JP2002090319A - Fluorescent x-ray analysis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of accurately correcting the influence of a characteristic X-ray from an X-ray tube in a fluorescent X-ray analysis device for analyzing the composition of a sample by an FP method. SOLUTION: This fluorescent X-ray analysis device is provided with a computing means 16 for estimating the measured intensity of scattered radiation of the characteristic X-ray from the X-ray tube 1, from theoretical intensity computed according to the composition of the sample 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluorescence analyzer for analyzing the composition of a sample by the FP method, which corrects the influence of characteristic X-rays from an X-ray tube.

[0002]

2. Description of the Related Art Conventionally, in fluorescent X-ray analysis, X
Primary X-rays are emitted from the X-ray tube, and the intensity of the generated fluorescent X-rays is measured with a detector or the like to analyze the composition of the sample. In addition, the characteristic X-ray of the substance attached to the X-ray tube window and the element of the structure in the X-ray tube,
A so-called impure line occurs. If this impure line is scattered by the sample and detected by the detector, it cannot be distinguished from fluorescent X-rays of the same wavelength generated from components in the sample.

On the other hand, for example, in the fundamental parameter method, that is, the FP method, calculation is performed assuming the converted intensity to a theoretical intensity scale based on the measured intensity of fluorescent X-rays and the content of each component (sample composition) in the sample. Fluorescent X
The theoretical intensities of the lines are compared for each of the corresponding components, and the content rates of the assumed components are successively and approximately corrected to calculate the content rates of the respective components so that the two intensities match. In order to correct the influence of the line, the scattering intensity of the impurity line is measured in advance using a blank sample that does not contain a component that uses the fluorescent X-ray having the same wavelength as the impurity line as the analysis line. Was subtracted from the measured intensity at the wavelength of, to obtain the measured intensity of only the fluorescent X-rays generated from the components in the sample.

[0004]

However, since the measured intensity of the impure line is affected by the composition of the sample, if the composition of the blank sample and the sample to be analyzed are significantly different, the influence of the impure line can be accurately determined. Cannot be corrected. Further, it is practically very difficult to prepare an enormous number of blank samples and measure the scattered intensity of the impure rays in order to handle samples of all kinds. A similar problem occurs when the sample contains the target element of the X-ray tube. That is, in such a case, the characteristic X-rays from the target of the X-ray tube are converted from the X-rays generated from the X-ray tube using a primary filter so as not to overlap the fluorescent X-rays generated from the sample. Although the primary X-rays are removed, they cannot be completely removed, and their effects cannot be corrected exactly as in the case of the above-mentioned impure lines. Further, the correction of the influence of the characteristic X-ray from the X-ray tube is performed not only when the wavelength of the characteristic X-ray from the analysis line and the characteristic X-ray from the X-ray tube are the same, that is, when the characteristic X-ray is the same, Is also necessary when the spectra are close and the spectra overlap.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. In an X-ray fluorescence analyzer for analyzing the composition of a sample by the FP method, the influence of characteristic X-rays from an X-ray tube can be corrected sufficiently accurately. It is intended to provide a device.

[0006]

In order to achieve the above object, an X-ray fluorescence spectrometer according to the present invention comprises an X-ray tube for irradiating a sample with primary X-rays and a secondary X-ray generated from the sample. Detecting means for measuring the intensity, and converting the intensity of the fluorescent X-rays measured by the detecting means to a theoretical intensity scale based on the measured intensity and the fluorescent X-ray calculated assuming the content of each component in the sample. Compare the theoretical intensity of the line for each corresponding component,
A calculating means is provided for sequentially and approximately correcting and calculating the assumed content of each component so that the two intensities coincide with each other to calculate the content of each component. That is, it is a fluorescent X-ray analyzer that performs analysis by the FP method.

[0007] Here, the calculation means uses a sample whose composition is known at the wavelength of the analysis line for a component that uses a fluorescent X-ray whose spectrum overlaps with the characteristic X-ray from the X-ray tube as an analysis line. The characteristic X from the X-ray tube in the sample to be analyzed is determined based on a previously determined impurity constant of the impurity device representing the correlation between the theoretical intensity and the measured intensity of the characteristic X-ray scattered radiation from the X-ray tube. The measured intensity of the scattered X-rays is estimated from the theoretical intensity, and is subtracted from the measured intensity by the detection means, and is used as the measured intensity of the fluorescent X-ray generated from the sample to be analyzed.

