This application is based upon and also claims the advantage of priority native Japanese Patent application No. 2017-199345, filed Oct. 13, 2017, the entire materials of i beg your pardon are included herein through reference.

You are watching: Stationary anode x-ray tube

FIELD

Embodiments explained herein relate typically to a stationary anode X-ray tube.

BACKGROUND

X-ray tubes room used, because that example, in diagnostic imaging tools for medical or dental for X-ray diagnosis, and likewise in industrial X-ray CT devices and also X-ray analyzers. The X-ray tube consist of a cathode i beg your pardon emits electrons in a vacuum envelope maintained at a vacuum airtight atmosphere, and an anode versus which emitted electrons collide. As soon as X-ray tube voltage is applied between the anode and the cathode, thermoelectrons are created in the filament that the cathode and enter a target surface ar of the anode with sped up speed, therefore radiating an X-ray native a focal spot developed on the target surface.

The strongness of an X-ray radiated indigenous a target surface ar is proportional come the square that the X-ray tube voltage, the X-ray pipe current, i beg your pardon is the flow of thermoelectrons, and the atomic variety of the facet of the target material. Regarding the generation of one X-ray, an electric power obtained by the product of the X-ray tube voltage and also the X-ray tube present is input to the anode, but only around 1% or less of the consumed power is converted right into an X-ray, and also the staying 99% or an ext is converted into thermal energy. As soon as an X-ray is radiated together electrons collide v the anode, recoil electrons space recoiled native the target surface. A standard drawback in this technology is the the recoiled recoil electron collide through the anode again to warmth the anode, or collide through the vacuum envelope to reason a damage. To remove such a drawback, there is a method in i m sorry an anode hood is installed about the anode come shield that from and also trap recoil electrons. The anode hood comprises an X-ray transmissive window made native beryllium or the like, attached thereto.

When employed for X-ray imaging diagnosis or the like, the picture quality (contrast) that the X-ray image needs to be enhanced for much more accurate diagnosis, and therefore it is required to additional increase the X-ray dosage radiated native the X-ray tube. To boost the X-ray dosage, the X-ray tube voltage and the X-ray tube existing to be applied to the X-ray tube need to be increase. However, together the X-ray tube voltage and the X-ray tube existing are rise further, the energy of the recoil electron recoiled native the target surface likewise increases. Here, one more drawback arises, in which as soon as the recoil electron collide v the X-ray transmissive window, the temperature that the material rises to cause melting and/or damage, etc., in the X-ray transmissive window. If the X-ray transmissive home window melts in the vacuum envelope, gas emission and also vapor deposition top top the vacuum envelope might occur. As a result, the resist voltage characteristic might fall, possibly leading to failure of the X-ray tube. Under this circumferences, the energy input come the X-ray tube is restricted.

BRIEF description OF THE DRAWINGS

FIG. 1 is a cross section showing a stationary anode X-ray tube according to an embodiment.

FIG. 2 is a partially expanded cross section reflecting the stationary anode X-ray pipe of FIG. 1.

FIG. 3 is a overcome section reflecting an anode hood and an X-ray transmissive home window taken along line in FIG. 2, and likewise showing an anode in arrangement view.

FIG. 4 is a overcome section mirroring a target layer presented in FIGS. 1 and also 2, and illustrating the relationship in between incident electrons entering the target layer and also recoil electrons recoiling on the target layer.

FIG. 5 is a diagram of a graph reflecting a adjust in recoil electron energy with respect come an angle presented in FIG. 4.

FIG. 6 is a diagram of a graph reflecting a adjust in X-ray intensity come the angle shown in FIG. 4.

DETAILED DESCRIPTION

In general, follow to one embodiment, therein listed a stationary anode X-ray tube consisting of a cathode which emits electrons, an anode disposed to oppose the cathode in a direction along a pipe axis and also comprising a target surface ar on i m sorry a focal point out which emits an X-ray is developed as emitted through an electron emitted indigenous the cathode, an anode hood addressed to the anode, expanding to a side of the cathode, bordering the target surface, set at a same potential as that that the anode and comprising a first opening allowing electrons directed to the target surface from the cathode to happen therethrough and also a 2nd opening allowing an X-ray emitted native the focal clues to happen therethrough, one X-ray transmissive window which blocks the second opening of the anode hood and transmits one X-ray and also an electrical insulating vacuum envelope i m sorry accommodates the cathode, the anode, the anode hood and the X-ray transmissive window. The target surface ar is one inclined surface disposed to be spaced further away from the cathode in the direction of a an initial direction typical to the tube axis. When, v respect come a 2nd direction command from the focal distance spot come a facility of the X-ray transmissive window, the anode and the X-ray transmissive window are perceived from the side of the cathode along the tube axis, an edge made v respect come the second direction once the first direction is pivoted clockwise or counter-clockwise is identified an edge θ, the angle θ is any kind of angle yet 0°.

