Assembled planar filament
Patent Information
- Application Number
- DE102024123364
- Authority / Receiving Office
- DE · DE
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-08-15
- Publication Date
- 2025-03-06
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
Scope of the invention
[0001] The present application relates to X-ray sources. background
[0002] X-rays have many uses, including imaging, X-ray fluorescence analysis, X-ray diffraction analysis, and electrostatic dissipation. A high voltage between the cathode and anode of the X-ray tube and a heated filament at the cathode can cause electrons to be emitted from the filament to the anode. The anode may contain a target. The target can generate X-rays in response to the electrons striking the cathode. Brief description of the drawings (the drawings may not be to scale) Fig. 1 is a plan view of a filament assembly 10 including a filament 11 and a pair of collector plates C1 and C2. Fig. Figure 2 is a cross-sectional side view of an x-ray tube 20 having a cathode 21 and an anode 22 that are electrically isolated from each other. The cathode 21 may include a filament assembly 10 as described herein. Fig. Figure 3 is a top view of the filament assembly 10 mounted on a first electrode 31 and a second electrode 32. The first electrode 31 is connected to the first collector plate C1 at a first hole H1, and the second electrode 32 is connected to the second collector plate C2 at a second hole H2. The filament assembly 10 is located at an opening of a cathode cup 33. Fig. Figure 4 is a side cross-sectional view of the filament assembly 10, the electrodes 31 and 32 and the cathode cup 33 of Fig. 3, taken along line 4-4 in Fig. 3. Fig. 5 is a plan view of the filament assembly 10 of Fig. 1, which illustrates the following possible radius ratios: R1 > Rf, R2 > Rf, and R1 > R2. Fig. 6 is a plan view of a filament group 60 having four filament assemblies 10. During manufacture, multiple filament groups 10 may be connected as shown.
[0003] Definitions. The following definitions, including their plural forms, apply to the entire patent application.
[0004] As used herein, the terms "on," "disposed upon," "disposed at," and "disposed over" mean directly disposed on or over another solid material in between. The terms "disposed directly against," "adjacent," "contiguous," and "adjacent" mean direct and immediate contact.
[0005] The term "parallel" in this context means exactly parallel, parallel within normal manufacturing tolerances, or almost exactly parallel, so that any deviation from exact parallelism would have negligible effects on the normal use of the device.
[0006] The term "X-ray tube" used here is not limited to tubular or cylindrical devices. The term "tube" is used because it is the standard term for X-ray devices. Detailed description
[0007] An X-ray tube may contain a filament for emitting electrons. A planar filament may be preferable for focusing the electron beam into a circular spot. However, it can be difficult to repeatedly position the filament correctly.
[0008] If the filament in a cathode shell is not correctly aligned in each manufactured X-ray tube, undesirable variations in the positioning of the X-ray spots between different X-ray tubes can occur.
[0009] Planar filaments can twist or warp, which can affect the shape and focus of the electron beam.
[0010] Placing a tiny filament on the electrodes can be difficult for operators and lead to variations between different X-ray tubes. Welding the filament to the electrodes can cause overheating of the filament or the surrounding material, which can further deform or damage the filament or other material.
[0011] A weld beneath the filament can be difficult or even impossible to inspect. Without proper inspection, X-ray tubes with improperly welded filaments can be sold and installed in expensive equipment. Improperly welded filaments can lead to premature failure of the X-ray tube and the equipment that uses it.
[0012] A filament can emit electrons in all directions. A planar filament typically emits electrons in a desired direction, toward the anode target, from a top surface of the planar filament that faces the target. The planar filament can also emit electrons in an undesired direction, toward a cathode cup, from a bottom surface of the planar filament. The bottom surface faces the top surface. The electrons from the bottom surface can change direction (e.g., by 180°) due to a negative voltage on the cathode cup, pass between the wires of the filament, and emit toward the target. These electrons from the bottom surface are not properly focused. Therefore, the electrons from the bottom surface can result in a misshapen electron spot on the target.
[0013] The filament assemblies 10 described herein can solve the aforementioned problems. Each embodiment can solve one, some, or all of these problems.
[0014] As in Fig. As shown in Figure 1, a filament assembly 10 may include a filament 11 and a pair of collector plates C1 and C2. The collector plates C1 and C2 may support the filament 11 and prevent twisting or warping of the filament 11.
[0015] The filament 11 may consist of or contain an elongated wire that extends non-linearly in a plane (parallel to the paper sheet in the Fig. 1, Fig. 3 and Fig. 5 or in level 45 in Fig. 4) extends between a first end E1 and a second end E2 of the filament 11. A planar dimension of the collector plate pair C1 and C2 may lie in this plane.
