Proportional counter and wavelength dispersive fluorescent x-ray analysis device

Abstract

The present disclosure relates to: a proportional counter (10) comprising a container (11) and a core wire (12) disposed within the container (11), wherein a gas is sealed within the container (11), the container (11) is provided with an entrance window (13), and a graphene sheet (14) is disposed in the entrance window (13); and a wavelength dispersive fluorescent x-ray analysis device (20, 40). The present disclosure provides the gas-filled proportional counter (10) that can be used for fluorescent X-ray analysis of ultra-light elements, and the wavelength dispersive fluorescent x-ray analysis device (20, 40) including the gas-filled proportional counter.

Description

Proportional counter and wavelength dispersive X-ray fluorescence analyzer

[0001] The present disclosure relates to a proportional counter and a wavelength dispersive X-ray fluorescence analyzer.

[0002] Japanese Patent Laid-Open Publication No. 2010-118333 (Patent Document 1) discloses a fluorescent X-ray detector equipped with a gas flow type proportional counter.

[0003] JP 2010-118333 A

[0004] In the X-ray fluorescence analysis of ultralight elements such as beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), and fluorine (F), gas flow proportional counters are often used as X-ray fluorescence detectors. However, gas flow proportional counters require that the gas used for measuring radiation be constantly flowing through the counter, which tends to increase running costs.

[0005] Furthermore, because gas flow proportional counters are constantly exposed to a flow of radiation measurement gas, the core wire tends to be easily contaminated by components of the X-ray measurement gas and impurities entering through the inlet or outlet, which can result in a decrease in resolution. Known methods for keeping the core wire clean include a core winding method, in which the contaminated core wire is wound up and a new core wire is fed out, and a method for scattering the dirt. However, with the core winding method, once the core wire is used up, it is necessary to replace it with a new core wire or clean the contaminated core wire. Furthermore, with the method for scattering the dirt, it is sometimes not possible to completely remove all the dirt, and depending on the level of contamination, the core wire may need to be replaced. As a result, maintenance costs and labor tend to increase, and there is also a risk of malfunction of the driving part.

[0006] Furthermore, fluorescent X-rays from ultralight elements tend to be easily absorbed by materials. Therefore, proportional counters used in X-ray fluorescence analysis of ultralight elements often use a material that does not easily absorb X-rays or a thin material for the X-ray entrance window. However, because materials that do not easily absorb X-rays or thin materials have low strength, when used in a gas-filled proportional counter, there is a risk that the entrance window will be damaged by changes in air pressure around the entrance window, etc. Typically, the materials used for the entrance window of a gas-filled proportional counter are resin films or metal foils, which have a thickness of several μm to several tens of μm, and therefore tend to be difficult for fluorescent X-rays from ultralight elements to pass through.

[0007] An object of the present disclosure is to provide a gas-filled proportional counter that can be used for X-ray fluorescence analysis of ultralight elements, and a wavelength-dispersive X-ray fluorescence analyzer including the same.

[0008] A first aspect of the present disclosure relates to a proportional counter including a container and a core wire disposed in the container, wherein a gas is sealed in the container, the container includes an entrance window, and a graphene sheet is disposed on the entrance window.

[0009] According to the present disclosure, by disposing a graphene sheet having a relatively small thickness and a relatively high electrical conductivity on the entrance window, it is possible to provide a proportional counter that can be used for X-ray fluorescence analysis of ultralight elements, and a wavelength dispersive X-ray fluorescence analyzer including the same. Also, according to the present disclosure, by disposing a highly strong graphene sheet on the entrance window of the proportional counter, it is possible to make the proportional counter a gas-filled type, which eliminates the need to constantly flow a gas for radiation measurement as in a gas-flow type proportional counter, and therefore tends to reduce running costs compared to a gas-flow type proportional counter, and also tends to reduce the cost and labor required for maintenance such as replacing the core wire because the core wire is not contaminated.

[0010] Fig. 1 is a longitudinal sectional view showing a proportional counter according to an embodiment of the present disclosure; Fig. 2 is a transverse sectional view showing a proportional counter according to an embodiment of the present disclosure; Fig. 3 is a plan view showing a proportional counter according to an embodiment of the present disclosure; Fig. 4 is a schematic view of a wavelength-dispersive X-ray fluorescence analyzer according to an embodiment of the present disclosure; Fig. 5 is a schematic view of a simultaneous wavelength-dispersive X-ray fluorescence analyzer according to an embodiment of the present disclosure.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the following embodiments. In all of the drawings, the scales of the components are appropriately adjusted to make them easier to understand, and the scales of the components shown in the drawings do not necessarily match the scales of the actual components.

