The present application is related to x-ray sources.
X-rays have many uses, including imaging, x-ray fluorescence analysis, x-ray diffraction analysis, and electrostatic dissipation.
A large voltage between a cathode and an anode of the x-ray tube, and a heated filament at the cathode, can cause electrons to emit from the filament to the anode. The anode can include a target. The target can generate x-rays in response to impinging electrons from the cathode.
The following definitions, including plurals of the same, apply throughout this patent application.
As used herein, the terms “on”, “located on”, “located at”, and “located over” mean located directly on or located over with some other solid material between. The terms “located directly on”, “adjoin”, “adjoins”, and “adjoining” mean direct and immediate contact.
As used herein, the term parallel means exactly parallel; parallel within normal manufacturing tolerances; or almost exactly parallel, such that any deviation from exactly parallel would have negligible effect for ordinary use of the device.
As used herein, the term “x-ray tube” is not limited to tubular/cylindrical shaped devices. The term “tube” is used because this is the standard term used for x-ray emitting devices.
An x-ray tube can include a filament for emission of electrons. A planar filament can be preferred for focusing the electron beam to a circular spot. It can be difficult, however, to place the filament repeatedly in the appropriate location.
Failure to align the filament within a cathode cup, in every x-ray tube manufactured, can result in undesirable variance in x-ray spot location between different x-ray tubes.
Planar filaments can twist or warp. This can adversely affect the electron beam shape and focusing.
Placing a tiny filament on electrodes can be difficult for operators, and can result in variation between different x-ray tubes. Welding the filament to electrodes can result in overheating of the filament or surrounding material, which can further warp or damage the filament or other material.
A weld beneath the filament can be difficult or impossible to inspect. Without proper inspection, x-ray tubes that lack a properly welded filament can be sold and installed in expensive equipment. Improperly welded filaments can result in early failure of the x-ray tube, and of the tool which uses the x-ray tube.
A filament can emit electrons in all directions. A planar filament typically emits electrons in a desirable direction, towards the anode target, from a top side of the planar filament that faces the target. The planar filament also can emit electrons in an undesirable direction, towards a cathode cup, from a bottom side of the planar filament. The bottom side is opposite of the top side. The electrons from the bottom side can change direction (e.g. about 180°), due to a negative voltage of the cathode cup, pass between filament wires, and emit towards the target. These electrons from the bottom side are not focused properly. Therefore, the bottom side electrons can result in a misshaped electron spot at the target.
The filament assemblies 10 described herein can solve the previously noted problems. Each embodiment can solve one, some, or all of these problems.
As illustrated in
The filament 11 can consist of or can include an elongated wire extending, non-linearly in a plane (parallel with the sheet of the paper in
A top side 47 of the pair of collector plates C1 and C2 and of the filament 11 can be aligned and co-planar with each other. The top side 47 can face the target 24 (
A bottom side 48 of the pair of collector plates C1 and C2 and of the filament 11 can be aligned and co-planar with each other. The bottom side 48 can face away from the target 24 (
The top side 47 can be aligned with a top plane 50. The bottom side 48 can be aligned with a bottom plane 46. The top plane 50 can be parallel to the bottom plane 46. A thickness of the pair of collector plates C1 and C2 can equal a thickness of the filament 11. The thickness can be measured perpendicularly to the plane 45.
The pair of collector plates C1 and C2 can be separated from each other (i.e. not directly touch, not adjoin). The pair of collector plates C1 and C2 can be electrically coupled to each other by the filament 11. The filament 11 can be the only structure that is in an electrical circuit between the pair of collector plates C1 and C2.
The pair of collector plates C1 and C2 can include a first collector plate C1 and a second collector plate C2. The first collector plate C1 can be electrically-coupled to the first end E1 of the filament 11. The first collector plate C1 can adjoin the first end E1 of the filament 11. The second collector plate C2 can be electrically-coupled to the second end E2 of the filament 11. The second collector plate C2 can adjoin the second end E2 of the filament 11.
As illustrated in
An inner perimeter I1 of the first collector plate C1 can have an arc shape. The arc shape of the inner perimeter I1 of the first collector plate C1 can match, or be similar to, an outer curvature of the filament 11. An inner perimeter 12 of the second collector plate C2 can have an arc shape. The arc shape of the inner perimeter 12 of the second collector plate C2 can match, or be similar to, an outer curvature of the filament 11.
As illustrated in
A transmission-target x-ray tube 20 is shown in
As illustrated in
An electrical current path can be from the first electrode 31 to and through the first collector plate C1, from the first collector plate C1 to the first end E1 of the filament 11 and through the filament 11 to the second end E2 of the filament 11, from the second end E2 of the filament 11 to and through the second collector plate C2 to the second electrode 32.
As illustrated in
A diameter d1 of the first hole H1 can be smaller than an outer diameter D1 of the first electrode 31. A diameter d2 of the second hole H2 can be smaller than an outer diameter D2 of the second electrode 32. Consequently, the first collector plate C1 can rest on top of the first electrode 31 and the second collector plate C2 can rest on top of the second electrode 32. This design avoids sharp electrical field gradients that would otherwise result if the electrodes 31 and 32 protruded through the holes H1 and H2, respectively.
The first electrode 31 can span the first hole H1. The first electrode 31 can cover completely an opening of the first hole H1. The second electrode 32 can span the second hole H2. The second electrode 32 can cover completely an opening of the second hole H2.
