HK1101049B - X-ray generating method and x-ray generating apparatus - Google Patents

Description

X-ray generation method and X-ray generation device

Technical Field

The present invention relates to an X-ray generation method and an X-ray generation apparatus for generating X-rays with ultra-high brightness.

Background

In the X-ray diffraction measurement, it is necessary to irradiate X-rays having an intensity as high as possible onto a sample. In this case, a conventional rotating anticathode type X-ray generating device is used for X-ray diffraction measurement.

The X-ray generating device of the rotating anticathode type is configured so as to irradiate an electron beam onto the outer surface of a cylindrical anticathode (target) through which a cooling medium flows while rotating the anticathode at a high speed. The rotating anticathode type X-ray generating device can exhibit extremely high cooling efficiency compared to the fixed target type X-ray generating device because the irradiation position of the electron beam on the anticathode changes with time. Therefore, in the X-ray generating device of the rotating anticathode type, an electron beam can be irradiated onto the anticathode at a high current, thereby generating X-rays of high intensity.

In addition, since the intensity of the generated synthetic X-ray is proportional to the electric power (the product of current and voltage) applied between the cathode and the counter-cathode, in the conventional rotary counter-cathode type X-ray generating apparatus, when the electron beam is irradiated onto the target with a spot size of 0.1 × 1mm, the intensity of the X-ray can be increased only to a maximum of 1.2kW, while in the ultra-high brightness rotary counter-cathode type X-ray generating apparatus, the intensity of the X-ray can be increased only to a maximum of 3.5 kW.

In view of this, japanese patent laid-open application No. 11-339704 discloses a technique of heating an anticathode to near its melting point using an electron beam, thus partially melting an electron beam irradiated portion of the anticathode, thereby generating high-intensity X-rays. However, with this technique, in the case of electron beam irradiation, X-rays cannot be stably generated over a long period of time, so it is necessary to improve the performance of the conventional X-ray generation device.

[ patent document No. 1] Japanese patent laid-open application No. 11-339704

Disclosure of Invention

An object of the present invention is to provide an X-ray generation method and an X-ray generation apparatus capable of stably generating X-rays of high intensity over a long period of time.

To achieve this object, the invention relates to a method for generating X-rays, comprising the steps of: repeatedly moving the anticathode along a rotation axis of the anticathode while rotating the anticathode around the rotation axis; and irradiating an energy beam onto a surface portion of the anticathode at a position resisting a centrifugal force generated by rotation of the anticathode, thereby partially melting the surface portion by heating the surface portion to near or above a melting point of the anticathode, thereby generating the X-ray exiting the rotating anticathode.

Meanwhile, the present invention relates to an apparatus for generating X-rays, the apparatus comprising: rotating the anticathode, the rotating anticathode being configured so as to rotate about its axis of rotation and to move repeatedly along the axis of rotation; and an energy source for irradiating an energy beam to a surface portion of the anticathode located opposite to a centrifugal force generated by rotation of the anticathode, thereby partially melting the surface portion by heating the surface portion to near or above a melting point of the anticathode, thereby generating X-rays exiting the rotating anticathode.

The inventors earnestly studied the reason why the intended high-intensity X-ray cannot be stably generated for a long period of time when the rotating anticathode is heated to near its melting point by the electron beam to partially melt the electron beam irradiated portion of the anticathode as described in japanese patent laid-open application No. 11-339704.

Therefore, the inventors found that when the rotating anticathode is heated to near its melting point by an electron beam to generate X-rays of a desired high intensity, the electron beam irradiated portion is depressed, so that the side wall of the depressed portion of the electron beam irradiated portion absorbs the X-rays generated by the electron beam irradiated portion.

In view of this, the inventors tried to prevent the formation of the concave portion at the electron beam irradiating portion of the rotating anticathode even if an energy beam such as an electron beam of high intensity is irradiated. Therefore, the inventors found that if the rotating anticathode is repeatedly moved along the rotation axis while rotating the rotating anticathode around the rotation axis, even if an energy beam of high intensity is irradiated onto the anticathode, the depth of the depressed portion of the energy beam irradiated portion can be reduced.