According to the X-ray fluorescence spectrometer of the present invention, the FP
In the method, the measured intensity of the scattered radiation of the characteristic X-ray from the X-ray tube is estimated from the theoretical intensity calculated according to the composition of the sample, so that the influence of the characteristic X-ray from the X-ray tube can be corrected sufficiently accurately. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus according to an embodiment of the present invention will be described below with reference to FIG. First, the configuration of this device will be described. This apparatus includes a sample stage 8 on which a sample 13 is placed and an X-ray for irradiating the sample 13 with primary X-rays 2.
The apparatus includes a tube 1 and a detection unit 10 for measuring the intensity of secondary X-rays 4 such as fluorescent X-rays generated from a sample 13. The detecting means 10 includes a spectroscopic element 5 for separating the secondary X-rays 4 generated from the sample 13 and a detector 7 for measuring the intensity of the secondary X-rays 6 separated by the spectroscopic element 5.

Further, this apparatus uses a fluorescent X-ray 4 calculated by assuming the converted intensity to a theoretical intensity scale based on the measured intensity of the fluorescent X-ray 4 measured by the detecting means 10 and the content of each component in the sample 13. Calculating means 16 for comparing the theoretical intensities of the respective components and calculating the content rates of the respective components by successively and approximately correcting and calculating the assumed content rates of the respective components so that the two intensities coincide with each other. It has. That is, the apparatus of this embodiment is an X-ray fluorescence analyzer that performs analysis by the FP method.

Here, the calculating means 16 of this apparatus determines that the composition of the component, which is the fluorescent X-ray 4 whose spectrum overlaps with the characteristic X-ray from the X-ray tube 1, is known at the wavelength of the analytical line. Based on a sensitivity constant of an impurity device indicating a correlation between the theoretical intensity and the measured intensity of the scattered radiation 4 of the characteristic X-rays from the X-ray tube 1 obtained in advance using the samples 3 and 23, The measured intensity of the scattered radiation 4 of the characteristic X-rays from the X-ray tube 1 in the sample 13 is estimated from the theoretical intensity, and is subtracted from the measured intensity by the detecting means 10;
It is used as the measured intensity of the fluorescent X-rays 4 generated from the sample 13 to be analyzed. The characteristic X-rays from the X-ray tube 1 include X-rays.
There are characteristic X-rays of elements adhered to the window of the X-ray tube 1 and elements of structures in the X-ray tube 1, so-called impure lines, and characteristic X-rays of target elements. Samples 3 and 23, whose compositions are used to determine the sensitivity constant of the impurity device, have a standard sample 3 whose composition is similar to the sample 13 to be analyzed, and characteristic X-rays and spectra from the X-ray tube 1. There is a blank sample 23 which does not contain a component having the fluorescent X-rays 4 to be analyzed as the analysis line.

The calculating means 16 of this apparatus obtains and stores in advance the fluorescent X-ray apparatus sensitivity coefficients A, B, and C and the impurity line apparatus sensitivity constants a, b, and c as follows. First, the fluorescent X-ray apparatus sensitivity coefficient A, B, C on the composition in the device using the measured intensities I _FM and calculated theoretical intensity I _FT was measured for a known standard sample 3, determined by the following equation (1) Can be

I _FT = AI _FM ² + BI _FM + C (1)

Here, taking as an example a case in which a sample 13 containing a component having the fluorescent X-ray 4 having the same wavelength as the impurity line as the analysis line is to be analyzed, such a component is expressed by the following equation (2). so, only the measured intensity I _FM of the fluorescent X-ray 4 generated from the reference sample 3, impure line of scattered radiation 4 measured intensity I _IM
The obtained by subtracting from the (net intensity to remove background) total measured intensity by the detection means 10 at the wavelength I _TM. Incidentally, it for other components, conventional FP method exactly, is used as the measured intensity I _FM of the total measured intensity I _TM as only the fluorescent X-ray 4 generated from the standard sample 3.

I _FM = I _TM -I _IM (2)

The measured intensity I _IM of the scattered radiation 4 of the impure radiation can be estimated as follows. First,
Impurity ray apparatus sensitivity constants a, b, and c representing the correlation between the theoretical intensity and the measured intensity of the scattered ray 4 of the impure ray, and the fluorescent X-ray apparatus sensitivity coefficients A, B, and C obtained by the above-described ordinary FP method. In the same manner as described above, the intensity I of the scattered radiation 4 of the impure radiation measured on the blank sample 23 which does not contain the component having the X-ray fluorescence 4 having the same wavelength as that of the impure radiation as the analysis radiation and has a known composition.
_{Using the IM} and the calculated theoretical intensity I _IT of the scattered radiation of the impure radiation (Thomson scattered radiation), it can be obtained from the following equation (3), and is stored in the calculation means 16 in advance. Then, based on the impurity constants a, b, and c of the impurity, the measured intensity I _IM of the scattered radiation 4 of the impurity in the standard sample 3 is calculated as shown in equation (3). From the theoretical strength I _{IT of} As the blank sample 23, Si
O ₂ or an acrylic plate can be used. The standard sample 3 used when obtaining the fluorescent X-ray apparatus sensitivity coefficients A, B, and C for each component may include a component that uses the fluorescent X-ray 4 having the same wavelength as the impurity line as the analytical line.

