JP3396460B2 - X-ray fluorescence analyzer and X-ray detector used therefor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent X-ray analysis apparatus for measuring fluorescent X-rays and analyzing a sample, and an X-ray detector suitable for use therein, and more particularly to X-ray fluorescence X-rays.
The present invention relates to the improvement of the window portion that leads into the line detector.

[0002]

2. Description of the Related Art Conventionally, for example, a fluorescent X-ray analyzer for measuring a fluorescent X-ray generated from a sample by irradiating the sample placed in a vacuum analysis chamber with the X-ray and analyzing the sample has been used in various fields. Has already been widely used in the analysis of various substances. In addition, in such a fluorescent X-ray analyzer, a proportional counter is generally used as an X-ray detector for measuring fluorescent X-rays generated from a sample. There are two types, a sealed type and a gas flow type.

An enclosed X-ray detector (proportional counter)
Is a container in which a detection gas such as Ar or Ne is enclosed in a highly airtight container, and is mainly used at present because of its ease of handling. In addition, the window material for such an enclosed X-ray detector has a thickness of about 12 μm (1 mm), which satisfies both requirements of high airtightness and good X-ray transparency.
Beryllium thin plate of 2 μm ± 2 μm) is mainly used, and such beryllium thin plate is used as the window material X
The line detector has high detection efficiency mainly in a so-called hard X-ray region whose wavelength is 1 nm or less.

On the other hand, in the so-called soft X-ray region having a wavelength of about 1 nm or more, a gas flow type is mainly used as an X-ray detector (proportional counter) having a relatively high detection efficiency for soft X-rays. It is used. It has a thickness of about 12
This is because a beryllium thin plate of about μm has a sharp decrease in the X-ray transmittance in the so-called soft X-ray region with a wavelength of 1 nm or more, and its entrance window is airtight due to its original properties. However, a polymer film (for example, a polyimide film) having a high X-ray transparency and a thickness of about 1 μm is used. In addition, in an X-ray detector using this polymer film as a window material, it is necessary to keep fresh detection gas continuously flowing into the detector during its operation in consideration of the decrease in airtightness. It was necessary to stabilize the detection efficiency (stabilize the gas concentration in the detector).

[0005]

That is, in the above-mentioned prior art, particularly in the fluorescent X-ray analysis apparatus employing the enclosed X-ray detector, the original characteristics of the enclosed X-ray detector (that is, Since it is not necessary to supply the detection gas into the detector), it is relatively easy to handle, but in the soft X-ray region with a wavelength of 1 nm or more, it is transmitted due to the nature of the window material (beryllium thin plate). There is a drawback in that the detection efficiency for long-wavelength soft X-rays is extremely deteriorated due to a sharp drop in the rate.

On the other hand, in a fluorescent X-ray analyzer using a gas flow type X-ray detector using a polymer film having a thickness of about 1 μm as a window material, even for X-rays in the long wavelength region (soft X-rays). Although it is possible to obtain a relatively high detection efficiency,
However, since it is necessary to constantly supply fresh detection gas during its operation, the structure thereof becomes complicated, and therefore, there is a drawback that the apparatus itself becomes very difficult to handle.

In view of the above-mentioned problems in the prior art, the present invention has improved a beryllium thin plate that has been widely used as a window material for X-ray detectors in the past, and is not limited to a hard X-ray region, and has a long length. A fluorescent X-ray analyzer capable of exhibiting high detection efficiency even for soft X-rays in the wavelength region and having a simple structure and handling, and an X-ray analyzer therefor
It is intended to provide a line detector.

[0008]

In order to achieve the above-mentioned object, according to the present invention, a sample placed in a sample chamber is irradiated with X-rays from an X-ray tube, and fluorescence X generated from the sample is emitted. An X-ray fluorescence analyzer for analyzing the sample by separating the X-rays by a spectroscopic means, measuring the intensity of the X-rays thus separated by an X-ray detector, and being provided in a part of the X-ray detector. A window member provided in the entrance window portion for guiding the spectral X-ray fluorescence into the X-ray detector is provided on one side surface or both side surfaces of a beryllium thin plate having a thickness of about 1 to 5 μm and a thickness of 50 to 500 nm.
There is provided an X-ray fluorescence analyzer formed by coating the above-mentioned boron thin film.

