X-ray cathode focusing element

Abstract

Various methods and systems for a cathode for an x-ray imaging system are provided. A method for manufacturing the cathode includes machining a plurality of focusing features on a focusing element and welding the focusing element to a base assembly.

Description

Technical Field

[0001] Implementations of the subject matter disclosed herein relate to cathodes for use in imaging systems (e.g., X-ray imaging systems). Background Technology

[0002] In an X-ray tube, ionizing radiation is generated by accelerating electrons from the cathode to the anode in a vacuum via an electric field. The electrons originate from a filament of the cathode assembly through which a current flows. The filament can be heated by the current flowing through it to release electrons from the cathode and accelerate them toward the anode. Additional filaments heated by currents of different voltages can be used to focus the electron beam toward the anode and influence the size and position of the X-ray emission point. The cathode can be configured with additional focusing elements, such as focusing architectures, to further influence the size and position of the X-ray emission point. Summary of the Invention

[0003] In one embodiment, a method for manufacturing a cathode for an imaging system includes machining a plurality of focusing features on a focusing element and welding the focusing element to a base assembly. The focusing element is welded to the base assembly at welding features along a first edge, a second edge, a third edge, and a fourth edge of the base assembly, and the welding stops at each of a first bending space between the first and second edges, a second bending space between the second and third edges, a third bending space between the third and fourth edges, and a fourth bending space between the fourth edge and the first edge.

[0004] It should be understood that the above brief description is provided to introduce selected concepts further described in the detailed embodiments in a simplified form. This is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed embodiments. Furthermore, the claimed subject matter is not limited to embodiments that address any shortcomings mentioned above or in any part of this disclosure. Attached Figure Description

[0005] The invention will be better understood by referring to the following description of non-limiting embodiments, in which: Figure 1 A block diagram of an example imaging system is shown.

[0006] Figure 2 The diagram shows that it can be included. Figure 1 A cross-sectional view of a portion of the X-ray system tube in an imaging system.

[0007] Figures 3A to 3C The illustration may include in Figure 2 The series of manufacturing stages of the cathode in an X-ray system.

[0008] Figure 4 Show Figures 3A to 3C An exploded view of the cathode components.

[0009] Figure 5 Show Figures 3A to 3C A cross-sectional view of the cathode.

[0010] Figure 6 It shows the manufacturing process. Figures 3A to 5 The method of cathode.

[0011] Figures 2 to 5 It is shown to approximate scale, but other relative dimensions may be used. Detailed Implementation

[0012] The following description relates to various embodiments of methods and systems for cathodes used in imaging systems, such as X-ray imaging systems. One method for manufacturing a cathode for an imaging system includes machining a plurality of focusing features on a focusing element and welding the focusing element to a base assembly. The resulting cathode includes a focusing element welded to a base assembly at welding features along a first edge, a second edge, a third edge, and a fourth edge, and welding gaps at each of a first bending space between the first and second edges, a second bending space between the second and third edges, a third bending space between the third and fourth edges, and a fourth bending space between the fourth edge and the first edge.

[0013] Smart cathodes are used in imaging systems, such as X-ray imaging systems, to provide focusing on a wound filament and produce a substantially infinite focal spot shape size with electrode features. A smart cathode can be manufactured by brazing at least two base elements together without focusing features or other cathode architectures, wherein the at least two base elements are joined using a filler metal. Features that provide focusing for the electrode are then machined onto the brazed elements, for example, using electrical discharge machining (EDM) at the component level. EDM can allow multiple feature geometries with linear shapes (e.g., where the planes of the geometry intersect at an angle, rather than a curved geometry). After EDM to produce the feature geometry, the resulting smart cathode can be cleaned. For example, the surface of the smart cathode can be sandblasted to remove brazing overflow and recast layers from the EDM process.

[0014] However, conventional methods for manufacturing smart cathodes present challenges. For example, using EDM to machine the focusing element can create focusing features with angled geometries, which can reduce the focusing range of the smart cathode and decrease the high-voltage stability of the focusing features. Potentially sharp focusing features (e.g., due to the angled geometry) can be positioned within the cathode cup or other shielding elements such that the height of the focusing feature is less than the height of the cathode cup. Furthermore, during the cleaning of the smart cathode after brazing and EDM, some surfaces of the cathode to be cleaned can be blocked from the sandblasting line of sight by the focusing feature geometry. For example, the ceramic insulator used to separate the first voltage applied to a first portion of the smart cathode from the second voltage applied to a second portion of the smart cathode can be blocked from sandblasting by the focusing feature geometry and therefore not cleaned. The aforementioned challenges can lead to electronic and / or voltage leakage, reduced smart cathode lifetime due to component degradation, and other challenges caused by reduced insulation of the ceramic insulator. Therefore, a method for manufacturing a smart cathode that offers increased high-voltage stability, increased usable lifetime, increased options for focusing feature geometry, and increased focusing range may be desired.

[0015] The following description relates to the cathode of an X-ray tube, wherein the X-ray tube may be included in an X-ray imaging system, an exemplary block diagram of which is shown in Figure 1 As shown in the figure, X-ray imaging systems can be interventional radiography imaging systems, fluorescence fluoroscopy imaging systems, mammography imaging systems, fixed or mobile radiography (RAD) imaging systems, tomography imaging systems, computed tomography (CT) imaging systems, etc.

