JPS6253800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to isotopic white
Regarding what lines are obtained.

[Conventional technology]

First, the background of the present invention will be explained. It is well known that X-rays can be used to measure stress in objects. This stress measurement is performed when the distance between possible atomic planes in the crystal of an object is d, X-rays of wavelength λ are incident at an angle θ with that plane, and scattered X-rays also make an angle θ with that plane. This is done by taking advantage of the relationship that 2d・sinθ=n・λ (n is an integer). As a method to perform this stress measurement, the wavelength λ
Using X-rays with a constant (constant energy), change the incident angle θ to find the angle at which the maximum detection output is obtained, find the interplanar spacing d from that angle, and calculate the value of the interplanar spacing or under a certain stress condition. A method of measuring stress from the difference between the interplanar spacing d ₁ and the interplanar spacing d ₂ in the measured stress-applied state, and with the incident angle θ constant and X
There is a method of using white X-rays as the line and determining the stress from the surface distance d or the difference from the maximum detection output.

Since the present invention is used for the latter stress measurement (however, the present invention is not used only for this stress measurement), the stress measurement method and problems with conventional X-ray sources will be explained next. do. FIG. 1 shows a schematic configuration of a stress measuring device using a white X-ray source. A is an X-ray source that targets a metal with a large atomic number, such as tungsten, and generates continuous X-rays by colliding electrons accelerated with a large accelerating voltage. The object B is installed so that the incident angle θ of the X-rays is constant. C is a detector installed at a reflection angle θ from the reflective surface of the object B, which converts each X-ray incident on this detector into an electric signal and outputs it,
As shown in FIG. 2, if the energy of the X-ray is large (the wavelength λ is small), the detection output is large. D is the detection output of the detector C, that is, as shown in FIG. 3, the detection output corresponding to the energy level of the input X-ray is input, and the detection level Δ is
It detects how many Li, ΔLj... are obtained per fixed time, and outputs a number signal for each level. E is a recorder, and as shown in FIG. 4, the number of X-rays corresponding to each energy level of X-rays is drawn on a curve a. The wavelength λ is determined from the peak of this curve a, and the interplanar distance d is determined from this λ.

In such a stress measuring device, the intensity of the X-rays emitted from the X-ray source A is determined at each energy level (since X-rays can also be understood as particles, the intensity can be considered as the number of X-rays at each energy level). ) must be constant. If we were to use an X-ray source that emits X-rays whose intensity increases as the energy level increases, recorder E would have a peak and an energy level that would be slightly to the right in the drawing compared to curve a. A curve b that appears to be deviated is obtained. On the other hand, if a curve is used in which the lower the energy level, the higher the intensity, the peak of the curve will deviate to the left in the drawing from curve a. Therefore, the correct wavelength λ cannot be obtained, so
As for the X-ray source, it is desirable that the intensity of each energy level is as constant as possible.

[Problem that the invention seeks to solve]

A conventional X-ray source that obtains a constant intensity over such a wide range of energy levels uses one configured to bombard metal with electrons. However, this conventional X-ray source requires a tube, a high-voltage large-capacity stable source device, a water cooling device, etc.
The disadvantage is that the entire device becomes very large-scale. It is desirable to use isotopes to make equipment compact and inexpensive, but
Isotopes generally do not have constant energy intensity.

The present invention was made in view of the above circumstances, and
The object is to obtain a compact white X-ray source that can obtain X-rays of constant intensity within a predetermined energy level range.

[Means for solving problems]

To achieve the above object, the isotopic white X-ray source of the present invention has an isotope that spontaneously emits bremsstrahlung X-rays having a continuous energy spectrum whose intensity decreases as the energy level increases, and an isotope that allows the bremsstrahlung X-rays to pass through. The screen is made of a material whose absorption coefficient decreases as the energy level increases.

[Effect]

With the above configuration, at low energy levels where the isotope's energy spectrum intensity is high, there is a lot of absorption by the screen, and on the contrary, at high energy levels where the spectral intensity is low, there is little absorption, so White X-rays with substantially uniform intensity can be obtained up to the high energy region.

When carrying out the present invention, it is necessary to match the continuous spectral characteristics of the isotope with the absorption characteristics of the screen material, but as a practical matter, it is first necessary to match the isotope with the emission characteristics of the above-mentioned tendency and the above-mentioned one. After selecting a screen material having absorption characteristics with a similar tendency, it is preferable to set the energies ν ₁ and ν ₂ on the energy spectrum, and determine the thickness of the screen by the following calculation.

If the incident X-ray intensity with energy ν ₁ is I ₁₀ , the linear absorption coefficient of the screen is μ ₁ , and the transmitted X-ray intensity after passing through the screen is I ₁ , then the screen thickness is x
As, I ₁ = I ₁₀・e ^- 〓 ^1X ...(1) Similarly, the incident X-ray intensity with energy ν ₂ is
I ₂₀ , the linear absorption coefficient of the screen is μ ₂ , and the transmitted X-ray intensity after passing through the screen is I ₂ , I ₂ = I ₂₀・e ^- 〓 ^2X ……(2) ∴I ₁ /I ₂ = I ₁₀ /I ₂₀ e ^-( 〓 ^1- 〓 ^2)X ...(3) Here, the transmitted X-ray intensity after passing through the screen I ₁ =
In order to set I ₂ , it is sufficient to set I ₁ /I ₂ = 1 on the left side of equation (3) above. That _is , I ₁₀ / _{I 20 =} e ⁽ 〓 ^1- 〓 ₂ ⁾
...(5) By setting the screen thickness x to be determined by the above equation (5), the transmitted X-ray intensity becomes equal at energy ν ₁ and energy ν ₂ .