Therefore, even if an energy beam of high intensity is irradiated, the side wall hardly absorbs the generated X-rays, so that the intended X-rays of high brightness can be stably generated for a long period of time.

In a preferred embodiment of the invention, the rotating anticathode is moved periodically along the axis of rotation. In this case, the energy beam irradiation portion of the rotating anticathode can be enlarged and the shape of the concave portion formed on the rotating anticathode is trapezoidal, so that the intended high-intensity X-ray can be stably generated for a long period of time.

In another preferred embodiment of the present invention, the length of the movement of the rotating anticathode along the axis of rotation may be determined according to the line width of the energy beam. Specifically, the moving length of the rotating anticathode is preferably longer than the line width of the energy beam. In this case, the depth of the concave portion of the energy beam irradiating portion can be greatly reduced.

In a further preferred embodiment of the invention, the length of the displacement of the rotating anticathode along the axis of rotation is at least twice the line width of the energy beam. In this case, the depth of the concave portion of the energy beam irradiating portion can be greatly reduced, so that the expected reduction value of the intensity of the X-ray is only 5% or less. Therefore, the intended X-ray can be generated with an efficiency of 95% or more over a long period of time.

As described above, according to the present invention, it is possible to provide an X-ray generation method and an X-ray generation apparatus capable of stably generating X-rays of high intensity over a long period of time.

Drawings

For a better understanding of the present invention, reference is made to the accompanying drawings, in which

FIG. 1 is a cross-sectional view illustrating an X-ray generating device according to the present invention;

FIG. 2 is an enlarged cross-sectional view illustrating a portion of the X-ray generating device shown in FIG. 1;

FIG. 3 is a view illustrating a state of an electron beam irradiating portion of the rotating anticathode in which the rotating anticathode is not repeatedly moved along the rotation axis and the rotating anticathode is rotationally moved around the rotation axis; and

fig. 4 is a diagram illustrating a state of an electron beam irradiation portion of the rotating anticathode repeatedly moving along the rotation axis and rotationally moving around the rotation axis.

Detailed Description

The present invention is described in detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view illustrating an X-ray generating device according to the present invention, and FIG. 2 is an enlarged cross-sectional view illustrating a portion of the X-ray generating device shown in FIG. 1.

The X-ray generating device includes a anticathode chamber 2 for housing a rotating anticathode 1, a cathode chamber 4 for housing a cathode 3, and a rotation driving section 6 for housing a driving motor 5, wherein the driving motor 5 is used for rotating the anticathode 1 separated from each other by airtight members 2a, 4a, and 6a adjacent to each other. A small hole 2c is formed in a partition wall 2b separating the cathode chamber 2 and the cathode chamber 4 so that the electron beam 30 emitted from the cathode 3 passes through the partition wall 2 b. In addition, vacuum outlets 2d and 4d are provided in the pair of cathode chambers 2 and 4, and the vacuum outlets 2d and 4d are connected to vacuum pumps (not shown), respectively.

Specifically, the drawing does not illustrate that, in the rotation driving section 6, the driving motor 5 includes a rotation motor that rotates the rotating anticathode around the rotation axis and a vertical movement motor that repeatedly moves the rotating anticathode along the rotation axis. The rotary motor is configured so as to rotate the rotary anticathode 1 at a speed of several thousands to ten thousands times per minute. The vertical movement motor is configured so as to repeatedly move the rotary anticathode 1 in the vertical direction at a speed of 0.01 to 1 times per minute.

The rotating anticathode 1 comprises a cylindrical portion 11 made of copper or the like, a disk 12 for sealing an opening of the cylindrical portion 11, and a rotary shaft 13 which shares a central axis with the cylindrical portion 11 and the disk 12 formed as a single body. The insides of the cylindrical portion 11, the disk 12 and the rotary shaft 13 are arranged with air holes so that cooling water can flow into the insides thereof. An electron beam is irradiated onto the inner wall of the cylindrical portion 11. In this case, there is a composite electron beam irradiation portion that resists the centrifugal force generated by the rotational motion of the anticathode rotated by the motor.

