Biased cathode assembly with improved thermal management for an X-ray tube and method of making the same

Abstract

The present invention is entitled "Biased cathode assembly with improved thermal management for an X-ray tube and method of manufacturing the same". Various systems and methods are provided herein for a biased cathode assembly (102, 170) with improved thermal management for an X-ray tube (100) and a method of manufacturing the same (200). In one example, a cathode assembly (102, 170) of an X-ray tube (100) includes: an emitter assembly (180) including an emitter (110) coupled to an emitter support structure (300); and an electrode assembly (210A, 220A, 230A, 240A, 250A) including an electrode stack (210A) and a plurality of bias electrodes (224, 226, 228). The emitter assembly (180) includes a plurality of separate components coupled together. The electrode assembly (210A, 220A, 230A, 240A, 250A) includes a plurality of separate components coupled together, and the transmitter assembly (180) is coupled to the electrode assembly (210A, 220A, 230A, 240A, 250A).

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to X-ray tubes and biased cathode assemblies for X-ray tubes that include enhanced thermal management. Background Art

[0002] In an X-ray tube, ionizing radiation is produced by accelerating electrons from an emitter in a cathode assembly to an anode target. The emitter is heated by having an electric current run through it to produce electrons, which are emitted from the emitter in the form of an electron beam that is accelerated toward the anode target. Multiple bias electrodes within the cathode assembly are used to shape, steer, and focus the electron beam toward the anode target.

[0003] An X-ray tube bias cathode assembly typically includes an emitter, a plurality of bias electrodes, and a plurality of bias electrode insulators separating the plurality of bias electrodes. The plurality of bias electrodes and the emitter must be precisely positioned relative to each other in order to control the electron beam generated from the emitter.

[0004] The X-ray tube bias cathode assembly may be formed from a monolithic stack of metal and ceramic materials. The metal bias electrodes must be electrically isolated from each other by ceramic bias electrode insulators. Difficulties arise if these bias electrode insulators overheat and begin to conduct electricity. The bias electrodes are configured to operate through a range of different voltages (kV range) to shape, steer and focus the electron beam generated by the emitter. The metal bias electrodes and ceramic bias electrode insulators are machined from a monolithic stack of metal and ceramic materials using a wire cut electrical discharge machining (EDM) process.

[0005] The EDM process imposes design constraints on the cathode assembly configuration and results in non-optimized brazing or welding between ceramic and metal components, resulting in heat transfer from the emitter through the bias electrode insulator. This results in increased thermal overload and current leakage when the bias electrode insulator is heated and the insulation becomes less. The EDM process is also complex, difficult, time consuming, and often requires correction process steps to clean and remove metal particles, and limits the cathode assembly design by forcing the bias electrode insulator into high heat areas (which may cause cracks in the ceramic insulating material and may also limit power output). The resulting cathode assembly is expensive and may be prone to thermal overload at higher power outputs.

[0006] Therefore, it is generally desirable to manufacture a cathode assembly for an X-ray tube by assembling multiple individual components using a high-precision mold to reduce manufacturing costs and improve thermal performance of the cathode assembly. Summary of the invention

[0007] In one embodiment or example, a cathode assembly of an x-ray tube includes an emitter assembly and an electrode assembly, the emitter assembly including an emitter coupled to an emitter support structure, the electrode assembly including an electrode stack and a plurality of bias electrodes. The emitter assembly includes a plurality of separate components coupled together. The electrode assembly includes a plurality of separate components coupled together, and the emitter assembly is coupled to the electrode assembly.

[0008] In another embodiment or example, a biased cathode assembly for an x-ray tube includes an emitter assembly including a cathode cup, at least one emitter insulator, and an emitter. The biased cathode assembly also includes an electrode assembly including at least one bias electrode and at least one bias electrode insulator. The cathode cup, at least one emitter insulator, and the emitter are separate components coupled together. The at least one bias electrode and the at least one bias electrode insulator are separate components coupled together, and the emitter assembly is coupled to the electrode assembly.

[0009] In yet another embodiment or example, a method of manufacturing a cathode assembly for an x-ray tube includes manufacturing an emitter assembly, the emitter assembly including an emitter coupled to an emitter support structure. The method also includes manufacturing an electrode assembly, including manufacturing an electrode stack and coupling a plurality of bias electrodes to the electrode stack. The method also includes assembling the emitter assembly and the electrode assembly together. Manufacturing the emitter assembly includes manufacturing a plurality of individual components to form an emitter support structure, and assembling the emitter to the emitter support structure. Manufacturing the electrode assembly includes: manufacturing a plurality of individual components to form an electrode stack; manufacturing a plurality of individual components to form a plurality of bias electrodes; assembling the electrode stack; assembling a plurality of bias electrodes to the electrode stack; and assembling the emitter assembly and the electrode assembly together.

[0010] It should be understood that the above brief description is provided to introduce in simplified form selected examples that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0012] Figure 1 A simplified schematic cross-sectional view showing the interior of an exemplary X-ray tube is illustrated.

[0013] Figure 2 A method of manufacturing a cathode assembly using a plurality of high-precision molds or jigs is illustrated.

[0014] Figure 3 Components of a transmitter assembly and methods of manufacturing the transmitter assembly are illustrated.

[0015] Figure 4A An exploded view illustrating placement of an emitter assembly within a cathode assembly using an emitter alignment tool.

[0016] Figure 4B A first cross-sectional view of placing an emitter assembly within a cathode assembly using an emitter alignment tool is illustrated.

[0017] Figure 4C A second cross-sectional view illustrating placement of an emitter assembly within a cathode assembly using an emitter alignment tool.

