JP2877534B2 - Total reflection X-ray fluorescence analysis method and analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a total reflection type fluorescent X-ray analysis method and analyzer, and more particularly to an improvement in an X-ray optical system, which is used to detect a trace substance on a sample surface with high sensitivity. The present invention relates to a suitable total reflection type fluorescent X-ray analysis method and analyzer.

[0002]

2. Description of the Related Art A total reflection type fluorescent X-ray analyzer comprises an X-ray source,
It is composed of a monochrome meter, a fluorescent X-ray detector, a sample measurement condition setting mechanism, a vacuum vessel and a vacuum evacuation device for mounting these components, and a control device for controlling the operation of the entire device and performing data processing. The sensitivity performance of the ultra-trace analysis of the total reflection type fluorescent X-ray is mainly determined by improving the intensity of the X-ray beam irradiating the sample and suppressing the amount of X-ray generated from the sample. In the conventional apparatus, for example, “Progress of X-ray analysis” 19, p237-24
9 (1988), a beam from an X-ray source is directly incident on the sample through a collimator, or as described in “Journal of the Crystallographic Society of Japan” 27, p61-72 (1985). The beam from the source was split by a flat crystal, and the electric vector of the X-ray beam was incident on the sample under conditions parallel to the sample surface. Under these conditions, a fluorescent X-ray detector was installed at a position several mm away from the sample surface, the fluorescent X-rays emitted from the sample surface were measured, and elements of trace substances were identified and quantitative analysis of the abundance was performed. .

In such an analysis method and apparatus configuration, a large rotating anode type X-ray source or a synchrotron radiation is used as an X-ray source to increase the sensitivity of ultra-trace analysis. There was no method other than increasing the intensity of the incident X-ray beam. However, when such a method is used, the distance from the X-ray source to the sample is inevitably increased, and even when a large-sized X-ray source is used, the capability of the source is increased. Not sufficiently reflected in the increase in strength.
In addition, there is a disadvantage that the detection efficiency is reduced due to an increase in the saturation time of the fluorescent X-ray detector due to an increase in the amount of scattered X-rays on the sample surface, and the sensitivity is not sufficiently increased.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and a first object of the present invention is to provide an X-ray source having the same output as the conventional one. By improving the X-ray spectroscopic optical system, the intensity of the X-ray beam incident on the sample is substantially increased, and the electric vector of the X-ray beam is controlled by the component perpendicular to the sample surface. By suppressing the scattered X-ray intensity on the sample surface,
It is an object of the present invention to provide an improved total reflection type fluorescent X-ray analysis method capable of increasing the sensitivity of ultra-trace analysis compared to the prior art, and a second object is to provide an analyzer thereof.

[0005]

According to the present invention, an X-ray beam system for irradiating a sample is constituted by an irradiation optical system in which a plurality of X-ray beams intersect at an analysis position of the sample. The above-mentioned object is achieved by substantially increasing the intensity of the X-ray beam incident on the substrate. Furthermore, in the present invention,
X-ray beam emitted from X-ray source as monochrome meter
Using a curved dispersive crystal that can monochromate and condense the light, and using the polarization selectivity determined by the diffraction phenomenon when monochromatizing, the electric vector of the X-ray beam is converted to a component perpendicular to the sample surface. , The scattering X on the sample surface
It suppresses the line intensity and increases the sensitivity of ultra-trace analysis. As means for taking out a plurality of X-ray beams, the same X-ray source may be provided with a plurality of different outlets, or may be provided with different independent X-ray sources in advance. Alternatively, a plurality of X-ray beams may be taken out.

[0006]

The X-ray optical system for irradiating the sample of the present invention can be obtained from a plurality of X-ray extraction ports of the same X-ray source, or obtained from a plurality of different X-ray sources independently provided in advance. The obtained X-ray beam is made monochromatic using an X-ray monochromator, then crossed over the sample, and the X-ray beam at the crossing portion is increased to obtain a crossed X-ray beam. , The X-ray irradiation intensity on the sample can be increased, and as a result, the analysis sensitivity can be increased. In addition, by using a curved monochrome meter for monochromaticizing and condensing the X-ray beam extracted from the X-ray source, the electric vector of the X-ray beam maximizes the vertical component of the sample surface. An optical system such as
The amount of scattered X-rays from the sample incident on the X-ray fluorescence detector can be reduced, and the analysis sensitivity can be increased.