The first collector plate C1 can be welded to the first electrode 31 at a perimeter of the first hole H1 and the second collector plate C2 can be welded to the second electrode 32 at a perimeter of the second hole H2. The weld can be formed by melting an end of the electrodes 31 and 32 nearest to the collector plates C1 and C2. Therefore, a first connection 41 between the first collector plate C1 and the first electrode 31 can be formed by a portion 43 of the first electrode 31 that was melted to form the first connection 41; and a second connection 42 between the second collector plate C2 and the second electrode 32 is formed by a portion 44 of the second electrode 32 that was melted to form the second connection 42.
The holes H1 and H2 allow visual alignment of the filament assembly 10 with the electrodes 31 and 32. Welding the filament assembly 10 to the electrodes 31 and 32 at the holes H1 and H2, respectively, can be performed at a lower temperature than if the weld were performed without the holes. The holes H1 and H2 allow visual inspection of the weld after it is completed.
The filament assembly 10 can be mounted on the pair of electrodes 31 and 32 within, at, or in front of an opening 49 of a cathode cup 33, as illustrated in
The filament assembly 10 can have a slightly smaller diameter than the cathode cup 33 so that the cathode cup 33 forces a central alignment of the filament assembly 10. This makes manufacturing easier and can result in reduced variation between different x-ray tubes.
A filament can emit electrons in all directions. A planar filament typically emits electrons in a desirable direction, towards the anode target 24, from a top side of the planar filament that faces the target 24. The planar filament also can emit electrons in an undesirable direction, towards the cathode cup 33, from a bottom side of the planar filament. The bottom side is opposite of the top side. The electrons from the bottom side can change direction (e.g. about 180°), due to a negative voltage of the cathode cup 33, pass between filament wires, and emit towards the target 24. These electrons from the bottom side are not focused properly. Therefore, the bottom side electrons can result in a misshaped electron spot at the target 24.
The collector plates C1 and C2 can block these electrons emitted from the bottom side, and can keep these electrons within the cathode cup 33. In order to effectively block such electrons, it is useful for the collector plates C1 and C2 to block a large percent of the opening 49 of the cathode cup 33 outside of the filament 11. For example, the filament assembly 10 can block ≥70%, ≥80%, ≥90%, or ≥95% of the opening 49 of the cathode cup 33 outside of the filament 11.
The collector plates C1 and C2 can encircle a large percent of the filament 11 in order to improve blocking of electrons emitted from the bottom side. For example, the collector plates C1 and C2 can encircle a majority of the filament 11, such as ≥70%, ≥80%, ≥90%, or ≥93% of the filament 11. As another example, the collector plates C1 and C2 can encircle at least 90% of the filament 11. If the collector plates C1 and C2 encircle too large of a percent of the filament 11, then there is risk of the collector plates C1 and C2 touching, resulting in a short circuit failure. Therefore, the collector plates C1 and C2 can encircle ≤95%, ≤97.5%, or ≤99% of the filament 11.
In order to allow a voltage across the collector plates C1 or C2 to cause an electrical current through the filament 11, it is desirable for no more than one of the collector plates C1 or C2 to touch the cathode cup 33. If both collector plates C1 and C2 touch the cathode cup 33, then there would be a short circuit through the cathode cup 33, and a desired amount of electrical current would not flow through the filament 11.
In order to avoid this short circuit, the collector plates C1 and C2 can have different radii with respect to each other (R1/R2), as illustrated in
Example relationships between R1 and R2 include the following: R1/R2≥1.01, R1/R2≥1.02, R1/R2≥1.03, or R1/R2≥1.04; and R1/R2≤1.05, R1/R2≤1.1, or R1/R2≤1.2.
An area (A1) of the first collector plate C1 is typically larger than an area (A2) the second collector plate C2. A larger area (A1) of the first collector plate C1 can allow it to rest on an edge of the cathode cup 33 and support the filament assembly 10. Example relationships between the area (A1) of the first collector plate C1 and the area (A2) the second collector plate C2 include the following: A1/A2≥1, A1/A2≥3, A1/A2≥5, or A1/A2≥6; and A1/A2≤8, A1/A2≤10, or A1/A2≤15. Both areas A1 and A2 are areas of the side of the first collector plate C1 and of the second collector plate C2 that face the target 24.
The radii R1 and R2 of the collector plates C1 and C2, respectively, can be substantially larger than a largest radius Rf of the filament 11, from a center 14 of the filament 11 to an outer edge 15 of the filament 11. Example relationships between Rf and R1 include the following: R1>Rf, R1/Rf≥1.5, R1/Rf≥2, or R1/Rf≥3; and R1/Rf≤4, R1/Rf≤6, or R1/Rf≤8. Example relationships between Rf and R2 include the following: R2>Rf, R2/Rf≥1.5, R2/Rf≥2, or R2/Rf≥3; and R2/Rf≤4, R2/Rf≤6, or R2/Rf≤8. A purpose of these relationships is to place the filament 11 in a small area at a center of the cathode cup 33, but also block nearly all of an area of an opening 49 of the cathode cup 33 outside of the filament 11.
The first collector plate C1 can include one, two, three, or more recessed regions 12 (
Tabs 12 on the first collector plate C1 can be sufficient for holding the filament assembly 10 during manufacturing. Therefore, the second collector plate C2 can be free of any recessed regions at an outer perimeter thereof. An entire outer perimeter of the second collector plate C2 can have an arc shape.
This application claims priority to US Provisional Patent Application Number U.S. 63/579,091, filed on Aug. 28, 2023, which is incorporated herein by reference.
Number | Date | Country | |
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63579091 | Aug 2023 | US |