JPS6140935B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to a method for linearly performing wavelength scanning in an X-ray spectrometer using a plane crystal as a spectroscopic element. In general, in an X-ray spectrometer, as shown in Figure 1, when a measurement sample 2 is irradiated with X-rays emitted from an X-ray tube 1, the X-ray spectrometer detects the characteristic Spectroscopic measurements are carried out, and since the wavelength and intensity of the characteristic X-rays are related to the type and concentration of elements contained in the sample, the sample can be analyzed qualitatively and quantitatively. Significant X-rays emitted from the sample pass through the first solar slit 3 and are spectrally separated by the spectroscopic crystal 4.
The diffracted X-rays pass through the second solar slit 5 and are detected by the detector 6. The output signal of this detector is displayed by an indicator after electrical processing. At this time, there is a relationship between the angle θ that the X-ray incident on the spectroscopic crystal 4 and the diffracted X-ray make with respect to the atomic plane of the spectroscopic crystal, the lattice constant d of the spectroscopic crystal, and the wavelength λ of the X-ray. It has the well-known relationship of Bratz's law, λ=2dsinθ (1). Therefore, by changing θ (d is determined by the spectroscopic crystal used), the value of λ can be determined. As mentioned above, since λ is unique to the element contained in the sample, qualitative analysis is possible. Further, quantitative analysis is performed by determining the X-ray intensity at a specific wavelength. In a conventional X-ray spectrometer, the spectroscopic crystal and the detector (the second solar slit rotates as a unit with the detector) are driven to rotate around the X-ray incident point B on the spectroscopic crystal shown in Figure 1. However, in this case, the detector and the second solar slit are driven in rotation with an angular velocity twice the rapidity of the spectroscopic crystal, and in large and low spectrometers are driven by a gear mechanism. 7 and 8 in FIG. 1 indicate these worm gears. The display on an indicator (for example, a recorder) obtained by this method is obtained as shown in FIG. 4, which shows the relationship between the X-ray intensity (vertical axis) and the angle θ (horizontal axis). Originally, characteristic X-rays are element-specific and are generally expressed by wavelength values, but with conventional spectrometers, the angle θ is determined from records, and from this the wavelength value can be calculated using equation (1). This means that we are conducting qualitative analysis to find out. With the method of the present invention, the relationship between X-ray intensity and wavelength can be directly determined and displayed at equal wavelength intervals (wavelength linear scanning), making it possible to accurately measure the wavelength of X-ray peaks in actual qualitative analysis. It has features that allow it to be used well. Recording by this method is obtained as shown in FIG. 5, which corresponds to FIG. 4. Next, the present invention will be explained with reference to the drawings. FIG. 2 is a diagram illustrating the outline of the present invention, in which the characteristic X-rays incident on the spectroscopic crystal 4 are separated and incident on the detector 6. Spectroscopic crystal 4 is attached to fixed point B with arm BH
The arm BH is rotatably installed around a straight line (rotation axis) perpendicular to the X-rays passing through the fixed point B and entering the spectroscopic crystal 4. The detector 6 is also mounted on an arm BC (hereinafter referred to as a detector arm) which is rotatable around the rotation axis. Link arms EF and GF are rotatable around points E and G on the detector arm and reference line BD, respectively, and the central axes of these rotations are parallel to the rotation axis of arm BH. Point F slides along arm BH. The reference line BD is an extension of the X-rays incident on the crystal D. Arm BH is rotated by a sine bar mechanism that changes the distance h between reference line BD and one point L on arm BH at a constant speed. arm
When BH rotates, the detector arm also links mechanism BE−
Rotates by EF-FG-BG, but BE=BG, FG
= FE, and the angle θ between the detected diffracted X-ray and the arm BH is maintained at the angle between the arm BH and the reference line BD. A more specific example of this mechanism is as shown in FIG. 4 is fixed to a second arm 8 which is rotatable around an axis passing through point B and perpendicular to the plane of the paper, and a second solar slit 5 and a detector 6 are fixedly attached to the first arm 7. Due to the link mechanism of the third and fourth link arms 9 and 10 and the first arm 7, the link arm 7 is rotated at B point with respect to the rotational drive angle θ with respect to the rotation center point B of the second link arm 8 and the reference line BD. A rotation of angle 2θ about the point is obtained. Note that 11 and 12 indicate connecting pins, and the center of pin 13 is located on BD. Also, pin 12
slides in the sliding groove 81 of the link arm 8.
(BE = BG, FG = FE are predetermined, BF is variable) The link arm 8 moves to point B by means of a feed screw 16 arranged perpendicular to the BD line and a sliding member 15 that moves back and forth by the rotation of these screws. rotated around the center. The spring 17 is used to press the pin 14 fixed to the link arm 8 onto the surface of the slider 15. 18 is a guide rod fixed to the slider 15, and the sliding surface 151 of the slider and the sliding surface 18 of the guide rod 8
1 and parallel to the base line BD, and the pin 14 is configured to be able to slide in contact with the surfaces 151 and 181. Note that the pin 14 is provided with a bearing mechanism to be rotatable, and the surfaces 151,
181. 19 is a device for displaying or recording the output of the detector, such as a recorder. Reference numeral 20 denotes, for example, a constant-speed rotary drive source, which is coupled to the feed screw 16 and the recording paper feeding device of the recorder 19 via motion transmission mechanisms 21 and 22 having a speed ratio switching mechanism. In addition, in some cases, the recording paper feed mechanism and feed screw 1
6 may linearly drive the other. (Control line 23). In this case as well, a transmission mechanism is provided as necessary. In addition, an encoder pulse generator 24 integrated with the screw 16 has a dedicated wavelength indicator,
Adjustable pulse rate down circuit 25, counter 2
It may be composed of 6. Next, the operation of the apparatus of the present invention will be explained using the apparatus of the embodiment shown in FIG.
The rays (characteristic X-rays) pass through the first solar slit 3 and enter the spectroscopic crystal 4 . The diffracted X-rays from the spectroscopic crystal 3 pass through the second solar slit 5 and enter the detector 6, where they are converted into an electrical signal proportional to the concentration of the element to be measured in the sample. Now, if the wavelength feed screw 16 is rotated and the slider 15 is moved at a constant speed, for example, in the direction of the arrow in the figure, ML=h will increase, but since BL is constant, the pin 14 will slide. By rotating or sliding on the surfaces 151 and 181 to the left in the figure, the crystal 4 rotates around B together with the arm 8, and the X-ray incident angle θ to the crystal 4 increases, and the link mechanisms 7 to 13 Accordingly, the detector 6 and the slit 5 are rotated about point B at a rate of 2θ. In this case, as can be seen from Figure 3, the baseline position
The distance h between the center position of the pin 14 from BD and the distance l between the rotation center B of the link arm 8 and the center L of the link arm 14
and the rotation angle θ of the crystal 4, the relationship sin θ=h/l (2) holds true. Therefore, equation (1) can be expressed as λ=2dsinθ=2dh/l (3). Here, d is the lattice constant of the crystal, which is determined by the type of crystal used, and l is constant, so 2d/l=k ₁ (constant) ......(4) and (3 ) formula becomes λ=K ₁ h (5). Equation (4) shows that there is a proportional relationship between the wavelength λ of the X-ray and h, and if the pitch of the feed screw 16 is P and the number of rotations is n, then h=nP ......(6) Therefore, when using a recorder as an indicator, if the recording paper is fed continuously at a constant speed, for example, in synchronization with the rotational drive of the screw 16 as shown in the following equation (7), the above result can be obtained. The results (shown in Figure 5) showing the relationship between X-ray intensity and wavelength are obtained, and the wavelength relationship shown as the horizontal axis is equidistant, that is, (8)
The wavelength will be linearly specified as shown in the equation. X=k ₂ n ………(7) X=k ₂・h/P=k ₂ λ/k ₁ P≡k ₃ λ……
(8) However, X: recording paper feeding amount or wavelength indicator reading amount, k ₂ , k ₃ : constants In the method according to the present invention, in addition to the advantage of wavelength linear scanning as described above, wavelength accuracy can be obtained. It has the following differences from the conventional method. (1) In the conventional method, as mentioned immediately, wavelength scanning is performed by rotating the crystal using a gear mechanism, so the wavelength accuracy △λ is obtained from (1): △λ = 2d・cosθ・△ θ can be considered as (9). Now, let us assume that the angular accuracy △θ is △θ=1/100 (10).
LiF, Gl, TEP, which are commonly used as crystals (although require advanced techniques in preparation)
The wavelength accuracy Δλ obtained when using ADP and TAP is determined as follows. The lattice constants shown in Table 1 are usually used, but
Among these, LiF, TEP and TAP are examples.