In the total reflection type fluorescent X-ray analyzer of the present invention, the path of the X-ray beam is set in a vacuum vessel, and the position of the X-ray source, the position of the monochromator and the position of the sample are defined by the vacuum vessel. By providing a control mechanism capable of controlling the movement from the outside, it is easy to adjust the optical system from the outside. Also,
By providing a control mechanism that allows the position of the X-ray beam irradiating the sample surface and the X-ray fluorescence detector to move the sample position horizontally or rotationally from the outside of the vacuum vessel, surface analysis of a large-area sample is improved. Can be done with sensitivity.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. (1) Explanation of Principle FIGS. 1 and 2 show explanatory views of the principle of the present invention.
Hereinafter, description will be made in accordance with these. In FIG. 1, 1 is an X-ray generator, and 2 is an X-ray source that actually generates X-rays. X
The X-ray beam 3 generated by the X-ray source 2 passes through the X-ray source 2 through an X-ray transmission window 4 for vacuum shutting off the X-ray generator 1 and the outside and a slit 5 for cutting off unnecessary X-rays. The light divergently enters the curved dispersive crystal 6 as the center. The X-ray transmission windows 4 serving as extraction windows for the X-ray beams 3 are provided at two locations as shown in the figure so that two X-ray beams can be extracted. Here, the X-ray beam 3 incident on the concave surface of the curved-type dispersive crystal 6 is diffracted by the curved-type dispersive crystal 6 and converted into a monochromatic X-ray beam 7 having only the wavelength λ. To the convergence point 9 through the slit 8 for suppressing the fluorescent X-rays generated from. After passing through the convergence point 9, it crosses the other X-ray beam 10 that has passed through the same path as the X-ray beam 7, and the X-ray intensity at the intersection can be increased. Then, the sample is set at a position not shown but including this intersection.

In this embodiment, an example is shown in which two X-ray beams obtained from one X-ray source 2 are used, but X-rays emitted from a plurality of independently provided X-ray sources are shown. Even when the beams cross each other via the respective X-ray optical systems, the X-ray intensity at the intersection can be similarly increased. Next, X-ray spectroscopy and convergence by the curved dispersive crystal will be described with reference to FIG. The X-ray beam divergently radiated from the X-ray source 2 is incident on the concave surface of the curved dispersive crystal 6.
The curved dispersive crystal 6 is obtained by elastically deforming a single crystal having a period d of the atomic plane in the thickness direction with a radius of 2R and then cutting the inner surface with a radius of R. Assuming that the atomic planes involved in the X-ray diffraction are cylindrical surfaces, X-rays emitted from one point of the X-ray source 2 with respect to the inner surface of the curved dispersive crystal 6 cover the entire inner surface of the cylindrical surface. The light beam reaches the convergence point 9 through an optical path that satisfies the geometrical condition that satisfies the Bragg's law shown in the following equation 1.

[0010]

2d · sin θ = n · λ (1) Here, θ means a diffraction angle, wavelength λ is the wavelength of X-rays irradiating the sample, and n is the order of diffraction. At this time,
The geometrical relationship between the X-ray source 2, the curved dispersive crystal 6, and the convergence point 9 is as shown in FIG.
Here, the angle φ formed by the curved dispersive crystal 6 at the X-ray source 2 and the convergence point 9 has a relationship represented by the following expression 2 when the arc length 上 の on the circumference of the curved dispersive crystal 6 is satisfied.

[0011]

## EQU2 ## In this embodiment, the curved dispersive crystal 6 is composed of a Ni single crystal, the arc length is 100 mm, the radius R is 200 mm, and X 1/8 radian of the X-ray beam generated by the source 2 is spectrally converged, and the beam diverges to 2π radian in a plane by using two optical systems (X-ray beams 3 and 10). Of them are spectrally converged at the sample position. The X-ray beam generated by the X-ray source 2 includes not only characteristic X-rays but also X-rays due to bremsstrahlung radiation having a continuous wavelength. Only the selected wavelength λ is applied to the sample (not shown).

Now, the wavelength of the X-ray irradiating the sample used here is Lα ray of Au (λ = 0.12764 nm),
Assuming that the atomic plane of the curved-type dispersive crystal is <311> of a Ni single crystal, the period is d = 0.10624 nm. Therefore, according to Equation 1, the diffraction angle is θ = 36.921 °. The X-ray beam emitted from the X-ray source 2 has no polarization, but when diffracted by the spectral crystal 6, the component of the electric vector in the direction perpendicular to the atomic plane involved in the diffraction decreases. The X-ray intensity after diffraction including this polarization is expressed by the following equation 3 and is called a polarization factor p.

