JPS6215822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray spectrometer used in an X-ray microanalyzer or the like.

In order to increase the intensity of X-rays, the X-ray spectrometer used in this type of device is designed so that the X-rays X emitted from the X-ray source 1 have a radius of curvature equal to the diameter of the Rowland circle 2, as shown in Figure 1a. Conventionally, a structure (Johann type) in which X-rays separated by spectroscopic crystal 3 are focused on detector 4 has been widely used. Note that the X-ray source 1, spectroscopic crystal 3, and X-ray detector 4 are arranged on the Rowland circle 2. Further, the angle of incidence (black angle) of the X-rays on the spectroscopic crystal 3 changes as the spectroscopic crystal is moved linearly by the drive rod 5. However, in such an X-ray spectrometer, by arranging a fixed slit 6 on the incident side of the spectroscopic crystal, the aperture angle of the incident X-rays is limited to a certain degree or less, and scattered X-rays, etc., which cause background noise, are suppressed. It reduces the incidence on the spectroscopic crystal.

In this case, the opening of the fixed slit 6 is determined as follows. First, the angle at which the X-ray source 1 looks at the spectroscopic crystal 3 within the Rowland circle shown in Figure 1a is equal to the circumferential angle that the spectrometer crystal 3 spans on the Rowland circle, and the Black angle of the X-rays incident on the spectrometer crystal is Even if the spectroscopic crystal is moved as shown by the dashed-dotted line a in the figure in order to change the angle, it remains approximately constant, so the width h of the fixed slit 6 is fixed so that the X-ray source 1 can be seen at that corner. Furthermore, FIG. 1b shows the relationship among the spectroscopic crystal 3, the X-ray source 1, and the slit 6 in the direction perpendicular to FIG. The angle φ that takes into account the width W of the spectroscopic crystal 3 in the direction perpendicular to the spectroscopic crystal 3 changes depending on the distance between the spectroscopic crystal 3 and the X-ray source 1. Therefore, the slit width W of the fixed slit is fixed to such a width that X-rays are incident on the entire surface of the spectroscopic crystal even when the spectroscopic crystal 3 is mechanically closest to the X-ray source 1.

By the way, when increasing the width of the spectroscopic crystal in the direction parallel to the Roland circular surface and increasing the aperture angle in order to obtain strong X-ray intensity, the Johann-type spectroscopic crystal suffers from aberrations due to the size of the aperture angle. Because of the presence of The ratio etc. will drop rapidly. Therefore, the aperture angle has its optimum value.
_ppt exists. Moreover, it has been found through experiments that this _ppt is not constant at each position of the spectroscopic crystal, but decreases as the spectroscopic crystal approaches the X-ray source, as shown by A in FIG. In the graph of FIG. 2, the vertical axis represents the optimum aperture angle, the horizontal axis represents the distance between the X-ray source and the spectroscopic crystal, and R represents the radius of the Rowland circle.

On the other hand, as shown in Figure 1b, there is an optimal aperture angle _ppt for incident X-rays even in the direction perpendicular to the Rowland circle, and this aperture angle _ppt is different for each position of the spectroscopic crystal. differ in
It was confirmed through experiments that the aperture angle _PPT exhibits a substantially opposite change in the direction parallel to the Rowland circular surface, as shown by B in FIG.

However, conventional devices do not take into account that the values of the aperture angle _ppt and φ _ppt of the X-rays incident on the spectroscopic crystal change depending on the position of the spectroscopic crystal, that is, the distance between the X-ray source and the spectroscopic crystal, and as described above. Since a fixed slit is used in the opening, the opening angle and φ are constant. Therefore, the aperture angle and φ of the incident X-ray are _pp
At the position of the spectroscopic crystal where the signal intensity becomes smaller than _t and φ _ppt , the signal intensity decreases, and conversely, at the position of the spectrometer crystal where it becomes larger, the detector cannot detect the target element due to aberrations based on the size of the aperture angle. In addition to the characteristic X-rays, characteristic X-rays of other nearby elements and continuous X-rays are incident, resulting in a disadvantage that the wavelength resolution decreases and background noise increases.

The present invention is intended to solve such inconveniences, and will be explained in detail below with reference to the drawings.

Note that the same numbers as in FIG. 1 indicate the same components.

FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 4 is a sectional view taken along line AA in FIG.
b are two slit plates facing each other. The slit plate is placed close to the X-ray source 1 shown in FIG. 1a, and is used to control the aperture angle of the X-rays incident on the spectroscopic crystal 3 in a direction parallel to the Rowland circular surface. Further, both the slit plates are held so as to be able to move in parallel by guide plates 8a and 8b placed above and below. 9a and 9b are two slit plates placed opposite each other on the slit plates 7a and 7b, and the slit plates 9a and 9b are arranged in a direction perpendicular to the other slit plate 7a and 7b, This is for controlling the aperture angle φ of the incident X-rays on the spectroscopic crystal 3 in the direction perpendicular to the Rowland circular surface. The slit plate is held by a guide member 10 placed on the left side through a dovetail and a dovetail groove (not shown) so as to be able to move in parallel. Two L-shaped arms 12a, 12b and 12 are connected to the slit plates 7a and 7b via shafts 11a and 11b.
c and 12d are each rotatably attached. These arms are all formed with equal dimensions, and the two arms attached to each shaft are arranged so that their inner sides face each other. The other ends of the arms 12a and 12c and 12b and 12d are connected to the slit 9 through shafts 13a and 13b, respectively.
It is rotatably attached to a and 9b. 14
is a cam placed between the slit plates 9a and 9b, and the cam is placed between the guide plate 1 as shown in FIG.
0 is fixed to a rotating shaft 15 that rotatably passes through the shaft. A gear 16 is fixed to the other end of the rotating shaft 15, and this gear is connected to the drive rod 5 via an intermediate gear 17 and a gear 18. The drive rod 5 is the first
As described in the figure, the spectroscopic crystal 3 is moved linearly to change the black angle of incident X-rays. A spring 19 is stretched between the slit plates 9a and 9b, and is used to keep both slit plates in constant contact with the cam 14.