I _IM = aI _IT ² + bI _IT + c (3)

When a single Bunraku sample 23 is used, a = c = 0 may be set.

The fluorescent X-ray apparatus sensitivity coefficients A, B, and C and the impurity line apparatus sensitivity constants a, b, and c for the component that uses the fluorescent X-ray 4 having the same wavelength as the impurity line as the analysis line are as follows. You can also ask.

That is, the equation obtained by substituting equation (3) into equation (2) is substituted into equation (1) to obtain the following equation (1-2).

[0021] _{I FT = A (I TM -aI} IT 2 -bI IT -c) 2 + B (I TM -aI IT 2 -bI IT - c) + C ... (1-2)

[0022] Using the theoretical strength I _IT scattered radiation of the total measured intensity I _TM and the calculated theoretical intensity I _FT and impure lines composition in the device was measured for a known standard sample 3, the equation (1-2) Fluorescent X-rays 4
The X-ray fluorescence device sensitivity coefficients A, B, and C and the impurity beam device sensitivity constants a, b, and c for the component having the analysis line as the analysis line are simultaneously obtained. Also in this case, a = c = 0 may be set. Further, some of the standard samples 3 to be used may not include a component that uses the fluorescent X-ray 4 having the same wavelength as the impurity line as an analysis line.

Next, the operation of the apparatus according to this embodiment will be described with reference to an example in which the influence of an impure line is corrected. The sample 13 placed on the sample stage 8 is irradiated with primary X-rays 2, and secondary X-rays 4 generated from each component (element) of the sample 13 are irradiated.
Measure the strength of Based on the measured intensity, the calculating means 16 calculates the content of each component by the FP method, for example, in the following procedure.

(Step 1) A converted intensity based on each measured intensity is obtained. That is, for each component, the measurement intensity IFM is _converted to the fluorescent X-ray apparatus sensitivity coefficients A, B,
In terms of the theoretical intensity scale using a C in terms of the intensity I _FT ^M
And Here, for the components to be analyzed line X-ray fluorescence 4 having the same wavelength as impure line, not deducted measured intensity I _IM scattered radiation 4 of impure lines, fluorescent X generated total measured intensity I _TM directly from the sample _Used as the measured intensity I _FM for line 4 only.

[0025] (Step 2) theoretical intensity I of the fluorescence X-rays from the pure substance Conversion intensity I _FT ^M and its components for each component
An initial value of the content W of each component is assumed from the intensity ratio with _FT .

(Step 3) From the assumed composition, the theoretical intensities I _FT and I _IT of the scattered X-ray and impure X-rays
Is calculated.

(Step 4) Fluorescence X of the same wavelength as the impure line
The components that the line 4 and the analysis line, by using the theoretical intensity I _IT of scattered radiation calculated impure lines, recalculate the converted intensity I _FT ^M obtained in step 1. That is, as shown in the above equation (3), the measured intensity I _IM of the scattered ray 4 of the impure ray is calculated based on the sensitivity constants a, b, and c of the impure ray apparatus, and the calculated theoretical intensity I _IT of the scattered ray of the impure ray is calculated. Then, the measured intensity I _IM of the scattered radiation 4 of the impure radiation is subtracted from the total measured intensity I _TM as in the above equation (2), and only the fluorescent X-rays 4 generated from the sample 13 are measured. used as the intensity I _FM. And
The measured intensity I of only the fluorescent X-rays 4 generated from the sample 13
_FM is _calculated by the fluorescent X-ray apparatus sensitivity coefficient A,
B, and in terms of the theoretical intensity scale with C, and a new conversion intensity I _FT ^M for the next step 5. For other components, the converted intensity I _FT ^M obtained in step 1 is used as it is.

[0028] (Step 5) for each component, from the theoretical intensity I _FT calculated in terms of the intensity I _FT ^M and Step 3 obtained in Step 1 or 4, to update the content of the following equation (4). Here, W ^{(n + 1)} is the content rate of the ^{(n + 1)} th time, W
⁽ⁿ⁾ is the content rate of the n-th time, and I _FTM ⁽ⁿ⁾ is the converted intensity of the n-th time (for the component using the fluorescent X-ray 4 having the same wavelength as the impurity line as the analysis line, the scattered ray of the impurity line is determined in step 4) Measurement intensity I of 4
_IM has been removed), and I _FT ⁽ⁿ⁾ is the nth theoretical intensity.

