JPH06118034A - Total reflection type fluorescent X-ray analysis method and analyzer - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if an X-ray source with an output equivalent to that of the conventional one is used, the intensity of X-rays irradiated on the sample can be substantially increased and detected by improving the X-ray spectroscopic optical system. Total reflection type fluorescent X with high sensitivity
A line analysis method and apparatus are realized. [Structure] A plurality of X-ray beams for irradiating a sample are prepared, and each X-ray beam is irradiated with an X-ray monochromator.
Are used for monochromatization, and these are crossed on the sample and irradiated. As a concrete X-ray irradiation increasing method, a plurality of X-rays generated by the X-ray source 2 are taken out from a plurality of taking-out ports through a transmission window 4, and these X-ray beams are made to pass through a slit 5.
It is incident on the curved dispersive crystal 6. The X-ray beam 3 diffracted by the concave portion of the dispersive crystal 6 is an X-ray having only the wavelength λ.
It becomes a line beam 7 and goes toward a convergence point 9 through a slit 8. After passing through the converging point 9, it intersects with the other X-ray beam 10 that has passed through the same route as the X-ray beam 7, and the X-ray intensity at this intersection is substantially increased.

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 improvement of an X-ray optical system, for detecting a trace amount of a substance on a sample surface with high sensitivity. The present invention relates to a preferable 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 is an X-ray source,
It is composed of a monochrome meter, a fluorescent X-ray detector, a sample measurement condition setting mechanism, a vacuum container for attaching them, a vacuum exhaust device, and a control device for controlling the operation of the entire device and processing the data. The sensitivity performance of the total reflection type fluorescent X-ray ultratrace analysis is mainly determined by improving the intensity of the X-ray beam irradiating the sample and suppressing the amount of scattering of the X-ray generated from the sample. In the conventional apparatus, for example, "Advances in X-ray analysis" 19, p237-24.
9 (1988), a beam from an X-ray source is directly incident on a sample through a collimator, or X-ray is detected as described in "Journal of the Crystal Society of Japan" 27, p 61-72 (1985). The beam from the radiation source was separated by a flat plate crystal, and the electric vector of the X-ray beam was incident on the sample under the condition parallel to the sample surface. Under this condition, 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 the element of a trace substance was identified and the abundance was quantitatively analyzed. .

In such an analysis method and apparatus configuration, as a means for increasing the sensitivity of ultratrace analysis, a large rotating anode type X-ray source or synchrotron radiation is used for a sample. There was no other way than to increase 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 long, and even if a large-sized X-ray source is used, the capacity of the radiation source is increased, resulting in the irradiation X-ray beam. Not sufficiently reflected in strength increase.
Further, there is a drawback in that the detection efficiency is reduced due to the increase in the saturation time of the fluorescent X-ray detector due to the increase in the scattered X-ray amount on the sample surface, which does not lead to a sufficient increase in sensitivity.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and the first object thereof is to use an X-ray source having an output equivalent to that of the prior art. The X-ray spectroscopic optical system was improved to substantially increase the intensity of the X-ray beam incident on the sample as compared with the conventional one, and the electric vector of the X-ray beam was dominated 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 X-ray fluorescence analysis method capable of increasing the sensitivity of ultratrace analysis as compared with the prior art, and a second object thereof is to provide an analyzer thereof.

[0005]

According to the present invention, an X-ray beam system for irradiating a sample is provided with 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. Furthermore, in the present invention,
X-ray beam emitted from an X-ray source as a monochrome meter
By using a curved dispersive crystal capable of monochromating the beam and collecting light, and utilizing the polarization selectivity determined by the diffraction phenomenon when monochromating, the electric vector of the X-ray beam is a component perpendicular to the sample surface. Scattering on the sample surface by controlling
It suppresses the line intensity and increases the sensitivity of ultratrace analysis. As a means for extracting a plurality of X-ray beams, the same X-ray source may be provided with a plurality of different outlets, or different X-ray sources may be provided 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 can be obtained from a plurality of different X-ray sources which are independently provided in advance. The X-ray beam to be crossed is made monochromatic by using an X-ray monochromator and then crossed on the sample, and the X-ray intensity at this crossing portion is increased to thereby cross the X-ray beam. It is possible to increase the X-ray irradiation intensity on the sample by the number of 10 times, and as a result, increase the analysis sensitivity. In addition, by using a curved type monochromator that monochromatically collects 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. It is possible to configure an optical system such as
The scattered X-ray dose from the sample incident on the X-ray fluorescence detector can be reduced and the analytical sensitivity can be increased.

