JPS6238350A - High-accuracy measuring instrument for fluorescence yield - Google Patents

Abstract

PURPOSE:To measure the fluorescence yield of a sample material with high accuracy by subtracting the intensity of the fluorescent X-ray generated by a higher harmonic X-ray from the fluorescent X-ray emitted from the sample. CONSTITUTION:The X-ray generated from an X-ray source focus 1 passes through a divergent slit 2 and a solar slit 3 and after the energy thereof is selected by a curved type spectroscope, the X-ray is irradiated through a filter 9a attached to a filter exchange mechanism 9, a photodetecting slit 5 and an incident X-ray intensity measuring instrument 6 to the sample 7. The fluorescent X-ray generated from the sample 7 is made incident to a fluorescent X-ray measuring instrument 8, by which the intensity is measured. The energy of the incident X-ray is selected by a goniometer 10. The incident X-rays on the instruments 6, 8 are subjected to energy analysis by respective multichannel pulse height analyzers 11, 12 by which the incident X-ray intensity, the high harmonic X-ray intensity and the fluorescent X-ray intensity are determined. These intensities are thereafter transferred to a data processing unit 13. The higher harmonic X-ray intensity is subtracted from the fluorescent X-ray intensity in the unit 13. The fluorescence yields are calculated by the prescribed equation with the energy steps of the respective incident X-rays. The structure of the fluorescent X-ray is analyzed in accordance with the calculated yields.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device for measuring the fluorescence absorption rate of a substance with respect to X-rays with high precision, and in particular, a high-precision fluorescence device suitable for a fluorescence X-ray structure analysis device. This invention relates to a yield measuring device.

[Background of the invention]

Conventionally, a device that accurately measures the fluorescence absorption rate of a substance for X-rays uses an X-ray counter with high resolution to measure the energy level of the fundamental wave, including harmonics, of the X-ray beam that enters the spectrometer. Then, this X-ray beam was guided to a two-crystal spectrometer to remove harmonics, and the X-ray beam from which the harmonics were removed was applied to a sample to measure the fluorescent X-rays generated from the sample. However, when the intensity of the X-rays incident on the two-crystal spectrometer is high, there is no problem, but when the intensity of the incident X-rays is low, the fundamental wave becomes weak, and the fluorescence is emitted from the sample.
No line was generated and measurement was impossible.

In addition, in order to remove harmonics, it was necessary to make complex adjustments to the double-crystal spectrometer with the above-mentioned complex structure (Review of Scientific Instruments).
ew of 5 scientific instruments
nt53(1), J an, 1982 and [Bunseki J 4.1981, etc.).

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a high-precision fluorescence yield that allows for easy operation and measurement of the fluorescence absorption rate of a sample material with high precision even when the X-ray intensity incident on the spectrometer is weak. To provide measuring equipment.

[Summary of the invention]

The above objective is achieved by measuring the intensity of harmonic X-rays in the X-rays emitted by the spectrometer, and subtracting the fluorescence X-ray intensity produced by the harmonic X-rays from the fluorescence X-rays emitted from the sample.

That is, the energy of the X-rays incident on the sample is analyzed and
The harmonic X-ray intensity of unnecessary energy values included in the radiation is also measured, and this value is used to determine the fluorescence X-rays generated from only the X-rays with energy based on the set fundamental wave among the fluorescence X-rays generated from the sample. By calculating the X-ray value of , the influence of harmonics caused by the X-ray spectrometer is eliminated, and the fluorescence yield measurement becomes highly accurate. In this way, there is no need to use a spectroscope with a complicated structure, there is no need to use a spectroscope with a complicated structure, and there is no need to make complicated adjustments to the spectrometer.

Furthermore, X-rays may be scanned with different energy levels.

[Embodiments of the invention]

The present invention will be explained below by way of an example. FIG. 1 is a schematic diagram of a fluorescence yield measuring device using a curved crystal spectrometer. The traveling direction of the X-rays emitted from the X''W source focal point 1 is restricted by a slit system consisting of a divergent slit 2 and a solar slit 3, and the generation of stray light due to scattering occurring on the inner wall of the apparatus is suppressed. Curved spectroscopy The device 4 and the light receiving slit 5 are arranged so that the X-ray source focal point l and the light receiving slit 5 are the X-ray convergence point by the curved spectroscopic crystal 4.

The X-rays that have passed through the light-receiving slit 5 are turned into X-rays with a desired energy as the main component by the curved spectroscopic crystal 4 . However, although the material and crystal structure of the spectroscopic crystal are selected to be as small as possible, it is essentially impossible to eliminate all harmonics.

Therefore, the X-rays having the desired energy include harmonic X-rays having an integral multiple of the energy. Therefore, both the incident X-ray intensity measuring device 6, which measures the intensity of the X-rays incident on the sample 7, and the fluorescent X-ray intensity measuring device 8, which measures the intensity of the fluorescent X-rays generated from the sample 7, are designed to be capable of energy analysis. , the effects of harmonics were removed by selecting multiple conditions for measurement and processing the data.

