JP3822032B2 - Defect evaluation equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to defect evaluation equipment. Further More specifically, the present invention, the time of disappearance positron of equipment for evaluating detect defects such as lattice defects or minute voids in the phenomenon DUT utilizing positron annihilation causing γ rays Regarding improvement.
[0002]
[Prior art]
In the bulk material, defects that cannot be detected from the outside, such as lattice defects and minute voids (cavities generated in the crystal), may occur. To detect such internal defects, positron annihilation Some use the phenomenon. As shown in FIG. 2, positrons (positrons) are injected into the object to be measured 101 to cause pair annihilation with the electrons therein, and the physical properties of the bulk material using the γ rays generated at that time as a clue. Or, it is intended to search for chemical properties, and utilizes the annihilation characteristics of positrons that recombine with electrons in the defective portion when they reach the defect 102 and disappear.
[0003]
Conventionally, when the defect 102 such as a crack, a pot or a void inside the object to be measured 101 is detected by using the positron as described above and the material is evaluated, the positron is made from a positron source using a radioisotope or an electron beam accelerator. It is common to irradiate toward.
[0004]
[Problems to be solved by the invention]
However, in general, the transmission characteristics of a positron metal material or the like are not high, and the penetration depth is on the order of several hundreds of microns, and data of a depth greater than that cannot be obtained. This penetration depth may be as low as about 0.3 mm. For this reason, as described above, the material evaluation using the positron presents a problem that sufficient defect evaluation cannot be obtained at a deeper position, and detailed information can be obtained about the surface of the bulk material. Detailed information was not available.
[0005]
In addition, when an electron beam accelerator is used, there is a problem that the apparatus becomes too large.
[0006]
The present invention has an object to provide a defect evaluation equipment that can be the status of internal defects a deeper position from the surface to effectively detect the evaluation of bulk materials such as the measured object.
[0007]
[Means for Solving the Problems]
In order to achieve such an object, the inventors of the present application are the detection and evaluation of defects using the positron annihilation phenomenon, in which the positron does not disappear at a conventional penetration depth, in other words, at a position deeper than the conventional positron. We have been studying technology that can eliminate the problem and have come to know such technology.
[0008]
The invention according to claim 1 is based on such knowledge, and a defect evaluation apparatus for detecting and evaluating defects such as lattice defects in a measured object using positron annihilation in which a positron at the time of annihilation generates characteristic γ rays. in a laser device for generating a pulsed laser having a pulse width of Sa Bupiko second order, and the condensing optical element for condensing the pulse laser to the condensing intensity 10 19 ^{W /} cm ^2, by Rukoto pulse laser is irradiated inside and a γ-ray detector for measuring the characteristic γ-rays emitted from the measurement object to produce positrons during positron annihilation by X-ray of Resona to generate X-rays, the generation timing of the characteristic γ-rays or it is intended to detect more defect evaluation in the energy spectrum.
[0009]
The present invention does not irradiate the positron directly, but generates a substance inside the object to be measured using an electromagnetic wave having a substance permeability, regardless of the depth from the surface of the defect inside the object to be measured. This makes it possible to eliminate the positron in the defective portion.
[0010]
Here, for example, X-rays (including γ-rays) with a high material permeability are usually irradiated with energy of about several tens of keV, and therefore only reach about 50 microns from the surface. Since a positron could not be created because the threshold value was less than 1.022 MeV (about 1.637 × 10 ⁻¹³ J), the present invention has a very high energy beam of the MeV class, for example, a laser of the order of subpicoseconds. To generate high-energy electrons of about picoseconds, and then generate high-energy X-ray pulses with a pulse width of about picoseconds by bremsstrahlung. A positron is generated in the measurement object by irradiating the measurement object. Then, the state of the defect is grasped based on the irradiation timing of γ-rays emitted when the positron disappears, the timing of catching, or the energy spectrum. At this time, the X-ray transmission characteristics are much better than those of positrons, so measurement in a large area of about several centimeters is possible, and it is possible to reach a depth about 100 times that when irradiating positrons. In addition, it is possible to effectively detect and evaluate internal defects in bulk materials such as structural materials.
[0011]
In addition, since high-energy X-rays (including γ-rays) can be generated by using a short pulse laser, it is not necessary to accelerate electrons using an electron beam accelerator or the like. . For this reason, the problem that the apparatus becomes too large can be solved.
Here, instead of irradiating the object to be measured with X-rays, a pulse laser is directly irradiated. In this case, since the pulse laser generates X-rays inside the object to be measured, a positron can be generated inside the object to be measured by the X-rays. Therefore, the state of the defect can be grasped from the irradiation timing, catching timing, or energy spectrum of the γ-rays emitted when the positron disappears.
[0016]
The invention described in claim 2 is the defect evaluation apparatus according to claim 1 , further comprising a PIN diode and a timer together with a γ-ray detector, and measuring characteristic γ-rays emitted when the positron disappears using a pulse laser as a trigger. Is to start. According to this, the timing of positron disappearance can be measured with higher accuracy.