In the total reflection type X-ray fluorescence analyzer of the present invention, the path of the X-ray beam is installed in the vacuum container, and the position of the X-ray source, the position of the monochrome meter and the position of the sample are set in the vacuum container. By providing the control mechanism capable of controlling the movement from the outside, it becomes easy to adjust the optical system from the outside. Also,
Since the position of the X-ray beam that irradiates the sample surface and the fluorescent X-ray detector are equipped with a control mechanism that allows the sample position to be moved horizontally or rotationally from outside the vacuum container, the surface analysis of a large-area sample can be highly performed. It can be done with sensitivity.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. (1) Description of principle FIGS. 1 and 2 are explanatory views of the principle of the present invention.
The following is a description according to 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 transmission window 4 for vacuum-blocking the X-ray generator 1 and the outside thereof, and the slit 5 for blocking unnecessary X-rays. The light is incident on the curved dispersive crystal 6 divergently as the center. The X-ray transmission window 4 serving as a window for taking out the X-ray beam 3 is provided at two places as shown in the figure so that two X-ray beams can be taken out. Here, the X-ray beam 3 incident on the concave surface portion of the curved dispersive crystal 6 is diffracted by the curved dispersive crystal 6 and becomes a monochromatic X-ray beam 7 having only the wavelength λ. To the convergence point 9 through the slit 8 that suppresses the fluorescent X-rays generated from the. After passing through the convergence point 9, it intersects with the other X-ray beam 10 that has passed through the same route as the X-ray beam 7, and the X-ray intensity at this intersection can be increased. Then, the sample is set at a position including this intersection, which is not shown.

In this embodiment, an example of using two X-ray beams obtained from one X-ray source 2 is shown, but X-rays emitted from a plurality of X-ray sources independently provided. Even if the beam intersects the respective X-ray optical systems, the X-ray intensity at the intersecting portion can be increased similarly. Next, with reference to FIG. 2, X-ray spectroscopy and focusing by the curved dispersive crystal will be described. The X-ray beam divergently emitted from the X-ray source 2 is incident on the concave surface portion of the curved dispersive crystal 6.
The curved dispersive crystal 6 is formed by elastically deforming a single crystal having an atomic plane period d in the thickness direction with a radius 2R and then cutting the inner surface with the radius R. When the atomic planes involved in the X-ray diffraction are cylindrical surfaces in this manner, the X-rays emitted from one point of the X-ray source 2 with respect to the inner cylindrical surface of the curved dispersive crystal 6 are used for the entire inner surface of the cylindrical surface. A convergence point 9 is reached through an optical path satisfying a geometric condition that satisfies the Bragg's law shown in the following Expression 1.

[0010]

## EQU1 ## 2d.sin .theta. = N..lamda. (1) where .theta. Means the diffraction angle, wavelength .lamda. Is the wavelength of the X-ray irradiating the sample, and n is the diffraction order. At this time,
The X-ray source 2, the curved dispersive crystal 6, and the convergence point 9 have a geometrical relationship as shown in FIG.
Here, when the angle φ that the curved dispersive crystal 6 extends between the X-ray source 2 and the convergence point 9 is the arc length Λ on the circumference of the curved dispersive crystal 6, the following relationship 2 is established.

[0011]

## EQU00002 ## .phi. (Radian) =. LAMBDA./4R (2) In the present embodiment, the curved dispersive crystal 6 is made of Ni single crystal, and the arc length .LAMBDA. Is 100 mm and the radius R is 200 mm, and X A beam diverging to 1π radian in the plane by spectrally converging 1/8 radian of the X-ray beam generated by the radiation source 2 and using two optical systems (X-ray beams 3 and 10). Of this, 1/4 radian is 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 having a continuous wavelength. However, by passing through the spectral focusing optical system through the slit 8, Only the selected wavelength λ is applied to the sample (not shown).

Now, the wavelength of the X-rays irradiated to the sample used here is Lα ray of Au (λ = 0.12764 nm),
Assuming that the atomic plane of the curved dispersive crystal is <311> of Ni single crystal, the period is d = 0.10624 nm, and therefore the diffraction angle is θ = 36.921 ° according to Equation 1. The X-ray beam emitted from the X-ray source 2 is not polarizable, but when it is diffracted by the dispersive crystal 6, the component of the electric vector in the direction perpendicular to the atomic plane involved in the diffraction is reduced. The X-ray intensity after diffraction including this polarization property is represented by the following expression 3 and is called a polarization factor p.

[Equation 3] 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.
Decrease to a degree. This value is about ⅓ of that when an X-ray optical system that does not consider the polarization property is used. As a result, the electric vector in the direction perpendicular to the sample surface increases, the electric vector in the horizontal direction decreases, and the scattering intensity of the incident X-ray beam on the sample surface can be suppressed small. In this embodiment, the X-ray is AuLα ray, but the X-ray is Fe, C.
Kα ray or Kβ ray of o, Cu, Mo, Ag, or T
Lα ray or Lβ of a, W, Re, Os, Ir, Pt
Similar effects can be obtained with lines and the like. Similarly, the curved dispersive crystal 6 is made of Ni single crystal, but other than that, for example, Cu, S
It is possible to use a single crystal of i, Ge, SiO ₂ , LiF or the like.