Next, a method for removing the influence of harmonics will be explained in detail. Now, if the period of the atomic arrangement on the crystal plane that contributes to diffraction of the spectroscopic crystal is d, the Black diffraction angle is θ, and the wavelength of the X-ray is λ, then diffraction occurs only when Equation 11 is satisfied.

2dsinθ−nλ・・・・・・Old and old・・・・・・
- Old... (1) The above formula +11 is known as the Bra-Tsuku rule. n on the right side of this equation is a natural number. and(
Equation 11 shows that X-rays with a wavelength of 1/n of the wavelength of n=1 will also be diffracted under the same conditions, and harmonics with n times the energy of the fundamental wave of n-1 will also be diffracted at the same time. It means that.

The intensity of harmonic X-rays is expressed as the product of the constituent elements of the spectroscopic crystal, the diffraction intensity term due to the crystal structure, and the wavelength (energy) vs. intensity characteristic of the X-ray source.

Among these, the term of diffraction intensity (1) is expressed by equation (2). However, F(n) and S in equation (2) are expressed by equations (31 and (41).

F (n) = Σfj (ns)・exp (2πn1(
hxj+kyj+j! zz) )・exp(-Bj”n
2s2) ・・・・・・・・・・・・・・・・・・(
3) S depth 5ins θ/λ ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・(4) In the above formula (11, (2), (3), A
is a factor such as X-ray absorption by a spectroscopic crystal, F is a structure factor, r
j is the scattering factor of the j-th atom, N is the number of atoms in the period of the crystal, (hkl) is the Miller index of the crystal plane contributing to diffraction, (xj yj zzj) is the coordinate of the j-th atom, Bj is the isotropic temperature factor of the j-th atom.

Among these, the functional form of fj (ns) is, for example, f of Si.
(ns) is shown in FIG. Also exp(-B j2n”
Since the term s2) is monotonically decreasing with respect to ns, F (n
) shows a decreasing tendency as n increases. Since the term of the geometrical structure factor exp (2πn1(hx+ky+ffz)) indicates the phase sum of all atoms in the repeating unit of the crystal, it takes a value that reflects the arrangement of atoms (crystal structure). U (n) U (n) = Σexp (2πn1(hxj +ky
When we calculate j + 1 zz)) - (5), we get the result shown in Figure 3. Ammonium dihydrogen phosphate (abbreviated as ADP)
(101) crystal plane of ADP (100) crystal plane,
The characteristics of each of the S1 (111) crystal planes are as follows.

i) ADP(101); U(n)/U(1)
<0.3ii) ADP(100); U(n)
=0. n: odd number U(4) = O iii) 5i(111); U(n) = 0
．． n: Even number On the other hand, the wavelength (energy) vs. intensity characteristics of the X-ray source differ depending on the method of generation of )l. In synchrotron orbital radiation, electron energy and deflection magnetic field strength.

In the electron beam excitation type, the short wavelength limit is determined by the electron beam acceleration voltage. Generally, this limit corresponds to 20-30 KeV in energy.

Considering these, the X-ray energy of n=1 is 5 K
The fluorescence extraction rate in the region larger than eV is ADP (100)
By selecting a crystal exhibiting spectral characteristics such as or 5i (111), harmonics can be easily removed. In the energy range lower than 5 KeV, it is difficult to remove harmonics using crystal properties alone, and especially below 2 KeV, it is necessary to use a crystal such as A D P (101) due to the mechanical limitations of the spectrometer. Therefore, harmonics must be removed by other methods.

When measuring the fluorescence absorption rate of SiKα X-rays with a fluorescence excitation energy of 1840 eV, A D P (101)
When attempting to irradiate X-rays of 2 KeV using a spectroscopic crystal, X-rays with energy that is a natural number times that amount will also be irradiated.

Now, if the incident intensity of X-rays of each energy is In, and the fluorescence extraction rate for each In is Cn, then the S generated from the sample is
The intensity G of the iKα fluorescent X-ray is expressed by equation (6).

G；ΣCn1n ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・(6) Incident X-ray intensity measuring device 6 in Fig. 1. If an energy analysis type is used as the fluorescence X-ray intensity measuring device 8, the relationship in equation (6) can be accurately determined even if other elements are mixed into the sample and different fluorescence X-rays are generated. . In this embodiment, a flow type proportional counter (FPC) with an energy resolution of about 0.8 Keν and a multichannel pulse height analysis type data acquisition device are used for both.

Now, as shown in FIG. 4, an incident X-ray filter mechanism 9 is installed between the spectroscopic crystal 4 and the light receiving slit 5, so that the filter material can be replaced. The attenuation of X-rays by the filter is (7)
, given by equation (8).

