JP3548478B2 - Elemental analyzer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus that irradiates a sample with an ion beam emitted from an accelerator, detects X-rays generated from the sample by an X-ray detector, and performs elemental analysis of the sample based on its spectrum.
[0002]
[Prior art]
BACKGROUND ART Conventionally, an elemental analysis method called Particle Induced X-ray Emission (Particle Induced X-ray Emission) has been known. In this method, an X-ray (characteristic X-ray) having energy peculiar to an element contained in a sample is generated by irradiating a sample with an ion beam such as protons, alpha particles, and heavy ions in a vacuum chamber, In this method, the characteristic X-ray is measured with an X-ray detector, and the element in the sample is analyzed from the X-ray spectrum.
In this method, when a sample is irradiated with an ion beam, continuous X-rays and scattered protons are generated from the sample in addition to characteristic X-rays. Further, the protons transmitted through the sample collide with the inner wall surface of the vacuum chamber facing the traveling direction and generate γ-rays. Scattered protons and scattered gamma rays enter the X-ray detector and become noise with respect to the characteristic X-ray spectrum, hindering accurate analysis. If a specific element is present in a large amount in the sample, a large amount of the corresponding characteristic X-ray is generated and enters the X-ray detector. If this exceeds the detectability of the X-ray detector, the analysis is similarly inhibited.
Therefore, conventionally, the direction and the opening area of the opening of the sleeve for receiving the X-ray of the X-ray detector are adjusted, the lead plate is wound around the tip of the sleeve, and the adjustment is performed by repeating the trial each time. The generation of noise is prevented. In the analysis of light elements, the adjustment is different from that in the analysis of heavy elements because the energy of characteristic X-rays generated is low. Therefore, the above adjustment is changed each time depending on whether the element contained in the sample is a light element or a heavy element.
[0003]
[Problems to be solved by the invention]
The above-described conventional method for preventing noise of an X-ray detector requires skill, cannot be performed uniformly and easily by anyone, and requires time and labor for adjustment. In addition, there is a problem that the vacuum for the chamber must be released each time the adjustment for preventing noise must be performed in accordance with the type of the element contained in the sample.
Therefore, the present invention prevents the scattering protons, γ-rays, and excessive characteristic X-rays that interfere with the analysis from entering the X-ray detector, and makes it possible to easily perform accurate analysis by preventing the entry. It is an object of the present invention to provide an easy-to-use element analyzer that can be applied to both heavy elements and light elements without changing the adjustment.
[0004]
[Means for Solving the Problems]
In the present invention, a heavy element X-ray detector 4 and a light element X-ray detector 5 are provided in a vacuum chamber. At the tip of the first sleeve 4a for introducing X-rays of the X-ray detector for heavy elements, an absorber 6 for shielding γ-rays and restricting the amount of X-rays is attached, and X-rays for light elements are provided. At the tip of the second sleeve 5a for introducing X-rays of the detector 5, in addition to the absorber 6, a scattered proton remover 10 for preventing the scattered protons from entering is mounted. The absorber 6 is attached so as to cover a gamma ray shielding cylinder 7 having a lead coating cylinder 7b attached so as to cover the tip part of the first sleeve 4a, and to close an open part at the tip of the gamma ray shielding cylinder 7. And a collimator 8 made of stainless steel. The amount of X-rays entering the first sleeve 4a is adjusted by the central opening 8c of the collimator 8. The scattered proton remover 10 is provided with a main body 11 for preventing the scattered protons from entering the X-ray detector 5 by a magnetic field, and a fitting cylinder 12 to be mounted on the tip of the absorber 6. The main body 11 includes two permanent magnet plates 14 arranged with their magnetic poles facing each other so as to generate substantially parallel magnetic flux therebetween. Is provided with a passage 16 that leads to The periphery of the passage 16 is surrounded by a covering wall made of synthetic resin, and a magnetic field is formed inside. Both ends of the passage 16 are opened, and the outer periphery of the permanent magnet plate 14 is covered with a yoke 15 made of iron. Since the permanent magnet plate 14 is covered with the yoke 15 all around and has very little magnetic flux leaking, there is no adverse effect on the semiconductor for detection of the X-ray detector 5, for example.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of a vacuum chamber in an element analyzer according to the present invention, and FIG. 2 is a cross-sectional view of an X-ray detector absorber according to the present invention.
[0006]
In FIG. 1, an ion beam introducing tube 2, a target frame 3, an X-ray detector 4 for heavy elements, and an X-ray detector 5 for light elements are provided in a vacuum chamber 1. The beam introduction tube 2 is connected to an accelerator (not shown), and guides the ion beam into the vacuum chamber 1 via a beam collimator. A target frame 3 is provided so as to face the tip of the beam introducing tube 2. The target frame 3 holds a plurality of samples S and is movable by remote control. By moving the target frame 3, the sample S to be irradiated with the ion beam can be changed arbitrarily.