[0012] A first aspect of the present disclosure will be described with reference to Fig. 1. A proportional counter 10 shown in Fig. 1 includes a container 11 and a core wire 12 disposed within the container 11. A gas is sealed within the container 11, the container 11 includes an entrance window 13, and a graphene sheet 14 is disposed on the entrance window 13. The proportional counter 10 can be a gas-filled proportional counter.

[0013] The container 11 is hollow and filled with gas. The container 11 may be cylindrical, for example. The container 11 can function as a cathode. The container 11 may be made of metal, such as stainless steel or aluminum. The components constituting the container 11 may be joined together, for example, by adhesive, soldering, or welding. The container 11 is composed of a tubular portion 16, a first side portion 17, and a second side portion 18. The tubular portion 16, the first side portion 17, and the second side portion 18 may be joined together.

[0014] The gas sealed in the container 11 may be a gas for X-ray measurement, such as helium (He), argon (Ar), and rare gases such as krypton (Kr), xenon (Xe), or methane (CH ４ The gas may be a mixture of nitrogen (N) gas and argon (Ar).

[0015] The core wire 12 can function as an anode. The core wire 12 is stretched without slack from the first side portion 17 along the tubular portion 16 to the second side portion 18. FIG. 2 is a cross-sectional view taken along line A-A' in FIG. 1. As shown in FIG. 2, the core wire 12 is disposed at the center of the container 11. The core wire 12 may be insulated from the container 11 by insulating members 15 disposed on the first side portion 17 and the second side portion 18. By connecting the positive side of a power source to the core wire 12 and the negative side of the power source to the inner wall surface of the tubular portion 16, a voltage can be applied between the core wire 12 and the inner wall surface of the tubular portion 16.

[0016] The entrance window 13 is disposed in the cylindrical portion 16. The entrance window 13 may be an entrance window for fluorescent X-rays. Fluorescent X-rays emitted from ultralight elements can enter the interior of the vessel 11 through the entrance window 13. FIG. 3 is a plan view of the proportional counter 10 as viewed from a direction perpendicular to the entrance window 13. When viewed from a direction perpendicular to the entrance window 13, the shape of the entrance window 13 may be rectangular, as shown in FIG. 3, or square.

[0017] A graphene sheet 14 is disposed on the entrance window 13. The graphene sheet 14 is stretched flat over the entrance window 13. The graphene sheet 14 is thin and has high electrical conductivity, making it transparent to fluorescent X-rays from ultralight elements. Furthermore, the graphene sheet 14 has sufficient strength to prevent breakage due to changes in air pressure around the entrance window. It is also impermeable to X-ray measurement gas, allowing the gas to remain sealed within the vessel 11. As a result, unlike gas flow detectors, it is not necessary to constantly flow the measurement gas into the vessel. This tends to reduce running costs, and the core wire is not contaminated, which tends to reduce the cost and labor required for maintenance, such as replacing the core wire. By disposing the graphene sheet 14 on the entrance window 13, a highly sensitive, maintenance-free detector for X-ray fluorescence analysis of ultralight elements can be realized.

[0018] The graphene sheet 14 is a sheet made of only graphene, and may be a single-layer sheet made of a single graphene layer, or a multi-layer sheet made of multiple graphene layers.

[0019] The proportional counter 10 can be used in an X-ray fluorescence detector for a wavelength dispersive X-ray fluorescence analyzer. The proportional counter 10 is suitable for an X-ray fluorescence detector for a wavelength dispersive X-ray fluorescence analyzer for ultralight elements.

[0020] A second aspect of the present disclosure relates to a wavelength-dispersive X-ray fluorescence analyzer. The wavelength-dispersive X-ray fluorescence analyzer includes a detector including the proportional counter of the first aspect. The wavelength-dispersive X-ray fluorescence analyzer may be a scanning wavelength-dispersive X-ray fluorescence analyzer, a simultaneous wavelength-dispersive X-ray fluorescence analyzer, or a wavelength-dispersive X-ray fluorescence analyzer that combines the scanning and simultaneous types.

[0021] A scanning wavelength-dispersive X-ray fluorescence analyzer will be described with reference to Fig. 4. The wavelength-dispersive X-ray fluorescence analyzer 20 shown in Fig. 4 includes an X-ray tube 21, a divergence slit 22, a spectroscopic element 23, a receiving slit 24, and a detector 25. The detector 25 can include a proportional counter 10.

[0022] In a wavelength-dispersive X-ray fluorescence analyzer 20, X-rays 26 are irradiated from an X-ray tube 21 toward a sample 27. Fluorescent X-rays 28 emitted from the sample 27 pass through a divergence slit 22 and are then dispersed by a spectroscopic element 23. The dispersed fluorescent X-rays 29 then pass through a receiving slit 24 and are observed by a detector 25.