(2) Description of X-Ray Generator (2) -1 Rotating Anode Part Next, the rotating anode part of the X-ray generator 1 used in this embodiment will be explained with reference to the vertical sectional front view shown in FIG. To do. Refrigerant 1
The rotating anode 16 having the double hollow rotating shaft 15 having the four flow channels is provided with a partition plate 18 at the portion on the back side of the electron beam irradiation surface 17 so that a sufficient flow rate of the refrigerant can be obtained. The rotating anode 16 has a cylindrical shape composed of a single metal that can obtain desired X-rays or a laminated body in which a metal film that obtains desired X-rays is provided on the surface of a base metal having high heat conductivity. ing. Since the rotary anode side of the flange 19 of the housing 19 is installed in a high vacuum, the rotary vacuum seal 21
Isolates the high vacuum from the atmosphere. Double hollow rotating shaft 15
The bearing 22 for holding is installed in the bearing mounting frame 23 in the vicinity of the rotary vacuum seal 21.

The rotor 24 of the electric motor is a double hollow rotary shaft 15
It 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. In the rotating electrode 26, the current of the electron beam captured by the rotating anode 16 is passed through the brush 27, the brush holding spring and screw 28, and the housing 19 to ground the high voltage power source for the electron beam which is not shown in FIG. It is installed so as to be connected to the potential side.

A bearing 29, which makes a pair with the bearing 22, is provided inside a bearing mounting frame 30. The refrigerant rotation seals 31 and 32 are
They are respectively installed in the coolant outlet mount 33 and the coolant inlet mount 34 to prevent the coolant from leaking. The refrigerant external discharge disk 35 is for rotating and discharging the refrigerant to the outside of the housing 19 when the refrigerant 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 cooling medium external discharge disk 35 has
The permanent magnet piece 36 is installed, and the rotation detection mechanism 37 can grasp the rotation state of the rotating anode 16. When the rotating speed is low or the rotating anode 16 cannot be rotated due to an accident, the rotating anode 16 is rotated. It is possible to block the electron beam irradiation to the.

The maximum electric power G that can irradiate the anode 16 with an electron beam 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 expressed as.

[Equation 4] Here, a means a proportional 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 in the device design.
Is.

Here, if the anode diameter D is increased, the X-ray generation tube becomes larger. In the conventional device, since the rotary anode was driven through the rotary drive mechanism such as a pulley, a sufficient rotation speed could not be obtained due to problems such as vibration, and the diameter of the anode was increased to irradiate the electron beam. The power G was set to be large. In the present invention, since the rotary shaft 15 of the rotary anode 16 and the drive motor (rotor 24) are integrated, problems such as vibration do not occur even if the rotational speed is increased. Therefore, by making N large, even if it is small, it is more than the conventional electronic beam.
The irradiation power G can be obtained. In this embodiment, D is set to 70 mm, and the rotation speed N is set to 9000 rpm by using an inverter motor (high frequency motor), so that the electron beam irradiation length in the rotation axis direction is set. 1m
m, electron beam irradiation power of about 5 kW was obtained with an electron beam irradiation length of 0.4 mm in the direction orthogonal 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 this 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, 40
Is a high voltage power supply for emitting an electron beam from an electron gun,
Reference numeral 41 is a vacuum container for mounting the rotating anode 16 and the electron gun 39, and 42 is a vacuum exhaust device for maintaining the vacuum container at a high vacuum. In the present embodiment, LaB ₆ is used as the thermionic emission source of the electron gun 39, because the rotating anode is less contaminated. As the vacuum evacuation device 42, a turbo molecular pump having a high evacuation speed in the medium to high vacuum region is used.

(3) Example of Configuration of Total Reflection X-Ray Fluorescence Analysis Apparatus Next, the total reflection X-ray fluorescence analysis apparatus of this embodiment will be described with reference to FIG. In FIG. 5, 1 is an X-ray generator, 44 is a spectrally converging X-ray optical system, 45 is a sample for ultra-trace analysis, 46 is the X-ray beam of the sample which is set under the condition of total reflection of X-rays. A sample setting mechanism in which the irradiation position can be freely selected, 47 is a reflected X-ray intensity detector for obtaining total reflection conditions, and 48 is fluorescent X-ray detection for measuring fluorescent X-rays emitted from the sample under total reflection conditions. Reference numeral 49 is a data processing for controlling the X-ray generator 1, the spectroscopic focusing 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 vacuum. Here, the fluorescent X-ray detector 48 is of a type that outputs a voltage pulse proportional to the energy of the X-ray emitted from the sample and incident on the detector. In this example, a Si (Li) detector was used. This detector has a resolution of fluorescent X-ray energy of 0.2 keV.
It can be made higher, and the fluorescent X-ray spectrum can be obtained by integrating the output of this detector into a multi-channel memory through an analog-digital (A / D) converter of the data processing controller 49. it can.