[0016] An X-ray imaging system includes an X-ray source (e.g., an X-ray tube) to generate an irradiating X-ray beam. An example cross-sectional view of an X-ray tube is shown in... Figure 2 As shown in the figure. The X-ray tube includes an anode assembly and a cathode assembly, wherein the cathode assembly includes a cathode, and a method for manufacturing the cathode is described herein. Figures 3A to 3C The diagram illustrates a series of manufacturing stages for the cathode, including brazing the components of the base assembly together, performing component-level electrical discharge machining (EDM) on the base assembly to machine local references and weld features, and welding the focusing element to the weld features of the base assembly. An exploded view of the cathode element is shown in... Figure 4 The exemplary assembly of the cathode is shown in a cross-sectional view. Figure 5 As shown in the image. Figure 6 It shows the manufacturing process. Figures 3A to 5 The method for obtaining a cathode includes machining a base assembly, cleaning the base assembly, machining a focusing element, and welding the focusing element to the base assembly.

[0017] Figures 2 to 5Exemplary configurations with the relative positioning of various components are shown. In at least one example, such components may be referred to as directly contacting or directly coupled if shown to be in direct contact or directly coupled. Similarly, in at least one example, components that are adjacent to or next to each other may be referred to as being adjacent to or next to each other. For example, components arranged to be in coplanar contact with each other may be referred to as being in coplanar contact. As another example, in at least one example, components positioned to be spaced apart from each other and having only space between them without other components may be described and referenced as such. As another example, components shown to be located above / below each other, on opposite sides of each other, or between the left / right sides of each other may be described and referenced relative to each other. Furthermore, as shown, in at least one example, the topmost component or point of the components may be referred to as the “top” of the component, and the bottommost component or point of the components may be referred to as the “bottom” of the component. As used herein, top / bottom, upper / lower, above / below may be relative to the vertical axis of the figure and may be used to describe the positioning of the components in the figure relative to each other. Thus, in one example, an component shown to be above other components is vertically positioned above other components. For example, the shape of the elements shown in the figure may be described as having these shapes (e.g., such as circular, straight, planar, curved, rounded, chamfered, angled, etc.). Furthermore, in at least one example, elements shown as intersecting each other may be described as intersecting elements or intersecting each other. Additionally, in one example, an element shown as being inside or outside another element may be described and referred to as such.

[0018] Before further discussing the methods used to manufacture the cathode in which the focusing element is welded to the base assembly, an exemplary imaging system in which the cathode can be implemented is shown. Now turn to Figure 1 The diagram illustrates a block diagram of an embodiment of an imaging system 10 according to an exemplary embodiment, configured to acquire raw image data and process the image data for display and / or analysis. It should be understood that various embodiments are applicable to numerous X-ray imaging systems implementing X-ray tubes, such as radiographic (RAD) imaging systems, X-ray mammography imaging systems, fluoroscopy imaging systems, tomography imaging systems, or CT imaging systems. The following discussion of imaging system 10 is merely an example of such an implementation and is not intended to limit it in terms of modality.

[0019] like Figure 1As shown, the imaging system 10 includes an X-ray tube or source 12 configured to project a beam of X-rays 14 through an object 16. The object 16 may include a human subject, luggage, or other object to be scanned. The source 12 may be a conventional X-ray tube that generates X-rays 14 having an energy spectrum typically ranging from thirty (30) keV to two hundred (200) keV. The X-rays 14 pass through the object 16 and, after attenuation, strike a detector assembly 18. Each detector module in the detector assembly 18 generates an analog electrical signal representing the intensity of the striking X-ray beam as the X-ray beam passes through the object 16, and thus the attenuated beam. In one embodiment, the detector assembly 18 is a scintillator-based detector assembly; however, direct conversion detectors (e.g., CdTe, CZT, Si detectors, etc.) are also contemplated.

[0020] Processor 20 receives signals from detector assembly 18 and generates an image corresponding to the scanned object 16. Computer 22 communicates with processor 20 to enable the operator to use operator console 24 to control scanning parameters and view the generated images. That is, operator console 24 includes some form of operator interface, such as a keyboard, mouse, voice-activated controller, or any other suitable input device that allows the operator to control imaging system 10 and view reconstructed images or other data from computer 22 on display unit 26. Additionally, console 24 allows the operator to store the generated images in storage device 28, which may include hard disk drive, floppy disk, optical disk, etc. The operator can also use console 24 to provide commands and instructions to computer 22 to control source controller 30, which provides power and timing signals to X-ray source 12.