Further, according to the present invention, as an X-ray detector used in such a fluorescent X-ray analyzer, a core wire for detecting incident X-rays is provided in a housing filled with a detection gas, and An X-ray detector having an incident window portion for internally injecting an X-ray for measuring intensity, wherein the incident window portion has one side surface of a beryllium thin plate having a thickness of about 1 to 5 μm or An X-ray detector provided with a window member coated with a boron thin film having a thickness of 50 to 500 nm on both sides is provided.

In addition, in the fluorescent X-ray analyzer and the X-ray detector according to the present invention, between the beryllium thin plate and the boron-coated thin film forming the window member provided in the entrance window of the X-ray detector. In addition, a carbon thin film layer having a thickness of about 10 to 30 nm may be formed, and the X-ray detector is particularly preferably an enclosed X-ray detector.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. First,
FIG. 4 shows a schematic configuration of a fluorescent X-ray analysis apparatus according to an embodiment of the present invention. In the figure, a detection sample S is transported in a vacuum chamber 100 in the apparatus, which is not shown. The sample S is placed at a predetermined position by the apparatus, and the sample S is irradiated with the X-ray XR from the X-ray tube 200. The fluorescent X-ray KX generated from the sample by this X-ray irradiation is adjacent to the vacuum chamber 100 and is also held in vacuum in the spectroscopic chamber 3
The spectroscopic element (spectroscopic means) 350 provided in 00 disperses the spectrum of the fluorescent X-ray KX. Then, the intensity of the dispersed fluorescent X-ray KX is measured by, for example, an X-ray detector 400 including a proportional counter, The sample will be analyzed.

The X-ray detector 400 is, for example, as shown in FIG. 2 attached, a slit-shaped one side surface of a member (housing) 410 made of, for example, a metal member and having a highly airtight outer cylindrical shape. The X-ray entrance window portion 420 is provided, and a so-called window member 430 is fixed so as to cover the window portion 420. Inside the X-ray detector 400, as shown in the attached FIG. 3, an X-ray detection gas G such as Ar or Ne is enclosed, and the central portion thereof has a diameter of, for example, about 50 μm. A core wire 440 made of Pt wire is stretched. In addition, in FIG.
And +1200 to the core wire 440 through the resistor R.
~ 1500V high voltage (HV) is supplied, while
X-ray detected by the core wire 440 (fluorescent X-ray KX)
Is taken out as an electric signal via a capacitor C, its amplitude is further amplified by an amplifier A in the subsequent stage, its intensity is measured as a pulse signal by a pulse height analyzer (PHA), and if necessary, other devices Will be transferred to the part.

Then, as the window member 430 for covering the entrance window portion 420 of the X-ray detector 400, for example, a beryllium plate, which is obtained by rolling and is formed into a thin plate having a thickness of about 1 to 5 μm, is prepared. 50 or more on one side or both sides
A window material coated with a 500 nm boron thin film is used. Needless to say, this window member is cut out into a shape corresponding to the entrance window portion 420 and is hermetically fixed by, for example, an adhesive agent, or by pressure bonding, caulking, caulking, or the like.

Here, FIG. 1 (A) shows a sectional structure of the window member 430. Reference numeral 431 is a beryllium thin plate, and reference numeral 432 is a coating of a boron thin film formed on the surface thereof. The layers are shown. The thickness of the beryllium thin plate 431 forming the window member is set to about 1 to 5 μm, as described above, in the case of a beryllium thin plate having a thickness of about 12 μm (12 μm ± 2 μm) which is conventionally used, the wavelength is Although high X-ray transmittance is exhibited in the hard X-ray region of 1 nm or less, however, it was noted that the X-ray transmittance sharply decreases in the so-called soft X-ray region having a wavelength of about 1 nm or more. It is a thing. As will be described in more detail later, the thickness of the beryllium thin plate is thinner than the conventional one, and the thickness is about 1 to 5 μm, so that the wavelength is about 1 nm as well as in the hard X-ray region of 1 nm or less. Even in the above-mentioned so-called soft X-ray region, high X
It is possible to maintain the linear transmittance. Thereby, the X-ray detector 4 having high detection efficiency in a wide wavelength range
00 can be realized.

