X-ray or gamma ray systems or devices – Specific application – Fluorescence
Reexamination Certificate
2001-04-06
2002-05-28
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Fluorescence
C378S143000
Reexamination Certificate
active
06396899
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a secondary target device which generates secondary X-rays called fluorescent X-rays by irradiating X-rays (primary X-rays) generated from an X-ray source, and a fluorescent X-ray analyzing apparatus in which the fluorescent X-rays generated from the secondary target device are irradiated to a sample, and fluorescent X-rays generated from the sample are used to carry out a qualitative and quantitative analysis.
In a fluorescent X-ray analysis, a wavelength and an intensity of characteristic X-rays generated from a sample by a irradiating X-rays to the sample are measured, to thereby carry out a qualitative and quantitative analysis of elements in the sample. In the fluorescent X-ray analysis, there have been known a direct irradiation method in which X-rays (primary X-rays) generated from an X-ray source are directly irradiated to a sample, and a secondary target method which uses a secondary target.
In the direct irradiation method, primary X-rays generated from an X-ray tube are directly irradiated to the sample, and fluorescent X-rays generated from the sample are detected by an X-ray detector, such as a semiconductor detector. In the direct irradiation method, since it is possible to analyze a wide range of elements, the direct irradiation method is suitable for a detection of unknown micro-elements.
On the other hand, the secondary target method improves a limit of detecting micro-elements by making excited X-rays monochromatic, and in the secondary target method, primary X-rays are irradiated to the secondary target formed of a material which differs from an anode target of an X-ray tube, to thereby generate fluorescent X-rays including characteristic X-rays which are inherent to the secondary target, so that continuous X-rays included in the primary X-rays are decreased. Therefore, a signal-to-noise (S/N) ratio of the fluorescent X-rays from the sample is improved, to thereby improve the limit of detecting the micro-elements.
In the fluorescent X-ray analyzing apparatus, it has been desired to have a wide applicability for both detection of an unknown micro-element and highly sensitive analysis of a specific micro-element, and there has been proposed an analyzing apparatus which can perform both analyses by the direct irradiation method and by the secondary target method by switching these methods.
Conventionally, as a structure for switching the analysis by the direct irradiation method and the analysis by the secondary target method, there has been used a secondary target device and a fluorescent X-ray analyzing apparatus, wherein a secondary target is disposed at a position diverting from a straight line connecting between an X-ray source and a sample in the secondary target device so as not to directly irradiate primary X-rays from an X-ray tube to the sample, so that only secondary X-rays from the secondary target are irradiated to the sample, and in case the primary X-rays are directly irradiated to the sample, an orientation of the X-ray source is changed.
In the secondary target device and the fluorescent X-ray device described above, although the direct irradiation method and the secondary target method are achieved by one apparatus, there have been the following problems. Namely, since a moving mechanism for rotating the X-ray source is necessary, the apparatus becomes a large size. Also, since an X-ray irradiating condition (irradiation angle and irradiation position) by the direct irradiation method does not always coincide with an X-ray irradiating condition by the secondary target method, there is a problem in an accuracy of a correspondence between the measured data by both methods.
Also, there has been proposed a secondary target device and a fluorescent X-ray device as disclosed in Japanese Patent Publication (KOKAI) No. 10-325814, in which a secondary target is disposed on a straight line connecting between an X-ray source and a sample. In a case of using the secondary target and a case of directly irradiating primary X-rays, irradiated X-rays are switched while an orientation of the X-ray source is fixed.
In the conventional secondary target device and the fluorescent X-ray analyzing apparatus, as described above, there are problems, such as an increase of the size of the apparatus, and an accuracy problem in the correspondence between the measured data due to the difference between the X-ray irradiating conditions with respect to the sample.
Also, in the proposed apparatus described above, since the irradiated X-rays can be switched while the orientation of the X-ray source is fixed, a hollow section of the secondary target is formed into a tapered form in which an opening section at an X-ray source side is large and an opening section at a sample side is narrowed. Therefore, primary X-rays from the X-ray source can be irradiated with a large effective solid angle to the secondary target, but an effective solid angle of the secondary target observed from the sample is reduced, and an angle of observing the sample from the secondary target is shallow, so that enough secondary X-rays can not be irradiated to the sample, resulting in difficulty in obtaining a high measurement sensitivity.
Also, in both conventional apparatus and proposed apparatus, since the secondary X-rays expand on a surface of the sample in a relatively large range, it is difficult to limit an irradiation area on the surface of the sample by the secondary X-rays into a very small area, so that these apparatuses can not be applied to an analysis of a minute portion.
Accordingly, the present invention has been made to solve the aforementioned problems, and an object of the invention is to provide a secondary target device in which X-ray irradiating conditions in switching the irradiated X-rays are held constant, to thereby irradiate enough secondary X-rays with respect to a sample and to irradiate the secondary X-rays to a minute portion of the sample.
Another object of the invention is to provide a fluorescent X-ray analyzing apparatus, in which X-ray irradiating conditions in switching the irradiated X-rays are held constant and enough secondary X-rays are retained to thereby improve a detection sensitivity, and to improve a sensitivity of analyzing the minute portion of the sample.
Further objects and advantages of the invention will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
To achieve the aforementioned objects, in the present invention, an X-ray irradiating condition in case of switching irradiated X-rays is maintained to be constant by disposing an X-ray source, a target main body, and a sample on a straight line, and further, in the structure described above, an effective solid angle of observing a target surface from the X-ray source and an effective solid angle of observing the target surface from a sample irradiation position are substantially enlarged, so that enough secondary X-rays are irradiated to the sample. Accordingly, a high detection sensitivity can be obtained in a fluorescent X-ray analyzing apparatus.
Also, in substantially enlarging the effective solid angles, the secondary X-rays irradiated from a plurality of target surfaces are condensed to an irradiation area of the sample, and an irradiation of the secondary X-rays to an area other than the irradiation area is limited, so that the secondary X-rays are irradiated to a minute portion of the sample. Accordingly, a sensitivity of analyzing the minute portion is increased in the fluorescent X-ray analyzing apparatus. Incidentally, the effective solid angle is a solid angle of observing a predetermined region or surface from a certain point, and in the secondary target device and the fluorescent X-ray analyzing apparatus of the invention, the effective solid angle is formed by treating the target surface as the predetermined region surface.
Therefore, in the target device of the invention, the X-ray source, a sample irradiation position, the target main body having a plurality of ta
Church Craig E.
Kanesaka & Takeuchi
Shimadzu Corporation
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