W ^{(n + 1)} = W ⁽ⁿ⁾ × ( _IFTM ⁽ⁿ⁾ / _IFT ⁽ⁿ⁾ ) (4)

(Step 6) For each component, the content ratio of the nth time and the content ratio of the (n + 1) th time are compared, and the convergence is made when the change in the content ratio of all the components becomes equal to or less than a predetermined value.
If the convergence has not occurred, the procedure from step 3 is repeated.

That is, the converted intensity obtained in step 1 or 4 and the theoretical intensity of the fluorescent X-rays calculated in step 3 assuming the content of each component in step 2 are
By comparing each corresponding component in step 6 and repeating steps 3 to 6, the content rates of the assumed components are successively and approximately corrected to calculate the content rates of the components so that both intensities match. calculate.

[0032] Thus, according to the fluorescent X-ray analyzer of the present embodiment, the FP method, the measured intensity I _IM scattered radiation 4 of impure line, calculated theoretical intensity I _IT according to the composition of the sample 13 Therefore, the influence of the impure line can be corrected sufficiently accurately.

In the above, the case of analyzing the sample 13 containing a component using the fluorescent X-ray 4 having the same wavelength as the impurity line as the analysis line by correcting the influence of the impurity line was taken as an example. The same can be applied to the case where the target element of the wire tube 1 is included. That is, in such a case, the sample 13
X-ray tube 1 so that it does not overlap with fluorescent X-rays 4 generated from
The characteristic X-rays from the target are removed from the X-rays generated from the X-ray tube 1 using a primary filter (not shown) to obtain primary X-rays 2. , Is treated in the same manner as the impure line described above, and its influence is corrected.
Therefore, by estimating the measured intensity I _IM of the scattered radiation 4 of the characteristic X-ray from the target of the X-ray tube 1 from the theoretical intensity I _IT calculated according to the composition of the sample 13, the target of the X-ray tube 1 Can be corrected sufficiently accurately.

When the spectrum of the analysis line and the characteristic X-ray from the X-ray tube 1 overlap, as described above, the wavelength of the analysis line and the characteristic X-ray from the X-ray tube 1 are the same, that is, the same characteristic. In addition to X-rays (eg, Rh-Kα rays)
There is a case where the two wavelengths are different but the spectra are close to each other and overlap (for example, the analysis line is a Cd-Kα line and the characteristic X-ray from the X-ray tube 1 is a Rh-Kβ ₂ line). Also, it is necessary to correct the influence of characteristic X-rays from the X-ray tube 1. Also in this case, the sensitivity constants a, b, and c of the impurity device are as follows:
This is for the wavelength of the analysis line, and is obtained from Equation (1) or (1-2) using the measured intensity and the theoretical intensity at the wavelength of the analysis line.

[0035]

As described in detail above, according to the X-ray fluorescence spectrometer of the present invention, in the FP method, the measured intensity of the scattered X-ray scattered radiation from the X-ray tube is changed according to the composition of the sample. Thus, the influence of the characteristic X-ray from the X-ray tube can be corrected sufficiently accurately.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an X-ray fluorescence analyzer according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... Primary X-ray, 3,23 ... Sample whose composition is known, 4 ... Secondary X-ray generated from a sample, 10 ... Detection means,
13: sample to be analyzed, 16: calculation means.

Claims (1)

[Claims] 1. An X-ray tube for irradiating a sample with primary X-rays, a detecting means for measuring the intensity of secondary X-rays generated from the sample, and a measuring intensity of fluorescent X-rays measured by the detecting means. The converted intensity to the theoretical intensity scale and the theoretical intensity of the fluorescent X-rays calculated by assuming the content of each component in the sample are compared for each corresponding component, and the above-mentioned components are assumed so that both intensities match. Calculating means for successively and approximately correcting and calculating the content of
In the X-ray analysis apparatus, the calculation unit uses a sample whose composition is known at a wavelength of the analysis line for a component that uses a fluorescent X-ray whose spectrum overlaps with a characteristic X-ray from the X-ray tube as an analysis line. On the basis of a previously determined impurity constant of the impurity device representing a correlation between the theoretical intensity and the measured intensity of the characteristic X-ray scattered X-rays from the X-ray tube, the X-ray intensity in the sample to be analyzed is determined.
Estimating the measured intensity of the scattered radiation of the characteristic X-ray from the tube from the theoretical intensity, subtracting from the measured intensity by the detection means,
An X-ray fluorescence analyzer for use as a measurement intensity of X-ray fluorescence generated from a sample to be analyzed.