[0018] Figure 5 A top perspective view of a cathode assembly including an emitter assembly and a plurality of subassemblies is illustrated.

[0019] Fig. 6A A simplified schematic cross-sectional view is illustrated showing a first exemplary cathode assembly showing various thermal management elements.

[0020] Figure 6B A simplified schematic cross-sectional view is illustrated showing a second exemplary cathode assembly with a heat shield showing various thermal management elements. DETAILED DESCRIPTION

[0021] The following description relates to an embodiment of a cathode assembly for an X-ray tube. An exemplary X-ray tube is shown in Figure 1 middle. Figure 2 A method of manufacturing a cathode assembly using a plurality of high-precision molds or jigs is illustrated. Figure 3 A method of manufacturing a transmitter assembly is illustrated. Figure 4A , Figure 4B and Figure 4C Placing an emitter assembly within a cathode assembly using an emitter alignment tool is illustrated. Figure 5 A cathode assembly including an emitter assembly and a plurality of subassemblies is illustrated. Fig. 6A and Figure 6B Various examples of cathode assemblies including various thermal management elements are illustrated.

[0022] Figures 1 to 5An exemplary configuration with relative positioning of various parts is shown. In at least one example, if shown as directly contacting or directly coupling each other, such elements may be referred to as directly contacting or directly coupling, respectively. Similarly, in at least one example, elements adjacent to or adjacent to each other may be adjacent to or adjacent to each other, respectively. For example, parts arranged to coplanarly contact each other may be referred to as coplanar contact. For another example, in at least one example, elements positioned to be spaced apart from each other and having only space therebetween without other parts may be described and cited as such. For another example, elements shown as being located above / below each other, located on opposite sides of each other, or located between the left / right sides of each other may be described and cited as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or point of an element may be referred to as the "top" of a part, and the bottommost element or point of an element may be referred to as the "bottom" of a part. As used herein, top / bottom, upper / lower, upper / lower may be relative to the vertical axis of the figure, and may be used to describe the positioning of elements relative to each other in the figure. Thus, in one example, an element shown as being located above other elements is vertically positioned above other elements. As another example, the shapes of elements shown in the figures may be referred to as having these shapes (e.g., such as being rounded, straight, planar, curved, rounded, chamfered, angled, etc.). In addition, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. In addition, in one example, elements shown as being within another element or shown as being outside another element may be described and referred to as such.

[0023] Figure 1 A simplified schematic cross-sectional view showing the interior of an X-ray tube 100 according to an embodiment of the present disclosure is illustrated. The X-ray tube 100 may be used for medical imaging examinations, such as using an X-ray imaging system, a fluoroscopic X-ray imaging system, a computed tomography (CT) imaging system, etc. In the currently contemplated configuration, the X-ray tube 100 includes a cathode assembly 102 and an anode assembly 104 disposed within an evacuated vacuum housing 106. It is noted that the X-ray tube 100 may include other components and is not limited to Figure 1 Parts shown.

[0024] The vacuum housing 106 may be an evacuated housing positioned within an outer housing (not shown) of the X-ray tube 100. The vacuum housing 106 is surrounded by a dielectric cooling oil (not shown) within the outer housing. Additionally, the cathode assembly 102 includes a cathode cup 108 having a plurality of bias electrodes (not shown) and an emitter assembly having an emitter 110 configured to emit electrons toward an anode target 112 of the anode assembly 104. Typically, current is applied from an X-ray generator power supply (not shown) to the cathode assembly 102 and the emitter 110 of the emitter assembly, which results in the generation of electrons.

[0025] The anode assembly 104 may include a rotating anode target 112, a rotor 114, a bearing assembly 116, and a stator (not shown) to rotate the anode target 112. The stator is located outside the vacuum housing 106 and is powered to generate a magnetic field to cause the rotor 114 and the anode target 112 to rotate. In addition, the anode target 112 is positioned in the direction of the emitted electrons to receive the electrons from the emitter 110. In one example, the anode target 112 includes a base 118, a substrate 120, and a target surface 122 having a high "Z" atomic material (such as rhodium, palladium, tungsten, etc.). The rotating anode target 112 rotates via the rotor 114 and the bearing assembly 116, generating a focal point (not shown) for the generation of X-rays from the anode target 112. The X-ray beam (not shown) generated from the focal point of the anode target 112 exits the housing 106 through a window 124 in the housing 106. It should be noted that a fixed anode target may also be used instead of a rotating anode target in an X-ray tube.

[0026] The components of the cathode assembly can be manufactured separately as individual components and then joined together to form a complete cathode assembly. The components of the cathode assembly may include an electrode assembly, a plurality of bias electrodes attached to the electrode assembly, and an emitter assembly integrated in the electrode assembly and the plurality of bias electrodes. The emitter assembly includes an emitter support structure and an emitter attached to the emitter support structure. It is very important that the plurality of bias electrodes and the emitter assembly are within the desired tolerances within the cathode assembly. If the spacing between the plurality of bias electrodes and the emitter assembly is not within the desired tolerances, the ability of the plurality of bias electrodes to control the shape and trajectory of the electron beam is limited. Each component of the cathode assembly is manufactured independently, with its own manufacturing variations and variations in its alignment relative to other components. These components are manufactured into subassemblies, which thus have their own tolerances. The subassemblies are joined together using high-precision molds or fixtures to position and align these key components in the correct orientation relative to each other, while connecting them together by brazing, welding or other joining techniques.