[0007]
As shown in FIGS. 1 and 2, the heavy element X-ray detector 4 has an X-ray introduction sleeve 4 a, and its open end is arranged to face a predetermined sample S on the target frame 3. ing. An absorber 6 for preventing or restricting scattered protons, γ-rays, excessive characteristic X-rays, and the like that prevent elemental analysis from entering the X-ray detector is provided at the tip of the sleeve 4a. Is attached.
[0008]
As shown in FIG. 2, the absorber 6 covers the outer periphery of the distal end of the sleeve 4a, a γ-ray shielding cylinder 7, a collimator 8 attached to the distal end of the γ-ray shielding cylinder 7, and closes an opening of the collimator 8. X-ray absorbing plate 9 mounted on collimator 8 as described above.
[0009]
The γ-ray shielding cylinder 7 is formed by covering the outer periphery of a substantially cylindrical aluminum core 7a with a lead coating cylinder 7b, and is detachable from the sleeve 4a.
[0010]
A collimator 8 is attached to the tip of the γ-ray shielding cylinder 7 so as to close the opening. The collimator 8 is made of stainless steel, and includes a fitting portion 8a detachably fitted to an open portion of the cylinder 7, and a flange portion 8b abutting on a distal end surface of the cylinder 7, and an opening 8c having a predetermined diameter in the center. Is formed. The opening 8c regulates the amount of X-rays entering the sleeve 4a depending on the size of the diameter. It is convenient to prepare several types of openings 8c having different diameters so that they can be replaced as appropriate according to the amount of characteristic X-rays generated.
[0011]
The X-ray absorption plate 9 is attached to the outer surface of the collimator 8 so as to close the opening 8c of the collimator 8. The X-ray absorbing plate 9 is a thin plate made of a synthetic resin such as polycarbonate, which can adjust the amount of transmitted X-rays and prevent the entry of useless gamma rays and scattered protons. For example, the X-ray absorbing plate 9 made of polycarbonate absorbs characteristic X-rays of a light element equal to or less than the Al element at a thickness of 300 μm and absorbs characteristic X-rays of a light element equal to or less than the K element at a thickness of 500 μm. Absorbs characteristic X-rays of light elements equal to or less than Se element at 1000 μm. Therefore, it is convenient to prepare a plurality of types of collimators 8 to which the X-ray absorbing plates 9 having different thicknesses are attached, and to appropriately replace the collimators 8 according to the elements contained in the sample S.
[0012]
When the sample S is irradiated with an ion beam through the beam introducing tube 2, continuous X-rays, characteristic X-rays, and scattered protons are generated from the sample S, and the protons transmitted through the sample S are in the chamber 1 where the protons are opposed in the traveling direction. It collides with the inner wall and generates gamma rays. The scattered γ-rays are prevented from entering the X-ray detector 4 by the γ-ray shielding cylinder 7. The collimator 8 adjusts the amount of X-rays incident on the X-ray detector 4 to limit the amount of X-rays so as not to exceed the detectability. Further, the small-diameter opening 8c prevents entry of γ-rays and scattered protons. . When the X-ray absorbing plate 9 is mounted, the X-ray is absorbed by the X-ray detector 4 by absorbing a certain range of X-rays, and the entry of γ-rays is more reliably prevented. Can be.
[0013]
In FIGS. 1 and 3, the light element X-ray detector 5 is arranged such that the open end of the X-ray introduction sleeve 5 a faces a predetermined sample on the target frame 3 and the light element X-ray detector 4 It is arranged at an angle different from that of the sleeve 4a. The scattering proton remover 10 is attached to the tip of the sleeve 5a.
[0014]
The scattered proton remover 10 is for preventing the scattered protons that hinder the analysis of light elements from entering the X-ray detector 5, and as shown in FIG. It is mounted on the sleeve 5 a so as to overlap the absorber 6. The scattering proton remover 10 includes a main body 11 and a fitting tube 12. The fitting cylinder 12 is made of aluminum and fits around the γ-ray shielding cylinder 7 of the absorber 6.
[0015]
As shown in FIGS. 5 to 7, the main body 11 of the scattered proton remover 10 has two strong permanent magnet plates 14 disposed opposite each other with a synthetic resin spacer 13 interposed therebetween, and surrounds the periphery thereof. The cover is made up of a soft iron yoke 15. The spacer 13 keeps a space between the pair of permanent magnet plates 14, forms an X-ray passage 16 therebetween, and constitutes a covering wall for covering the passage 6 so that the permanent magnet plate 14 is not directly exposed. And a pair of first spacers 13a and second spacers 13b. The first spacer 13a is for maintaining a gap between the pair of permanent magnet plates 14 and forming a gap. A pair of the first spacers 13a are arranged with a gap therebetween, and a passage 16 is formed in the gap between the two. A substantially parallel magnetic field is formed in the passage 16. The second spacer 13b is disposed so as to cover opposing surfaces of the pair of permanent magnet plates 14.
