JP2002093594A - X-ray tube and x-ray analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube capable of irradiating a sample with X-rays suitable for X-ray analyses of both fluorescence and diffraction, and an X-ray analyzer. SOLUTION: For the vertical X-ray tube 10, electrons 45 are emitted on a target 44 to which positive voltage is applied from an earthed filament 48, thereby generating continuous X-rays and specific X-rays from the target 44. The X-ray tube is equipped with a beryllium-made windows 41, 42, which permit transmitting both X-rays, at the tips of a tube bulb. The windows are composed of the first window 41 which permits discharging both X-rays from the target 44 in a normal direction of the surface of the target 44 and the second window 42 which permits transmitting both X-rays from the target 44 in a direction near to a tangential direction of the surface of the target 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tube and an X-ray analysis apparatus capable of performing both X-ray diffraction analysis and X-ray fluorescence analysis with one apparatus.

[0002]

2. Description of the Related Art In an X-ray diffraction method, a structure of a sample can be analyzed based on diffracted X-rays reflected by the sample, and for example, the type and structure of a compound can be known. On the other hand, in the fluorescent X-ray analysis, primary X-rays are emitted toward a sample, and elemental analysis of the composition constituting the sample is performed based on the fluorescent X-rays from the sample.

[0003] In general, these two analytical methods are performed by separate apparatuses, and Japanese Patent Publication No. Hei 11-502025 discloses a technique that enables two analyzes with one apparatus. In this conventional example, two analysis methods can be performed with a single X-ray tube, and the number of expensive X-ray tubes is reduced to reduce costs.

[0004]

However, in the above prior art, since primary X-rays are taken out of the X-ray tube in one direction and irradiated to the sample, X-rays suitable for each of fluorescence and diffraction analysis are obtained. Cannot be irradiated on the sample.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an X-ray tube and an X-ray analyzer capable of irradiating a sample with X-rays suitable for each of X-ray analysis of fluorescence and diffraction.

In order to achieve the above object, an X-ray tube according to the present invention uses a grounded filament to impinge electrons on a target to which a positive voltage is applied, thereby causing continuous X-rays and characteristic X-rays (hereinafter referred to as primary X-rays) from the target. A vertical X-ray tube provided with a beryllium window that allows emission of the primary X-rays at the tip of a tube, wherein the primary X-rays are emitted from a target. A first window allowing emission along a normal direction of the surface of the target, and a second window allowing emission of the primary X-rays from the target in a direction close to a tangential direction of the surface of the target. A window is provided.

In the present invention, "direction close to tangential direction"
Is, for example, 2 ° to 8 ° with respect to the surface of the target.
A shallow angle.

According to the present X-ray tube, the X-rays taken out of the first window are emitted along the normal direction of the surface of the target, so that even if the output of the primary X-rays is small, they are collected. By illuminating, the intensity of fluorescent X-rays can be increased. On the other hand, the X-rays taken out from the second window are emitted in a direction close to the tangential direction of the surface of the target, so that X-rays having a line focus suitable for X-ray diffraction analysis can be obtained. In addition, by making monochromatic X-rays incident on the sample, the accuracy of X-ray diffraction analysis can be improved.

Further, in the present invention, since a vertical X-ray tube having a target to which a positive voltage is applied is used, scattering of scattered electrons from the target can be prevented. Therefore, the beryllium window material can be made thinner, so that low-energy spectra pass through the window material, so that X-ray fluorescence analysis of light elements and X-ray diffraction analysis of a sample having a large lattice spacing can be performed. Becomes

Further, in the present invention, the X-ray tube may be provided with a third window which allows the light to be emitted obliquely to the surface of the target. Here, the “diagonal direction” refers to an angle of about 20 ° to 70 ° with respect to the surface of the target, but preferably 30 ° to
X-rays are extracted at an angle of about 60 °.

Since the X-rays taken from the oblique direction have a long optical path to the sample and a bent optical path with respect to the sample, the X-rays emitted in the normal direction are inserted by inserting a spectral element into the optical path. An excited X-ray having energy different from that of the X-ray can be obtained.