[0027] The cathode assembly consists of individual components that are manufactured independently, positioned using high precision dies for proper positioning and alignment, and then brazed or welded together. Any problems with manufacturing an individual component will not result in loss or rework of the entire cathode assembly, thereby reducing costs. If an individual component or subassembly fails inspection, the rework effort will be to rework or replace that individual component or subassembly, resulting in a significantly reduced cost compared to reworking or replacing the entire cathode assembly.

[0028] The cathode assembly in an X-ray tube includes an emitter assembly precisely positioned between a plurality of bias electrodes that control the direction and shape of the electron beam. Bias electrode is a general term meaning any of the length electrodes, width electrodes, or focus electrodes, or any other electrode designed to control the shape, size, or position of the focal point, cut off the electron beam, or control the magnitude of the electron beam. If the spacing between the emitter assembly and the bias electrodes is outside of acceptable tolerances, this will limit the ability to control the shape or trajectory of the electron beam and may result in high voltage instabilities.

[0029] Figure 2 A method 200 of manufacturing a cathode assembly 170 using a plurality of high precision molds or jigs according to an embodiment of the present disclosure is illustrated.

[0030] Improve assembly accuracy by designing high precision alignment dies so that key components and subassemblies are positioned and aligned within critical tolerances. This means that individual part variations can be compensated for and each assembly accuracy will be based on the die rather than individual component tolerances. This can also result in a lower cost cathode assembly by reducing the tolerances on non-essential features.

[0031] Go to Figure 2 , a first method step 210 of manufacturing an electrode assembly 210A is shown. The electrode assembly 210A includes a plurality of alternating metal conductor rings 212 and ceramic insulator rings or bias electrode insulators 214, which are topped with at least two top metal conductor components 215 that control focus deflection. The plurality of alternating metal conductor rings 212 and ceramic insulator rings or bias electrode insulators 214 are concentrically arranged to form openings 218 therethrough and may be concentric about a central axis 216. Additionally or alternatively, only one metal conductor component may be required for a cathode that only controls focus size.

[0032] The first method step 210 shows a perspective view of a first subassembly 210A or an assembled electrode assembly 210A including a plurality of alternating metal and ceramic components, and a cross-sectional view of a brazing fixture 210B for the electrode assembly. The brazing fixture 210B is a high-precision alignment tool for aligning the electrode assembly 210A for brazing together a plurality of alternating metal conductor rings 212, ceramic insulator rings 214, and at least two top metal conductor components 215. The metal-ceramic components are joined together by brazing. In a representative method, the metal conductor rings 212 are joined to the ceramic insulator rings 214 in an alternating stacking relationship by brazing the metal conductor rings 212 to the ceramic insulator rings 214, and brazing the ceramic insulator rings 214 to at least two top metal conductor components 215. The brazing fixture 210B allows lower precision components to be assembled to higher tolerances, thereby avoiding tolerance stacking of components. In addition, the residual stress caused by the attachment method is reduced compared to the current manufacturing method. This will reduce the risk of warping or deformation during the entire life of the part.

[0033] The next method step 220 shows a perspective view of assembling a first bias electrode of a plurality of bias electrodes, at least two width electrodes 224 to an electrode assembly 210A, and a perspective view of a first electrode welding fixture 220B. A width electrode is an electrode that controls the focus in the "width" direction, which is the smaller dimension of the focus. The at least two width electrodes 224 can be manufactured separately as a width electrode subassembly, allowing for improved uniformity and / or low manufacturing costs. Method step 220 shows a perspective view of at least two width electrodes 224 assembled to an electrode assembly 210A, and a perspective view of a first electrode welding fixture 220B. The first electrode welding fixture 220B can be a width electrode welding fixture. Method step 220 shows a second subassembly 220A, which includes an electrode assembly 210A having a width electrode subassembly, the width electrode subassembly including at least two width electrodes 224 attached to at least two top metal conductor components 215. The at least two width electrodes 224 can include a rod 222 extending from each width electrode. The at least two width electrodes 224 are separately manufactured components and are inserted into the opening 218 of the electrode assembly 210A for attachment to the at least two top metal conductor components 215. The electrode assembly 210A and the at least two width electrodes 224 are inserted into a first welding jig or a width electrode welding jig 220B for positioning and aligning the at least two width electrodes 224 on the at least two top metal conductor components 215. The width electrode welding jig 220B is a high-precision alignment tool for aligning the at least two width electrodes 224 with the electrode assembly 210A and for laser welding or otherwise assembling the at least two width electrodes 224 to the at least two top metal conductor components 215, wherein the at least two width electrodes 224 are positioned opposite to each other and spaced apart from each other within the opening 218 of the electrode assembly 210A. The electrode assembly 210A is precisely aligned relative to the at least two width electrodes 224 using the first welding jig or the width electrode welding jig 220B.