[0021] Figure 2 It shows that it can be included Figure 1 A cross-sectional view of the X-ray source 200 in the imaging system. For example, the X-ray source 200 can be... Figure 1An exemplary embodiment of the X-ray source 12 is shown, which is formed by an X-ray tube 40 including an anode assembly 42 and a cathode assembly 44. A set of reference axes 201, indicating the x-axis, y-axis, and z-axis, is provided for comparison between the views shown. The X-ray tube 40 is supported by the anode assembly 42 and the cathode assembly 44 within a housing or frame 46, which houses an anode 48 having a target 66, a bearing assembly 50, and a cathode 52. The frame 46 defines a region of relatively low pressure (e.g., vacuum) compared to the environment, where high voltage may be present. Furthermore, the frame 46 may be positioned within a housing (not shown) filled with a cooling medium (such as oil), which may also provide high voltage insulation. Although the anode 48 with the target 66 is described above as a common component of the X-ray tube 40, in alternative X-ray tube embodiments, the anode 48 and the target 66 may be separate components.

[0022] In operation, an electron beam is generated by a cathode assembly 44. Specifically, a cathode 52 receives one or more electrical signals via a series of electrical leads 56. The electron beam occupies a space 54 between the cathode 52 and a target 66 of the anode 48. The electrical signals may be timing / control signals that cause the cathode 52 to emit an electron beam at one or more energies and at one or more frequencies. The electrical signals may also at least partially control the potential between the cathode 52 and the anode 48. The cathode 52 includes a central insulating housing 58 from which a mask 60 extends. The mask 60 encloses the electrical leads 56, which extend to a cathode cup 62 mounted at the end of the mask 60. In some embodiments, the cathode cup 62 serves as an electrostatic lens that focuses electrons emitted from the filament within the cathode cup 62 to form an electron beam.

[0023] In CT applications, X-rays 64 are generated when high-speed electrons from the electron beam are directed from the cathode 52 to the target 66 formed on the anode 48 via a potential difference of, for example, 60,000 (60,000) volts or higher. The X-rays 64 are directed toward the detector array (such as, ...) through radiation emission channels 68 formed in the frame 46. Figure 1 The detector component 18) is emitted.

[0024] The anode assembly 42 includes a rotor 72 and a stator (not shown) located outside the X-ray tube 40 and surrounding the rotor 72, for causing rotation of the anode 48 during operation. The anode 48 is rotatably supported by a bearing assembly 50, which, upon rotation, also causes the anode 48 to rotate about its centerline 70. Thus, the centerline 70 defines the axis of rotation of the anode 48 and the bearing assembly 50. As shown, the anode 48 has an annular shape, and the anode includes an annular opening 74 at its center for receiving the bearing assembly 50.

[0025] The anode 48 can be made of various metals or alloys, such as tungsten, molybdenum, copper, or any material that contributes to bremsstrahlung (i.e., decelerating radiation) when bombarded by electrons. The target 66 of the anode 48 can be selected to have a relatively high refractory value in order to withstand the heat generated by electrons impacting the anode 48. Furthermore, the space between the cathode assembly 44 and the anode 48 can be evacuated to minimize collisions between electrons and other atoms and maximize the potential.

[0026] To prevent the anode 48 from overheating when bombarded by electrons, the rotor 72 rotates the anode 48 around the centerline 70 at a high speed (e.g., 90 Hz to 250 Hz). In addition to the rotation of the anode 48 within the frame 46, in CT applications, the X-ray tube 40 as a whole is rotated around the object (such as...) at a rate typically 1 Hz or faster. Figure 1 The object 16 in the imaging system 10 rotates.

[0027] Different embodiments of the bearing assembly 50 can be formed, such as having multiple suitable ball bearings, but in the exemplary embodiment shown, the bearing assembly includes a liquid metal hydrodynamic bearing having sufficient load-carrying capacity and an acceptable acoustic noise level, in order to Figure 1 The imaging system operates within 10 minutes.

[0028] Generally, bearing assembly 50 includes stationary components (such as central shaft 76) and rotating parts (such as sleeve 78 to which anode 48 is attached). Although relative to Figure 2 The central shaft 76 is described as a stationary component of the bearing assembly 50 and the sleeve 78 as a rotating component of the bearing assembly 50; however, embodiments of this disclosure also apply to embodiments in which the central shaft 76 is a rotating shaft and the sleeve 78 is a stationary component. In such a configuration, the anode 48 will rotate as the central shaft 76 rotates.

[0029] The central shaft 76 may optionally include a cavity or coolant flow path 80 through which coolant (not shown) (such as oil) can flow to cool the bearing assembly 50. Thus, the coolant allows heat generated from the anode 48 of the X-ray tube 40 to be extracted from the anode and transferred from the X-ray tube 40 to the outside. In a straddle-mounted X-ray tube configuration, the coolant flow path 80 extends along the longitudinal length of the X-ray tube 40 (e.g., along the centerline 70). In an alternative embodiment, the coolant flow path 80 may extend only through a portion of the X-ray tube 40, such as in a configuration where the X-ray tube 40 is cantilevered when placed in an imaging system.

[0030] As described above, methods for manufacturing smart cathodes (referred to herein as "cathodes") are expected to produce cathodes with increased high voltage stability, increased lifetime, increased options for focusing feature geometry, and increased focusing range. One method described herein for manufacturing a cathode for an imaging system includes machining multiple focusing features on a focusing element and welding the focusing element to a base assembly. Therefore, the methods described herein can create focus bias electrodes (e.g., focusing elements) in smart cathodes to improve reliability and emission performance.

