JP2004150990A - Fluorescent x-ray analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent X-ray analyzer capable of analyzing a plurality of trace elements, in a measurement sample whose atomic numbers are apart with each other in a single analysis operation. <P>SOLUTION: A primary filter 7 contains first and second elements whose atomic numbers are different each other as filter elements and the first element mainly absorbs a first energy band 31 in primary X-rays 3; while the second element mainly absorbs a second energy band 32 that has large energy as compared with the first energy band 31 in the continuous X-rays of the primary X-rays and is not adjacent to the first energy band 31. The primary X-rays 3 after absorption include third and fourth energy bands 33, 34 on both sides of the second energy band 32 as first and second exciting components. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to X-ray fluorescence analysis, particularly to a primary filter.
[0002]
[Prior art]
In fluorescent X-ray analysis, a primary filter may be used to reduce the background. However, when trying to detect elements (for example, light elements and heavy elements) with different atomic numbers in a sample, it was necessary to replace the filter for each type of element (for example, see Patent Document 1). Therefore, a plurality of measurements are required for one measurement sample, and the analysis time becomes longer.
[0003]
[Patent Document 1]
JP-A-5-240808 (page 2-3, FIG. 1)
[0004]
BACKGROUND OF THE INVENTION
By the way, in recent years, harmful substances contained in soil and waste have become a problem. As a countermeasure, in Europe, a draft directive on the “Restriction of the Use of Specific Hazardous Substances in Electrical and Electronic Equipment (RoHS)” has been adopted. The use of certain hazardous substances is severely restricted. Also in Japan, the Soil Contamination Countermeasures Law is scheduled to be enforced from January 2003, and it is essential to investigate harmful heavy metals such as factory sites. Under such circumstances, a device capable of easily measuring various harmful elements has been demanded.
[0005]
To meet these demands, for example, elemental analysis can be performed with an X-ray analyzer using a spectral crystal. However, when the X-rays are separated by the spectral crystal, only a part of the X-rays is separated as excited X-rays, so that the total amount of the X-rays is significantly reduced. Therefore, a large X-ray tube must be used. Therefore, it causes an increase in cost. Further, since the spectral crystal and the artificial lattice are expensive and require a crystal exchanger, the cost is also high in this respect.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to provide a relatively inexpensive fluorescent light capable of analyzing a plurality of elements having different atomic numbers in a measurement sample by one analysis operation. An X-ray analyzer is provided.
[0007]
[Principle of the invention]
First, the principle of the present invention will be described with reference to FIGS.
FIG. 2A is a table showing the spectrum of the primary X-ray 3 and the distribution of the first to fourth energy bands 31 to 34. FIG. 2B is a chart showing spectra of Cr, Hg, As, Se, Pb, Br, Cd, and Sn specific X-rays (analytical lines) in relation to the spectrum diagram of FIG. 2A. It is.
[0008]
The primary filter 7 shown in FIG. 1 includes first and second elements as filter components. The first element of the primary filter 7 mainly absorbs the first energy band 31 of the primary X-ray 3 shown in FIG. On the other hand, the second element of the primary filter 7 mainly absorbs the second energy band 32 of the primary X-ray 3. The second energy band 32 is a band having higher energy than the first energy band 31, and is an energy band separated from the first energy band 31. The first energy band 31 includes a characteristic X-ray 5 (for example, a K-ray such as an As-Kα ray) generated from a metal such as Cr, Hg, As, Se, Pb, and Br (bromine) shown in FIG. And an L line such as a Pb-Lα line) having a relatively low energy as a background. On the other hand, the second energy band 32 is a band having a relatively high energy as a background for the intrinsic X-rays 5 (for example, K-rays such as Cd-Kα rays) generated from a metal such as Cd or Sn. .
The first energy band 31 is an energy band including a range from Cr-Kα (5.411 KeV) to Br-Lα (11.907 KeV). On the other hand, the second energy band 32 is an energy band including a range from Cd-Kα (23.106 KeV) to Sn-Kα (25.191 KeV).
[0009]
The absorbed primary X-rays 3 mainly include a third energy band 33 having an energy higher than that of the first energy band 31 and a lower energy than the second energy band 32; A fourth energy band 34 having higher energy than the band 32 is included. The X-rays in the third energy band 33 act as one of the first excitation components that excite a light element such as Cr. On the other hand, the X-rays in the fourth energy band 34 act as one of the second excitation components that excite heavy elements such as Cd.