[0019]
Further, even when the object to be measured is directly irradiated with a pulse laser, X-rays can be generated inside the object to be measured, and therefore, internal defects can be detected and evaluated in the same manner as when X-rays are irradiated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.
[0021]
FIG. 1 shows an embodiment of the present invention. The defect evaluation apparatus 1 for detecting and evaluating the lattice defect 3 in the object to be measured 2 is a laser apparatus (not shown) that can generate laser light having a wavelength in the subpicosecond order, and a condensing optical element 4 that condenses the laser light. , A laser target 5 to be irradiated with a laser, a γ-ray converter 6, a γ-ray detector 7, a noise shielding plate 8, a PIN diode 9, a timer 10, and an analyzer 11.
[0022]
The condensing optical element 4 condenses the laser light emitted from the laser device into a spot of about 10 microns and irradiates the laser target 5 at one point. The laser target 5 is suitably a plastic or metal solid or a supersonic gas jet ejected from a nozzle.
[0023]
Here, the laser beam applied to the laser target 5 is preferably a high-energy laser beam having a pulse width on the order of sub-picoseconds. Such high-energy laser light has a low-intensity precursor pulse component (pre-pulse), and thereby the laser target 5 is turned into plasma. For example, laser light such as infrared light can be used as the laser light.
[0024]
When this pulsed laser target 5 is irradiated with a pulse main body, electrons are accelerated by a mechanism of (1) Bondiamotive force, (2) Resonance absorption, (3) Barnell heating, or Wakefield acceleration. At this time, when the light collecting intensity is, for example, about 10 ¹⁹ W / cm ^2, it becomes possible to generate high-energy electrons that reach several MeV (megaelectron volts).
[0025]
These electrons are irradiated to a target γ-ray converter 6 made of a substance having a high atomic number, such as tungsten or lead, and charged particles (electrons) receive the Coulomb force of the nuclei in the γ-ray converter 6, so that bremsstrahlung ( High energy gamma rays are generated by bremsstrahlung). The gamma rays generated here are effective when they are 1 MeV (about 1.6022 × 10 ⁻¹³ J) or more.
[0026]
This γ-ray is irradiated to the object to be measured 2 (here, assumed to be a metal or the like), passes through, and generates an electron pair through a process of γ-ray attenuation inside. In other words, after propagating a distance of about several centimeters and reaching the inside of the DUT 2, an electron (electron) and positron pair is generated.
[0027]
Thus, the positron generated inside the DUT 2 loses its energy within about 1 picosecond and is supplemented by the lattice defect 3. Thereafter, they recombine with electrons again in a time depending on the size of the defect, and two characteristic γ rays having an energy of about 511 keV (about 8.187 × 10 ⁻¹⁴ J) are emitted by positron annihilation. The characteristic γ-ray is detected by the γ-ray detector 7, the time from the time of laser irradiation is measured, and the γ-ray transmission time is subtracted from the value to obtain the positron extinction time. Note that the noise shielding plate 8 installed on the side of the γ-ray detector 7 blocks the influence of γ-rays before the object 2 is irradiated.
[0028]
Here, as shown in FIG. 1, X-rays generated by laser plasma in addition to electron beams are generated from the laser target 5 irradiated with the laser light. Therefore, in this embodiment, a PIN diode 9 and a timer 10 are provided together with the γ-ray detector 7, and this X-ray is used as a trigger for measuring the laser irradiation timing. In this case, it is possible to improve the accuracy as compared with the case where the laser beam is directly condensed and used as a trigger.
[0029]
As described above, the timing (specifically, the lifetime of the positron) is measured with the irradiation and the characteristic γ-ray, and the energy distribution of the characteristic γ-ray is obtained using the analyzer 11 and a microchannel analyzer (not shown). The defect density and size of the lattice defect 3 can be estimated from the timing and the state of the energy spectrum, and the inside of the DUT 2 can be detected and evaluated.
[0030]
Here, in the present embodiment, γ rays are transmitted and a positron is generated inside the DUT 2, so that a penetration depth of the order of mm (millimeter) or even cm (centimeter) can be obtained. it can. For this reason, even when the lattice defect 3 is located deep from the surface, it can be detected and sufficient defect evaluation can be obtained, so that detailed information is obtained not only in the vicinity of the surface of the bulk material but overall.
[0031]
Moreover, in the present embodiment, high-energy γ-rays are generated only by irradiating a short pulse laser, so that high-intensity γ-rays can be obtained without accelerating electrons using an electron beam accelerator or the like. Easy to do. The problem that the defect evaluation apparatus 1 becomes too large can be solved.
[0032]
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the present embodiment, the case where the lattice defect 3 of the object to be measured 2 is detected has been described. However, the lattice defect 3 is only one aspect of the internal defect of the object to be measured 2, and the defect evaluation apparatus 1 of the present invention is used. For example, positron annihilation can be used to detect various defects inside the bulk material such as cracks and pots.