[0031] The base assembly can be manufactured by brazing an upper extension to a first surface of the insulator and a lower extension to a second surface of the insulator opposite the first surface. Welding features and local datums can be machined onto the base assembly using EDM. The base assembly with welding features and local datums can be cleaned, for example, by sandblasting. Therefore, the surfaces of the base assembly, including the surface of the insulator, can be cleaned before the focusing element is welded to the base assembly. The focusing element can be machined by the cathode manufacturer or by a third party, wherein the machining of the focusing element includes machining focusing features with rounded edges and smooth geometry. The focusing element can then be electropolished to improve the high-level voltage stability of the focusing element. The focusing element is then welded to the base assembly along the welding features of the base assembly.

[0032] Therefore, the method briefly described above and further described herein allows for the fabrication of cathodes with improved reliability and emission performance. Since the focusing features of the focusing element are machined separately from the EDM of the base assembly, focusing feature geometries with rounded edges, smooth geometries, and other geometries that may not require EDM machining can be machined. The usable lifetime of the cathode can be increased by cleaning the base assembly surface, including the cathode surface, to remove solder overflow and recast layer from the EDM. Electropolishing the focusing element before soldering it to the base assembly improves the high voltage stability of the focusing element and, in addition to the rounded edges of the focusing features, allows the height of the focusing element to extend beyond the height of the cathode cup, thereby increasing the focusing capability of the cathode by increasing the number of potential focus field sizes and / or shape options.

[0033] Figures 3A to 3C This illustrates a series of manufacturing stages for the cathode. Figure 3C The image shows the assembled cathode 300. The cathode 300 can be... Figure 2 Example of cathode 50. Figure 3A Phase 1 manufacturing 310 and Figure 3B The second manufacturing stage 320 includes assembling the cathode base assembly 360. Figure 3C The third manufacturing stage 330 includes welding the focusing element to the base assembly 360 to form the cathode 300. Regarding the manufacturing process... Figures 3A to 3C Further details of the method for the cathode 300 shown are in Figure 6 The description is as follows. A set of reference axes 350, indicating the x-axis, y-axis, and z-axis, is provided for comparison between the views shown.

[0034] Figure 3A The first manufacturing stage 310 shown includes a brazing base assembly 360. The base assembly 360 includes an upper extension 302, a lower extension 304, and a solder pad 306. Each of the upper extension 302, lower extension 304, and solder pad 306 may be manufactured by the same or different parties. Furthermore, the upper extension 302, lower extension 304, and solder pad 306 may be brazed together using flame brazing, induction brazing, resistance brazing, or another brazing method, wherein the upper extension 302, lower extension 304, and solder pad 306 are joined by filler metal.

[0035] The upper extension 302 is annular, having rounded corners connecting the straight edge and the hollow center. The upper extension may be formed of a metal, such as nickel, steel, Kovar alloy, or niobium. The upper extension may include a first edge 312, a second edge 314, a third edge 316, and a fourth edge 318. The length of the first edge 312 may be equal to the length of the third edge 316, and the length of the second edge 314 may be equal to the length of the fourth edge 318. The lengths of the first edge 312 along the x-axis and the third edge 316 along the x-axis may be greater than the lengths of the second edge 314 along the z-axis and the fourth edge 318 along the z-axis. The width of each of the first edge 312 and the third edge 316 along the z-axis may be approximately equal to the widths of the second edge 314 and the fourth edge 318 along the z-axis.

[0036] The rounded corner may include a first curved space 322 between the first edge 312 and the second edge 314, a second curved space 324 between the second edge 314 and the third edge 316, a third curved space 326 between the third edge 316 and the fourth edge 318, and a fourth curved space 328 between the fourth edge 318 and the first edge 312.

[0037] The architecture of the upper extension 302 may include welding bases positioned along each edge of the upper extension. For example, a first welding base 332 may be positioned along the length of a first edge 312, a second welding base 334 may be positioned along the length of a second edge 314, a third welding base 336 may be positioned along the length of a third edge 316, and a fourth welding base 338 may be positioned along the length of a fourth edge 318.

[0038] Each of the welding bases may have a stepped geometry, wherein a first step is aligned with the interior of the annular upper extension 302. Alternatively, the first step may be aligned with the central hollow portion of the annular upper extension 302. Each first step of the welding base may have a first height along the y-axis. For example, the first height of the first step of the first welding base 332 is equal to the first height of the first step of the second welding base 334. Each of the welding bases may also have a second step, wherein the second step of the first welding base 332, the second step of the second welding base 334, and the second step of the fourth welding base 338 are each aligned with the outer edge of the annular upper extension 302. The second step of the third welding base 336 may be positioned approximately at the midpoint of the width of the third edge 316 along its length. The height of each second step of the first, second, third, and fourth welding bases may be equal, and this height may be greater than the first height of each of the first steps.

[0039] The solder pad 306 may be an annular insulator formed of ceramic or other insulating material, which fully insulates the upper extension 302 from the lower extension 304, and is referred to herein as insulator 306. Insulator 306 may be positioned between the upper extension 302 and the lower extension 304, and circumferentially surrounds a second layer of the lower extension. The length and width of insulator 306 may be similar to the length and width of the upper extension 302, respectively. Insulator 306 may also have a height along the y-axis, which may be greater than the total height of the upper extension 302, such as... Figure 4 Further details are provided below.