In the present invention, in order to reduce the thickness of the window material, it is preferable to form each window separately and individually.
However, in the present invention, each window may be formed continuously.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment. The X-ray analyzer is portable, and the measuring device 1 of FIG.
It includes a measurement controller (not shown) and a personal computer (arithmetic unit).

The measuring apparatus 1 includes one X-ray tube 40, first and second optical systems 10, 20, and first and second X-ray detectors 1D, 2D.

The first optical system 10 and the first X-ray detector 1D are for performing X-ray fluorescence analysis. on the other hand,
The second optical system 20 and the second X-ray detector 2D are for performing X-ray diffraction analysis. The X-ray detector 1
As D and 2D, it is preferable to use an electronically cooled silicon drift detector.

The X-ray tube 40 has a case 49 at the tip of the tube. The inner surface of the case 49 is coated with the same material as the target 44. The case 49 is provided with first and second windows 41 and 42. The first window portion 41 allows the primary X-rays 11 emitted in the normal direction of the surface of the target among the primary X-rays generated from the target 44 to be emitted. On the other hand, among the primary X-rays generated from the target 44, the second window 42 emits a primary X-ray emitted in a direction close to the connection direction of the surface of the target 44 (for example, an angle Δ = 6 °). 21 is emitted.

As shown in FIG. 2A, the target 44 has an elongated rectangular shape (3 mm × 0.5 mm), and the second window 42 extends in a direction substantially perpendicular to the longitudinal direction L of the target 44.
Is provided so that a line focus suitable for X-ray diffraction analysis can be formed.

As shown in FIG. 2B, the X-ray tube 40 is a vertical (end window type) air-cooled X-ray tube, and the filament 48 has a ground voltage, while the target 44 has a positive voltage. Is applied. Therefore, the target 44
Since scattered electrons are less likely to be generated by the electrons 45 colliding with the substrate, the beryllium film, which is the window material of each of the windows 41 and 42, is less likely to be degraded by heat, so that the window material can be thinned to 75 μm. The tube voltage of the X-ray tube 40 can be set to an appropriate value.

The first optical system 10 condenses the primary X-rays 11 from the first window portion 41 and irradiates the primary X-rays 11 on the sample 100 on the first sample stage 50. 13 and a light shielding plate (light shielding member) 14.

The spectral element 12 is composed of a spectral crystal or a multilayer artificial lattice. The inner peripheral surface of the spectral element 12 separates the primary X-rays 11 and reflects the diffracted X-rays 111. That is, the spectral element 1
The sample 100 is irradiated with monochromatic intrinsic X-rays 111 that are Bragg-reflected only the primary X-rays 11 incident on the sample 100 at a predetermined incident angle. The spectroscopic element 12 has an inner peripheral surface formed in a barrel shape and reflects the primary X-rays 11 by Bragg reflection.

The total reflection collimator 13 is disposed substantially coaxially with the spectroscopic element 12 inside the spectroscopic element 12, and totally reflects and condenses X-rays on the inner surface. This total reflection collimator 1
3 is preferably formed on the inner surface of a thin cylinder, but a solar slit in which a plurality of flat plates are arranged in parallel may be employed.

The light shielding plate 14 is provided with a total reflection collimator 13.
The primary X-ray 112 between the spectroscopic element 12 and the sample 100 is restricted (blocked) by the primary X-ray 112 emitted from the
One path is provided so as to be freely inserted and retracted. The light-shielding plate 14 is provided with a passage hole 16 that allows passage of the specific X-rays 111 separated by the light-splitting element 12.

The second optical system 20 shown in FIG. 1 separates the primary X-rays 21 from the second window 42 into parallel beams and converts the monochromatic parallel beams 211 to the second sample stage 2.
4 irradiates the sample 200 above. As an element of the second optical system 20, for example, an artificial multilayer grating having a parabolic surface and having a period of the grating plane interval increasing along the reflecting surface as the distance from the X-ray tube 40 increases (eg, for example) can be used. And JP-A-6-82398). in this way,
By irradiating the sample 200 with the monochromatic parallel beam 211, the background can be removed, so that the accuracy of the diffraction analysis is improved.