[0033]
In the present embodiment, the object to be measured 2 is irradiated with γ rays, but the irradiation is not particularly limited to γ rays. In general, X-rays have lower energy, but it is sufficient to have energy necessary for electron pair generation (for example, 1 MeV (about 1.6022 × 10 ⁻¹³ J) or more). There is no such thing as strictly distinguishing.
[0034]
Even more, in the present embodiment generates a pulse X-rays by using a pulsed laser of high energy, but something that generates the internal depot Jitoro down of the object 2, the defect detection according to the present invention utilizing a pulsed laser Not limited to. For example, in the case of using an electron beam accelerator, it is possible to generate a high energy internal depots Jitoro down likewise in the object 2 and the present embodiment as long as it can be irradiated with X-rays.
[0035]
In this embodiment, the laser target 5 is irradiated with a pulse laser, and γ rays (or X-rays) generated thereby are irradiated onto the object 2 to be measured. However, the pulse laser is directly applied without passing through the laser target 5. It is also possible to irradiate the object 2 to be measured. In such a case, the pulse laser so generating X-rays within the object to be measured 2, it is possible to generate the internal depot Jitoro down of the object 2 by the X-ray. Therefore, the irradiation timing of γ-rays emitted when positron disappears, the timing of catching, or the state of defects is grasped by the energy spectrum, and the inside of a bulk material such as a structural material as in the case of γ-ray (X-ray) irradiation Effective detection and evaluation of defects becomes possible.
[0036]
【Example】
When the DUT 2 is actually Fe57Cr16Ni17, the time waveform of the characteristic X-ray detected when the recombination time of the positron is excluded will be examined. The γ-ray detector 7 has a diameter of 3 inches, ignores its thickness, and is installed at a position 5 cm from the γ-ray irradiation position. The detection efficiency for incident γ rays is 100%. The width of the pulse distorted from the γ-ray transmission time at this time is about 200 picoseconds, which is a level at which the influence can be removed by a method such as deconvolution. Further, if the detection efficiency of characteristic γ rays in the depth direction is examined, it can be seen that measurement up to a depth of about 5 cm is possible. The detection efficiency of characteristic X-rays per γ-ray photon is about 0.0004 at the maximum of 5 MeV (about 8.011 × 10 ⁻¹³ J) γ-rays. If approximately 10 photons are generated as the amount of γ rays generated per laser irradiation, almost one characteristic X-ray can be detected per laser irradiation. If the laser repetition rate becomes 1 kHz in the future, 1,000,000 characteristic X-rays can be observed in 20 minutes.
[0037]
【The invention's effect】
As apparent from the above description, according to the defect evaluation apparatus according to claim 1, in order that easy to produce Po Jitoro emissions (Po Jitoronbimu) from there with a pulse X-ray picosecond level, a material deep Positron annihilation measurement can be performed, which enables effective measurement and detection of lattice defects and microvoids deep inside the bulk material and evaluation of deterioration due to this, which was impossible in the past.
[0038]
In addition, since high-energy X-rays (including γ-rays) can be generated by using a short pulse laser, it is not necessary to accelerate electrons using an electron beam accelerator or the like. For this reason, the problem that the apparatus becomes too large can be solved.
Furthermore, according to the defect evaluation apparatus of the first aspect, X-rays can be generated in the object to be measured by irradiating the object to be measured with a pulse laser, and a positron can be generated by the X-ray. Therefore, positron annihilation measurement at the deep part of the material becomes possible.
[0041]
Further, according to the defect evaluation apparatus according to claim 2, by starting the measurement of positron annihilation PROPERTIES γ ray laser over as a trigger, it becomes possible to measure the timing more accurately positron annihilation.
[Brief description of the drawings]
FIG. 1 is a schematic view of a defect evaluation apparatus showing an embodiment of the present invention.
FIG. 2 is a schematic view showing a state of positron annihilation in conventional defect evaluation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Defect evaluation apparatus 2 Measured object 3 Lattice defect (defect)
5 Laser target

Claims (2)

In the defect evaluation apparatus for defect detecting the assessment of such lattice defects in positron is the object to be measured by using positron annihilation to generate a characteristic γ-rays at the time of extinction, the pulse laser having a pulse width of Sa Bupiko second order a laser device for generating, X-rays of the converging optical element for condensing the pulse laser to the condensing intensity 10 19 ^{W /} cm ^2, Resona to generate X-rays within the Rukoto said pulse laser is irradiated from the measurement object to produce a positron and a γ-ray detector for measuring the characteristic γ-rays emitted when the positron annihilation to detect more defect generation timing or energy spectrum of the characteristic γ-rays evaluated by A defect evaluation apparatus characterized by: The defect evaluation apparatus according to claim 1 , further comprising a PIN diode and a timer together with the γ-ray detector, and starting measurement of characteristic γ-rays emitted when the positron is extinguished using the pulse laser as a trigger. .

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