[0040] The first surface of the upper extension 302 can be brazed to the first surface of the insulator 306. Furthermore, the second surface of the insulator opposite the first surface can be brazed to the lower extension 304. For example, the upper extension 302, the lower extension 304, and the pad 306 can be brazed together using flame brazing, induction brazing, resistance brazing, or another brazing method, wherein the upper extension 302, the lower extension 304, and the pad 306 are joined by filler metal.

[0041] The lower extension 304 may have a continuous stepped structure including a first level 342 and a second level 344. The first level 342 may define a first length 346 and a first width 345 of the lower extension 304. The second level 344 may define a second length 348 and a second width 347 of the lower extension, wherein the second length 348 and the second width 347 are less than the first length 346 and the first width 345. The second level 344 may have a second height 354 greater than the first height 352 of the first level 342, such that the second level 344 extends through the hollow portion of the insulator 306 and the upper extension 302. The top surface of the second level 344 may be aligned with the first height of the first step of each of the welding bases 332, 334, 336, and 338 of the upper extension 302. Therefore, the insulator 306 may be positioned between the upper extension 302 and the lower extension 304, and circumferentially surrounds the second level 344 of the lower extension 304.

[0042] Figure 3B The second manufacturing stage 320 shown includes component-level EDM of local references and welding features on the base assembly 360. Welding features are machined on each of the first welding base 332, second welding base 334, third welding base 336, and fourth welding base 338 of the upper extension 302. Each of the first welding feature 362, second welding feature 364, third welding feature 366, and fourth welding feature 368 (e.g., corresponding to the first to fourth welding bases, respectively) may have an L-shaped geometry, wherein the first height of the first step (e.g., of the corresponding welding base) and the width of the second step (e.g., of the corresponding welding base) are reduced using EDM. The reduced first height of the first step is referred to herein as the third height. The reduced width of the second step is referred herein as the fourth width of the first welding feature 362 and the third welding feature 366 along the z-axis, and the fifth width of the second welding feature 364 and the fourth welding feature 368 along the x-axis. The third height of each welding feature may be less than the fourth or fifth width of the corresponding welding feature. Using EDM to machine the welding features of the welding base from the upper extension 302, a space 361 with a sixth width 356 along the z-axis and a seventh length 358 along the x-axis can be created on the top of the base assembly 360, allowing the focusing element to be positioned within this space, such as... Figure 3C As shown. The third height of each welded feature of the upper extension may partially surround the focusing element, as further described below.

[0043] Component-level EDM with local datums may include machining a first datum 370 and a second datum 372. The first datum 370 and the second datum 372 allow for the attachment of a cathode shield (e.g., at the lower extension 304) to a refractory cup assembly (e.g., ...) via welding. Figure 5 (The cathode cup shown).

[0044] Figure 3C The third manufacturing stage 330 shown includes welding the focusing element 375 to the base assembly 360 at welding features. For example, the focusing element 375 is attached to the base assembly along welding features of the base assembly via welding couplings (e.g., weld metal). The focusing element 375 includes focusing features with channels for positioning filaments, and other geometries and architectures for emitting and focusing electrons into a single electron beam to strike the anode and generate an X-ray beam, as described above. Further details of the focusing element 375 are described in... Figure 5 As described in the text. See also: Figure 3C The focusing element 375 has an eighth width 376 along the x-axis and a ninth length 378 along the z-axis. The eighth width 376 and the ninth length 378 of the focusing element 375 may be smaller than the seventh length 358 and the sixth width 356, respectively (in... Figure 3B (As depicted in the image). The focusing element 375 can therefore be positioned within the space formed by the welding feature of the upper extension 302, and the base of the focusing element 375 can rest on the welding feature, such as... Figure 5 As further shown in the text.

[0045] The focusing element 375 is welded to the base assembly 360 at each of the weld features in the base assembly. In one example, laser welding is used for welding. However, other suitable welding methods can be used, which allow the base assembly to be coupled to the focusing element without thermal deformation (e.g., melting or other degradation) of the focusing element and / or the base assembly. The focusing element 375 is welded along the first weld feature 362 ( Figure 3C (Not specifically shown in the image), second welding feature 364, third welding feature 366, and fourth welding feature 368 are welded to the base assembly 360. Welded connections along each of the welding features can connect the focusing element and the corresponding welding feature along the length of each of the first welding feature 362, second welding feature 364, third welding feature 366, and fourth welding feature 368. Positioning the welding features away from the focusing element's focusing feature can reduce thermal deformation of the focusing features during the welding process.

[0046] Welding stops at each bend in the bend space between the weld features. For example, a gap exists in the weldment within the first bend space (e.g., Figure 3A The first curved space 322), the second curved space 324, the third curved space 326, and the fourth curved space (e.g., shown) are illustrated. Figure 3AAt the fourth bend space 328 shown. The height of the gap can be equal to (e.g., the third height of the first step of the weld feature). The gap in the weld at each bend space between the welds at the weld feature allows the weld and other metallic features of the cathode to expand when heated, thus reducing the likelihood of the weld deteriorating due to stress.