Although the transmitted X-ray intensity is not strictly constant at points other than ν ₁ and ν ₂ , it is uniform to the extent that it can be considered constant in practical terms.

In the present invention, bremsstrahlung X-rays refer to X-rays emitted from radioisotopes and having a continuous spectrum.
Bremsstrahlung X-rays are generated when charged particles receive negative acceleration when passing through a strong electric field, such as the clone field of an atomic nucleus.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to FIGS. 5 to 7. In FIG. 5, 1 is a container made of an X-ray shield containing a radioactive isotope 2, 3 is a window with a small X-ray absorption rate that closes the opening of the container to prevent the isotope 2 from leaking, and 4 is a container 1 A hole 5 is made in the center of the plate, and a screen 6 that partially absorbs the X-rays is placed in the hole 5 to close the hole. Fixed. A cylindrical shield 7 is provided with a solar slit 8 for converting X-rays into a parallel beam, and one end of the shield is fixed so as to match the opening of the shield 4. A perspective view of the cylindrical shield 7 and solar slit 8 is shown in FIG. This cylindrical shield 7 is for preventing scattering of X-rays in unspecified directions.

As isotope 2 that generates X-rays, Kr ⁸⁵ (half-life 10.4 years) is most suitable from the viewpoint of the energy range used as white X-rays and half-life (the longer it is, the more stable it can be used as a radiation source). Figure 6 shows the energy spectrum. As shown in this figure, the intensity of the bremsstrahlung X-rays emitted from Kr ⁸⁵ decreases as the energy level increases.
However, the amount of X-rays absorbed by the screen 6 is greater as the energy decreases. That is, the X-ray intensity after passing through the screen 6 is flattened by appropriately selecting the material and thickness of the screen. When aluminum foil is selected as the screen material, the X-ray absorption coefficient of aluminum is as shown in Figure 7, so the 10
Approximately 0.2mm when flattening ~100keV X-rays
If you make a screen out of aluminum foil, you can get flat white X-rays.

FIG. 8 shows another embodiment of the present invention in which the isotope 9 is not a gas but a solid at room temperature. Although solid isotopes do not have nuclides with long half-lives, so it is difficult to obtain a radiation source with stable intensity, they have the advantage of being easy to manufacture because they are easy to seal.

In the above embodiments, the case was described in which the substance that partially absorbs X-rays is aluminum foil, but other metal foils such as tin foil may also be used. However, when combined with Kr ⁸⁵ , the use of aluminum foil provides output X-rays with uniform intensity. The reason for this is that in the case of other metals such as tin foil, the absorption coefficient of X-rays increases rapidly in a region with a low energy level.

Moreover, a liquid or gas can be used instead of metal such as aluminum foil. In the case of a liquid or gas, the absorption coefficient of X-rays is smaller than that of metals, so as shown in the embodiment of FIG. 9, the absorption path of the liquid 10 for X-ray absorption is longer than the thickness when using metals. must be created in such a way that When using liquids or gases, the degree to which their absorption coefficient increases as the energy level decreases is smaller than that of metals, and the change in absorption coefficient with respect to changes in energy level has an approximately linear relationship. Therefore, X-rays covering lower energy levels can be obtained.

Moreover, by using not only one type of X-ray absorbing substance but a combination of multiple types, it is also possible to make the intensity more uniform.

〔Effect of the invention〕

As described above, the present invention makes it possible to obtain white X-rays with broadband energy by combining an isotope and an absorbing substance. Since a device and a water cooling device are not required, it can be manufactured very compactly. Moreover, the miniaturization facilitates X-ray stress measurement of complex-shaped objects to be measured or large structures.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of an X-ray stress measuring device to which the present invention is applied, and Fig. 2 is a diagram showing the relationship between X-ray energy and detection output in the detector shown in Fig. 1. , FIG. 3 is a diagram showing the output of the detector of FIG. 1, FIG. 4 is a diagram showing an example of recording in the recorder of FIG. 1, and FIG. 5 is a diagram showing an embodiment of the white X-ray source according to the present invention. 6 is the X-ray energy spectrum of Kr ⁸⁵ , FIG. 7 is the X-ray absorption coefficient of aluminum, FIG. 8 is a sectional view showing another embodiment of the white X-ray source according to the present invention, and FIG. 9 FIG. 2 is a cross-sectional view showing yet another embodiment of the white X-ray source according to the present invention. FIG. 10 is a perspective view of a cylindrical shield with solar slits. 1... Container, 2... Isotope (gas), 3
... window, 6 ... screen, 8 ... solar slit, 9 ... isotope (solid), 10 ... screen (liquid).

Claims (1)

[Claims] 1. Braking X having a continuous energy spectrum in which the intensity decreases as the energy level increases.
An isotope comprising an isotope that spontaneously emits radiation, and a screen that allows the bremsstrahlung X-rays to pass through, the screen being composed of a substance whose absorption coefficient decreases as the energy level increases. White X-ray source. 2. The isotopic white X-ray source according to claim 1, wherein the isotope is Kr ⁸⁵ and the screen is aluminum foil.