[0034] The next method step 230 shows a perspective view of assembling a second bias electrode of the plurality of bias electrodes, at least two length electrodes 226 to the electrode assembly 210A, and a cross-sectional view of a second electrode welding fixture 230B. The length electrode is an electrode that controls the focus of the focus in the "length" direction, which is the larger dimension of the focus. The at least two length electrodes 226 can be manufactured as a single individual length electrode subassembly or as two separate individual length electrodes, allowing for improved uniformity and / or low manufacturing costs. Method step 230 shows a perspective view of at least two length electrodes 226 assembled to the electrode assembly 210A, and a perspective view of the second electrode welding fixture 230B. The second electrode welding fixture 230B can be a length electrode welding fixture. Method step 230 shows a third subassembly 230A including a first subassembly including an electrode assembly 210A having at least two width electrodes 224 attached to at least two top metal conductor components 215 and a length electrode subassembly including at least two length electrodes 226 attached to the electrode assembly 210A. The separate length electrode subassembly including the at least two length electrodes 226 is a separately manufactured component and is inserted into the opening 218 of the electrode assembly 210A for attachment to the electrode assembly 210A. The electrode assembly 210A, the at least two width electrodes 224, and the at least two length electrodes 226 are inserted into a second welding fixture or length electrode welding fixture 230B for positioning and alignment of the length electrode subassembly including the at least two length electrodes 226 in the electrode assembly 210A. The length electrode welding fixture 230B is a high precision alignment tool for aligning the length electrode subassembly including at least two length electrodes 226 with the electrode assembly 210A, and for laser welding the length electrode subassembly including at least two length electrodes 226 to the electrode assembly 210A, wherein the at least two length electrodes 226 are positioned opposite to each other and spaced apart from each other within the opening 218 of the electrode assembly 210A. The alignment of the electrodes relative to each other is most important, so it is important to align the length electrodes with the width electrodes and also with the electrode assembly (the electrode stack that does not have any effect on the electron beam focusing). The electrode assembly 210A is accurately aligned relative to the length electrode subassembly including at least two length electrodes 226 using the second welding fixture or the length electrode welding fixture 230B.

[0035] The next method step 240 shows a perspective view of assembling a third bias electrode of the plurality of bias electrodes, at least one focus electrode 228 to the electrode assembly 210A, and a cross-sectional view of a third electrode welding fixture 240B. The focus electrode is an electrode that controls the overall focal spot size. A focus electrode may or may not be required, especially in designs that include length electrodes and width electrodes. At least one focus electrode 228 may be manufactured as a single separate focus electrode subassembly, allowing for improved uniformity and / or low manufacturing costs. Method step 240 shows a perspective view of at least one focus electrode 228 assembled to the electrode assembly 210A and a cross-sectional view of the third electrode welding fixture 240B. The third electrode welding fixture 240B may be a focus electrode welding fixture. Method step 240 shows a fourth subassembly 240A, which includes the electrode assembly 210A, at least two width electrodes 224 attached to at least two top metal conductor components 215, at least two length electrodes 226 attached to the electrode assembly 210A, and at least one focus electrode 228 attached to the electrode assembly 210A. The separate focusing electrode subassembly including at least one focusing electrode 228 may include at least one rod 229 extending from the focusing electrode. The at least one focusing electrode 228 is a separately manufactured component and is inserted into the opening 218 of the electrode assembly 210A for attachment to the electrode assembly 210A. The electrode assembly 210A, at least two width electrodes 224, the length electrode subassembly, and the focusing electrode subassembly are inserted into a third welding fixture or a focusing electrode welding fixture 240B for positioning and alignment of the focusing electrode subassembly including at least one focusing electrode 228 in the electrode assembly 210A. The focusing electrode welding fixture 240B is a high-precision alignment tool for aligning the focusing electrode subassembly including at least one focusing electrode 228 with the electrode assembly 210A and for laser welding the focusing electrode subassembly including at least one electrode 228 to the electrode assembly 210A, wherein the at least one focusing electrode 228 is positioned in the opening 218 of the electrode assembly 210A. The alignment of the electrodes relative to each other is most important, so it is important to align the focus electrode with the length electrode and the width electrode, rather than with the electrode assembly (the electrode stack that has no effect on the electron beam focusing). The electrode assembly 210A is accurately aligned relative to at least one focus electrode 228 using a third welding fixture or focus electrode welding fixture 240B.

[0036] The final method step 250 shows a perspective view of assembling the cathode cup support plate 254 to the electrode assembly 210A, and an exploded perspective view of the cathode cup welding fixture 250B. The emitter assembly is positioned in the electrode assembly, attached to the electrode assembly, and the cathode assembly 170 is completed. The method step 250 shows the final subassembly 250A, which includes the electrode assembly 210A, at least two width electrodes 224 attached to at least two top metal conductor components 215, a length electrode subassembly with at least two length electrodes 226 attached to the electrode assembly 210A, a focus electrode subassembly with at least one focus electrode 228 attached to the electrode assembly 210A, and an emitter assembly attached to the electrode assembly. The cathode cup welding fixture 250B includes a top piece 252, a cathode cup support plate 254, an emitter assembly fixture 256, and fasteners 258. The cathode cup support plate 254 includes a plurality of openings 255, which are configured to receive rods 222, 229 extending from the bias electrode. The emitter assembly fixture 256 includes a protrusion 262 that can extend through a central opening 264 in the cathode cup support plate 254. The emitter assembly fixture 256 also includes a plurality of openings 257 that are configured to accommodate the rods 222, 229 extending from the bias electrode. The fastener 258 can extend through the protrusion 262 and engage with the top piece 252 to hold the cathode cup welding fixture 250B together while laser welding the cathode cup support plate 254 to the electrode assembly 210A. In the illustrated example, the fastener 258 and the top piece 252 are arranged on opposite sides of the cathode assembly 170 so that the fastener 258 extends through the entire length of the cathode assembly 170 to engage with the top piece 252. In one example, the top piece 252 is arranged at a first end of the cathode assembly 170, and the fastener is arranged at a second end opposite the first end.

[0037] The method includes inserting the emitter assembly into the emitter assembly fixture 256 of the cathode cup welding fixture 250B for positioning and alignment of the emitter assembly within the bias electrode in the electrode assembly 210A. The cathode cup welding fixture 250B is a high precision alignment tool for aligning the emitter assembly with the bias electrode and the electrode assembly 210A and for laser welding the emitter assembly to the electrode assembly 210A, wherein the emitter assembly is positioned within the opening 218 of the electrode assembly 210A. The cathode cup welding fixture 250B is used to precisely align the electrode assembly 210A relative to the emitter assembly.