[0016]
The yoke 15 is for suppressing the leakage magnetic field to the periphery of the permanent magnet plate 14, and is composed of six rectangular iron plates 15 a to 15 f, that is, up, down, left, right and front, and covers the entire circumference of the permanent magnet plate 14. Openings 15g, 15h are formed in the center of the front and rear iron plates 15a, 15b at positions corresponding to the passages 16. With this yoke 15, the leakage magnetic field near the surface can be suppressed to several gauss. In addition, a synthetic resin plate 17 for preventing generation of γ-rays due to collision of scattered protons is attached to the front surface of the front iron plate 15e. The synthetic resin plate 17 has an opening 17a corresponding to the opening 15g.
[0017]
In the analysis of light elements, when the absorber 6 equipped with the X-ray absorption plate 9 is used to absorb scattered protons, the energy of characteristic X-rays generated from the light element is low. 9 will be absorbed. The scattered proton remover 10 does not impede the entry of low-energy characteristic X-rays, but only blocks the entry of scattered protons. That is, the scattered protons having entered the passage 16 are deflected by the magnetic field generated by the permanent magnet plate 14 and do not reach the X-ray detector 5. The permanent magnet plate 14 is covered by the yoke 15 all around and has very little magnetic flux leaking, so that there is no adverse effect on the semiconductor for detection of the X-ray detector 5, for example.
[0018]
【The invention's effect】
As described above, in the present invention, accurate analysis is performed by preventing the scattered protons, γ-rays, and excess characteristic X-rays from entering the X-ray detector so as not to enter the X-ray detector. It is possible to provide an easy-to-use element analyzer that can be easily performed and can be widely applied to heavy elements and light elements without changing the adjustment.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic configuration of a vacuum chamber in an element analyzer according to the present invention.
FIG. 2 is a sectional view of an X-ray detector absorber according to the present invention.
FIG. 3 is a partially cutaway front view of a scattered proton remover for an X-ray detector according to the present invention.
FIG. 4 is a side view of a scattered proton remover for an X-ray detector according to the present invention.
FIG. 5 is a sectional view taken along line VV in FIG. 3;
FIG. 6 is a sectional view taken along line VI-VI in FIG. 4;
FIG. 7 is a sectional view taken along line VII-VII in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Beam introduction tube 3 Target frame 4 X-ray detector for heavy elements 4a X-ray introduction sleeve 5 X-ray detector for light elements 5a X-ray introduction sleeve 6 Absorber 7 γ-ray shielding cylinder 7a Core 7b Coating cylinder 8 Collimator 8a fitting portion 8b flange portion 8c opening 9 X-ray absorbing plate 10 scattering proton remover 11 main body 12 fitting tube 13 spacer 13a first spacer 13b second spacer 14 permanent magnet 15 yokes 15a to 15f iron plate 15g opening 15h opening 16 passage 17 Opening of synthetic resin plate 17a

Claims (3)

An apparatus that irradiates a sample in a vacuum chamber with an ion beam emitted from an accelerator, detects X-rays generated from the sample with an X-ray detector, and performs elemental analysis based on an X-ray spectrum,
The X-ray detector includes a heavy element X-ray detector and a light element X-ray detector,
The heavy element X-ray detector has a first sleeve for introducing X-rays arranged in the vacuum chamber so that the tip is open,
At the tip of the first sleeve, an absorber for shielding γ-rays and restricting the amount of X-rays is attached,
The absorber is a gamma ray shielding cylinder having a lead coating cylinder attached so as to cover the distal end of the first sleeve,
A metal collimator mounted to close the opening at the end of the γ-ray shielding cylinder, having an opening with a predetermined diameter in the center, and adjusting the amount of X-rays entering the first sleeve. Equipped,
The light element X-ray detector has a second sleeve for introducing X-rays arranged in the vacuum chamber so that the tip is open,
At the tip of the second sleeve, in addition to the absorber, a scattered proton remover for preventing the entry of scattered protons is mounted,
The scattered proton remover includes a main body that blocks the entry of scattered protons into the light element X-ray detector by a magnetic field, and a fitting cylinder for mounting the tip of the absorber.
The main body includes two permanent magnet plates arranged with their magnetic poles facing each other so that a substantially parallel magnetic flux is generated therebetween, and penetrates between the two permanent magnet plates and passes through the fitting cylinder to surround the periphery. It is characterized by comprising a passage surrounded by a synthetic resin covering wall and through which the magnetic flux can pass, and an iron yoke that opens both ends of the passage and covers the outer periphery of the permanent magnet plate. Elemental analyzer. An X-ray absorbing plate made of a synthetic resin is mounted on the collimator so as to close the opening of the collimator in the absorber attached to the first sleeve, and an amount of X-rays entering the first sleeve is adjusted, 2. The elemental analyzer according to claim 1, wherein the entry of useless gamma rays and scattered protons is prevented. 3. The gamma ray shielding cylinder in the absorber mounted on the first sleeve, wherein the outer periphery of a substantially cylindrical aluminum core is covered with a lead coating cylinder. Elemental analyzer.

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