Diffracted X-rays 2 emitted from the sample 200
Numeral 12 passes through the solar slit 22 and enters the second X-ray detector 2D. The second sample stage 2 on which the sample 200 is placed
4, the solar slit 22 and the second X-ray detector 2D
They are attached to a rotation mechanism 23 that rotates them at an angular speed ratio of 1: 2.

Next, a method of performing X-ray fluorescence analysis will be described. First, when analyzing heavy elements in the sample 100, the light-shielding plate 14 is inserted into the path of the primary X-ray 11 in FIG. 2 and the tube voltage of the X-ray tube 40 is set to 50 kV. Is used as the intrinsic X-ray. In this case, the primary X-ray 112 that has passed through the total reflection collimator 13 is shielded from light by the light shielding plate 14,
Primary X-ray (unique X-ray) 11 monochromatized by the spectral element 12
1 enters the sample 100 through the passage hole 16 and the sample 10
The fluorescent X-rays 19 from 0 are detected by the X-ray detector 1D. As described above, since the sample 100 is excited by the monochromatic light of high energy, heavy elements can be analyzed with high accuracy.

On the other hand, when light elements in the sample 100 are to be analyzed, the light shielding plate 14 is retracted from the path of the primary X-rays 11 and the tube voltage of the X-ray tube 40 is set to 20 kV or less. L-series X-rays with low energy are used as an excitation source. In this case, the specific X-rays 111 separated by the spectroscopic element 12 and the primary X-rays 112 that have passed through the total reflection collimator 13 enter the sample 100, and
The fluorescent X-rays 19 from 0 are detected by the X-ray detector 1D. In this case, only the low-energy L-ray component is emitted from the X-ray tube 40, and the intensity of the primary X-ray also decreases. For this reason, since the sample 100 is excited only by the L line of the low energy component,
Analysis of light elements becomes possible.

Next, the case where the structure of the sample is analyzed by the X-ray diffraction method will be described. Sample 2 by X-ray diffraction
When analyzing the sample 200, the primary mechanism 21 emits primary X-rays 21 from the X-ray tube 40 and irradiates the sample 200 with the monochromatic parallel beam 211.
The X-ray detector 2D is rotated, and the X-ray intensity is measured by the second X-ray detector 2D. From the angle θ, the structure of the sample 200 can be known from the intensity of the diffracted X-ray 212 incident on the second X-ray detector 2D and the following expression (1) (Bragg's expression). 2d sin θ = nλ (1) where d: spacing between crystals θ: incidence angle, diffraction angle λ: wavelength of X-ray n: order of reflection

FIG. 3 shows a second embodiment. The X-ray analyzer has a third optical system 30 for X-ray fluorescence analysis in addition to the first and second optical systems 10 and 20. X-ray tube 4
0 has a third window 43 in addition to the first and second windows 41 and 42.

The first optical system 10 includes a first capillary 12A having an elliptical reflecting surface and a light shielding plate 14A. The first capillary 12A is connected to the first window 4
The primary X-rays 11 emitted from 1 are condensed and irradiated on the surface of the sample 100 on the first sample stage 50 on the reflection surface. The light shielding plate 14A is provided so as to be able to enter and retract in the optical path of the first optical system 10. The light shielding plate 14A may be provided between the X-ray tube 40 and the first capillary 12A,
It may be provided between the first capillary 12A and the sample 100.

The third window 43 of the X-ray tube 40 allows the primary X-ray 31 emitted obliquely to the surface of the target 44 to be emitted. The primary X-ray 31
Is monochromatized by the third optical system 30 and is condensed and irradiated onto the surface of the sample 100 on the first sample stage 50 as described below.

The third optical system 30 includes a second capillary 30 a for converting the primary X-ray 31 emitted from the third window 43 of the X-ray tube 40 into a parallel beam 32,
A monochromatizing crystal 30c and a monochromatic parallel beam 33 from the monochromatizing crystal 30c to form an excitation X-ray 3
And a third capillary 30b for irradiating the sample 4 with the sample 4. The second and third capillaries 30a,
30b is formed of a known polycapillary formed by collecting a large number of hollow thin tubes (see Japanese Patent No. 3,057,378).