[0038] The relative positions of the multiple bias electrodes with respect to each other and the transmitter assembly are critical and will be referenced Figure 3 , Figure 4A , Figure 4B and Figure 4C The transmitter assembly is a separate subassembly and is manufactured separately from the electrode assembly and the plurality of bias electrodes.

[0039] Figure 3 Components of an emitter assembly according to an embodiment of the present invention and a method of manufacturing an emitter assembly 180 are shown. The emitter assembly 180 is a separately manufactured component that includes an emitter support structure 300, an emitter 190, and an optional heat shield 350.

[0040] The transmitter support structure 300 provides a structure for mounting the transmitter 190 thereto. The transmitter support structure 300 includes a crossbar 302 having a pair of openings 304 extending therethrough, the pair of openings being positioned at opposite ends of the crossbar and being configured to receive a pair of insulator posts or transmitter insulators 306 therein. The crossbar 302 may preferably be made of a metallic material, while the insulator posts or transmitter insulators 306 may preferably be made of a ceramic material. In one example, the insulator posts 306 may be brazed to the crossbar 302. The insulator posts 306 may be hollow cylinders, wherein each insulator post has an opening 307 extending through its entire length. A pair of conductors 310 may be inserted through the openings 307. The first conductor 310 extends through the opening 307 in the first insulator post 306, and the second conductor 310 extends through the opening 307 in the second insulator post 306. A cover 312 may be attached to the top end 308 of each of the insulator posts 306. The cover 312 may preferably be made of a metallic material and brazed to the insulator post 306. The conductor 310 may be brazed to the insulator post 306. In one example, the cover 312 is nickel. After the conductor 310 is inserted into the insulator post 306 through the opening 307, the emitter 190 is laser welded to the top of the cover 312 of the emitter assembly 180. The emitter 190 may preferably be made of tungsten. In addition to laser welding, other welding techniques may include welding a platinum bead to facilitate bonding the tungsten emitter to the nickel cover.

[0041] A thermal path is formed from the emitter to the insulator post 306 by heating the crossbar 302, which then heats the insulator post 306 at a critical location where the insulator post 306 is coupled to the crossbar 302. This is the point where the emitter insulator needs to be insulated. In one example, a heat shield 350 can be arranged below the emitter 190, attached to the top of the crossbar 302. The heat shield 350 is preferably attached to the top of the crossbar 302 by a heat shield support 352. The heat shield support 352 can physically couple the heat shield 350 to the crossbar 302. The heat shield support 352 can be relatively small to minimize the conductive heat path between the heat shield 350 and the crossbar 302. The heat shield 350 can protect the insulator column or emitter insulator 306, the cross bar 302, and the bias electrode insulator from radiant heat from the emitter 190, such that the temperature of the insulator column or emitter insulator 306, the cross bar 302, and the bias electrode insulator is lower than the temperature without the heat shield 350. Additionally or alternatively, the heat shield 350 can reflect and / or re-radiate heat back to the emitter 190.

[0042] By doing so, the temperature of the emitter can be raised at a given emitter power level. This may be beneficial in order to reduce the size of the power supply and to reduce the total heat injected into the cathode assembly. In addition, in order to achieve the desired function of the cathode assembly, it is desired that the emitter temperature is relatively hot compared to the crossbar while still preventing heat transfer to adjacent structures. The emitter needs to be at a given temperature for the cathode assembly to function properly, and it is desirable to keep the emitter hot without heating all other components around it. The heat shield 350 can maintain heat in close proximity to the emitter 190, which can maintain the high temperature of the emitter 190 and enhance electron emission. It should be understood that the size, shape, position, and coupling of the heat shield 350 can be adjusted without departing from the scope of the present disclosure. In one example, the heat shield 350 can be directly coupled to the insulator column 306. In addition or alternatively, there may be more than one heat shield 350.

[0043] A high precision tool such as the emitter support structure alignment tool 330 is used to position and align the emitter assembly 180 (including the emitter support structure 300 and the emitter 190) to be held together in a desired position and aligned within a desired tolerance during welding. An opening 322 in the top of the emitter support structure alignment tool 330 allows access for platinum bead placement and / or laser welding.

[0044] In one example, the transmitter support structure alignment tool 330 may be used only during the process of welding the transmitter 190 to the transmitter support structure 300. The transmitter support structure alignment tool 330 may be removed after welding. During welding, the transmitter support structure alignment tool 330 may contact the outer perimeter of the transmitter 190 and the outer perimeter of the crossbar 302. When the transmitter support structure alignment tool 330 contacts these outer perimeters, it may maintain a desired tolerance between the transmitter 190 and the crossbar 302 to place the transmitter 190 in a desired position.

[0045] Figure 4A An exploded view of placing an emitter assembly within a cathode assembly using an emitter alignment tool is shown according to an embodiment of the present disclosure. Figure 4B A first cross-sectional view of placing an emitter assembly within a cathode assembly using an emitter alignment tool is shown according to an embodiment of the present disclosure. Figure 4C A second cross-sectional view of placing an emitter assembly within a cathode assembly using an emitter alignment tool according to an embodiment of the present disclosure is shown. Figure 4A , which shows an exploded view 400 of the emitter assembly 180 being inserted into the electrode assembly 210A of the cathode assembly 170. The emitter alignment tool 410 can be used to align the emitter assembly 180 within the electrode assembly 210A. In one example, the emitter alignment tool 410 is a high precision tool that enters the opening 218 of the electrode assembly 210A from the first end 402 and engages with the emitter assembly 180. In one example, the emitter assembly 180 can enter the electrode assembly 210A through the opening 455 of the cathode cup support plate 254 and into the electrode assembly 210A. In addition or alternatively, the emitter assembly 180 can be inserted through the opening 218 from the second end 404 of the electrode assembly 210A. The emitter alignment tool 410 includes at least two spacer pads 462 and at least two contact pins 464.