[0010]
As described above, since the X-rays in the first and second energy bands are almost absorbed by the first element and the second element of the primary filter, the background is reduced, while the third and the excitation components are excited. The proportion of X-rays in the fourth energy band increases significantly. Therefore, a plurality of elements having different atomic numbers can be simultaneously analyzed with high accuracy.
[0011]
As the first element contained in the primary filter of the present invention, it is preferable to use an element having an atomic number of 6 or more and 29 or less, and more preferably Mg (No. 12), Al (No. 13), Si ( No. 14), a simple substance of Cu (No. 29) or an oxide thereof (MgO ₂ , SiO _2, etc.).
On the other hand, as the second element, it is preferable to use an element having an atomic number of 24 to 74, more preferably a simple substance of Cu (29), zirconium Zr (40) or molybdenum Mo (42). Is used.
Generally, as the second element, it is preferable to use an element whose atomic number is 10 or more away from the first element.
[0012]
In the present invention, the definitions of “light element (filter component)” and “heavy element (filter component)” in the primary filter 7 are defined by a relative relationship between the two elements. That is, with respect to the first element and the second element having different atomic numbers, the element with the smaller atomic number is a light element and the element with the larger atomic number is a heavy element.
Therefore, an element used as a light element filter component in a certain primary filter 7 may be used as a heavy element filter component in another primary filter 7. Conversely, an element used as a heavy element filter component in one primary filter 7 may be used as a light element filter component in another primary filter 7.
[0013]
In the present invention, the filter component generally contains at least 10 mol% or more, preferably 5 mol% or more of the first element or the second element with respect to the total atomic weight of the filter excluding the first element and the second element. Means
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, heavy metals (for example, Cr, Hg, As, Se, Pb, Br, Cd, and Sn) harmful to the human body contained in soil and electronic materials are analyzed, and the content thereof is set to a predetermined reference value. The following describes an example of an inspection machine that performs pass / fail determination of whether or not the following is true.
[0015]
In FIG. 1A, the inspection apparatus includes a sample table 2 on which a measurement sample 1 is placed, an X-ray source 4 such as an X-ray tube for irradiating the measurement sample 1 with primary X-rays 3, and a measurement sample 1 And a detector 6 for detecting the fluorescent X-rays 5 generated from. A primary filter 7 is provided in the optical path of the primary X-ray 3. The primary X-ray 3 is applied to the measurement sample 1 through the primary filter 7, through a window 21 provided on the sample table 2. The primary filter 7 reduces or eliminates a background component of the analysis line, as described later.
The sample stage 2 divides a sample room 20 and an irradiation room 22, and the X-ray source 4, the detector 6 and the primary filter 7 are accommodated in the irradiation room 22.
[0016]
The primary filter 7 is provided at a position that does not absorb the fluorescent X-rays 5 traveling from the measurement sample 1 to the detector 6. Therefore, the primary filter 7 absorbs and transmits only the primary X-rays 3 and does not absorb the fluorescent X-rays 5.
In order to improve the analysis accuracy, a secondary filter may be provided in the optical path of the fluorescent X-ray 5. The secondary filter reduces or eliminates background caused by X-rays scattered by the measurement sample 1 or the like.
[0017]
When inspecting harmful heavy metal elements with this inspection apparatus, W (tungsten) or Mo is used as a target of the X-ray tube used for the X-ray source 4 from the viewpoint of reducing the background, and particularly removing the interference line. It is generally preferred to use (molybdenum).
[0018]
As the detector 6, for example, a detector that is excellent in energy resolution and performs cooling by a Peltier element regardless of liquid nitrogen, such as a silicon drift detector (SDD), is preferably employed.
[0019]
As shown in FIG. 1B, the primary filter 7 is formed by laminating a first thin film 8 containing a first element as a filter component and a second thin film 9 containing a second element as a filter component. ing. A plurality of types of the primary filters 7 are provided so as to be slightly spaced from each other in the longitudinal direction 17 of the flat frame 27. The frame 27 is provided movably along the longitudinal direction 17 (FIG. 1A).
The first and second thin films 8 and 9 may be formed in a thin plate. Further, either one may be a thin film and the other may be a thin plate. Further, the thin film may be integrally formed on one of the thin plates or the thin film by vapor deposition or the like.