## EQU3 ## p = (1 + cos2θ) / 2 (3)

According to this embodiment, the component of the electric vector in the direction perpendicular to the atomic plane from the diffraction angle θ is 25% of the total X-ray intensity.
To a degree. This value is about 1/3 of the case where an X-ray optical system that does not consider the polarization is used. As a result, the electric vector in the direction perpendicular to the sample surface increases, and the electric vector in the horizontal direction decreases, so that the scattering intensity of the incident X-ray beam on the sample surface can be reduced. In this embodiment, the X-rays are AuLα rays, but the X-rays are Fe, C
o, Cu, Mo, Ag Kα ray or Kβ ray, or T
a, W, Re, Os, Ir, Pt Lα ray or Lβ
A similar effect can be obtained with a wire or the like. Similarly, the curved-type dispersive crystal 6 is a Ni single crystal.
It is possible to use a single crystal such as i, Ge, SiO ₂ or LiF.

(2) Description of X-ray generator (2) -1 Rotating anode section Next, the rotating anode section of the X-ray generator 1 used in the present embodiment will be described with reference to the vertical sectional front view shown in FIG. I do. Refrigerant 1
A rotary anode 16 having a double hollow rotary shaft 15 provided with four flow paths is provided with a partition plate 18 at a portion on the back side of the electron beam irradiation surface 17 so as to obtain a sufficient flow rate of the refrigerant. The rotating anode 16 has a cylindrical shape composed of a single metal capable of obtaining desired X-rays or a laminate formed by applying a metal film capable of obtaining desired X-rays on the surface of a base metal having high heat conductivity. ing. Since the rotating anode side from the flange 20 of the housing 19 is installed in a high vacuum, the rotating vacuum seal 21
Isolates high vacuum from the atmosphere. Double hollow rotary shaft 15
Is installed in a bearing mounting frame 23 at a position near the rotary vacuum seal 21.

The rotor 24 of the electric motor has a double hollow rotary shaft 15.
Is fixed directly near the center of the. The stator 25 of the electric motor is installed inside the housing 19 so as to surround the rotor 24. The rotating electrode 26 receives the current of the electron beam captured by the rotating anode 16 through a brush 27, a brush holding spring, a screw 28, and a housing 19, and grounds a high-voltage power supply for the electron beam not shown in FIG. It is installed to be connected to the potential side.

A bearing 29, which forms a pair with the bearing 22, is provided inside a bearing mounting frame 30. The refrigerant rotary seals 31 and 32 are
Each is provided in the refrigerant outlet mount 33 and the refrigerant inlet mount 34 to prevent the refrigerant from leaking. The coolant external discharge disk 35 is used to discharge the coolant to the outside of the housing 19 by rotation when the coolant rotary seal 31 is damaged and leaks along the outer periphery of the double hollow rotary shaft 15. It is a safety mechanism. Further, the refrigerant external discharge disk 35 includes:
A permanent magnet piece 36 is provided, and the rotation detecting mechanism 37 can detect the state of rotation of the rotating anode 16. When the rotating speed is low or when rotation becomes impossible due to an accident, the rotating anode 16 is rotated. It is possible to shut off the irradiation of the electron beam to the device.

The maximum power G that can irradiate the electron beam to the anode 16 is given by the following equation (4), where Tm is the melting point of the anode material, g is the thermal conductivity, C is the specific heat, D is the rotating anode diameter, and N is the rotating speed. It is represented as

(Equation 4) Here, a means a proportionality coefficient. Of the constants in Equation 4,
Tm, g, and C are uniquely determined when the anode material is determined, and N and D can be determined on the device design.
It is.

Here, when the diameter D of the anode is increased, the X-ray generating tube becomes large. In the conventional apparatus, since the rotating anode is driven via a rotary drive mechanism such as a pulley, a sufficient rotation speed cannot be obtained due to problems such as vibration, and the diameter of the anode is increased to irradiate the electron beam. The power G was increased. In the present invention, since the rotating shaft 15 of the rotating anode 16 and the drive motor (rotor 24) are integrated, no problem such as vibration occurs even if the rotation speed is increased. Therefore, by increasing N, even if it is small, the electron beam is equal to or more than the conventional one.
It is possible to obtain the beam irradiation power G. In this embodiment, D is set to 70 mm, and the rotation speed N is set to 9000 revolutions per minute using an inverter motor (high-frequency motor), so that the irradiation length of the electron beam in the rotation axis direction is increased. 1m
m, an electron beam irradiation power of about 5 kW is obtained with an electron beam irradiation length of 0.4 mm in the direction perpendicular to the rotation axis. This power value is about twice the value of the conventional device having the same D.