[0047] Use as described Figures 3A to 3C The cathode 300 manufactured by the steps shown can be implemented in the X-ray tube of an imaging system, such as... Figure 2 The X-ray tube. In Figure 6 The method is detailed in Figures 3A to 3C The steps are as follows. Before further discussing the methods used to manufacture the cathode, in which the focusing element is welded to the base assembly, an exploded view of the cathode element is shown in... Figure 4 The cross-sectional view of the cathode is shown in the figure. Figure 5 As shown in the image.

[0048] Figure 4 Show Figures 3A to 3C An exploded view of the cathode 300 element is shown in Figure 400. Similar components are... Figures 3A to 3C Similar numbering is used in the above description. In addition to the previously described focusing element 375, upper extension 302, insulator 306, and lower extension 304, the cathode 300 may also include a first brazing foil 402 and a second brazing foil 404. The first brazing foil 402 and the second brazing foil 404 are used to braze the insulator 306 (e.g., formed of ceramic or other insulating material) to the upper extension 302 and the lower extension 304, as previously described. Figures 3A to 3C The description in and in Figure 6 As further described herein, a set of reference axes 401, indicating the x-axis, y-axis, and z-axis, is provided for comparison between the views shown.

[0049] As described above, the length and width of the insulator 306 can be similar to the length and width of the upper extension 302, respectively. The length and width of the first brazing foil 402 and the second brazing foil 404 can also be equal to the length and width of the insulator 306 and the upper extension 302, respectively. Therefore, the length of the first brazing foil 402, the second brazing foil 404, the insulator 306, and the upper extension 302 can be equal to the tenth length 420. Furthermore, the width of the first brazing foil 402, the second brazing foil 404, the insulator 306, and the upper extension 302 can be equal to the eleventh width 422. The tenth length 420 and the eleventh width 422 can be greater than the first width 345 and the second length 348 of the second layer of the lower extension 304, respectively.

[0050] Insulator 306 may also have a height 424 along the y-axis, as measured between the first surface 432 and the second surface 434 of insulator 306, which may be greater than the total height of the upper extension 302 and approximately equal to the second height 354 of the second level 344 (in Figure 3A (as depicted in the diagram). Therefore, when the insulator 306 is positioned between the upper extension 302 and the lower extension 304, the first surface 430 of the upper extension 302 can rest on the first surface 432 of the insulator 306 (e.g., the first solder foil 402 is positioned therebetween), and the second surface 434 of the insulator 306 opposite to the first surface 432 of the insulator 306 can rest on the lower extension 304 (e.g., the second solder foil 404 is positioned therebetween).

[0051] In one example, the insulator 306, the first brazing foil 402, and the second brazing foil 404 may also be configured with two pairs of notches 408, 410 for positioning tenons. The positioning tenons can be positioned on at least one of the lower extension 304 and the upper extension 302, such that when the upper extension 302, the first brazing foil 402, the insulator 306, the second brazing foil 404, and the lower extension 304 are... Figure 3C As shown in the positioning (e.g., in the assembly configuration of cathode 300), positioning tenons extend into the pair of cutouts 408, 410 to provide overall fixation of the cathode. In one example, the two pairs of cutouts 408, 410 may be centered along the width 422 of each element and may span the height 424 of insulator 306 and the heights of the first brazing foil 402 and the second brazing foil 404, wherein the height of the brazing foil is less than the height of the upper extension. Positioning tenons extending through the cutouts 408, 410 connect the upper extension 302, insulator 306, and lower extension 304. The first brazing foil 402 may be sandwiched between the upper extension 302 and insulator 306. The second brazing foil 404 may be sandwiched between insulator 306 and lower extension 304. The distance between the upper extension 302 and lower extension 304 may be equal to the height 424 of insulator 306.

[0052] Both the first brazing foil 402 and the second brazing foil 404 may be configured with dimensions and geometries similar to each other, the upper extension 302, the insulator 306, and the lower extension 304, including a tenth length 420 and an eleventh width 422. The first brazing foil 402 and the second brazing foil 404 may be annular structures having internal dimensions similar to the insulator 306 and the upper extension 302, having a first wall thickness 447, a second wall thickness 445, and a third wall thickness 443. The first wall thickness 447 may be greater than the second wall thickness 445, and the second wall thickness may be greater than the third wall thickness 443. The annular structure allows a second layer 344 of the lower extension 304 to protrude through the center of the second brazing foil 404, the insulator 306, and the first brazing foil 402. In one example, the top of the second layer 344 may be flush with the top of the first brazing foil 402. In another example, the second layer 344 may extend through the upper extension 302, such as... Figure 5 As further shown in the text.

[0053] Figure 5 It shows Figures 3A to 3C The cross-sectional view of the cathode 300 is shown in Figure 500, as shown along... Figure 4 The horizontal cut defined by the dashed line 4-4 in the diagram. Similar components and... Figures 3A to 4 The components are similarly numbered and include a focusing element 375, an upper extension 302, an insulator 306, and a lower extension 304. Figure 5 The illustrated embodiment also includes a cathode cup 510, which can be... Figure 2 Example of cathode cup 62.