[0020]
Here, for convenience of explanation, the plurality of types of primary filters 7 are shown as 7i (i = 1 to n, a natural number) and are distinguished from each other. Similarly, the first thin film 8 and the second thin film 9 corresponding to each primary filter 7 are also indicated as 8i and 9i, respectively.
The plurality of types of primary filter 7i, the first thin film _{81, 82} of the first and second primary filter ₇ 1, _{7 2,} single light elements of the same first element (e.g., Cu) It is a filter component. On the other hand, the second thin films 9 ₁ and 9 ₂ each use a single element of a different second element (for example, Zr and Mo) as a heavy element filter component.
Further, in the third primary filter _{7 3,} light elements filter components of the first thin film _{8 3} is, for example, MgO, heavy elements filter components of the second thin film _{9 3} is a single Cu. Thus, each primary filter 7 ₁ to _7-n to each other, at least one of said first element and second element are formed to be different from each other.
[0021]
Control configuration:
As shown in FIG. 3B, the present inspection machine includes a control unit 10. The X-ray source 4, detector 6, filter exchanger 37, inserter 35, output means 36, and input means 38 are connected to the control means 10 via an interface (not shown). The filter changer 37 moves the frame 27 of FIG. 1B in the longitudinal direction 17 (a direction orthogonal to the paper surface of FIG. 1A). Thereby, the filter exchange 37 selectively inserts one primary filter 7i among the plurality of types of primary filters 7 _{1 to} 7 _n into the optical path of the primary X-ray 3 and the other primary filters 7 _{1 to} 7 _n. Evacuate the filter.
[0022]
The inserter 35 moves a plurality of standard samples 25 described later in the longitudinal direction 17 and selectively inserts one standard sample 25 into a calibration position 30 described later.
[0023]
The control means 10 includes a CPU (correction means) 11 and a memory 12.
The memory 12 stores reference value data and a correction program in advance. As shown in FIG. 3 (c), the reference value data is stored in association with a predetermined measurement sample 1, for each element, in association with a reference value as a criterion for pass / fail determination. On the other hand, the correction program is a well-known program for performing correction described below.
The CPU 11 compares the detection value from the detector 6 with the reference value data to determine whether or not the content of each element is equal to or less than a reference value, and outputs the determination result to the output. Output to the means 36. Further, the CPU 11 executes the correction program stored in the memory 12 to perform a function as a correction unit that performs correction described later.
[0024]
The control means 10 controls the operation of the equipment connected to the control means 10 to perform elemental analysis of the measurement sample 1 and to perform calibration work of the present inspection machine. The calibration work includes, for example, X-ray energy calibration and standardization of a calibration curve. When performing the calibration operation, the standard sample 25 is used. However, the present inspection machine has a plurality of standard samples 25 built therein. The standard sample 25 contains one or more types of heavy metal elements to be analyzed. The standard samples 25 differ from each other in at least one or more of a plurality of types of elements contained therein. As shown in FIG. 3A, the standard sample 25 is provided in the irradiation chamber 22 including the optical path of the primary X-ray 3 from the X-ray source 4 to the detector 6.
[0025]
The standard sample 25 is provided close to the surface 2 a of the sample stage 2 on the side of the irradiation chamber 22, and can be inserted into a calibration position 30 facing the measurement sample 1 with the sample stage 2 interposed therebetween. The control means 10 controls the inserter 35 to sequentially insert and withdraw each of the standard samples 25 at the calibration position 30. The fluorescent X-rays 5 from the standard sample 25 are detected by the detector 6.
[0026]
The standard sample 25 inserted into the calibration position 30 and the mounting surface 2b of the measurement sample 1 are separated by a distance d. The measurement sample 1 is irradiated with primary X-rays 3 at an irradiation angle θ1 (FIG. 1A). On the other hand, to the standard sample 25, the primary X-rays 3 are irradiated at an irradiation angle θ2 slightly different from the irradiation angle θ1. Therefore, based on the difference in the position between the standard sample 25 and the measurement sample 1 and the difference in the irradiation angle of the primary X-ray 3, the analysis value of the standard sample 25 and the analysis value of the measurement sample 1 are compared. Is shifted. The deviation of the analysis value is corrected by the CPU 11. The CPU 11 reads the correction program from the memory 12 and executes the correction program to correct the deviation of the analysis value.