The rotating shaft 13 is rotatably supported by a pair of bearings 13a and 13b located in the rotation driving chamber 6.

At the root of the shaft 13 near the disc 12, a shaft seal 13c is provided, and the inside of the cathode chamber 2 is kept under vacuum by installing the shaft 13 and the airtight member 6a under airtight conditions.

A fixed spacer 15 is inserted in the rotating anticathode 1 so that cooling water flows along the inner wall of the electron beam irradiating portion 11 a. The fixed spacers 15 are formed in a cylindrical shape, enlarged in accordance with the circle 12, and elongated not to exceed the inner wall of the cylindrical portion 11.

In other words, the fixed spacer 15 separates the inner space of the rotating anticathode 1 to form a sleeve structure. The outer tube 14a of the jacket structure communicates with the cooling water inlet 14. Here, a shaft seal 14 is provided on the left cylindrical surface of the rotating shaft 13, so that the cooling water introduced from the inlet 16 is introduced into the outer pipe 14a of the sleeve structure, so as not to leak into the regulation space where the bearings 13a, 13b and the drive motor 5 are installed.

The cooling water introduced from the inlet 16 flows into the outer tube 14a of the jacket structure, returns from the inner wall of the cylindrical portion 11, and flows into the inner tube 14b of the jacket structure. In this case, the cooling water cools the inner wall of the electron beam irradiating portion 11a, and the remaining cooling water flows into the inner tube 14b and is then discharged from the outlet 17.

On the airtight member 2a located in the vicinity of the electron beam irradiating portion 1a of the rotating anticathode 1, there is an X-ray window 21 for taking out the X-ray 20 generated by irradiating the electron beam 30 onto the electron beam irradiating portion 11 a. On the X-ray window is an X-ray transparent film 22 made of a material that is transparent to X-rays, such as beryllium, so that the desired X-rays can be taken out of the device while maintaining the cathode chamber 2 under vacuum.

The cathode 3 includes an insulating structural member 32, a filament 33 and a wenner 34, and is configured to generate and irradiate an electron beam 30 onto the anticathode 1 by applying a high voltage of several tens KV and a filament electric power introduced from the high voltage introducing portion 31.

In the X-ray generating apparatus as described above, the cooling water is introduced from the inlet 16, rotates the rotating anticathode 1 around the rotation shaft at a high speed, and repeatedly moves the rotating anticathode 1 in the rotation shaft direction by the driving motor 5. At the same time, an electron beam 30 from the cathode is irradiated onto the electron beam irradiating portion 11a of the counter cathode 1, thereby generating the X-ray 20 of high intensity. In this case, the intensity of the electron beam 30 is set so as to partially melt the electron beam irradiating portion 11 a. The electron beam irradiating portion 11a becomes a depressed portion due to the irradiation of the electron beam, but the depth of the above depressed portion can be reduced as compared with the depth of the depressed portion which rotates the anticathode without repeatedly moving in the direction of the rotation axis. The reduction in the depth of the depressed portion due to the repeated moving rotation of the counter cathode will be explained below.

FIG. 3 is a view illustrating a state of an electron beam irradiating portion of the rotating anticathode in which the rotating anticathode is not repeatedly moved along the rotation axis and the rotating anticathode is rotationally moved around the rotation axis; fig. 4 is a diagram illustrating a state of an electron beam irradiation portion of the rotating anticathode repeatedly moving along the rotation axis and rotationally moving around the rotation axis.

As shown in fig. 3, when the electron beam is irradiated onto the inner wall 11a, the electron beam irradiated portion becomes a concave portion defined by a bottom surface having a width w and a side surface having a height h. In this case, assuming that the expected extraction angle and emission efficiency of X-rays are α and E, respectively, since the side surface of the concave portion causes partial interference with the X-rays, the depth h of the concave portion can be expressed by the following equation_E：

h_E＝(1-0.01 E)wtanα (1)

Then, the emission efficiency E (%) of X-rays can be represented by the following formula:

100×(1-h_E/wtanα) (2)

here, the emission efficiency E (%) of the X-ray is normalized according to the emission amount of the X-ray when the concave portion is not formed in the electron beam irradiation portion. The emission efficiency E (%) of X-rays can also be represented by the following formula: e-100 (w-x)/w. Since the equation x may also be established as h/tan α (tan α as h/x), equation (1) may be obtained from the above two equations by eliminating x.