[0023] The wavelength-dispersive X-ray fluorescence analyzer 20 may further include a goniometer. The angle between the fluorescent X-rays 28 irradiated from the sample 27 and the spectroscopic element 23 is defined as θ, and the angle between the fluorescent X-rays 28 irradiated from the sample and the dispersed fluorescent X-rays 29 is defined as 2θ. By scanning while maintaining the relationship between θ and 2θ, elements can be measured one by one. The wavelength-dispersive X-ray fluorescence analyzer 20 may further include a crystal exchange mechanism that exchanges the type of crystal in the spectroscopic element depending on the element to be measured.

[0024] The wavelength-dispersive X-ray fluorescence analyzer 20 may further include a control unit 30. The control unit 30 may include, for example, a quantification unit that calculates the intensity of the observed fluorescent X-rays to perform quantitative analysis, and an output unit that outputs the results of the quantitative analysis.

[0025] A simultaneous wavelength-dispersive X-ray fluorescence analyzer will be described with reference to Fig. 5. The wavelength-dispersive X-ray fluorescence analyzer 40 shown in Fig. 5 includes an X-ray tube 41 and a fixed spectrometer 42. The wavelength-dispersive X-ray fluorescence analyzer 40 is equipped with multiple fixed spectrometers, thereby enabling simultaneous measurement of multiple elements. The wavelength-dispersive X-ray fluorescence analyzer 40 can be equipped with a fixed spectrometer optimized for each element to be measured.

[0026] The fixed spectrometer 42 includes a divergence slit 43, a spectroscopic element 44, a receiving slit 45, and a detector 46. The detector 46 may include the proportional counter 10 of the first embodiment.

[0027] In the wavelength-dispersive X-ray fluorescence analyzer 40, X-rays 47 are irradiated from the X-ray tube 41 toward a sample 48. Fluorescent X-rays 49 emitted from the sample 48 pass through a divergence slit 43 and are then dispersed by a spectroscopic element 44. The dispersed fluorescent X-rays 50 then pass through a receiving slit 45 and are observed by a detector 46. The wavelength-dispersive X-ray fluorescence analyzer 40 is equipped with a fixed spectrometer optimized for each element to be measured, thereby enabling the simultaneous measurement of multiple elements.

[0028] A wavelength-dispersive X-ray fluorescence analyzer is capable of performing X-ray fluorescence analysis of ultralight elements by being equipped with a detector including the proportional counter of the first aspect, and because the proportional counter is of a gas-filled type, running costs tend to be lower than those of a gas-flow type proportional counter, and the labor required for maintenance work also tends to be reduced.

[0029] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0030] (Item 1) A proportional counter according to one aspect includes a container and a core wire disposed within the container, the container being filled with gas, the container including an entrance window, and a graphene sheet disposed on the entrance window.

[0031] (2) In the proportional counter of the 1st paragraph, the graphene sheet is transparent to fluorescent X-rays emitted from ultralight elements.

[0032] (Item 3) A wavelength dispersive X-ray fluorescence analyzer according to another aspect includes a detector including the proportional counter according to item 1.

[0033] (4) The wavelength dispersive X-ray fluorescence analyzer of the third paragraph is a scanning wavelength dispersive X-ray fluorescence analyzer.

[0034] (Item 5) The wavelength dispersive X-ray fluorescence analyzer of item 3 is a simultaneous wavelength dispersive X-ray fluorescence analyzer.

[0035] REFERENCE SIGNS LIST 10 proportional counter, 11 container, 12 core wire, 13 entrance window, 14 graphene sheet, 15 insulating member, 16 cylindrical portion, 17 first side portion, 18 second side portion, 20, 40 wavelength dispersive X-ray fluorescence analyzer, 21, 41 X-ray tube, 22, 43 divergence slit, 23, 44 spectroscopic element, 24, 45 receiving slit, 25, 46 detector, 26, 47 X-ray, 27, 48 sample, 28, 49 fluorescent X-ray, 29, 50 dispersed fluorescent X-ray, 30 control means, 42 fixed spectrometer.

Claims

1. A proportional counter comprising a container and a core wire disposed within the container, a gas is sealed within the container, the container has an entrance window, and a graphene sheet is disposed on the entrance window.

2. The proportional counter of claim 1, wherein the graphene sheet is transparent to fluorescent X-rays emitted from ultralight elements.

3. A wavelength dispersive X-ray fluorescence analysis device equipped with a detector including the proportional counter according to claim 1.

4. The wavelength dispersive X-ray fluorescence analyzer according to claim 3, which is a scanning type wavelength dispersive X-ray fluorescence analyzer.

5. The wavelength-dispersive X-ray fluorescence analyzer according to claim 3, which is a simultaneous wavelength-dispersive X-ray fluorescence analyzer.

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