On the other hand, as the thickness of the beryllium thin plate is reduced (thinned), the mechanical strength as the window member 430 of the X-ray entrance window portion 420 and the airtightness thereof are reduced. In particular, the so-called enclosed X-ray detector (proportional counter) in which the gas G for X-ray detection such as Ar or Ne is hermetically sealed inside the X-ray detector 400 has a simple structure and is easy to handle. Therefore, in the case of such an encapsulation type, which is currently mainly used, the mechanical strength and airtightness are reduced due to the reduction (thinning) of the thickness of the beryllium thin plate.

Therefore, in the present invention, the above-mentioned thickness is about 1 to 5 μm.
On one surface of the beryllium thin plate of m, or both surfaces thereof,
A window material was obtained by coating a boron thin film having a thickness of 50 to 500 nm. The boron thin film does not cause a significant decrease in the X-ray transmittance, and the thickness thereof is set to a thickness suitable for keeping the transmittance of the beryllium thin plate high.

In general, so-called pinholes are formed on the surface of the beryllium thin plate obtained by rolling or the like in the process of processing, which causes a decrease in airtightness particularly in the beryllium thin plate. Was also a cause of requiring a plate thickness (about 12 μm). Therefore, by coating the above-mentioned boron by vapor deposition or the like, the evaporated beryllium particles are uniformly aligned on the surface and fill the pinholes, so that even a thin beryllium plate having a thickness of about 1 to 5 μm has sufficient mechanical strength. Since it is possible to improve the airtightness, it is effective for thinning the beryllium plate. Incidentally, the boron coating thin film is to improve the airtightness by filling the pinholes on the beryllium thin plate, and in order to improve its mechanical strength, according to the experimental confirmation by the present inventors, It has been confirmed that at least a thickness of 50 nm or more is necessary, and in addition, if the thickness exceeds the upper limit of 500 nm, it is easy to peel off from the surface of the beryllium thin plate, and it is known to be unfavorable. .

(Example) Two types of beryllium thin plates having a thickness of 5 μm and a thickness of 1 μm were prepared, and two types of boron coating films having a thickness of 50 nm and a thickness of 500 nm were sputter-deposited on one surface of each thin plate. Formed by. Then, in order to evaluate the performance of these X-ray incident window portions as a window member, these are used as the incident window 420 of the X-ray detector 400.
In particular, the transmittance was measured in the soft X-ray region. At the same time, for comparison, the same measurement was performed for an X-ray detector using a conventional beryllium thin plate having a thickness of 12 μm as a window material for the entrance window. The results are shown in Table 1 below.
Shown in.

[Table 1]

In Table 1 above, “Type A” is a beryllium (Be) thin plate having a thickness of 5 μm and a boron coating film having a thickness of 500 nm is applied, and “Type B” is a beryllium thin plate having a thickness of 5 μm. With a 50 nm thick boron coating film, "Type C" is a 1 μm thick beryllium thin plate with a 500 nm thick boron coating film, and “Type D” is a 1 μm thick film.
m beryllium thin plate coated with a boron coating film having a thickness of 50 nm. The "conventional type" is a beryllium thin plate having a thickness of about 12 μm as a window member.

From Table 1 above, it can be seen that by reducing the thickness of the beryllium thin plate to 5 μm, the transmittance of the spectral wavelength in the soft X-ray region with a wavelength of about 1 nm or more is remarkably improved. 0.989 nm fluorescent X-ray Mg-Kα, wavelength 1.19 nm fluorescent X-ray Na
-Kα, fluorescent X-ray F-Kα with a wavelength of 1.83 nm). Further, it becomes possible to transmit even fluorescent X-rays O-Kα having a wavelength of 2.36 nm. Although not shown in this table, the transmittance in the so-called hard X-ray region having a wavelength of about 1 nm or less is similar to or higher than the conventional one.