On the other hand, if the rotating anticathode 1 is repeatedly moved at a constant speed to have a size of T times the line width w of the electron beam, the electron beam irradiated portion becomes a concave portion having a bottom surface with a width of w × (T-2), slope portions at both ends of the concave portion with a width of w, and sidewalls with a height of h', so that the shape of the concave portion formed is an inverted trapezoid. In this case, since the angle γ of the slope portion is smaller than the extraction angle α, the X-ray generated from the bottom surface of the recess portion by irradiation of the electron beam can be extracted from the recess portion with 100% efficiency.

Assuming that the extraction efficiency of the X-ray at the slope portion is E' (%), the total extraction efficiency of the X-ray at the concave portion can be expressed by the following equation:

[100×{w×(T-2)}+E′×2w]/wT (3)

in fact, as shown in fig. 4, when the moving rotation anticathode 1 is repeatedly moved to a size twice the line width w of the electron beam, even if the depth of the concave portion (electron beam irradiated portion) is increased to about 100 μm when T is 3 and w is 1mm, the emission efficiency of the X-ray can be improved to 95%.

On the other hand, as shown in fig. 3, in the case where the rotating anticathode is not repeatedly moved, in order to achieve 95% emission efficiency when w is 1mm, it is necessary to reduce the depth of the depressed portion (electron beam irradiated portion) to about 10 μm. If the depth of the concave portion is increased, the emission efficiency of X-rays is decreased from 95%.

In this way, in the present embodiment, since the number of times of repeated movement of the rotating anticathode is twice or more the width of the electron beam, even if the depth of the concave portion (electron beam irradiation portion) is enlarged ten times, the intended X-ray can be taken out from the concave portion with 95% efficiency.

In the present embodiment, no special treatment is required for the cylindrical portion 11 of the cathode 1, so the electron beam irradiating portion 11a is located on the inner wall of the cylindrical portion 11, provided that the side wall of the cylindrical portion 11 is parallel to the rotation axis. However, the inner wall of the cylindrical portion 11 may be inclined by one-tenth to several tens of degrees.

Specifically, the inner wall of the cylindrical portion 11 may be inclined inward by several tenths of a degree to several tens of degrees toward the direction of the rotation axis. In this case, the melted electron beam irradiating portion 11a can be more stably located on the inner wall of the cylindrical portion 11 facing the centrifugal force. Therefore, the external sputtering of the electron beam irradiating portion 11 can be more effectively prevented. In contrast, the inner wall of the cylindrical portion 11 may be inclined outward from the rotational axis by a few tenths of an degree to a few tens of degrees. In this case, the intended X-ray is easily taken out from the apparatus, provided that the external sputtering of the melted electron beam irradiating portion 11a can be prevented.

If the electron beam irradiating portion 11a is formed so that its sectional shape is a V-shaped groove or a U-shaped groove, external sputtering of the electron beam irradiating portion 11a can be more effectively prevented. In this case, the width and depth of the V-shaped groove or the U-shaped groove are determined so that the desired X-ray can be easily taken out from the apparatus. Further, since the shape of the electron beam irradiating portion 11a becomes a trapezoid defined by "T" and "w", if the electron beam irradiating portion is processed into a corresponding trapezoid having a mirror effect, the surface deformation of the electron beam irradiating portion 11a due to melting can be suppressed.

In addition, if the electron beam irradiating portion 11a is made of a target material depending on the kind of X-ray to be generated, and the region surrounding the electron beam irradiating portion 11a is made of a material having a higher melting point and/or thermal conductivity than that of the target material, the cooling efficiency for the cathode can be provided overall, and the desired X-ray can be stably generated for a long period of time.