An embodiment will be defined with recommendation to the accompanying drawings. The disclosure is a mere example, and also arbitrary change of gist which deserve to be conveniently conceived through a human being of ordinary skill in the arts naturally falls within the inventive scope as long as the subject matter of the embodiments is maintained. To better clarify the explanations, the illustrations may pictorially present width, thickness, shape, etc., the each portion as compared with an really aspect, yet they are mere examples and also do no restrict the interpretation of the invention. In the current specification and drawings, after structural elements are each explained once with reference to the drawings, there is a case where their explanations will certainly be omitted as appropriate, and those identical to or comparable to the described structural facets will it is in denoted through the same reference numbers, respectively, as the defined structural elements.

As shown in FIG. 1, a stationary anode X-ray tube 1 comprises a cathode 10, an anode 20, one anode hood 30, a cathode structure 40, a vacuum envelope 50 and a radiator 70.

The cathode 10 has a filament 11 together an electron emission resource which emits electrons, and a concentrating electrode 12. In this embodiment, negative high voltage and a filament present are applied to the filament 11. An adverse high voltage is used to the focusing electrode 12. The cathode 10 is resolved to the cathode framework 40.

The anode 20 comprises one anode target 21 and an anode extending part 22 associated to the anode target 21.

The anode target 21 is disposed to protest the filament 11 (cathode 10) to regarding be personally therefrom in a direction along a pipe axis A. In this embodiment, the anode 20 is grounded. The anode target 21 contains a target body 21a and a target great 21b. The target body 21a is formed into a cylindrical shape. The target human body 21a is created of a high heat conductive metal such as copper or a copper alloy.

The target class 21b is listed in a part of an end surface of the target human body 21a. The target layer 21b is formed of a high melting-point steel such together tungsten (W) or a tungsten alloy. A target surface ar 21c that the target layer 21b, i beg your pardon is located on a side opposing the cathode 10 is inclined through respect to a virtual aircraft perpendicular come the tube axis A. The target surface ar 21c is one inclined surface ar disposed to be spaced additional from the cathode 10 in the direction of a very first direction d1, i m sorry is regular to the tube axis A. ~ above the target surface 21c, electrons emitted indigenous the filament 11 and converged through the concentrating electrode 12 space collided to type a focal clues (focal clues F, which will be described later) which emits one X-ray.

As in the instance of the target human body 21a, the anode extending part 22 is created to be cylindrical indigenous a high warm conductive metal such as copper or a copper alloy. The anode extending part 22 offer to fix the anode target 21 and transmit heat generated from the anode target 21 come the surroundings. In this embodiment, the radiator 70 is associated to the anode extending section 22. The radiator 70 is created of an electric insulating or conductive material. Because that example, the radiator deserve to be developed using ceramics, i m sorry has terrific properties in heat conduction and withstand voltage. V use of the radiator 70, the heat transfer indigenous the X-ray tube 1 to the outside thereof deserve to be promoted. Keep in mind that the radiator 70 need to be listed in the X-ray tube 1 only if needed.

The anode hood 30 is resolved to the anode 20. In this embodiment, the anode hood 30 is addressed to the target body 21a by brazing. The anode hood 30 extends to a cathode 10 next so regarding surround the target surface ar 21c. In this embodiment, the anode hood 30 consists of a cylindrical part 31 expanding along the tube axis A and also a lid portion 32 located in between the cathode 10 and the anode 20 and blocking an finish of the cylindrical part 31.

The anode hood 30 is formed of a conductive material such as a metal. The anode hood 30 is collection to the exact same potential together that that the anode 20. The lid section 32 (anode hood 30) comprises a first opening OP1 which enables electrons to pass therethrough from the cathode 10 come the target surface ar 21c.

The vacuum envelope 50 accommodates the cathode 10, the anode target 21, the anode hood 30 and the like. The vacuum envelope 50 is created so as to expose the anode extending section 22. The vacuum envelope 50 is formed into a cylindrical form with one end portion airtightly blocked by the cathode structure 40 and also another end part airtightly blocked by the anode 20. The within of the vacuum envelope 50 is maintained at a predetermined degree of vacuum. Note that the inside of the vacuum envelope 50 is evacuated by making use of an exhaust harbor 53. The exhaust harbor 53 is airtightly sealed.

The vacuum envelope 50 consists of an electric insulating container created from an electric insulating material, and a steel container 52 formed from a metal. Instances of the electric insulating material described over are glass such together borosilicate glass and ceramics such as alumina. In this embodiment, the electrical insulating material is glass, and the electrical insulating container is a glass container 51.

