Patent Number: 
Section: description

The following description is provided to enable any person skilled in the X-ray analytical instrument industry to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in these arts, since the generic principles of the present invention have been defined herein specifically to provide an instrument with an economical X-ray shielding structure. FIG. 1 shows essential parts of a fluorescent X-ray spectroscope which is an example of an X-ray analysis microscope using a leaking X-ray shielding mechanism 1 according to the present invention. In the explanations described hereinbelow, materials represented by the same symbols as in FIG. 3 are the same or equivalent materials and detailed explanations of these materials are therefore omitted. In FIG. 1, 1a represents an X-ray cartridge (hereinafter referred to as xe2x80x9cXGT cartridgexe2x80x9d) and 2 represents an X-ray source which irradiates the XGT cartridge 1a with X-rays Rx. The XGT cartridge 1a comprises an X-ray guide tube 3, a mount base 4 mounted with the X-ray guide tube 3, a protective pipe unit 5 for the X-ray guide tube 3 and an X-ray shielding plate 6. The X-ray guide tube 3 is a hollow glass tube used to narrow the X-rays Rx to irradiate the sample S with the narrowed X-rays Rx. In this embodiment, the X-ray guide tube 3 includes two X-ray guide tubes 3a and 3b with inside diameters of 10 xcexcm and 100 xcexcm, respectively. Specifically, the X-ray guide tube 3a with an inside diameter of 10 xcexcm serves to condense the X-rays Rx in a thinner region to irradiate the sample, enabling an analysis with higher resolution. On the other hand, the use of the X-ray guide tube 3b with an inside diameter of 100 xcexcm ensures that more intense X-rays Rx can be applied and that the measurement can be made faster. In this embodiment, these X-ray guide tubes 3a and 3b are designed to be optionally switched by the operator. 4 is an example of a mechanism by which these X-ray guide tubes 3a and 3b are switched with each other and used, and which is namely a mount base supporting these X-ray guide tubes 3a and 3b. This mount base 4 makes the above X-ray guide tubes 3a and 3b slide as shown by both arrows A to be able to use the guide tube 3a or 3b by selectively switching from one to the other. 5 represents a protective pipe unit of stainless steel or other X-ray blocking material which cover the outside of X-ray guide tubes 3a and 3b. The protective pipe unit consists of protective pipes or tubes 5a and 5b, which protect the X-ray guide tubes 3a and 3b, respectively. Also, the protective pipe unit 5 is formed of a material, such as a metal, e.g., stainless steel, which has a dense weight sufficient to prevent the transmission of X-rays over the length of the tube so that X-rays which diagonally penetrate the X-ray guide tubes 3a and 3b will not be applied to the sample S. The above protective pipes 5a and 5b are respectively installed on the mount base 4. The length of the protective pipe unit 5 is regulated to the extent that it does not block the observation field when the sample S is monitored, specifically, its lower end portion (the side of the output end) is made to stop short of the output end of the X-ray guide tubes 3a and 3b. The protective tubes 5a and 5b can have an approximate wall thickness of 0.2 mm and an approximate length of 90 mm. Also, an X-ray shielding pipe 4b made of a metal, e.g., brass, associated with flange 4a connected thereto is installed on the upper surface of the mount base 4. The length of this X-ray shielding pipe 4b is defined by the depth of the insertion portion 2c in the X-ray source 2. An X-ray shielding plate 6 having X-ray transmission windows 6a and 5b corresponding to the X-ray guide tubes 3a and 3b respectively is provided on the upper surface (the side of the input end) of the X-ray shielding pipe 4b.  The XGT cartridge 1a having the above structure enables the X-rays Rx from the X-ray source 2 to enter the X-ray guide tubes 3a and 3b by inserting the upper end portion (input end portion) thereof into the insertion portion 2c of the X-ray source 2. Then, among the X-rays Rx which are made to enter the X-ray guide tubes 3a and 3b, only the X-rays Rx passing through the hollow portion or aperture of the X-ray guide tube 3a or 3b are applied to the sample S and the remainder of the X-rays are blocked. FIG. 2 is a view for explaining the positional relationship between the materials 3a, 5a and 6a. In the case of this embodiment, as shown in FIG. 2, the above X-ray shielding plate 6 is positioned at a distance of x1 from the X-ray generating point P and the upper end portion of the above protective pipe 5 is positioned at a distance of x2 from the X-ray generating point P in such a condition that, as aforementioned, the XGT cartridge 1a is being inserted in the insertion portion 2c of the X-ray source 2. In order to block leaking X-rays without fail by the protective pipes 5a and 5b when the size of each inside diameter of the side of the input end of the protective pipes 5a and 5b is r2, the size of the X-ray generated point P is r0 and the deviation between the center of the X-ray guide tubes 3a and 3b and the center of the protective pipes 5a and 5b is d, the size r1 of each inside diameter of the above transmission windows 6a and 6b must fulfill the relationship shown by the following inequality (1).                                                                         r                1                            2                        +                                                            r                  0                                ⁢                                  2                                            2                                            x            1                           less than                                                             r                2                            2                        +                                                            r                  0                                ⁢                                  2                                            2                        -            d                                x            2                                              (        1        )             Here, if r0 and d can be disregarded, the aforementioned equality (1) may be simplified as shown by the following formula (2). In short, it is understood that the transmission windows 6a and 6b with a size r1 satisfying the inequality (2) suffice for the requirement.                                           r            1                                x            1                           less than                               r            2                                x            2                                              (        2        )             The above structure ensures that even if the X-rays Rx emitted from the X-ray source 2 diverge, forming a broadened angle, the XGT cartridge 1a still has two abilities of forming fine beams of the X-rays Rx and shielding from the X-rays Rx. It is to be noted that although an example in the case of selecting the X-ray guide tube 3a is disclosed in FIG. 2, this is the same as the case of selecting the X-ray guide tube 3b.  Also, in the aforementioned embodiment, an instance in which two X-ray guide tubes 3a and 3b are switched with each other to make it possible to irradiate the sample S with X-rays Rx with different diameters is explained. However, the present invention is not limited to this instance. Specifically, one fixed X-ray guide tube 3 may be disposed. This eliminates the necessity of the provision of the mount base 4 which makes the X-ray guide tube 3 slide. Moreover, the protective pipe unit 5 protecting the X-ray guide tube 3 is not limited to the type which is disposed at the side of the output and extending from the position determined by the aforementioned formulae (1) and (2) but may be of a type which protects almost the entire length extending from the input end up to a position which lies a little short of the output end. Also, various modifications are possible, for instance, the protective pipe unit 5 may be disposed not on the mount base 4 but on the X-ray source 2. As stated in detail, according to the leaking X-ray shielding mechanism of the present invention, X-rays can be narrowed by the X-ray guide tube and X-rays which leak from the side surface of the X-ray guide tube can be blocked. Briefly, the X-ray cartridge has two abilities of forming the fine beams of the X-rays Rx and providing shielding from the X-rays Rx. Especially, when the relation, r1/x1 less than r2/x2, is established between the diameter r1 of the entrance window of the X-ray shielding plate, the distance x1 from the X-ray generated point of the X-ray source to the X-ray shielding plate, the distance x2 from the X-ray generated point to the input end of the protective pipe and the inside diameter of r2 of the protective pipe, leaking X-rays can be blocked only by X-ray shielding of a limited range, which reduces the production cost that much more. In each of the above embodiments, the different positions and structures of the present invention are described separately in each of the embodiments. However, it is the full intention of the inventor of the present invention that the separate aspects of each embodiment described herein may be combined with the other embodiments described herein. Those skilled in the art will appreciate that adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.