[0046] Figure 4B A first cross-sectional view 450 is shown of the emitter assembly 180 being placed within the electrode assembly 210A of the cathode assembly 170 using the emitter alignment tool 410. Figure 4B The assembled cathode assembly 170 is shown in the first cross-sectional view 450 in FIG. 4 with the emitter alignment tool 410 still disposed therein. Figure 4C A second cross-sectional view 470 is shown of placing the emitter assembly 180 within the electrode assembly 210A of the cathode assembly 170 using the emitter alignment tool 410. The first cross-sectional view 450 and the second cross-sectional view 470 may differ in that the views are taken from opposite angles of the cathode assembly 170. For example, the first cross-sectional view 450 is taken along the width of the emitter alignment tool 410, and the second cross-sectional view 470 is taken along the length of the emitter alignment tool 410.

[0047] The first cross-sectional view 450 and the second cross-sectional view 470 illustrate the emitter 190 engaged with the at least two spacers 462 and the at least two contact pins 464 of the emitter alignment tool 410. In one example, the at least two spacers 462 are centering shims configured to properly align or center the emitter 190 within the opening 218 of the cathode assembly 500. In one example, the at least two contact pins 464 are height alignment pins configured to set the appropriate height of the emitter 190. The at least two spacers 462 and the at least two contact pins 464 of the emitter alignment tool 410 can contact the plurality of bias electrodes and the emitter 190 to properly position the emitter 190 relative to each other within the plurality of bias electrodes and within a desired tolerance. The magnets 466 can couple the emitter alignment tool 410 directly to the plurality of bias electrodes, while the combination of the at least two spacers 462 and the at least two contact pins 464 are positioned offset from the plurality of bias electrodes.

[0048] When the emitter assembly 180 is inserted into the electrode assembly 210A from the second end 404 and the emitter alignment tool 410 is inserted into the electrode assembly 210A from the first end 402, at least two spacers 462 can center the emitter 190 on the emitter alignment tool 410 and at least two contact pins 464 can vertically position the stack. The emitter assembly 180 can be arranged in the electrode assembly 210A, wherein the at least two spacers 462 can center the emitter 190 and space it between the plurality of bias electrodes in the desired position. The crossbar 302 of the emitter support structure 300 can be laser welded to the electrode assembly 170. In one example, the crossbar 302 is laser welded to the inner portion of the electrode assembly 210A. The emitter alignment tool 410 can then be removed by pulling upward and releasing the magnet.

[0049] As described above, the manufacture of the cathode assembly includes strategically utilizing high precision molds to reduce manufacturing costs. High precision molds can be used to align components with tolerances greater than the required tolerances. The components can be aligned by high precision molds that are formed to engage each component. The components can then be brazed or welded in place. By making high precision molds that can be used multiple times, the manufacturing cost of the cathode assembly can be reduced. The proposed assembly method using high precision molds also allows lower precision components to be assembled to higher tolerances.

[0050] Figure 5 A top perspective view of an assembled cathode assembly 500 including an emitter assembly and a plurality of bias electrodes is shown according to an embodiment of the present disclosure. Figure 5An assembled cathode assembly 500 is shown, which includes a plurality of separately manufactured components and subassemblies. The plurality of separately manufactured components and subassemblies include: an electrode assembly 210A, the electrode assembly having a width electrode subassembly including at least two width electrodes 224, a length electrode subassembly including at least two length electrodes 226, a focus electrode subassembly including at least one focus electrode 228; and an emitter assembly within the cathode cup, the emitter assembly including an emitter support structure and an emitter 190.

[0051] The electrode assembly 210A includes a plurality of alternating metal conductor rings 212 and ceramic insulator rings or bias electrode insulators 214, which are topped with at least two top metal conductor components 215. The plurality of alternating metal conductor rings 212 and ceramic insulator rings 214 are concentrically arranged to form an opening 218 therethrough. The emitter 190 of the emitter assembly protrudes through the opening 218 of the electrode assembly 210A. The cathode assembly 500 itself includes a plurality of components and subassemblies that are manufactured separately from each other and joined together to provide the desired configuration. The plurality of separately manufactured independent components and subassemblies are used to isolate high heat components from heat sensitive components, thereby allowing the cathode assembly to have a higher power output in a similar size package.

[0052] A key benefit of the disclosed design is the separation of the emitter support structure (primary thermal path) from the electrode assembly insulator, which has a limited temperature range due to leakage current. The leakage current of the insulator increases as the insulator heats up. If the temperature is too high, the leakage current may exceed the capacity of the cathode assembly power supply and cause the voltage present on the electrode to become unstable, resulting in loss of electron beam control. Keeping the insulator cool is key to increasing the power output of the cathode assembly for a given package size.

[0053] Increasing the spacing between the emitter and the insulator can keep them cool, but the methods disclosed herein improve the thermal management of the cathode assembly without increasing the size or size of the cathode assembly. This allows the emitter to be spaced apart from the insulator, thereby reducing the amount of heat transferred to the insulator. It is not preferred to have the heat travel through the electrode assembly, but it is preferred to have the heat remain close to the emitter. However, it is preferred to have the energy incident on the electrode assembly or the emitter assembly be conducted outwardly, further away from other support structures. The multiple bias electrodes and bias electrode insulators of the bias electrode subassembly are manufactured separately, enabling optimization of geometry and the use of cost-effective methods. Insulating components are included around the emitter to reduce heat transfer. Selectively positioning a heat shield around the emitter can reflect heat away from the insulating components and back to the emitter, thereby improving energy efficiency.

