Fluorescent X-ray analyzer with path switching device

Details Fluorescent X-ray analyzer with path switching device Fluorescent X-ray analyzer with path switching device

1999-12-07

2001-05-29

Kim, Robert H. (Department: 2882)

X-ray or gamma ray systems or devices

Specific application

Fluorescence

C378S046000

Reexamination Certificate

active

06240159

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a so-called scanning fluorescent X-ray analyzer and, more particularly, to a path switching device used in association with the scanning fluorescent X-ray analyzer for selecting one of three or more optical detection paths along which respective beams to be analyzer travel.
2. Description of the Prior Art
Hitherto, the fluorescent X-ray analyzer of a so-called wavelength divergence type is, as shown in
FIG. 4
, so designed as to irradiate a sample piece
1
with a primary X-ray
3
, generated from an X-ray source
4
such as, for example, an X-ray tube, to cause the sample piece
1
to generate a fluorescent X-ray (secondary X-ray)
5
which is, after having been passed through a divergent slit
13
, subsequently monochromatized by a monochromator
6
to provide a monochromatized fluorescent X-ray
7
that is finally detected by a detector
8
. In this type of the fluorescent X-ray analyzer, the detector
8
makes use of two counters, i.e., a gas-flow proportional counter tube (hereinafter referred to as “F-PC”)
8
A for detection of the low-energy fluorescent X-rays and a scintillation counter (hereinafter referred to as “SC”)
8
B for detection of the high-energy fluorescent X-rays. A light receiving slit
11
A is disposed in front of the SC
8
B, whereas the F-PC
8
A has a light receiving slit (not shown) built therein at a front thereof.
According to the prior art, when the high-energy fluorescent X-ray
7
is desired to be measured, in order to vary the wavelength of the fluorescent X-ray
7
incident upon the SC
8
B, the use has been made of a linkage means (not shown) for continuously associating the monochromator
6
with both of the light receiving slit
11
A and the SC
8
B so that fluorescent X-rays
5
generated from various elements contained in the sample piece
1
can be monochromatized according to respective wavelengths with the intensity thereof subsequently measured.
In other words, when the fluorescent X-ray
5
impinges upon the monochromator
6
at an angle of incidence &thgr;, an extension
9
of the path of travel of the fluorescent X-ray
5
having passed through the divergent slit
13
and the fluorescent X-ray
7
that has been monochromatized by the monochromator
6
form an angle of diffraction 2&thgr; which is twice the angle of incidence &thgr;. However, the linkage means referred to above serves to vary the angle of diffraction 2&thgr; to vary the wavelength of the monochromatized fluorescent X-ray
7
so that the monochromatized fluorescent X-ray
7
can enter the SC
8
B through the light receiving slit
11
A. In other words, the linkage means is operable to rotate the monochromator
6
about a pivot axis O lying perpendicular to the plane of a sheet of the drawing of FIG.
4
and passing across the center of a light receiving surface of the monochromator
6
, and also to turn, in synchronism with rotation of the monochromator
6
, both of the light receiving slit
11
A and the SC
8
B about the pivot axis O along a circular path
12
A through an angle that is equal to twice the angle of rotation of the monochromator
6
.
More specifically, a &thgr; spindle (not shown) having the monochromator
6
mounted thereon with the pivot axis O passing through the light receiving surface of the monochromator
6
and coaxially occupied by the &thgr; spindle is rotated to cause a 2&thgr; spindle (not shown), on which the F-PC
8
A and both of the light receiving slit
11
A and the SC
8
B are mounted in side-by-side relation in a direction conforming to the direction of turn thereof, to be turned an angle equal to twice the angle of rotation of the &thgr; spindle.
On the other hand, where the intensity of the low-energy fluorescent X-ray
7
is desired to be measured, the angle at which the monochromator
6
is fitted to the &thgr; spindle is turned to a predetermined angle so that the fluorescent X-ray
7
monochromatized by the monochromator
6
can enter the F-PC
8
A. (This also applies where the analyzer includes a plurality of monochromators and one of the monochromators is selectively utilized.) The linkage means operates in a manner similar to that described above.
Thus, in this prior art fluorescent X-ray analyzer, a detection path extending from the monochromator
6
to the SC
8
B via the light receiving slit
11
A and a detection path extending from the monochromator
6
to the F-PC
8
A can be selectively utilized one at a time.
With the prior art fluorescent X-ray analyzer, it has been found that since the SC
8
B is fixed in position at a location rearwardly of the light receiving slit
11
A and mounted on the 2&thgr; spindle, it is impossible to position the SC
8
B at a location rearwardly of the F-PC
8
A. Accordingly, a third detection path can in no way be selected, which would be necessitated where even though the fluorescent X-ray
7
has been received by the F-PC
8
A, a portion of the fluorescent X-ray
7
having passed beyond the F-PC
8
A without being measured as to its intensity completely is to be measured by the SC
8
B so that the intensity of the fluorescent X-ray
7
as a whole can be accurately measured by summing the intensity of the fluorescent X-ray
7
measured by the F-PC
8
A and the intensity of the remaining portion of the fluorescent X-ray
7
measured by the SC
8
B together.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been devised with a view to substantially eliminating the above discussed problems inherent in the prior art fluorescent X-ray analyzer of the type discussed hereinabove and is intended to enable the scanning fluorescent X-ray analyzer to select one of three or more optical detection paths along which respective fluorescent X-rays to be analyzer travel.
In order to accomplish this object of the present invention, there is provided a fluorescent X-ray analyzer comprising a sample bench for support thereon of a sample piece, an X-ray source for radiating a primary X-ray towards the sample piece on the sample bench, and a monochromator for monochromatizing a secondary X-ray emitted from the sample piece. A first detector is utilized for measuring the intensity of at least a portion of the secondary X-ray monochromatized by the monochromator while allowing the remaining portion of the secondary X-ray to pass therethrough. The fluorescent X-ray analyzer also comprises a light receiving slit member operable to pass therethrough the secondary X-ray which has been monochromatized by the monochromator, and a second detector for measuring the intensity of the secondary X-ray which has been passed through the first detector or the light receiving slit member.
The fluorescent X-ray analyzer furthermore comprises a first spindle having a longitudinal axis and carrying the monochromator with the longitudinal axis thereof passing in touch with a light receiving surface of the monochromator; a first drive mechanism for driving the first spindle; a second spindle having a longitudinal axis coaxial and common with the longitudinal axis of the first spindle and carrying the first detector and the light receiving slit member in a side-by-side fashion; a second drive mechanism for driving the second spindle; a third spindle having a longitudinal axis coaxial and common with the longitudinal axis of the first spindle and carrying the second detector; and a third drive mechanism for driving the third spindle. A control means is utilized to control the first and second drive mechanisms to vary a wavelength of the secondary X-ray incident upon the first detector or the light receiving slit member and for controlling the third drive mechanism to cause the secondary X-ray, having passed through the first detector or the light receiving member, to impinge upon the second detector.
According to the present invention, since the second detector is carried by the third spindle which is different and independent from the second spindle by which the first detector and the light receiving slit member are carried

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