(2) -2 Configuration of X-ray Generator Next, the configuration of the X-ray generator 1 of the present embodiment will be described with reference to FIG. In FIG. 4, 16 is a rotating anode, 39
Is an electron gun for irradiating the rotating anode with an electron beam;
Is a high voltage power supply for emitting electron beams from the electron gun,
Reference numeral 41 denotes a vacuum container for mounting the rotary anode 16 and the electron gun 39, and reference numeral 42 denotes a vacuum exhaust device for maintaining the vacuum container at a high vacuum. In this embodiment, LaB ₆ that causes little contamination of the rotating anode was used as the thermionic emission source of the electron gun 39. Further, a turbo molecular pump having a high evacuation speed in a medium vacuum to high vacuum region was used as the vacuum evacuation device 42.

(3) Configuration Example of Total Reflection X-ray Fluorescence Spectrometer Next, the total reflection X-ray fluorescence spectrometer of this embodiment will be described with reference to FIG. In FIG. 5, 1 is an X-ray generator, 44 is a spectrally convergent X-ray optical system, 45 is a sample to be subjected to ultra-trace analysis, 46 is an X-ray beam which sets the sample to X-ray total reflection conditions, and A sample setting mechanism for freely selecting an irradiation position; 47, a reflected X-ray intensity detector for obtaining total reflection conditions; 48, a fluorescent X-ray detection for measuring fluorescent X-rays emitted from a sample under total reflection conditions And 49, data processing for controlling the X-ray generator 1, the spectral convergent X-ray optical system 44, and the sample setting mechanism 46 based on the data of the reflected X-ray intensity detector and the fluorescent X-ray detector. The control device 50 is a vacuum container for keeping the entire X-ray path in a vacuum. Here, the fluorescent X-ray detector 48 is of a type that emits a voltage pulse proportional to the energy of X-rays emitted from the sample and incident on the detector. In this example, a Si (Li) detector was used. This detector has a fluorescent X-ray energy resolution of 0.2 keV.
By integrating the output of this detector through an analog-to-digital (A / D) converter of the data processing controller 49 into a multi-channel memory, a fluorescent X-ray spectrum can be obtained. it can.

(4) Results of Sample Analysis In this embodiment, the Lα ray of Au was used as an X-ray beam for exciting the sample, but the wavelength and energy of the X-ray were used.
Is 0.12764 nm and 9.712 keV. Therefore, as the fluorescent X-ray excited by K-shell excitation of the element, Zn (8.6
It is possible to measure an element having an atomic number smaller than 30 keV). For example, Fe (6.398 keV), Co
(6.924 keV), a fluorescent X-ray spectrum capable of sufficiently distinguishing Ni (7.471 keV), Cu (8.040 keV) and the like can be obtained. The amounts of these elements contained in the sample are proportional to the integrated intensities of the respective fluorescent X-ray peaks shown in FIG. 6, and the amounts of the trace elements are measured by analyzing the spectra integrated in the multi-channel memory. be able to. At this time, if the intensity of the scattered X-rays from the sample is high, an X-ray beam for exciting the sample having an energy of 9.712 keV is incident on the fluorescent X-ray detector 48, and detection of a small amount of fluorescent X-rays is performed. It can be difficult. Especially Zn
(8.630 keV) fluorescent X-ray, as shown in FIG.
On the measured fluorescent X-ray spectrum, a large integrated peak of the incident X-ray makes it difficult to obtain a precise integrated intensity. Also, if the scattered X-ray intensity is high, the time for A / D conversion is used for useless measurement of the scattered intensity, and the dead time of the detector and the A / D converter becomes longer, so that the substantial sensitivity is reduced. Will be.

