JP2002162371A - Nondestructive inspection method and its device utilizing inverse compton scattered light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perspective diagram or a cross section diagram showing inside a rather thicker inspected object which has ever been impossible to be imaged by conventional X-ray, X-ray radiography or CT. SOLUTION: By using laser inverse Compton photon, take advantage of high-directivity, quasi-monochromaticity, energy variability, etc., contained in this photon to conduct destructive inspection for physical matters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nondestructive inspection using X-rays and γ-rays, radiography, tomography, and the like, and in particular, energy-variable quasi-monochromatic photon generation using laser inverse Compton scattering at a photon generation part. The present invention relates to a device provided with a device.

[0002]

2. Description of the Related Art For examination of the inside of a human body, radiography using an X-ray or an X-ray CT apparatus, such as an X-ray photography, is used, and a projection view or a sectional view is obtained. For industrial nondestructive inspection, γ such as ¹³⁷ Cs or ⁶⁰ Co is used as a radiation source.
X-ray emitting radioisotopes are used, and projections and cross-sections have been obtained in the same manner as X-ray radiography and X-ray CT.

[0003] In these methods, if the human body, a substance of the same size as the human body, or a metal of about several cm or less,
There is an advantage that the projection and the slice can be examined.

[0004]

However, devices such as X-ray radiography and CT usually require several tens of keV
Since X-rays with relatively low energy of about 10 keV are used, there is a problem that it is difficult to inspect an object larger than a human body or a substance composed of an element having a higher atomic number.

[0005] In industrial nondestructive inspection equipment, high energy γ-rays of several hundred keV to several MeV emitted from radioisotopes are used. This γ-ray has a higher penetrating power than X-rays, and transmits several percent of metal or concrete with a thickness of about several cm or less, so it is possible to project materials covered with thin metal or thin concrete or metal inside. By obtaining an image, its internal defects can be examined. However, γ
Since the radiation source emits radiation in all directions, a very high-intensity radiation source must be used to irradiate the target non-inspected body with gamma rays of sufficient intensity. For this reason, there has been a problem that an accident has occurred in which the worker is exposed to the bomb, and it is dangerous to perform the work.

Another problem is that it cannot be used for inspection of metal or concrete having a thickness exceeding several cm in the energy range of a normal γ-ray source.

[0007]

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention utilizes a laser inverse Compton photon to take advantage of the high directivity, quasi-monochromaticity, energy variability, and the like of the photons. I decided to use it.

Further, in the present invention, ordinary radiography and CT techniques and apparatuses can be used as a measurement system. Like a laser inverse Compton photon, γ of several MeV or more
The advantage of performing CT with X-rays is that the interaction with almost all substances is electron pair generation. The photoelectric effect is proportional to the 4th to 5th power of the atomic number, the Compton effect is proportional to the atomic number, and the electron pair generation is proportional to about 1/2 power of the atomic number. Therefore, above a few MeV, there is almost no contribution of scattering due to the photoelectric effect, and the result obtained by the transmission type CT reflects the atomic density of the substance. Further, since the cross-sectional area of the reaction is smaller than that of the photoelectric effect, even a thick object can be easily transmitted. For example, when inspecting a 10 cm thick iron, using 100 keV X-ray, 1 MeV Co-60 gamma ray, and 10 MeV laser Compton light, the same image quality can be obtained by the first approximation. Assuming that X-ray is 1 second, Co-6
It is 100 ns at 0 and 2 ns at 10 MeV laser Compton light. It is about 1/50 as compared with Co-60, and it is possible to perform measurement in an extremely short time even in CT in which several irradiations are performed from multiple directions.

[0009] Laser Compton light has a high directivity comparable to that of emitted light. The divergence angle is about 1 mrad. With current equipment, a beam several centimeters in diameter can be used at 14 m from the photon source. Although it is a substantially parallel beam, it has a high energy and a high directivity, so it is a source that is not suitable for imaging. Actually, imaging and transfer using synchrotron radiation have achieved remarkable results. Since the laser Compton light has excellent directivity, the dose other than the irradiated part is zero, and the large dose
This is a safe radiation source with extremely low possibility of exposure accidents that occur during nondestructive inspection using RI.