The glass container 51 is developed cylindrical. The glass container 51 develops a gap in between the anode hood 30 and also itself. The glass container 51 can be prepared, for example, by airtightly bonding a plurality that glass members together by fusion. Because the glass container 51 is radiolucent, the X-ray emitted from the anode target 21 passes through the glass container 51 to it is in emitted come the external of the vacuum envelope 50.

The steel container 52 is airtightly associated to the glass container 51 and the anode 20. The metal container 52 is airtightly solved to at least one the the target body 21a and the anode extending portion 22. Here, the metal container 52 is airtightly connected to the anode extending portion 22 by brazing. Further, the steel container 52 and the glass container 51 room airtightly connected to each other by fusion. In this embodiment, the steel container 52 is created annular. Further, the metal container 52 is formed, because that example, making use of Kovar. The coefficient the thermal development of the metal container 52 is considerably equal to that of the glass container 51.

As presented in FIG. 2, the cylindrical part 31 (anode hood 30) comprises a second opening OP2 which enables an X-ray emitted indigenous the focal spot F created on the target surface 21c, to happen therethrough. In this embodiment, the second opening OP2 opposes the target surface ar 21c follow me a direction perpendicular to the pipe axis A. Through the second opening OP2 provided, the absorptivity of the obtainable X-ray by the anode hood 30 can be lessened to 0%.

The X-ray transmissive window 60 blocks the second opening OP2 of the anode hood 30, and also transmits X-rays. The X-ray transmissive home window 60 is likewise accommodated in the vacuum envelope 50. The X-ray transmissive window 60 is created from a product containing at least one that beryllium, graphite, chlorofluorocarbon (CFC), beryllia, boron (B), boron nitride (BN) and boron carbide (B4C).

In this embodiment, the X-ray transmissive home window 60 is formed from a material largely containing among beryllium, graphite, CFC, beryllia, B, BN and boron carbide.

As displayed in FIG. 3, the focal suggest F has a long axis. When the anode 20 is perceived from the cathode 10 side follow me the tube axis A, the long axis the the focal allude F extends follow me the an initial direction d1 explained above. Here, a direction come the facility of the X-ray transmissive home window 60 native the focal suggest F when the anode 20 and the X-ray transmissive home window 60 are perceived from the cathode 10 side along the pipe axis A, is identified as a 2nd direction d2. Further, an angle made through respect to the 2nd direction d2 as soon as the first direction d1 is pivoted clockwise or counter-clockwise is identified as θ. In this embodiment, the edge θ is an angle made through respect come the 2nd direction d2 versus the an initial direction d1 together it is pivoted clockwise. The angle θ is any type of angle but 0 degree.

Preferably, it should be: 0°1 presented in FIG. 4.

As presented in FIGS. 4 and 5, regarding the recoil electron of an electron beam made occurrence on the target surface ar 21c in ~ an angle θ0 with respect come a regular thereof, a ingredient A1 that the angle θ0 exhibits the maximum energy, and the energy reduces as the edge θ1 changes.

Further, the inventors likewise researched the angle circulation in X-ray intensity.

As presented in FIG. 6, if the edge θ presented in FIG. 3 is set to 15°, around 85% the X-ray intensity deserve to be acquired in the second direction d2. Keep in mind that the X-ray intensity in the an initial direction d1 is 100% as a reference. Moreover, as can be watched from FIG. 5, when θ=15°, 50% or more of recoil electron energy can be absorbed by the anode hood 30.

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According to the stationary anode X-ray pipe 1 that the embodiment configured as described above, the X-ray tube 1 comprises a cathode 10, an anode 20, one anode hood 30, one X-ray transmissive home window 60 and also a vacuum envelope 50. The anode hood 30 can capture recoil electrons ejected the end of the anode target 21. Therefore, the quantity of the recoil electron return to the target surface 21c, and the lot of the recoil electron rushing right into the glass container 51 can be reduced.

The angle θ might be any type of degree however 0°. As contrasted to the instance where: θ=0°, the quantity of the recoil electron emitted in the second direction d2, i m sorry is likewise a main direction of the X-ray radiation can be suppressed, and thus the amount of the recoil electron i beg your pardon collides v the X-ray transmissive window 60 have the right to be reduced. As a result, the increase of the temperature the the X-ray transmissive window 60 can be suppressed. In the situation where the X-ray tube voltage is no higher than 125 kV, i beg your pardon is usually provided for X-ray tubes largely in diagnosis, the palliation of X-ray dosage in a wanted direction that X-ray radiation is little even if the angle is set to 0°