[0054] Fig. 6AA simplified schematic cross-sectional view is illustrated of a first exemplary cathode assembly showing various thermal management elements according to an embodiment of the present disclosure. Figure 6B A simplified schematic cross-sectional view of a second exemplary cathode assembly with a heat shield showing various thermal management elements is illustrated in accordance with an embodiment of the present disclosure.

[0055] Now go to Fig. 6A , which shows a cross section of cathode assembly 600. In one example, cathode assembly 600 is an example of a cathode assembly manufactured via multiple components or subassemblies. Cathode assembly 600 includes at least one bias electrode 602, an emitter 604, a cathode cup 606, an interface material 607, an emitter insulator 612, and at least one bias electrode insulator 614. In one example, emitter insulator 612 is Figure 3 606. In one example, cathode cup 606 and interface material 607 are metal and can absorb heat (e.g., act as a heat sink). Arrows 620 show the radiant heat path or direction in which radiant heat from emitter 604 is radiated to various components of cathode assembly 600. In previous prior art examples of cathode assemblies, emitter insulator 612 and at least one bias electrode insulator 614 were combined into a single monolithic insulator, which resulted in a much shorter thermal path and much higher cathode assembly component temperatures. Fig. 6A In the example of , by separating the emitter insulator 612 and the at least one bias electrode insulator 614 into separate insulators, the radiative heat path and the conductive heat path are much longer relative to previous prior art cathode assembly examples. Arrow 630 shows the conductive heat path from the emitter 604 through the emitter insulator 612, through the cathode cup 606 to the at least one bias electrode insulator 614. In conductive heating, heat flows in a direction of decreasing temperature. Therefore, less heating of the cathode assembly components may occur.

[0056] Now go to Figure 6B, which shows a cross-section of a cathode assembly 650. Cathode assembly 650 is substantially the same as cathode assembly 600, except that cathode assembly 650 includes a heat shield 652. As shown, heat shield 652 can be a cylindrical heat shield and can extend from cathode cup 606 into the space between emitter 604, emitter insulator 612, and at least one bias electrode insulator 614. Heat shield 652 can be coupled to cathode cup 606. Arrow 620 shows the radiant heat path or direction in which radiant heat from emitter 604 is radiated to various components of cathode assembly 650. In one example, heat shield 652 substantially blocks radiant heat 620 from emitter 604 from radiating toward at least one bias electrode, cathode cup 606, and at least one bias electrode insulator 614. Heat shield 652 can keep heat in close proximity to emitter 604, which can keep the emitter 604 at a high temperature and enhance electron emission. Additionally or alternatively, the heat shield 652 can reflect and / or re-radiate heat back to the emitter 604. Arrow 630 shows a conductive heat path from the emitter 604 through the emitter insulator 612, through the cathode cup 606, to the at least one bias electrode insulator 614. In conductive heating, heat flows in a direction of decreasing temperature. Therefore, less heating of the cathode assembly components can occur.

[0057] Fig. 6A and Figure 6B Longer conductive and radiative heat paths in the cathode assembly are shown than in previous prior art examples of cathode assemblies (including a monolithic insulator), which results in much shorter heat paths and much higher cathode assembly component temperatures. The cathode assembly of the present disclosure includes much longer conductive and radiative heat paths, which can be shielded with a heat shield, such as Figure 6B As shown. The most critical temperature in the cathode assembly is the temperature of the bias electrode insulator. The cathode assembly design of the present disclosure takes the single insulator of the prior art cathode assembly design and separates it into a separate emitter insulator and a separate bias electrode insulator. This keeps the bias electrode insulator much cooler because the conductive heat path and the radiative heat path are much longer. The additional heat shield between the emitter, emitter insulator and bias electrode insulator blocks the radiative heat path.

[0058] The emitter, emitter insulator, and bias electrode insulator are separate components. In one example, a heat shield can be added between the emitter and bias electrode insulator. The heat shield keeps the bias electrode insulator cool. Leakage current is highly voltage dependent, and the emitter insulator needs to insulate several kV, while the emitter insulator only needs to insulate a few volts. Therefore, it is critical to keep the bias electrode insulator cool; the emitter insulator can get hotter than the bias electrode insulator. If the emitter insulator does get too hot, a Figure 3Heat shield as shown. This is desirable in order to minimize the size of the power supply and reduce the total heat injected into the cathode assembly. The emitter needs to be at a given temperature for the cathode assembly to function properly. It is best to keep the emitter hot without heating up all the other components around the emitter.

[0059] The emitter insulator is a separate component from the bias electrode insulator and is thermally decoupled from the bias electrode insulator. This is achieved by using individual subassemblies or components and maximizing both the conductive heat path and the radiative heat path from the emitter to the bias electrode insulator, resulting in less heating within the cathode assembly. Maximizing the conductive heat path and the radiative heat path does not mean maximizing the heat transferred through the heat path. In one example, a heat shield may be added between the emitter and the bias electrode insulator to substantially block the radiant heat from the emitter and reflect and / or re-radiate the heat back to the emitter. The much longer heat path results in less heating of the cathode assembly.

[0060] The cathode assembly of the X-ray tube can be manufactured by joining multiple components or subassemblies. By dividing the cathode assembly into multiple components or subassemblies, each component or subassembly can be manufactured based on its own manufacturing tolerance, thereby allowing components or subassemblies with lower tolerance thresholds to be manufactured with relatively less precise manufacturing techniques. The bias electrode may include any of a width electrode, a length electrode, or a focus electrode.