[0016] A top surface 47 of the collector plate pair C1 and C2 and the filament 11 may be aligned and coplanar. The top surface 47 may face the target 24 ( Fig. 2 and Fig. 4).
[0017] A bottom side 48 of the collector plate pair C1 and C2 and the filament 11 can be aligned coplanarly with each other. The bottom side 48 can face away from the target 24 ( Fig. 2 and Fig. 4). The bottom side 48 may be opposite the top side 47.
[0018] The top surface 47 can be aligned with an upper plane 50. The bottom surface 48 can be aligned with a lower plane 46. The upper plane 50 can be parallel to the lower plane 46. The thickness of the collector plate pair C1 and C2 can correspond to the thickness of the filament 11. The thickness can be measured perpendicular to the plane 45.
[0019] The collector plate pair C1 and C2 may be separated from each other (i.e., not directly touching, not adjacent to each other). The collector plate pair C1 and C2 may be electrically coupled to each other by the filament 11. The filament 11 may be the only structure located in an electrical circuit between the collector plate pair C1 and C2.
[0020] The pair of collector plates C1 and C2 may include a first collector plate C1 and a second collector plate C2. The first collector plate C1 may be electrically coupled to the first end E1 of the filament 11. The first collector plate C1 may be adjacent to the first end E1 of the filament 11. The second collector plate C2 may be electrically coupled to the second end E2 of the filament 11. The second collector plate C2 may be adjacent to the second end E2 of the filament 11.
[0021] As in Fig. As shown in Figure 1, an outer periphery O1 of the first collector plate C1 may have an arcuate shape. The arcuate shape of the outer periphery O1 of the first collector plate C1 may correspond to or be similar to an outer curvature of the filament 11. An outer periphery O2 of the second collector plate C2 is arcuate. The arcuate shape of the outer periphery O2 of the second collector plate C2 may correspond to or be similar to an outer curvature of the filament 11.
[0022] An inner circumference I1 of the first collector plate C1 may have an arc shape. The arc shape of the inner circumference I1 of the first collector plate C1 may correspond to or be similar to an outer curvature of the filament 11. An inner circumference I2 of the second collector plate C2 may be arc-shaped. The arc shape of the inner circumference I2 of the second collector plate C2 may correspond to or be similar to an outer curvature of the filament 11.
[0023] As in Fig. 2, the filament assembly 10 described herein may be used in an x-ray tube 20. The x-ray tube 20 may include a cathode 21 and an anode 22 that are electrically isolated from each other (e.g., by a vacuum and by a ceramic or glass tube 25). The cathode 21 may include the filament assembly 10, with the filament 11 configured to emit electrons toward the anode 22. The filament assembly 10 may be mounted on a pair of electrodes 31 and 32 and housed in a cathode cup 33. The anode 22 may include a target 24 comprising a high atomic number material. The target 24 may generate x-rays 27 in response to incident electrons 26 from the filament 11.
[0024] In Fig. Figure 2 shows a transmission target X-ray tube 20 in which the target 24 is located on an X-ray window 23. The filament arrangement 10 described here is also applicable to X-ray tubes with a reflection target and side window.
[0025] As in Fig. As shown in Figure 2, a first electrode 31 and a second electrode 32 may each extend from the outside of the x-ray tube 20 into the interior of the x-ray tube 20. A power supply may provide a voltage across the first electrode 31 and the second electrode 32, causing an electric current to flow through and heat the filament 11, so that the filament may be heated by the voltage and electric current via the electric current path.
[0026] An electrical current path may extend 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.
[0027] As in the Fig. 3 and Fig. As shown in Figure 4, the first collector plate C1 may have a first hole H1 aligned with the first electrode 31, and the second collector plate C2 may have a second hole H2 aligned with the second electrode 32. The first electrode 31 may be connected to the first collector plate C1 at the first hole H1, and the second electrode 32 may be connected to the second collector plate C2 at the second hole H2.
[0028] The diameter d1 of the first hole H1 may be smaller than the outer diameter D1 of the first electrode 31. A diameter d2 of the second hole H2 may be smaller than an outer diameter D2 of the second electrode 32. Consequently, the first collector plate C1 may rest on top of the first electrode 31, and the second collector plate C2 may rest on top of the second electrode 32. This design avoids strong electric field gradients that would otherwise arise if the electrodes 31 and 32 protruded through the holes H1 and H2, respectively.
