdenum etc. are used and, to obtain the strongest K.alpha. characteristic rays alone, monochromators which utilize the reflection at the (002) plane of graphite are commonly used. Also, neutrons are actively used for the study of material properties and, they are made monochromatic by the use of graphite monochromators. In the latter case, graphite monochromators are used, besides to make neutrons monochromatic by passing them through a graphite monochromator before their incidence upon a sample, also to cut off 1/2 higher harmonics by passing the neutrons reflected by the sample through a graphite monochromator. The latter monochromator is sometimes called an analyzer or a filter. Hitherto, for graphite monochromators, highly oriented pyrolytic graphite (hereinafter abbreviated as "HOPG") has been used which is obtained by graphitizing pyrolitic carbon at a high temperature and a high pressure of, for example, 3,000.degree. C. and 400 kg/cm.sup.2. However, the HOPG mentioned above has disadvantages in that it requires a special apparatus for its production since the production involves steps of preparing pyrolytic carbon by thermal decomposition of hydrocarbon gas and then graphitizing the carbon under severe conditions mentioned above, that only a small portion of the HOPG thus obtained is usable for a monochromator, and that a great difficulty is encountered in preparing a curved monochromator used for focusing X-rays. Accordingly, it is eagerly awaited in the art to obtain a graphite monochromator from a material which can be highly oriented easily and can be worked into a curved form without difficulty. The object of this invention is to provide a graphite monochromator which can overcome the above-mentioned deflects. According to this invention, there is provided a graphite monochromator for X-rays and neutrons which uses a graphitized product obtained by pyrolyzing a polymer film in an inert atmosphere at a temperature of 2,000 to 3,500.degree. C. This invention has been accomplished based on the finding that a graphitized product obtained by pyrolyzing a polymer film in an inert atmosphere under specified conditions can be easily worked into a curved form and can exhibit an excellent property when used for a graphite monochromator for X-rays and neutrons. The graphite film thus obtained has an extremely excellent plane orientation. Further, when subjected to pretreatment, the film has an excellent smoothness and an excellent characteristic for a monochromator, namely a mosaic spread of 4.degree. or less. Further, the mosaic spread of the graphite monochromator can be controlled by varying the heat treatment conditions. This invention is now described in detail below.