[0061] A technical effect of manufacturing the components or subassemblies separately is that the individual components or subassemblies or parts thereof can be manufactured with high precision, thereby increasing the reliability of the manufactured cathode assembly and improving manufacturing consistency. Another beneficial effect of manufacturing the components or subassemblies separately is the optional inclusion of a heat shield that can promote enhanced emitter operation and increased thermal separation of the emitter from other components of the cathode assembly. The cathode assembly is manufactured by joining together multiple components or subassemblies that meet tolerance specifications, providing both manufacturability and thermal benefits.

[0062] As used herein, the elements or steps listed in the singular and beginning with the word "one" or "a kind of" should be understood as not excluding multiple elements or steps, unless such exclusion is clearly stated. In addition, the reference to "an embodiment" of the present invention does not exclude the existence of additional embodiments or examples that also include the cited features. In addition, unless explicitly stated to the contrary, the embodiment of "including", "comprising" or "having" an element or multiple elements with a specific characteristic may include additional such elements without the characteristic. The terms "including" and "in..." are used as the concise language equivalents of the corresponding terms "including" and "wherein". In addition, the terms "first", "second" and "third" etc. are only used as marks, and are not intended to impose numerical requirements or specific positional order on their objects.

[0063] The methods and processes described herein may be performed by a computer, a processor, a machine, an apparatus or other hardware components or a combination thereof. Therefore, the various actions, operations, processes, steps and / or functions described and / or shown may be performed in the described and / or shown sequence, performed in parallel, or omitted in some cases. Similarly, the order of processing is not necessarily necessary to realize the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, processes, steps and / or functions shown may be repeatedly performed according to the specific strategy used. In addition, the actions, operations, processes, steps and / or functions may be implemented by instructions, software codes and / or firmware in a non-transient memory of a computer-readable storage medium programmed into an electronic control system, wherein the actions are performed by executing instructions, software codes and / or firmware of an electronic control system, including various components described above in conjunction with an electronic controller, a computer or a processor.

[0064] This written description uses examples to disclose the present disclosure, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the present disclosure, including making and using any device or system and performing any method. The patentable scope of the present disclosure is defined by the claims, and may include other examples that occur to a person of ordinary skill in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements or method steps that do not differ from the literal language of the claims, or if they include equivalent structural elements or method steps that have minor differences from the literal language of the claims.

Claims

1. A cathode assembly (102, 170) of an X-ray tube (100), comprising: A transmitter assembly (180) comprising a transmitter (110) coupled to a transmitter support structure (300); and an electrode assembly (210A, 220A, 230A, 240A, 250A), the electrode assembly comprising an electrode stack and a plurality of bias electrodes; wherein the transmitter assembly (180) comprises a plurality of separate components coupled together; wherein the electrode assembly (210A, 220A, 230A, 240A, 250A) comprises a plurality of independent components coupled together; and wherein the transmitter assembly (180) is coupled to the electrode assembly (210A, 220A, 230A, 240A, 250A), The emitter support structure (300) includes a crossbar (302), at least two insulating posts (306) extending through at least two openings (304) in the crossbar (302), and wherein a thermal path from the emitter (110) to the at least two insulating posts (306) is formed by heating the crossbar (302).

2. The cathode assembly (102, 170) of claim 1, wherein the electrode assembly (210A, 220A, 230A, 240A, 250A) is configured to receive the emitter assembly (180) therein.

3. A cathode assembly (102, 170) according to claim 2, wherein the emitter support structure (300) includes a plurality of individual components, which are coupled together and precisely aligned within the opening (218) of the electrode assembly (210A, 220A, 230A, 240A, 250A) and coupled to the electrode assembly (210A, 220A, 230A, 240A, 250A) using at least one high precision alignment tool.

4. The cathode assembly (102, 170) of claim 1, wherein the emitter support structure (300) further comprises at least one heat shield (350) attached to a top surface of the crossbar (302) using at least two heat shield supports (352).

5. The cathode assembly (102, 170) of claim 1, wherein the electrode assembly (210A, 220A, 230A, 240A, 250A) comprises a plurality of alternating metal conductor rings (212), a plurality of ceramic insulator rings (214), and a plurality of bias electrodes (224, 226, 228).

6. The cathode assembly (102, 170) of claim 5, wherein the plurality of alternating metal conductor rings (212) and ceramic insulator rings (214) are concentrically arranged to form the electrode stack (210A), the electrode stack having an opening (218) extending therethrough.

7. The cathode assembly (102, 170) of claim 6, wherein the electrode assembly (210A, 220A, 230A, 240A, 250A) further comprises a plurality of bias electrodes (224, 226, 228) coupled to the electrode stack (210A).

8. The cathode assembly (102, 170) of claim 7, wherein the plurality of bias electrodes (224, 226, 228) includes at least two width electrodes (224), at least two length electrodes (226), and at least one focus electrode (228).

9. The cathode assembly (102, 170) of claim 1, wherein the electrode assembly (210A, 220A, 230A, 240A, 250A) comprises: a plurality of conductors (212); a plurality of insulators (214) positioned between the plurality of conductors (212) and separating the plurality of conductors (212) to form an electrode stack (210A); and a plurality of bias electrodes (224, 226, 228) positioned within the electrode stack (210A) for controlling and focusing the electron beam generated by the emitter (110, 190), wherein the plurality of bias electrodes (224, 226, 228) are precisely aligned within the electrode stack (210A) using a high precision mold.

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