[Table] Select the wavelength λ for the angle θ = 0 to 90° (1)
The relationship between the wavelength accuracy Δλ and the corresponding angle obtained from the equations (9) and (10) is shown by dotted lines in FIGS. 6 to 8. (2) On the other hand, the wavelength accuracy Δλ obtained in the method according to the present invention can be obtained from equation (3) as Δλ=2d/lΔh (11). In the lean arm, l = 400 mm, and with a pitch error easily obtained in normal screw processing, that is, △h = 5/1000 [mm], the wavelength accuracy for each crystal is shown in Figure 6 ~
It is shown with a solid line in FIG. As can be easily understood from the above, the method using the sine bar mechanism according to the present invention can obtain extremely high wavelength accuracy compared to the conventional angle scanning method, and can maintain a constant wavelength accuracy within the scanning range. can. Also, since the operating mechanism uses a link mechanism, it is extremely simple. Although the above scanning range has been explained as an angle of 0 to 90 degrees, it is not necessary to use the range around 0 and 90 degrees in an actual apparatus. In addition, from the point of view of efficiency with respect to the wavelength of the crystal, in X-ray spectrometers the crystal is replaced. No problem arises by changing the relationship between the wavelength indicator and the drive of the wavelength indicator depending on the value of the lattice constant of the crystal. For this purpose, for example, the motion transmission mechanism 21 or 22
Gear ratio and pulse rate down circuit 2
The rate down rate of 5 may be changed in conjunction with the switching of crystals so that the ratio of k ₂ /k ₁ in equation (8) remains constant.