[0054] The cathode cup 510 can be used as an electrostatic lens to focus electrons emitted from a thermionic filament within the cathode cup to form an electron beam. The cathode cup 510 can be a hollow rectangular shell formed of metal (such as nickel or Kovar alloy) having an open top and an open bottom surrounding at least a portion of the upper extension 302, the insulator 306, the lower extension 304, and the focusing element 375, as will be further described below.

[0055] The focusing element 375 may be a single continuous architecture having at least one channel sized such that a thermionic filament can be positioned therein, and having at least one focusing feature on either lateral side of the at least one channel, such as... Figures 3A to 4 As shown. In one example, the focus element 375 can be machined using EDM and a five-axis milling machine. The focus features and channels of the focus element can have rounded corners and edges, as well as smooth geometry, which is the opposite of corners intersecting at linear angles. Other methods can be used to machine the focus element, which allows for rounded edges and smooth geometry.

[0056] The focusing element 375 can be configured as a continuous single-architecture (e.g., monolithic) grid electrode with an electron-emitting filament positioned in each of at least three channels having a geometry that focuses emitted electrons into a single electron beam. The focusing element 375 can have a bowl shape, for example, the sides of the focusing element can have a greater height than the center of the focusing element. For example, the focusing element can have a first side height 533 greater than the second internal height 535.

[0057] The focusing element geometry may include a first lateral edge feature 502 and a second lateral edge feature 504 at opposite ends of the eighth width 376. Each of the first lateral edge feature 502 and the second lateral edge feature 504 may be configured with a lateral recess 506 that helps to focus the electron beam. Each lateral recess 506 of the first lateral edge feature 502 and the second lateral edge feature 504 is positioned at a vertical height higher than the vertical height of the adjacent filament, wherein the vertical height of the recess is defined as the distance from the bottom point of the recess to the face of the adjacent upper extension 302 of the focusing element 375. The edges of the lateral recess 506 may be rounded.

[0058] The focusing element 375 may also include at least one thermionic filament positioned within a channel of the focusing element architecture. Figure 4 In one implementation, the small filament 512 is positioned in the first channel 522, the medium filament 514 is positioned in the second channel 524, and the large filament 516 is positioned in the third channel 526. Each of the small filament 512, medium filament 514, and large filament 516 can be positioned at a different height within the corresponding channel relative to the top of the second level of the lower extension 304. Each filament can be positioned approximately at the center of the corresponding channel relative to the channel width.

[0059] Additional focusing features may be positioned between each channel in the channel along an eighth width 376 of the focusing element 375, which may extend along a ninth length 378 of the focusing element 375, such as... Figures 3C to 4 As shown.

[0060] A first focusing feature 528 is positioned between a second channel 524 and a first channel 522, and a second focusing feature 530 is positioned between a first channel 522 and a third channel 526. Each of the first focusing feature 528 and the second focusing feature 530 may be configured with a geometry that focuses electrons emitted from a filament on either side into a single electron beam for focusing element 375. Thus, the channels may be spaced apart by the width of the focusing features between the respective channels. As described above, when the filaments are centered with respect to the width of the respective channels, the distance between each filament may be greater than the distance between each channel. A first lateral edge feature 502, a second lateral edge feature 504, a first focusing feature 528, and a second focusing feature 530 are configured as a continuous single architecture of focusing element 375. The first lateral edge feature 502 and the second lateral edge feature 504 may be referred to herein as focusing features.

[0061] The focusing element geometry (including channel walls and focusing features) of focusing element 375 is configured with integrated edge focusing, wherein the edges of the focusing element are rounded, such as having a radius of at least 120µm, as opposed to sharp edges defined as having a radius of less than 80µm (e.g., the intersection of two straight planes at 90 degrees). In one example, all edges of the focusing element geometry are configured as rounded edges. In one example, the focusing element can be machined using EDM and five-axis milling. Thus, the focusing features and channels of the focusing element have rounded corners and edges, as well as a smooth geometry, as opposed to corners intersecting at linear angles. Other methods can be used to machine the focusing element, which allows for rounded edges and smooth geometry.

[0062] The focusing element 375 may be configured with a hollow space 532 located below the plane of the filament, through which the insulating legs of the filament may pass. When a voltage is applied to the filament via current feed to heat the filament and emit electrons, each filament leg may be insulated, for example, by a leg insulator, to minimize the charge lost to the environment and to isolate the current feed charge from the charge applied to the focusing element 375, the charge of the upper extension 302, and the charge of the lower extension 304.

[0063] The hollow region provides a gap region between the focusing element 375 and the top of the second layer 344 of the lower extension 304. Furthermore, since the first width 345 of the second layer of the lower extension 304 is smaller than the eleventh width 422 of the insulator 306 and the upper extension 302, and smaller than the eighth width 376 of the focusing element 375, the gap region extends around the side of the second layer 344 of the lower extension 304. A lateral gap 540 thus exists between the second layer 344 of the lower extension 304 and the insulator 306, between the second layer 344 and the upper extension 302, and between the second layer 344 and the focusing element 375 (e.g., around the circumference of the second layer 344). The width of the lateral gap 540 between the second layer and the upper extension 302 is equal to the width of the lateral gap 540 between the insulator 306 and the second layer. The lateral gap 540 has a first width equidistant around the circumference of the second layer. The lateral gap 540 between the second layer 344 and the focusing element 375 can be circular, such that the width of the lateral gap 540 between the second layer 344 and the focusing element 375 is smaller than the width of the lateral gap 540 between the insulator 306 and the second layer.