[0029] The first electrode 31 can span the first hole H1. The first electrode 31 can completely cover an opening of the first hole H1. The second electrode 32 can span the second hole H2. The second electrode 32 can completely cover an opening of the second hole H2.
[0030] The first collector plate C1 can be welded to the first electrode 31 at a periphery of the first hole H1, and the second collector plate C2 can be welded to the second electrode 32 at a periphery of the second hole H2. The weld can be formed by melting one end of the electrodes 31 and 32 closest to the collector plates C1 and C2. Therefore, a first joint 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 has been melted to form the first joint 41; and a second joint 42 between the second collector plate C2 and the second electrode 32 is formed by a portion 44 of the second electrode 32 that has been melted to form the second joint 42.
[0031] Holes H1 and H2 allow for visual alignment of the filament assembly 10 with the electrodes 31 and 32. Welding of the filament assembly 10 with the electrodes 31 and 32 at holes H1 and H2, respectively, can be performed at a lower temperature than if the welding were performed without the holes. Holes H1 and H2 allow for visual inspection of the weld after its completion.
[0032] The filament arrangement 10 can be mounted on the electrode pair 31 and 32 inside, at or in front of an opening 49 of a cathode cup 33, as shown in the Fig. 3 and Fig. 4. The cathode shell 33 may be connected to the cathode 21. The plane 45 of the filament 11 and the collector plate pair C1 and C2 may run parallel to the opening 49 of the cathode shell 33.
[0033] The filament assembly 10 may have a slightly smaller diameter than the cathode cup 33, so that the cathode cup 33 enforces a central alignment of the filament assembly 10. This facilitates manufacturing and may result in less variation between different X-ray tubes.
[0034] A filament can emit electrons in all directions. A planar filament typically emits electrons in a desired direction, toward the anode target 24, from a top surface of the planar filament that faces the target 24. The planar filament can also emit electrons in an undesired direction, toward the cathode cup 33, from a bottom surface of the planar filament. The bottom surface faces the top surface. The electrons from the bottom surface can change direction (e.g., by 180°) due to a negative voltage on the cathode cup 33, pass between the wires of the filament, and emit toward the target 24. These electrons from the bottom surface are not properly focused. Therefore, the electrons from the bottom surface can result in a misshapen electron spot on the target 24.
[0035] The collector plates C1 and C2 can block these electrons emitted from the bottom and keep them in the cathode shell 33. To effectively block such electrons, it is useful for the collector plates C1 and C2 to block a large portion of the opening 49 of the cathode shell 33 outside the filament 11. For example, the filament assembly 10 can block ≥ 70%, ≥ 80%, ≥ 90%, or ≥ 95% of the opening 49 of the cathode shell 33 outside the filament 11.
[0036] Collector plates C1 and C2 can enclose a large portion of the filament 11 to improve blocking of electrons emitted from the bottom surface. For example, collector plates C1 and C2 can enclose a large portion of the filament 11, such as ≥ 70%, ≥ 80%, ≥ 90%, or ≥ 93% of the filament 11. Another example: Collector plates C1 and C2 can enclose at least 90% of the filament 11. If collector plates C1 and C2 enclose too large a portion of the filament 11, there is a risk that collector plates C1 and C2 will touch each other, resulting in a short circuit. Therefore, collector plates C1 and C2 can enclose ≤ 95%, ≤ 97.5%, or ≤ 99% of the filament 11.
[0037] In order for a voltage at collector plates C1 or C2 to cause an electric current through filament 11, it is desirable that no more than one of collector plates C1 or C2 touches cathode cup 33. If both collector plates C1 and C2 touched cathode cup 33, a short circuit would occur through cathode cup 33, and the desired amount of electric current would not flow through filament 11.
[0038] To avoid this short circuit, the collector plates C1 and C2 can have different radii to each other (R1 ≠ R2), as in Fig. 5. Example: R1 > R2, where R1 is the largest radius from the center 14 of the filament 11 to the outer edge O1 of the first collector plate C1 and R2 is the largest radius from the center 14 of the filament 11 to the outer edge O2 of the second collector plate C2.
[0039] Examples of 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.
[0040] An area (A1) of the first collector plate C1 is typically larger than an area (A2) of the second collector plate C2. A larger area (A1) of the first collector plate C1 may 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) of the second collector plate C2 are 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. The two areas A1 and A2 are areas of the side of the first collector plate C1 and the second collector plate C2 that face the target 24.
[0041] The radii R1 and R2 of the collector plates C1 and C2, respectively, can be substantially larger than the largest radius Rf of the filament 11 from the center 14 of the filament 11 to the 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. One purpose of these relationships is to place the filament 11 in a small area in the center of the cathode shell 33, but also to block almost the entire area of an opening 49 of the cathode shell 33 outside the filament 11.