Further, the cylindrical portion 11 to which the anticathode 1, particularly the electron beam 30 is irradiated, is made of a target material, and a high melting point and/or high thermal conductivity material may be used at the rear of the target material, so that the cylindrical portion 11 may be a double structure. In this case, the cylindrical portion 11 is cooled with the cooling medium while generating the intended X-ray by irradiating the electron beam 30 onto the cylindrical portion 11, and the electron beam 30 does not pass through the cylindrical portion 11 due to the synergistic effect of the great heat resistance and the great cooling effect caused by the high melting point and/or high thermal conductivity material used at the rear of the target material. Therefore, the cooling medium does not leak.

Examples of the cooling medium may be cooling water and cooling oil.

In the present embodiment, since the electron beam irradiation portion 11a is melted, melting of the target material in the cathode chamber 2 increases the metal vapor pressure, thereby contaminating the X-ray transmission window 22. In this case, a roll protective film made of Ni, BN, Al or a polyester film for protection against recoil electrons and switchable may be installed in front of the X-ray transmission window 22. A supply roller and a winding roller are arranged in the X-ray window, and a reel protective film is tensioned between the supply roller and the winding roller. The thickness of the protective film is appropriately adjusted according to the energy of the recoil electrons and the X-ray absorption.

In the present embodiment, although an electron beam is used as the energy beam, other energy beams such as a laser beam or an ion beam may be used.

Although the present invention has been described in detail with reference to the above examples, the present invention is not limited to the above disclosure, and various changes and modifications may be made without departing from the scope of the present invention.

Claims (32)

1. A method for generating X-rays, the method comprising the steps of:

repeatedly moving a counter-cathode along a rotation axis of the counter-cathode while rotating the counter-cathode around the rotation axis; and

irradiating an energy beam to a surface portion of the anticathode at a position overcoming a centrifugal force generated by rotation of the anticathode, thereby partially melting the surface portion by heating the surface portion to near or above a melting point of the anticathode, thereby generating X-rays from the rotating anticathode,

wherein a moving length of the rotating anticathode along the rotation axis is set to be at least twice a line width of the energy beam.

2. The generation method as defined in claim 1 wherein said rotating is performed periodically with respect to the movement of the cathode along said axis of rotation.

3. The generation method as defined in claim 1 wherein the length of movement of the rotating anticathode along the axis of rotation is determined based on the linewidth of the energy beam.

4. The generation method as defined in claim 3, wherein a moving length of said rotating anticathode is set to be larger than a line width of said energy beam.

5. The generation method as defined in claim 1, wherein a reduction in intensity of the X-rays to be emitted due to a concave portion of the surface portion of the anticathode formed by irradiation of the energy beam is 5% or less.

6. The generation method as defined in claim 1, wherein said concave portion has an inverted trapezoidal shape with a flat bottom surface at its center and slope portions rising from said bottom surface at given angles at both ends, the given angles being set smaller than an extraction angle of said X-rays leaving said concave portion.

7. The generation method as defined in claim 1, wherein said rotating anticathode includes a cylindrical portion provided along a periphery of said rotating anticathode so as to irradiate said energy beam onto an inner wall of said cylindrical portion.

8. The generation method as defined in claim 7, wherein a side wall of said cylindrical portion is inclined inward toward a central axis direction of said rotating anticathode, thereby suppressing outward sputtering of said surface portion of said anticathode to which said energy beam is irradiated by melting said surface portion.

9. The generation method as defined in claim 7 wherein said side walls of said cylindrical portion are inclined outwardly from a central axis of said rotating anticathode to enable extraction of said X-rays from said anticathode.

10. The generation method as defined in claim 1, wherein the surface portion to which the energy beam is irradiated is formed into a V-shaped groove or a U-shaped groove.

11. The generating method as defined in claim 10, wherein the V-shaped groove or the U-shaped groove is formed in the same shape as the surface portion being melted to which the energy beam affected by the centrifugal force is irradiated.

12. The generation method as defined in any one of claims 1 to 11, further comprising a step of, in the anticathode, making a region around the surface portion to which the energy beam is irradiated with a material whose melting point and/or thermal conductivity is higher than that of a target material of the anticathode which contributes to the generation of the X-ray.