[Brief explanation of the drawing]

Figure 1 is an example of a conventional X-ray spectrometer; Figure 2;
FIG. 3 is a schematic diagram of an X-ray spectrometer according to an embodiment of the present invention, FIG. 4 is a recording of measurement results by a conventional X-ray spectrometer, and FIG. 5 is a diagram showing measurement results by an X-ray spectrometer of the present invention. The record diagram is shown. 6 to 8 are diagrams comparing the wavelength accuracy obtained from measurements by a conventional X-ray spectrometer and an X-ray spectrometer according to the present invention, respectively. 1... X-ray source, 2... Sample, 3... Solar slit, 4... Spectroscopic crystal, 5... Solar slit,
6...Detector, 7,8,9,10...Link mechanism, 11,12,13,14...Pin, 15,1
6...Screw feed mechanism.

Claims (1)

[Claims] 1. An arm BH is installed to be rotatable about a rotation axis about a straight line that is perpendicular to the X-rays incident on the spectroscopic crystal 4 and passes through a fixed point B. a sine bar mechanism that changes at a constant speed a distance h between a reference line BD, which is an extension of the X-rays incident on the spectroscopic crystal 4, and a point L on the arm BH; A detector arm BC is rotatably installed around a rotation axis, and a detector 6 mounted on this detector arm BC detects the X-rays from the spectroscopic crystal 4.
and a link arm GF that is rotatably installed around a straight line that is parallel to the rotation axis and passes through a point G on the reference line BD, and whose one end F slides along the arm BH, and the rotation of the arm BH. The link arm is installed rotatably around a straight line that is parallel to the axis and passes through point E on detector arm BC.
A link arm EF is provided which maintains the same position as the end F of the GF and slides along the arm BH, and the distance between points B, E, F, and G on each arm is such that BE=BG and
By having the relationship EF = FG, the angle θ between the detected diffraction X-ray and arm BH is
and a reference line BD.