[0042] Fig. Figure 6 is a top view of a filament group 60 comprising four filament assemblies 10. During manufacturing, multiple filament assemblies 10 can be interconnected as shown. The shape of each filament assembly 10 can be cut into a metal sheet by laser ablation or by patterning and etching.
[0043] The first collector plate C1 may have one, two, three or more recessed areas 12 ( Fig. 1 and Fig.5) on an outer periphery. Each recessed region 12 may have a tab 13 extending outwardly from the recessed region 12 for attachment to other filament assemblies 10 in the filament group 60 during manufacture. The recessed region 12 may prevent the tab 13 from extending beyond a radius R1 of the first collector plate C1 after cutting. For example, the largest radius 16 from the center 14 of the filament 11 to the recessed region 12 may be smaller than the largest radius R1 from the center 14 of the filament 11 to the outermost edge O1 of the first collector plate C1. This is to prevent the tab 13 from interfering with insertion of the filament assembly into the cathode cup 33.
[0044] The tabs 12 on the first collector plate C1 may be sufficient to hold the filament assembly 10 during manufacturing. Therefore, the second collector plate C2 may be free of recesses along its outer periphery. The entire outer periphery of the second collector plate C2 may have an arcuate shape.
Claims
[1] An X-ray tube comprising: a cathode and an anode electrically isolated from each other, the cathode including a filament configured to emit electrons toward the anode, and the anode including a target for generating x-rays in response to incident electrons from the filament; a filament assembly comprising the filament and a pair of collector plates; the filament comprising an elongated wire extending nonlinearly in a plane between a first end and a second end of the filament; a flat dimension of the collector plate pair lies in the plane; the two collector plates are separated from each other; the pair of collector plates encloses a large part of the filament; the pair of collector plates includes a first collector plate electrically coupled to the first end of the filament and a second collector plate electrically coupled to the second end of the filament; a first electrode and a second electrode each extending from the outside of the x-ray tube into the interior of the x-ray tube, the first electrode and the second electrode configured to provide a voltage across the filament; the first collector plate has a first hole aligned with the first electrode and the second collector plate has a second hole aligned with the second electrode; the first electrode is connected to the first collector plate at the first hole and the second electrode is connected to the second collector plate at the second hole; an electrical current path runs from the first electrode to and through the first collector plate, from the first collector plate to the first end of the filament and through the filament to the second end of the filament, from the second end of the filament to and through the second collector plate to the second electrode; and The filament is designed to be heated by the voltage and an electric current through the current path. [2] The X-ray tube according to claim 1, wherein an outer periphery of the first collector plate has an arc shape and an outer periphery of the second collector plate has an arc shape. [3] The X-ray tube according to claim 2, wherein: the arcuate shape of the outer circumference of the first collector plate corresponds to an outer curvature of the filament; and the arcuate shape of the outer circumference of the second collector plate corresponds to an outer curvature of the filament. [4] The X-ray tube according to claim 1, wherein an inner periphery of the first collector plate has an arc shape and an inner periphery of the second collector plate has an arc shape. [5] The X-ray tube according to claim 4, wherein: the arcuate shape of the inner circumference of the first collector plate corresponds to an outer curvature of the filament; and the arcuate shape of the inner circumference of the second collector plate corresponds to an outer curvature of the filament. [6] The X-ray tube according to claim 1, wherein: a diameter of the first hole is smaller than an outer diameter of the first electrode; the first collector plate rests on the first electrode; a diameter of the second hole is smaller than an outer diameter of the second electrode; and the second collector plate rests on the second electrode. [7] The X-ray tube according to claim 1, wherein: a first connection between the first collector plate and the first electrode is formed by a portion of the first electrode that has been melted to form the first connection; and a second connection between the second collector plate and the second electrode is formed by a part of the second electrode which has been melted to form the second connection. [8] An X-ray tube according to claim 1, wherein R1 > R2, where R1 is the largest radius from the center of the filament to an outer edge of the first collector plate and R2 is the largest radius from the center of the filament to an outer edge of the second collector plate. [9] An X-ray tube according to claim 8, wherein 2 ≤ R1 / Rf and 2 ≤ R2 / Rf, where Rf is the largest radius from the center of the filament to the outer edge of the filament. [10] An X-ray tube according to claim 9, wherein 3 ≤ R1 / Rf ≤ 6 and 3 ≤ R2 / Rf ≤ 6.