X-ray fluorescence spectrometer

Details X-ray fluorescence spectrometer X-ray fluorescence spectrometer

2002-04-22

2003-11-11

Dunn, Drew A. (Department: 2882)

X-ray or gamma ray systems or devices

Specific application

Fluorescence

C378S044000

Reexamination Certificate

active

06647090

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an X-ray fluorescence spectrometer having an optical system by so-called parallel beam method.
2. Description of the Prior Art
In the X-ray fluorescence analysis, for example, a sample is in the form of a disc of a predetermined size, after having been retained by a predetermined sample holder, placed on a sample support table and is then irradiated by primary X-rays emitted from an X-ray source such as an X-ray tube so as to impinge upon a surface of such sample. In general, in order to increase the sensitivity of the spectrometer, the X-ray source is positioned as close to the sample as possible. Considering, however, that it is at the same time necessary for the X-ray source not to disturb and interfere the field of view of the detecting means aimed at the sample surface, the X-ray source such as the X-ray tube is generally disposed slantwise relative to the sample surface.
However, it has been found that if the distance between the X-ray source and the sample surface is chosen to be very small, slight change of such distance as a result of the presence of irregularities, warps or deflections up to about 1 mm on the sample surface brings about an unnegligible change in intensity of the fluorescent X-rays emitted from the sample, resulting in insufficient improvement over the analyzing accuracy.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been devised to substantially eliminate the inconveniences inherent in the prior art X-ray fluorescence spectrometer and is intended to provide an improved X-ray fluorescence spectrometer capable of providing a stable fluorescent X-ray intensity.
In order to accomplish the foregoing object, the present invention provides an X-ray fluorescence spectrometer which includes a sample support table for supporting thereon a sample to be analyzed, an X-ray source for radiating primary X-rays so as to impinge slantwise on a flat surface of the sample and including a primary X-ray limiting diaphragm having an aperture for limiting a bundle of the primary X-rays emitted therefrom towards the sample surface, and a detecting means positioned so as to aim slantwise at the sample surface for measuring an intensity of fluorescent X-rays emitted from a site of interest of the sample. The detecting means includes a field limiting diaphragm having an aperture for limiting a field of view encompassing the sample surface and a soller slit for collimating the fluorescent X-rays emitted from the sample. The aperture of the primary X-ray limiting diaphragm is of a shape effective to allow change in intensity of the fluorescent X-rays measured by the detecting means to be not higher than 1% in the event that a height of the sample surface relative to the X-ray source and the detecting means changes 1 mm at maximum.
According to the present invention, since the aperture of the primary X-ray limiting diaphragm is of a shape uniquely designed as to allow change in intensity of the fluorescent X-rays measured by the detecting means to be not higher than 1% in the event that a height of the sample surface relative to the X-ray source and the detecting means changes 1 mm at maximum, the stable fluorescent X-ray intensity can be secured regardless of the presence of the irregularities or the like on the sample surface and, accordingly, the analyzing accuracy can be sufficiently increased.
Also, a similar effect can be equally obtained even if the respective apertures of the primary X-ray limiting diaphragm and the field limiting diaphragm are uniquely designed and shaped.
For example, the aperture of the primary X-ray limiting diaphragm may be of a substantially round shape with a portion thereof blocked, the aperture of the field limiting diaphragm may be of a substantially oval shape with a portion thereof blocked.
Preferably a rotary mechanism is employed to rotate the sample.


REFERENCES:
patent: 5280513 (1994-01-01), Meltzer
patent: 6337897 (2002-01-01), Kawahara et al.
patent: 6389102 (2002-05-01), Mazor et al.
patent: 6442231 (2002-08-01), O'Hara

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