[0027]
When performing the calibration work, a predetermined operation is performed by the input means 38 to set the calibration mode. In the calibration mode, the control means 10 and the CPU 11 perform the following operations.
First, as shown in FIG. 3A, in a state where the measurement sample 1 is not mounted on the sample table 2, the control means 10 drives the insertion machine 35 to move one standard sample 25 to the calibration position. Insert into 30. The standard sample 25 is irradiated with primary X-rays 3 from the X-ray source 4. The standard sample 25 is excited by the primary X-rays 3 to generate fluorescent X-rays 5. The fluorescent X-rays 5 are detected by the detector 6. The detector 6 outputs a detection value to the CPU 11.
The CPU 11 analyzes the detection value to calculate a calibration coefficient, and creates and standardizes a calibration curve for each element of the standard sample 25. The calibration coefficient is used as a parameter of the correction program executed by the CPU 11 on the analysis value of the measurement sample 1. The calibration curve is used as a comparison target when performing quantitative analysis of the measurement sample 1.
[0028]
When the calibration operation using one standard sample 25 is completed, the calibration operation using another standard sample 25 is similarly performed as necessary. In this way, the calibration work required for performing the inspection is completed.
[0029]
The control means 10 may be set so as to automatically perform the calibration work at a predetermined frequency. Then, since the calibration work does not require any manpower, the running cost of the present inspection machine including the labor cost can be remarkably reduced. In addition, since the troublesome (requiring skill) calibration work is automatically performed, anyone can use the present inspection machine easily.
[0030]
Next, how to use the present inspection machine will be described.
First, before starting the inspection, the above-mentioned calibration work is performed as necessary. Subsequently, the operator operates the input means 38 to select the measurement sample 1 (for example, the electronic material A) of the reference value data of FIG. 3C. Thereby, the reference value data to be compared in the pass / fail judgment is changed and set.
[0031]
When the inspection is started, the primary X-ray 3 is emitted from the X-ray source 4 shown in FIG. The first and second energy bands 31 and 32 of the primary X-ray 3 are absorbed by the first and second elements of the primary filter 7. The X-rays in the third energy band 33 and the fourth energy band 34 remaining after the absorption are applied to the measurement sample 1 through the window 21. The X-rays in the third and fourth energy bands 33 and 34 include a part of continuous X-rays. Therefore, continuous X-rays contained in two energy bands 33 and 34 separated from each other are incident on the measurement sample 1. Continuous X-rays in the third energy band 33 having low energy act as a first excitation component, and excite the measurement sample 1. On the other hand, continuous X-rays in the fourth energy band 34 having high energy act as the second excitation component to excite the measurement sample 1. Therefore, both the trace light element and the trace heavy element contained in the measurement sample 1 can be accurately analyzed.
[0032]
The fluorescent X-rays 5 from the measurement sample 1 are detected by a detector 6. The detector 6 outputs a detection value to the CPU 11. The CPU 11 compares the detected value with the reference value data and performs the above-described predetermined pass / fail determination. The result of the pass / fail judgment is output to the output means 36. The output unit 36 displays (outputs) the determination result on a monitor or a lamp, for example, and allows the operator to recognize whether the result is acceptable or not.
[0033]
The output from the CPU 11 may be output to another device (not shown). For example, the configuration may be such that the CPU 11 outputs a pass / fail signal to the sorting device to line out NG products.
The present inspection machine can also be used as an analyzer. In such a case, if the detailed spectrum analysis result of the measurement sample 1 is displayed by the output means 36, the quantitative analysis result of each element can be easily confirmed.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a primary X-ray having two energy bands separated from each other as excitation components while reducing the background by the primary filter. Therefore, the analysis of a plurality of elements having different atomic numbers can be accurately performed by a single analysis operation without replacing the primary filter, so that the analysis time can be significantly reduced.
In addition, since a lower-output X-ray tube can be used as compared with the case where a spectral crystal is used, cost reduction can be realized. Moreover, since a continuous X-ray having a high output can be used as an excitation component, a plurality of elements can be efficiently excited.
[0035]
In addition, by using a primary filter containing both a light element and a heavy element, both the low energy band and the high energy band separated from each other in the primary X-ray can be absorbed. The range expands.
[0036]
Further, if a primary filter is formed by laminating thin films or thin plates formed by separating the first element and the second element from each other, the formation of the primary filter is facilitated and the cost is reduced.