This tendency becomes more remarkable as the thickness of the beryllium sheet becomes thinner. On the other hand, from the mechanical strength required for using the beryllium thin plate as the window material of the entrance window of the X-ray detector, at least a thickness of about 1 μm is required. In the beryllium thin plate having a thickness of 1 μm, as is clear from types C and D, 3.1 having a longer wavelength is used.
Even in N-Kα of 6 nm and C-Kα of 4.46 nm, although the value is small, an effective X-ray transmittance can be obtained. That is, the thickness of this beryllium thin plate is selected to be a value that enables measurement and analysis of fluorescent X-rays (detection wavelength) to be detected while conforming to the measurement sample and measurement conditions in the range of 5 μm to 1 μm. Preferably.

Regarding the thickness (film thickness) of the boron coating film formed by vapor deposition on the beryllium thin plate, as shown in Table 1 above, the transmittance tends to decrease as the thickness increases. Therefore, as for the thickness of the boron coating film, the thickness of the beryllium thin plate (5 μm to 1 μm) is in the range of 50 nm to 500 nm.
Also, it is preferable to select appropriately while adapting to the measurement sample and the measurement conditions.

Next, the airtightness test by the helium leak detector was conducted on each of the above-mentioned window members. The results are shown in Table 2 below. The term "conventional type" as used herein means only a beryllium thin plate having a thickness of 5 μm. Here, as a result of the airtightness test by the helium leak detector, for example, the quality was judged based on the helium leak of about 1 × 10 ⁻⁹ Atm · Cm ³ / sec.

[Table 2]

As is clear from Table 2 above, the thickness is 5 μm.
When only a beryllium thin plate of m (conventional type) is used, sufficient airtightness cannot be obtained with an X-ray detector using this as a window member of an X-ray entrance window. However, 50n on the surface
It can be seen that sufficient airtightness can be obtained by forming the boron coating film with a thickness in the range of m to 500 nm. In particular, for a beryllium thin plate having an extremely thin thickness of 1 μm, sufficient airtightness has been obtained by forming a boron coating film having a thickness of 500 nm on the surface thereof. In the case of about 50 nm, some variation was found in the test results. However, even in that case, good airtightness was obtained with a yield of about 50%.

From the above, in the case of an enclosed X-ray detector which is required to have an airtightness, when a beryllium thin plate having an extremely thin thickness of 1 μm is used as a window member of the X-ray entrance window, it has a thickness of about 500 nm. It can be seen that it is preferable to apply a thick boron coating film.

Further, the window materials for the above-mentioned types of incident windows are
Changes in operating characteristics (deterioration) of the counter when mounted in a sealed proportional counter and left in a vacuum container for a long period of time.
Was inspected. From the inspection results, no particular change (deterioration) in performance was observed in all the mounted X-ray incident window portions even after being left for 3 months.

Next, a second embodiment of the present invention will be described below with reference to FIG. That is, according to the present inventors, in the window member in the first embodiment, that is, the one in which the boron coating film 432 is directly applied on the beryllium thin plate 431, it is peeled off to the formed film particularly in a high humidity environment. Was found to occur. Therefore, based on the above findings by the inventor, in order to further improve the adhesion thereof, in the second embodiment, the adhesive layer 43 made of carbon is provided between the beryllium thin plate 431 and the boron coating film 432.
3 is formed. The adhesive layer 433 made of carbon is also formed by the sputter deposition method in the same manner as described above, and its thickness does not affect the transmittance of X-rays necessary for the entrance window of the X-ray detector. , That is,
It is set in the range of 10 nm to 30 nm.

X according to the second embodiment of the present invention described above
According to the window member of the incident window portion of the line detector, no peeling of the boron coating film from the beryllium thin plate was observed even in an environment where peeling of high humidity was likely to occur.