(4) Sample analysis result In this example, the Lα ray of Au was used as the X-ray beam for exciting the sample, and the wavelength and energy of the X-ray were used.
Is 0.12764 nm and 9.712 keV. Therefore, Zn (8.6) is used as the fluorescent X-ray for K-shell excitation of the element.
Measurement is possible for elements with atomic numbers smaller than 30 keV). For example, Fe (6.398 keV), Co
It is possible to obtain a fluorescent X-ray spectrum capable of sufficiently distinguishing (6.924 keV), Ni (7.471 keV), Cu (8.040 keV) and the like. The amounts of these elements contained in the sample are proportional to the integrated intensity of each fluorescent X-ray peak shown in FIG. 6, and the abundance of trace elements is measured by analyzing the spectrum integrated in the multi-channel memory. be able to. At this time, if the intensity of scattered X-rays from the sample is high, an X-ray beam for exciting the sample with energy of −9.712 keV enters the fluorescent X-ray detector 48, and a small amount of fluorescent X-ray is detected. It can be difficult. Especially Zn
The fluorescent X-ray of (8.630 keV) is as shown in FIG.
Due to the huge scattering peak of incident X-rays on the measured fluorescent X-ray spectrum, it becomes difficult to obtain precise integrated intensity. In addition, when the scattered X-ray intensity is large, the time for A / D conversion is unnecessary and is used for scattering intensity measurement, and the dead time of the detector and the A / D converter becomes long, so that the sensitivity is substantially lowered. It will be.

[0022]

As described above, according to the present invention,
Even when an X-ray source with the same output as the conventional one is used, the intensity of the X-ray beam incident on the sample can be made higher than before by the highly efficient X-ray spectroscopic optical system, and the electric vector of the X-ray beam By making the component perpendicular to the sample surface dominant,
The intensity of scattered X-rays on the sample surface can be suppressed, and the sensitivity of ultratrace analysis can be significantly increased as compared with the conventional technique.

[Brief description of drawings]

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

FIG. 2 is an explanatory view of the principle of X-ray spectroscopy and focusing by a curved dispersive crystal.

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

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

FIG. 5 is a block diagram showing a schematic configuration of a total reflection type fluorescent X-ray analysis apparatus as an embodiment of the present invention.

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

[Explanation 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 ... Focus 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 ... Electric motor Rotor 25 ... Stator of electric motor 26 ... Rotating electrode 27 ... Brush 28 ... Spring and screw for brush holding 29 ... Bearing 30 ... Bearing mounting frame 31 ... Refrigerant rotating seal 32 ... Refrigerant rotating seal 33 ... Refrigerant outlet mount Reference numeral 34 ... Refrigerant inlet mount 35 ... Refrigerant external discharge disc 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.

Claims (7)

[Claims] 1. A total reflection type fluorescent X-ray analysis method for analyzing trace substances on a sample surface by totally reflecting X-rays on the sample surface and reducing the amount of scattered X-rays entering a fluorescent X-ray detector, A plurality of X-ray beams for irradiating the sample are prepared, and each X-ray beam is irradiated with an X-ray monochromator.
The method for total reflection X-ray fluorescence analysis, which comprises the steps of: 2. Total reflection having means for analyzing a trace substance on the surface of a sample by total reflection of X-rays on the surface of the sample and reducing the amount of scattered X-rays incident on a fluorescent X-ray detector. -Type fluorescent X-ray analyzer comprising means for illuminating a plurality of X-ray beams by using an X-ray monochromator to cross-irradiate them on the sample. Type X-ray fluorescence analyzer. 3. The total reflection type X-ray fluorescence analyzer according to claim 2, further comprising means for taking out the plurality of X-ray beams from different outlets of the same X-ray source. 4. A total reflection type X-ray fluorescence analyzer according to claim 2, further comprising means for taking out the plurality of X-ray beams from different X-ray sources independent of each other. 5. A curved monochromator for monochromaticizing and condensing the X-ray beam extracted from the X-ray source is provided in the X-ray beam path so that the X-ray beam can be emitted. By constructing 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 path of the X-ray beam is arranged in a vacuum container, and the position of the X-ray source, the position of the X-ray monochromator and the position of the sample can be controlled to be moved from outside the vacuum container. The total reflection type X-ray fluorescence analyzer according to claim 2, further comprising a control mechanism. 7. A control mechanism for controlling the position of the X-ray beam irradiating the sample surface and the position of the sample with respect to the fluorescent X-ray detector from the outside of the vacuum container in a horizontal or rotational movement. Total reflection X-ray fluorescence analyzer.