[0022]

As described above, according to the present invention,
Even when an X-ray source having the same output as the conventional one is used, the intensity of the X-ray beam incident on the sample is increased by the high-efficiency X-ray spectroscopic optical system and the electric vector of the X-ray beam is increased. By dominating the component perpendicular to the sample surface,
The intensity of scattered X-rays on the sample surface can be suppressed, and the sensitivity of ultra-trace analysis can be remarkably increased as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a spectral focusing optical system using a plurality of X-ray beams for explaining the principle of the present invention.

FIG. 2 is a diagram illustrating the principle of X-ray spectroscopy and convergence by a curved-type spectroscopic crystal.

FIG. 3 is a vertical sectional front view of a rotating anode part of the X-ray generator used in one embodiment of the present invention.

FIG. 4 is a partially cutaway front view showing a configuration example of an X-ray generator according to one embodiment of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a total reflection X-ray fluorescence spectrometer according to an embodiment of the present invention.

FIG. 6 is an X-ray fluorescence spectrum curve measured according to an example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray generator 2 ... X-ray source 3, 10 ... X-ray beam 4 ... X-ray transmission window 5 ... Slit 6 ... Curved dispersive crystal 7 ... X-ray beam 8 ... Slit 9 ... Convergence point 14 ... refrigerant 15 ... double hollow rotating shaft 16 ... rotating anode 17 ... electron beam irradiation surface 18 ... partition plate 19 ... housing 20 ... flange 21 ... rotating vacuum seal 22 ... bearing 23 ... bearing mounting frame 24 ... motor Rotor 25 ... Motor stator 26 ... Rotating electrode 27 ... Brush 28 ... Brush suppressing spring and screw 29 ... Bearing 30 ... Bearing mounting frame 31 ... Refrigerant rotating seal 32 ... Refrigerant rotating seal 33 ... Refrigerant outlet mount 34 ... Refrigerant inlet mount 35 ... Refrigerant outside discharge disk 36 ... Permanent magnet small piece 37 ... Rotation detection mechanism 39 ... Electron gun 40 ... High voltage power supply 41 ... Vacuum container 42 ... Vacuum exhaust device 44 ... Spectral focusing X-ray optical system 45 … Fee 46 ... sample setting mechanism 47 ... reflection X-ray intensity detectors 48 ... fluorescent X-ray detector 49 ... de - data processing control unit 50 ... vacuum vessel.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 23/223

Claims (7)

(57) [Claims] 1. A total reflection type fluorescent X-ray analysis method for analyzing a trace substance on a sample surface by totally reflecting X-rays on a sample surface and reducing the amount of scattered X-rays incident on a fluorescent X-ray detector, A plurality of X-ray beams for irradiating the sample are prepared, and each of the X-ray beams is converted to an X-ray monochrome meter.
A total reflection type fluorescent X-ray analysis method, which comprises the steps of: irradiating each sample with a single color and crossing over the sample. 2. A total reflection device having means for analyzing a trace substance on the sample surface by totally reflecting X-rays on the surface of the sample and reducing the amount of scattered X-rays incident on the X-ray fluorescence detector. Type X-ray fluorescence spectrometer, wherein a plurality of X-ray beams are monochromatized using an X-ray monochromator, and a means for irradiating them with crossing on the sample is provided. X-ray fluorescence analyzer. 3. A total reflection X-ray fluorescence analyzer according to claim 2, further comprising means for extracting the plurality of X-ray beams from different extraction ports of the same X-ray source. 4. The total reflection type fluorescent X-ray analyzer according to claim 2, further comprising means for extracting the plurality of X-ray beams from independent X-ray sources. 5. An X-ray beam path is provided with a curved monochrome meter for monochromaticizing and condensing the X-ray beam taken out of the X-ray source. By configuring an optical system in which the electric vector maximizes the vertical component of the sample surface, the amount of scattered X-rays from the sample incident on the X-ray fluorescence detector is reduced, and the analysis sensitivity is increased. The total reflection type fluorescent X-ray analyzer according to claim 2. 6. The X-ray beam path is provided in a vacuum vessel, and the position of an X-ray source, the position of an X-ray monochromator, and the position of a sample can be controlled from outside the vacuum vessel. The total reflection type fluorescent X-ray analyzer according to any one of claims 2 to 5, further comprising a control mechanism. 7. The apparatus according to claim 6, further comprising a control mechanism capable of controlling the position of the X-ray beam for irradiating the sample surface and the position of the sample with respect to the fluorescent X-ray detector from the outside of the vacuum vessel either horizontally or rotationally. Total reflection type fluorescent X-ray analyzer.