13. The generation method as defined in claim 1, wherein the energy beam is an electron beam.

14. The generation method as defined in claim 13, wherein said electron beam is emitted from a cathode facing said rotating anticathode, an anticathode chamber for accommodating said rotating target and a cathode chamber for accommodating said cathode are located in the vicinity of each other and made of a gas-tight member, thereby forming a through hole or a tube on a partition wall between said anticathode chamber and said cathode chamber, and the insides of said anticathode chamber and said cathode chamber are evacuated by a vacuum pump.

15. The generating method as defined in claim 14, wherein the X-ray is taken out through an X-ray transmitting film provided on the airtight member.

16. The generation method as defined in claim 15, further comprising a step of providing a protective film on the X-ray transparent film so as to prevent vapor of a target material contributing to the generation of the X-rays from contaminating the X-ray transparent film.

17. An apparatus for generating X-rays, comprising:

a rotating anticathode configured so as to rotate about its rotation axis and repeatedly move along the rotation axis; and

an energy source for irradiating an energy beam onto a surface portion of the anticathode at a position overcoming a centrifugal force generated by rotation of the anticathode, thereby partially melting the surface portion by heating the surface portion to near or above a melting point of the anticathode, thereby generating X-rays from the rotating anticathode,

wherein a moving length of the rotating anticathode along the rotation axis is set to be at least twice a line width of the energy beam.

18. The generating means as defined in claim 17 wherein said rotating is periodic with respect to movement of the cathode along said axis of rotation.

19. The generation apparatus as defined in claim 17, wherein a length of movement of the rotating anticathode along the axis of rotation is determined in accordance with a linewidth of the energy beam.

20. The generation apparatus as defined in claim 19 wherein a movement length of said rotating anticathode is set to be greater than a line width of said energy beam.

21. The generation apparatus as defined in claim 17, wherein a reduction in intensity of the X-rays to be emitted due to the recessed portion of the surface portion of the anticathode formed by irradiation of the energy beam is 5% or less.

22. The generating means as defined in claim 17, wherein said concave portion has a shape of an inverted trapezoid with a flat bottom surface at its center and slope portions rising from said bottom surface at given angles at both ends, the given angles being set smaller than an extraction angle of said X-rays leaving said concave portion.

23. The generation apparatus as defined in claim 17, wherein said rotating anticathode includes a cylindrical portion provided along a periphery of said rotating anticathode so as to irradiate said energy beam onto an inner wall of said cylindrical portion.

24. The generating device as defined in claim 23, wherein a side wall of said cylindrical portion is inclined inward toward a central axis direction of said rotating anticathode, thereby suppressing outward sputtering of said surface portion of said anticathode to which said energy beam is irradiated by melting said surface portion.

25. The generating device as defined in claim 23 wherein said cylindrical portion has sidewalls that slope outwardly from a central axis of said rotating anticathode to extract said X-rays from said anticathode.

26. The generating device as defined in claim 17 wherein said surface portion onto which said energy beam is directed is shaped as a V-shaped or U-shaped groove.

27. The generating means as defined in claim 26 wherein the shape of said V-shaped groove or said U-shaped groove is the same as the shape of said surface portion being melted onto which said energy beam is irradiated under the influence of said centrifugal force.

28. The generating device as defined in claim 17, further comprising a step of making a region in said anticathode around said surface portion to which said energy beam is irradiated, with a material having a melting point and/or a thermal conductivity higher than that of a target material of said anticathode contributing to the generation of said X-ray.

29. The generating device as defined in claim 17 wherein said energy beam is an electron beam.

30. The generating device as defined in claim 29, wherein said electron beam is emitted from a cathode facing said rotating anticathode, an anticathode chamber for accommodating said rotating target and a cathode chamber for accommodating said cathode are located in the vicinity of each other and made of a gas-tight member, thereby forming a through hole or a tube on a partition wall between said anticathode chamber and said cathode chamber, and the insides of said anticathode chamber and said cathode chamber are evacuated by a vacuum pump.

31. The generating device as defined in claim 30, wherein said X-rays are taken out through an X-ray transmitting film provided on said airtight member.

32. The generating device as defined in claim 31 further comprising a protective film on said X-ray transparent film to prevent vapors of target material contributing to the generation of said X-rays from contaminating said X-ray transparent film.