JP7370899B2 - x-ray tube - Google Patents

Description

Embodiments of the invention relate to x-ray tubes.

Generally, in an X-ray tube, electrons emitted from a cathode filament collide with an anode target to generate X-rays. The generated X-rays are output from the output window of the vacuum envelope. When electrons collide with the anode target, X-rays and secondary electrons are generated at the same time, and these secondary electrons may collide with parts other than the anode target and excite impurity lines.
In particular, analytical X-ray tubes are required to output highly purified X-rays and improve analysis accuracy.

Japanese Patent Application Publication No. 5-135718 Japanese Patent Application Publication No. 9-82252 Japanese Patent Application Publication No. 11-224626

The purpose of this embodiment is to provide an X-ray tube that can improve analysis accuracy.

The X-ray tube of this embodiment is
a vacuum envelope provided with an output window that transmits X-rays; an anode target provided within the vacuum envelope and facing the output window; and a convergence electrode provided to surround the anode target. , a cathode filament that is provided outside the focusing electrode and emits electrons to be irradiated to the anode target, and in the focusing electrode, an inner circumferential surface facing the anode target is made of the same material as the anode target. Coated with a coating layer.

FIG. 1 is a cross-sectional view schematically showing the configuration of an X-ray tube 1 according to this embodiment. FIG. 2 is a perspective view showing the internal structure of the X-ray tube 1 shown in FIG. FIG. 3 is a plan view showing the internal structure of the X-ray tube 1 shown in FIG.

This embodiment will be described below with reference to the drawings. Note that the disclosure is merely an example, and any modifications that can be easily made by those skilled in the art while maintaining the spirit of the invention are naturally included within the scope of the present invention. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is just an example, and the drawings are merely examples of the present invention. It does not limit interpretation. In addition, in this specification and each figure, the same reference numerals are given to components that perform the same or similar functions as those described above with respect to the existing figures, and overlapping detailed explanations may be omitted as appropriate. .

FIG. 1 is a cross-sectional view schematically showing the configuration of an X-ray tube 1 according to this embodiment. The X-ray tube 1 described here is, for example, an analytical X-ray tube.

The X-ray tube 1 includes a vacuum envelope 2, an anode target 3, an anode support 4, a focusing electrode 5, a cathode filament 6, and a cathode support 7.

The outer diameter of the vacuum envelope 2 is gradually tapered at the tip, and the tip is flat. A flat portion of the vacuum envelope 2 is provided with an output window 8 that transmits X-rays. The output window 8 is made of a material with low attenuation of X-rays, such as Be (beryllium), and has a thickness of several tens to several hundreds of μm.

The anode target 3 , the anode support 4 , the focusing electrode 5 , the cathode filament 6 , the cathode support 7 , and the like are provided inside the vacuum envelope 2 .

Anode target 3 is arranged to face output window 8 . The anode target 3 is formed into a disk shape and is made of, for example, Rh (rhodium), W (tungsten), molybdenum (Mo), chromium (Cr), or the like. The anode support 4 is formed to become thinner as a whole toward the tip, and is made of, for example, Cu (copper). The anode support 4 supports the anode target 3 at its tip.

The focusing electrode 5 is provided so as to surround the anode target 3. The focusing electrode 5 is made of a material different from that of the anode target 3, and is made of, for example, iron (Fe), stainless steel, or the like. The cathode filament 6 is provided outside the focusing electrode 5 and emits electrons 9 that are irradiated onto the anode target 3. The cathode support 7 is provided outside the focusing electrode 5 and supports the cathode filament 6. The cathode support 7 is made of stainless steel, for example.

In the focusing electrode 5, an inner peripheral surface 5A facing the anode target 3 is coated with a coating layer 10 made of the same material as the anode target 3. The coating layer 10 is made of rhodium (Rh), tungsten (W), molybdenum (Mo), chromium (Cr), or the like. For example, if the anode target 3 is made of Rh (rhodium), a coating layer 10 of the same Rh is applied, and if the anode target 3 is made of W (tungsten), the coating layer 10 of the same W is applied. applies. As a coating method, plating, thermal spraying, vapor deposition, etc. can be applied.

Note that on the outside of the X-ray tube 1 and in front of the output window 8, a measurement material 20 and a detector 21 are arranged. When the measurement material 20 is irradiated with the X-rays 22 that have passed through the output window 8, the measurement material 20 excites fluorescent X-rays 23, and the excited fluorescent X-rays 23 pass through a mechanism such as a slit or a spectroscopic crystal to a detector. Detected at 21. Then, in the detector 21, the substance constituting the measurement material 20 is analyzed based on the detected fluorescent X-rays 23.