[0010] Further, all RI sources of 8 MeV or more generate neutrons. Therefore, when a semiconductor is used for the detector part of CT, radiation damage is remarkable. On the other hand, laser Compton light is an extremely clean radiation source that does not generate any neutrons from the radiation source itself, so that damage to the detector is extremely small. In addition, since neutrons generate secondary gamma rays from surrounding structural materials, it is necessary to largely shield non-inspection objects and detectors, but laser Compton light requires almost no shielding.

As described above, according to the present invention, the use of the energy-variable quasi-monochromatic photon generator makes it possible to set the energy of X-rays or γ-rays to a desired value in a quasi-monochromatic and to form a narrow beam. Even with a large non-inspection object, an image of the inside of the inspection object can be obtained with high resolution with a small dose as a whole.

[0012]

FIG. 1 is a schematic diagram of a first embodiment of the present invention. The photon generator 1 includes an electron accelerator 2 and a laser 3, and generates an energy-variable photon by laser inverse Compton scattering. This photon flux, at its center,
It has the highest energy and a low distribution at the periphery.
Therefore, this photon flux passes through the collimator 4 and has a diameter of several meters.
By narrowing down to m, a quasi-monochromatic and pencil beam can be obtained. The quasi-monochromatic photon 5 is transferred to the YZ-θ moving stage 6
A non-destructive inspection of the inside is performed by irradiating the inspection object 7 placed on the substrate and measuring the intensity of transmitted light with the photon detector 8 and the photon intensity monitor 9. A projection view or a sectional view can be obtained by sequentially moving the object to be inspected.

FIG. 2 is a schematic diagram of a second embodiment of the present invention. The photon generator 1 includes an electron accelerator 2 and a laser 3, and generates an energy-variable photon 5 by laser inverse Compton scattering. YZ- without collimating this
A non-destructive inspection is performed by irradiating the inspection object 7 placed on the θ moving stage 6 and measuring the intensity of transmitted light with a plurality of photon detectors 8 and photon intensity monitors 9. This method
This method is effective only when the mass attenuation coefficient of the non-test object does not depend much on the energy, but is a method capable of obtaining a high-resolution image in a very short time. The area to be irradiated is several cm.

[0014]

As described above, by using the present method and apparatus, a perspective view or a cross section inside a thick test object, which was impossible with conventional X-ray and γ-ray radiography or CT, was obtained. Figures can be obtained with high resolution.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of a gamma ray CT and a nondestructive inspection apparatus according to a first embodiment.

FIG. 2 is an overall schematic diagram of a gamma ray CT and a nondestructive inspection apparatus according to a second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photon generator 2 electron accelerator 3 laser 4 collimator 5 quasi-monochromatic photon 6 YZ-θ moving stage 7 object 8 photon detector 9 photon intensity monitor

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2G001 AA01 AA02 BA11 CA01 CA02 JA07 KA03 KA20 NA16 PA11 PA12 PA02

Claims (5)

[Claims] 1. A non-destructive inspection method for irradiating a test object with photons generated by inverse Compton scattering and detecting transmitted light to obtain information on the composition and density distribution of a substance inside the test object. 2. A quasi-monochromatic photon is extracted from photons generated by inverse Compton scattering, and the quasi-monochromatic photon is irradiated on the object to be inspected, and the transmitted light is detected, whereby the composition and density of the substance inside the object to be inspected are detected. Non-destructive inspection method to obtain information about distribution. 3. A nondestructive inspection device comprising: an inverse Compton scattered light generator, a device for irradiating the object to be inspected with the quasi-monochromatic photons, and a photon detector. 4. An inverse Compton scattered light generator, a device for extracting quasi-monochromatic photons from scattered light generated in the device,
A non-destructive inspection device comprising: a device for irradiating the inspection object with the quasi-monochromatic photons; and a photon detector. 5. The nondestructive inspection device according to claim 4, wherein the device for extracting quasi-monochromatic photons is a collimator.