According to the X-ray detector equipped with the window material according to the present invention described above in its entrance window, and the fluorescent X-ray analysis apparatus equipped with such an X-ray detector, the conventional beryllium thin plate is used. On the basis of the above, further, in a wide range (that is, not only in a so-called hard X-ray region having a wavelength of about 1 nm or less, but also in a so-called soft X-ray region having a wavelength of about 1 nm or more), It becomes possible to measure fluorescent X-rays, and the performance as a fluorescent X-ray analyzer can be improved. Further, in particular, X according to the present invention
By enclosing the X-ray detector, in addition to the above-mentioned expansion of the detectable X-ray region, it becomes unnecessary to supply the detection gas into the detector. It becomes possible to provide a fluorescent X-ray analysis device that is simple, inexpensive, and easy to handle.

[0030]

As is apparent from the above detailed description, according to the present invention, sufficient detection efficiency is exhibited not only in the hard X-ray region but also in the X-ray in the long wavelength soft region. Fluorescent X that can be manufactured and its structure and handling are simple
The excellent effect of making it possible to provide a line analyzer and an X-ray detector therefor is exhibited.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a window member of an X-ray detector, which is a feature of an X-ray fluorescence analyzer of the present invention.

FIG. 2 is a perspective view showing an example of the structure of an X-ray detector in the X-ray fluorescence analyzer of the present invention.

FIG. 3 is a block diagram showing an example of an internal structure of the X-ray detector and a related circuit thereof.

FIG. 4 is a diagram showing a main configuration of a fluorescent X-ray analysis apparatus according to the present invention.

[Explanation of symbols]

100 vacuum chamber 200 X-ray tube 300 spectroscopy room 350 Spectroscopic element (spectral means) 400 X-ray detector 410 X-ray detector member (housing) 420 X-ray entrance window 430 window member 431 Beryllium thin plate 432 Boron coating film 433 carbon adhesive layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-102214 (JP, A) JP-A-11-108861 (JP, A) JP-A-8-313642 (JP, A) JP-A-8- 194065 (JP, A) JP 9-49882 (JP, A) JP 6-302289 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 23/223 G01T 1 / 18 G01T 7/00 H01J 47/06

Claims (5)

(57) [Claims] 1. A sample placed in a sample chamber is irradiated with X-rays from an X-ray tube, fluorescent X-rays generated from the sample are dispersed by a spectroscopic means, and the intensity of the dispersed fluorescent X-rays is X-rays. An X-ray fluorescence analyzer for analyzing the sample by measuring with a detector, the X-ray fluorescence X being provided in a part of the X-ray detector
A window member provided in an incident window portion for guiding the X-ray into the X-ray detector is formed by coating one or both sides of a beryllium thin plate having a thickness of about 1 to 5 μm with a boron thin film having a thickness of 50 to 500 nm. An X-ray fluorescence analyzer characterized in that 2. The fluorescent X-ray analysis device according to claim 1, wherein a beryllium thin plate and a boron coating thin film forming a window member provided in an entrance window portion of the X-ray detector have a thickness of about 10 nm to about 10 nm. An X-ray fluorescence analyzer, wherein a carbon thin film layer of 30 nm is formed. 3. The fluorescent X-ray analysis apparatus according to claim 1, wherein the X-ray detector is an enclosed X-ray detector. 4. A core wire for detecting an incident X-ray is provided in a housing filled with a detection gas, and an incident window portion for injecting an X-ray for measuring intensity into a part of the housing is provided. X
A line detector, wherein the incident window portion is provided with a window member in which one or both sides of a beryllium thin plate having a thickness of about 1 to 5 μm is coated with a boron thin film having a thickness of 50 to 500 nm. Characteristic X-ray detector. 5. The X-ray detector according to claim 4, further comprising between the beryllium thin plate and the boron-coated thin film forming the window member, the thickness being about 10 nm to 30 n.
An X-ray detector having a carbon thin film layer of m.