However, when the cam 14 is rotated to separate the slit plates 9a and 9b from each other, the arm 12
a, 12c and 12b, 12d axes 13a and 13
Since the portion b is similarly spaced apart, the shafts 11a and 11b at the other end of the arm are drawn toward each other, so that the slit plates 7a and 7b to which the shafts 11a and 11b are fixed, respectively, approach each other. Conversely, when the slit plates 9a and 9b are brought close to each other, the arm 1
2a, 12b and 12c, 12d axes 11a and 1
1b portion moves in the opposite direction to that described above, and the slit plates 7a and 7b are separated from each other. In other words, the slit plates 7a, 7b and 9a, 9b are constructed such that the slit widths of the slit plates 7a, 7b and 9a, 9b change inversely to each other as the cam 14 rotates. Therefore, by appropriately selecting the shape of the cam 14, the slit plates 7a, 7b and 9
The slit widths at a and 9b, that is, the aperture angle and φ can be changed approximately corresponding to the curve shown in FIG. Therefore, the cam 14 is connected to the drive rod 5 as shown in FIG. 4, and as the distance between the spectroscopic crystal 3 and the X-ray source 1 increases, the aperture angle becomes larger and the aperture angle φ becomes smaller. , the aperture angle _ppt and φ _ppt approximately shown in FIG. 2 can be obtained depending on the position of the spectroscopic crystal.

By configuring as described above, the present invention achieves the optimal aperture angle _pp of incident X-rays at each position of the spectroscopic crystal.
_t and φ _ppt , it is possible to improve the S/N ratio without reducing the X-ray signal intensity and wavelength resolution over the measurement of all wavelengths, which has a great practical effect. have

It should be noted that the above description is an illustration of the present invention, and many modifications may be made in implementing the present invention.

For example, in the above-mentioned embodiment, the slit plate between the X-ray source and the spectroscopic crystal was controlled according to the distance between the X-ray source and the spectroscopic crystal to limit the area of the X-ray incident portion of the spectroscopic crystal. Instead of doing this, X-rays are incident on almost the entire surface of the spectroscopic crystal, and a slit is provided between the spectroscopic crystal and the detector, so that only the X-rays separated from a specific surface of the spectroscopic crystal are guided to the detector. You can also do it. In this case, as the distance between the X-ray source and the spectroscopic crystal increases, the slit width of one of the two sets of slit plates (the slit plate that opens and closes in a direction parallel to the Roland circular surface) becomes wider, and the slit width of the other (the Roland The slit width of the slit plate (which opens and closes in a direction perpendicular to the circular surface) is narrowed to limit unnecessary X-rays from entering the detector depending on the position of the spectroscopic crystal. Note that when the slit plate is placed between the spectroscopic crystal and the detector, the detector 4 moves in accordance with the position of the spectroscopic crystal 3, that is, the black angle of the X-rays incident on the spectroscopic crystal, so that the two sets of The slit must be attached to the support stand of the detector 4 or the support stand of the spectroscopic crystal 3, and the rotation shaft 15 of the cam 14 that controls the opening and closing of the drive rod 5 and the two sets of slits is connected using a flexible wire. Need to be connected.

[Brief explanation of the drawing]

Figure 1 a and b show X-ray spectroscopy using a Johann-type curved crystal, where a shows the spectral state parallel to the Rowland circle, and b shows the spectral state perpendicular to the Rowland circle. , FIG. 2 is a graph showing the optimum aperture angle with respect to the distance between the X-ray source and the spectroscopic crystal, and FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention.
FIG. 4 is a cross-sectional view taken along line AA in FIG. 3. In Figures 3 and 4, 3 is a spectroscopic crystal, 5 is
is a drive rod, 7a, 7b, 9a and 9b are slit plates, 8a, 8b and 10 are guide plates, 11a, 11
b, 13a and 13b are shafts, 12a to 12d are arms, 14 is a cam, 15 is a rotating shaft, 16 and 18
17 is a gear, 17 is an intermediate gear, and 19 is a spring.

Claims (1)

[Claims] 1. In a device configured such that the X-ray source, spectroscopic crystal, and detector are located on the Roland circumference, either the X-ray path between the X-ray source and the spectroscopic crystal or between the spectroscopic crystal and the detector a first set of slit plates for controlling the passage of X-rays in a direction parallel to the Roland circular surface; and a second set of slit plates for controlling the passage of X-rays in a direction perpendicular to the Roland circular surface; slit means comprising a plate, and further, as the distance between the X-ray source and the spectroscopic crystal increases, the slit width of the first set of slit plates of the slit means is increased, and the slit width of the second set of An X-ray spectrometer, characterized in that it is provided with slit width control means for narrowing the slit width of a set of slit plates.