[0037]
Further, if a filter changer for exchanging a plurality of types of primary filters is provided, it is possible to select and use a primary filter having optimum conditions according to each measurement sample in elemental analysis. Will be higher.
[0038]
In addition, if a plurality of standard samples are built in the irradiation chamber and control means for performing a calibration operation using the plurality of standard samples and correction means for correcting a deviation of the analysis value are provided, it is possible for an operator other than a skilled operator. Since the present inspection apparatus can be easily used even by a person, it can be suitably used as an X-ray inspection apparatus.
[Brief description of the drawings]
FIG. 1A is a schematic view showing an X-ray fluorescence inspection apparatus according to an embodiment of the present invention, and FIG. 1B is a plan view and a cross-sectional view showing a filter of the inspection apparatus.
FIG. 2 is a table showing a relationship between energy bands absorbed and transmitted by a primary filter.
FIG. 3A is a schematic diagram illustrating a fluorescent X-ray inspection machine during a calibration operation, and FIG. 3B is a schematic configuration diagram illustrating a control configuration of the inspection device.
[Explanation of symbols]
1: Measurement sample 2: Sample stage 3: Primary X-ray 4: X-ray source 5: X-ray fluorescence generated from the measurement sample 6: Detector 7: Primary filter 8: First thin film 9: Second thin film 10: Control means 11: CPU (correction means)
25: standard sample 31, 32: energy band of primary X-ray absorbed by primary filter 33, 34: energy band of primary X-ray remaining after absorption by primary filter

Claims (6)

By irradiating the measurement sample with primary X-rays from the X-ray source via the primary filter and detecting the fluorescent X-rays from the measurement sample having received the primary X-rays with a detector, the measurement sample In a fluorescent X-ray analyzer for performing elemental analysis,
The primary filter includes a first element and a second element having different atomic numbers as filter components,
The first element mainly absorbs a first energy band in the primary X-ray,
The second element mainly absorbs a second energy band not adjacent to the first energy band in a band having a larger energy than the first energy band in the continuous X-ray of the primary X-ray,
The absorbed primary X-rays include third and fourth energy bands on both sides of the second energy band as first and second excitation components,
An X-ray fluorescence analyzer, wherein the first and / or second excitation components include a part of continuous X-rays. In claim 1,
The absorbed primary X-ray includes, as one of the first excitation components, a component of a third energy band having higher energy than the first energy band and lower energy than the second energy band. And
The primary X-ray after the absorption includes a component of a fourth energy band having a higher energy than the second energy band as one of the second excitation components,
An X-ray fluorescence analyzer in which the first and second excitation components each include a part of continuous X-rays. In claims 1 and 2,
The primary filter includes a first element having an atomic number of 6 to 29 as a light element filter component,
The primary filter comprises a fluorescent element including, as a heavy element filter component, a second element having an atomic number of 24 or more and 74 or less and an atomic number which is at least 10 or more away from the atomic number of the first element. X-ray analyzer. In Claims 1, 2, and 3,
The X-ray fluorescence analyzer, wherein the primary filter is formed by stacking a first thin film or thin plate containing the first element and a second thin film or thin plate containing the second element. In claim 1, 2, 3, or 4,
A plurality of types of the primary filters are provided;
The primary filters are formed such that at least one of the first element and the second element is different from each other,
An X-ray fluorescence analyzer comprising a filter exchanger for selectively inserting one primary filter out of the plurality of types of primary filters into the optical path of the primary X-ray and retracting the other primary filters. In claim 1, 2, 3, 4, or 5,
In an irradiation chamber including an optical path from the X-ray source to the detector, a plurality of standard samples including light elements and heavy elements having different atomic numbers are incorporated,
The standard sample is provided so as to be able to be inserted into a calibration position close to the surface on the irradiation chamber side of the sample stage on which the measurement sample is mounted, and facing the measurement sample with the sample stage interposed therebetween.
An insertion machine that selectively inserts one of the standard samples into the calibration position,
Control means for sequentially inserting the standard sample into the calibration position by the inserter, retreating, and analyzing the fluorescent X-rays from the standard sample,
An X-ray fluorescence analyzer comprising: a correction unit configured to correct a difference between a position of the standard sample and the measurement sample and a deviation of an analysis value based on a difference in an irradiation angle of the primary X-ray.

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