The dispersive crystal 30c is different from another dispersive crystal 30d.
At the same time, it is attached to a well-known crystal switching device. The two dispersive crystals 30c and 30d have different lattice plane intervals, so that the energy (wavelength) of the excitation X-ray 34 guided to the sample 100 by the third optical system 30 can be selected. In this embodiment, since the third window 43 is provided, there is an advantage that the intensity of the excited X-rays incident on the sample 100 is generally higher than that of the first embodiment in FIG.

The second optical system 20, like the third optical system, has a pair of polycapillaries 20a, 20b and spectral crystals 20c, 20d having different lattice spacings. A line or a short X-ray 211 can be selectively incident on the sample 200.
Therefore, it is possible to analyze samples having various structures from the sample 200 having a small lattice spacing to the sample 200 having a large lattice spacing.

The other construction is the same as that of the first embodiment, and the same or corresponding parts are denoted by the same reference characters.
The detailed description is omitted.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an X-ray analyzer according to a first embodiment of the present invention.

FIG. 2 is an enlarged view showing an X-ray tube and a first optical system.

FIG. 3 is a schematic configuration diagram illustrating an X-ray analyzer according to a second embodiment.

[Explanation of symbols]

 10: First optical system 20: Second optical system 30: Third optical system 40: X-ray tube 41: First window 42: Second window 43: Third window 44: Target 48: Filament 100 : Sample 200: Sample 1D: First X-ray detector 2D: Second X-ray detector

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2G001 AA01 AA09 AA10 AA20 BA04 BA18 BA30 CA01 DA01 DA02 DA06 EA02 EA03 EA09 GA01 GA09 GA13 JA06 JA08 KA01 KA08 NA16 PA12 SA01 SA02 SA05 SA10 SA30 4C092 AA05 BD12

Claims (7)

[Claims] 1. A method in which electrons are collided with a target to which a positive voltage is applied from a grounded filament to generate continuous X-rays and characteristic X-rays from the target, and the two X-rays are emitted to the tip of a tube. A vertical X-ray tube provided with a beryllium window that permits the emission of both X-rays from a target in a direction normal to the surface of the target; An X-ray tube comprising: a second window that allows the X-rays to be emitted from the target in a direction close to a tangential direction of the surface of the target. 2. The X-ray tube according to claim 1, further comprising a third window that allows the two X-rays to be emitted from the target in an oblique direction to the surface of the target. 3. The X-ray tube according to claim 1, wherein the windows are separately formed. 4. The X-ray tube according to claim 1, a first optical system for irradiating the sample with X-rays from the first window, and fluorescence from the sample irradiated with X-rays by the first optical system. A first X-ray detector for detecting X-rays, a second optical system for irradiating the sample with X-rays from the second window, and a diffraction diffracted by the sample irradiated with X-rays by the second optical system An X-ray analyzer, comprising: a second X-ray detector that detects X-rays; and an arithmetic unit that performs predetermined X-ray fluorescence analysis and diffraction X-ray analysis based on outputs from the first and second X-ray detectors. 5. The X-ray tube according to claim 1, a first optical system that collects X-rays from the first window and irradiates the sample with the X-rays, and the first optical system irradiates the X-rays. A first X-ray detector that detects fluorescent X-rays from the sample; a second optical system that splits both X-rays from the second window and irradiates the sample with monochromatic X-rays; A second X-ray detector for detecting diffracted X-rays diffracted by a sample irradiated with X-rays by the system; and a predetermined X-ray fluorescence analysis and diffraction by an output from the first and second X-ray detectors, respectively. An X-ray analyzer comprising: a computing unit for performing X-ray analysis. 6. The X-ray tube according to claim 5, further comprising a third window portion that allows the X-rays to be emitted from the target in a diagonal direction with respect to a surface of the target. Both X-rays from the three windows are collected and split,
An X-ray analysis apparatus comprising: a third optical system that irradiates a sample with monochromatic X-rays; and a light-blocking member that is provided so as to be able to enter and retract in an optical path of the first optical system. 7. The target according to claim 4, 5 or 6, wherein the target is an elongated rectangular target, and the second window is provided in a direction substantially orthogonal to a longitudinal direction of the target, and a linear shape is formed on the sample. X-ray analyzer that can focus light on