FIG. 2 is a perspective view showing the internal structure of the X-ray tube 1 shown in FIG. FIG. 3 is a plan view showing the internal structure of the X-ray tube 1 shown in FIG.
The focusing electrode 5 is formed in a cylindrical shape and has a notch 5B in a part thereof. The inner circumferential surface 5A is formed in a cylindrical shape and surrounds almost the entire circumference of the anode target 3 (excluding a portion facing the cathode filament 6). The coating layer 10 is formed over almost the entire inner peripheral surface 5A.
The cathode support 7 is provided in the notch 5B and is electrically insulated from the focusing electrode 5. That is, as shown in FIG. 3, an insulating material 30 is interposed between the focusing electrode 5 and the cathode support 7. The insulating material 30 is made of ceramic, for example.
The voltage applied to the focusing electrode 5 is higher than the voltage applied to the cathode filament 6 and the cathode support 7, and lower than the voltage applied to the anode support 4.

Next, the functions and effects of the X-ray tube 1 according to this embodiment will be explained.
As shown in FIG. 1, when the X-ray tube 1 is in operation, electrons 9 are generated from the cathode filament 6. The electrons 9 are accelerated by the potential difference between the cathode filament 6 and the anode target 3, are focused by the focusing electrode 5, collide with the anode target 3, and generate X-rays 22. Most of the X-rays 22 generated by the anode target 3 are emitted in the direction of the output window 8 . The generated X-rays 22 pass through the output window 8 and are irradiated onto the measurement material 20 .

On the other hand, in the anode target 3, when the electrons 9 collide, the secondary electrons 24 are generated simultaneously with the X-rays 22. The secondary electrons 24 are scattered in the entire circumferential direction of the anode target 3, and some of the secondary electrons 24 collide with the inner circumferential surface 5A of the focusing electrode 5. Since the focusing electrode 5 is formed of a metal material different from that of the anode target 3, when the secondary electrons 24 directly collide with the focusing electrode 5, X-rays ( impure line) is excited. Such impurity lines become a cause of deterioration of analysis accuracy.

In this embodiment, since the voltage applied to the focusing electrode 5 is higher than the voltage applied to the cathode filament 6 and the cathode support 7 and lower than the voltage applied to the anode support 4, the secondary electrons 24 generated at the anode target 3 are It is absorbed by the focusing electrode 5. Thereby, it is possible to suppress the collision of the secondary electrons 24 with a portion that may generate impurity lines, such as the anode support 4.
Further, the inner peripheral surface 5A of the focusing electrode 5 is coated with a coating layer 10 made of the same material as the anode target 3. When the secondary electrons 24 scattered toward the focusing electrode 5 collide with the coating layer 10 on the inner peripheral surface 5A, X-rays are excited. The X-rays generated in the coating layer 10 are genuine X-rays having the same wavelength as the X-rays 22 generated in the anode target 3.
Therefore, generation of impurity rays within the X-ray tube can be suppressed.

Thereby, not only the X-rays 22 generated by the anode target 3 but also the X-rays generated by the coating layer 10 can be used for analyzing the measurement material 20, and high-intensity X-ray output can be obtained. Furthermore, since impurity rays are reduced, highly pure X-ray output can be obtained.
According to this embodiment described above, it is possible to provide an X-ray tube that can improve analysis accuracy.

It should be noted that the present invention is not limited to the above-described embodiment itself, and can be embodied by modifying the constituent elements within the scope of the invention at the stage of implementation. Moreover, various inventions can be formed by appropriately combining the plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components from different embodiments may be combined as appropriate.

1... X-ray tube 2... Vacuum envelope 3... Anode target 4... Anode support 5... Focusing electrode 5A... Inner peripheral surface 5B... Notch part
6... Cathode filament 7... Cathode support 8... Output window 8
10...Coating layer 30...Insulating material

Claims (3)

a vacuum envelope provided with an output window that transmits X-rays;
an anode target provided within the vacuum envelope and facing the output window;
a focusing electrode provided to surround the anode target;
a cathode filament that is provided outside the focusing electrode and emits electrons to irradiate the anode target;
a cathode support supporting the cathode filament;
an anode support supporting the anode target;
Equipped with
In the focusing electrode, an inner peripheral surface facing the anode target is coated with a coating layer made of the same material as the anode target ,
The X-ray tube, wherein the voltage applied to the focusing electrode is higher than the voltage applied to the cathode filament and the cathode support, and lower than the voltage applied to the anode support. The X-ray tube according to claim 1, wherein the coating layer is made of rhodium (Rh), tungsten (W), molybdenum (Mo), or chromium (Cr). The focusing electrode is formed in a cylindrical shape and has a notch in a part thereof,
The cathode support is provided in the cutout,
The X-ray tube according to claim 1, wherein an insulating material is interposed between the focusing electrode and the cathode support.

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