It=Isexp(-It)・・・・・・・・・・・・
・・・・・・・・・・・・(71μ=μm (E) ρ
・・・・・・・・・・・・・・・・・・・・・(8
) Here, 10 is the incident X-ray intensity, It is the absorption coefficient μ, and the X-ray intensity after passing through a filter with a thickness of 7 μm (E) is the mass absorption coefficient at the energy E of the incident X-ray, and ρ is the density of the filter. It is. μm (E) is a function for energy E as shown in equation (9).

μ” (E) = 3 E-3・・・・・・・・・・・・
(9) Here, a is a constant determined by the filter. Therefore, by selecting the material and thickness of the filter from the form of equation (7), it is possible to construct an X-ray optical system that hardly transmits X-rays with energy below a certain energy E.

By performing measurements with n types of filter conditions and obtaining equation (6), it is possible to form n-element simultaneous equations, and by solving this, the light extraction rate C1 required for fluorescence X-ray structure analysis can be calculated.
It is possible to determine minute fluctuations due to the incident X-ray energy E.

The measurement operation by the apparatus of this embodiment will be explained with reference to FIG. 4, which is a block diagram of the apparatus of this embodiment. X-rays generated from the X-ray source focal point 1 are passed through the divergent slit 2. After energy selection by the curved spectroscopic crystal 4 through the solar slit 3, the filter 9a attached to the filter exchange mechanism 9 and the light receiving slit 5. A sample 7 located behind the incident X-ray intensity measuring device 6 is irradiated.

The fluorescent X-rays generated from the sample 7 enter a fluorescent X-ray intensity measuring device 8, and the intensity is measured. The energy of the incident X-rays is selected by a goniometer 10.

The X-rays incident on the incident X-ray intensity measuring device 6 and the fluorescence X-ray intensity measuring device 8 are transmitted to the respective multichannel pulse height analyzers 1.
1 and 12, the incident X-ray intensity,
After the harmonic X-ray intensity and fluorescence X-ray intensity are determined, they are transferred to the data processing device 13.

The data processing device 13 controls the filter exchange mechanism 9, inserts each filter and collects data, and then controls the goniometer 10 to change the energy of incident X-rays and measure the next data.

After collecting measurement data for each incident X-ray energy step, the data processing device 13 calculates the fluorescence extraction ratio C5 of equation (6) for each energy, and performs fluorescence X-ray structure analysis based on this. These calculation processes can be controlled by the keyboard 14, and the measurement data and results are displayed on the CRT 15 and output to the external recording device 16.

The device of this embodiment also allows the following measurement operation to shorten the data collection time. Compared to the fluorescence extraction ratio C3 due to an incident X-ray with an energy slightly higher than the fluorescence excitation energy of a certain element, the fluorescence extraction ratio Cn due to its 0th harmonic changes smoothly with almost no minute fluctuations. By using this, there is no need to always replace the filter 0 times for each incident It is possible to make measurements of the rate C1.

〔Effect of the invention〕

According to the present invention, the influence of harmonics caused by the spectroscopic crystal can be removed, and especially when the X-ray source has characteristic X-rays, harmonics
Since it is possible to remove the influence of radiation on the fluorescence absorption rate measurement, it is possible to precisely measure minute fluctuations in the fluorescence absorption rate in the low energy X-ray region of 5 KeV or less, and to perform high-precision fluorescence X-ray measurement. This has the effect of configuring a line structure analysis device.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the X-ray optical system of the fluorescence yield measurement device, Figure 2 is the functional form of the atomic scattering factor using Si as an example, and Figure 3 is the functional form of the atomic scattering factor using Si as an example.
The figure shows the geometric structure factors of the spectroscopic crystal used in this example device.
FIG. 4 is a block diagram of the apparatus of this embodiment. 1... X-ray source focal point, 2... Diverging slit, 3...
Solar slit, 4... Curved spectrometer, 5... Slit, 6... Incident X-ray intensity measuring device, 7... Sample,
8... Fluorescence X-ray intensity measuring device, 9... Filter exchange mechanism, 1o... Goniometer, 11.12... Multi-channel energy analyzer, 13... Data processing device. Agent Patent Attorney Tadashi Akimoto Figure 2 0 0.250,500.75 1.00 +, 25
1.50 ns Fig. 3 1 2 3 4
5 nFigure 4

Claims (1)

[Claims] an X-ray generating means, a means for selecting the wavelength of the X-ray containing harmonics generated by the X-ray generating means, a means for measuring the intensity of the X-ray having the selected wavelength, and a means for applying the X-ray having the selected wavelength to the sample. means for inserting various filters between the means for irradiating, the means for measuring the intensity of fluorescent rays generated from the sample, the means for selecting the wavelength, and the means for measuring the intensity of the X-rays having selected the wavelengths; A means for measuring the energy of incident X-rays on the filters is provided before the means for inserting the various filters, and the X-ray energies and fluorescent X-rays incident on the plurality of filters are measured by the means for measuring the energy of incident X-rays on the filters. A high-precision fluorescence yield measuring device characterized by comprising means for analyzing the relationship between intensities and removing the effects of harmonics.