[0064] As described above, the filaments can be laterally spaced across the width of the focusing feature. Each of the filaments in the first channel, the second channel, and the third channel has an unequal lateral spacing relative to its adjacent filaments, wherein the lateral spacing is defined as the lateral distance relative to a horizontal axis (e.g., the x-axis) between the center point of the first filament diameter and the center point of the second filament diameter. Specifically, the small filament 512, which can be positioned between the medium and large filaments, can be offset from the center of the total width of the focusing element 375 (e.g., equal to the eighth width 376). From the impact anode target (such as...) Figure 2 Ions emitted by the electron beam from the anode (48) and target (66) are most likely to strike the center of the focusing feature. Therefore, potential degradation of the filament can be prevented by positioning the small filament to the left of the center point of the focusing feature.

[0065] Furthermore, the height 537 of the focusing element 375 may extend at least partially above the height of the cathode cup 510. As described above, the focusing element 375 is electropolished before being welded to the welding features of the upper extension 302, which can increase the high voltage stability of the focusing element 375. The focused field that can be guided by the focusing element 375 can therefore be increased because the focusing element can extend above the height of the cathode cup 510, while reducing degradation due to high voltage.

[0066] Figure 6 It shows the manufacturing process. Figures 3A to 5 An exemplary method 600 for a cathode. Method 600 may be implemented by an X-ray imaging system manufacturer, a cathode manufacturer, etc.

[0067] At 602, method 600 includes manufacturing a base assembly. The cathode base assembly may include an upper extension, a lower extension, and a bonding pad, such as... Figures 3A to 5 As shown. The solder pad can be an annular insulator formed of ceramic or other insulating material, which fully insulates the upper extension from the lower extension, and is referred to herein as the insulator. The insulator can be positioned between the upper and lower extensions and circumferentially surrounds a second layer of the lower extension.

[0068] At 604, manufacturing the base assembly includes brazing the upper extension, the insulator, and the lower extension together. A first face of the upper extension may be brazed to a first face of the insulator, and a second face of the insulator opposite to the first face of the insulator may be brazed to the lower extension. The upper extension, the lower extension, and the solder pad may be brazed together using flame brazing, induction brazing, resistance brazing, or another brazing method, wherein the upper extension, the lower extension, and the solder pad are joined by filler metal.

[0069] At point 606, manufacturing the base assembly also includes component-level electrical discharge machining (EDM) to perform local datum and weld features. Local datum and weld features are machined on the upper extension of the base assembly. For example... Figures 3A to 5 As shown, the welding features are machined on each of the first, second, third, and fourth edges of the second surface of the upper extension, and there is a bending space between each of the welding features.

[0070] At 608, after brazing the base assembly, method 600 includes cleaning the base assembly. Cleaning the base assembly removes potential solder overflow and / or recast layer from the EDM process. In one example, cleaning is performed by sandblasting the base assembly. Since the focusing element has not yet been attached (e.g., soldered) to the base assembly, solder overflow and EDM recast layer in the insulator, as well as in the upper and lower extensions, can be removed.

[0071] Method 600 may optionally include machining a focusing element at 610. The machining of the focusing element may include machining a single continuous structure having at least one channel sized such that a filament can be positioned therein, and at least one focusing feature on either lateral side of the at least one channel, such as... Figures 3A to 5 As shown. In one example, the focus element can be machined using EDM and five-axis milling. The focus features and channels of the focus element can have rounded corners and edges, as well as smooth geometry, which is the opposite of corners intersecting at linear angles. Other methods can be used to machine the focus element, which allows for rounded edges and smooth geometry. In another example, the focus element is manufactured by a third party and can include a similar architecture (e.g., at least one channel having at least one focus feature on either side) or an architecture different from the one described above.

[0072] Processing the focusing element can also include electropolishing the focusing element at 612. Electropolishing the focusing element can improve the high voltage stability of the focusing element. High voltage stability allows the focusing features of the focusing element to extend above the height of the cathode cup, such as... Figure 5 As shown. The extension of the focusing feature above the cathode cup height increases the focusing field of the cathode and increases the amount of electrons emitted from the filament that strike the anode.

[0073] At 614, method 600 includes welding a focusing element to a base assembly at a welding feature. The focusing element is welded to the base assembly at the welding feature along a first edge, a second edge, a third edge, and a fourth edge of the second surface of the upper extension. Welding stops at each of a first bending space between the first and second edges, a second bending space between the second and third edges, a third bending space between the third and fourth edges, and a fourth bending space between the fourth edge and the first edge, as shown below. Figures 3A to 5 As shown, laser welding methods can be used to weld the focusing element to the base assembly.

[0074] In this manner, cathodes for X-ray imaging systems can be manufactured, wherein the focusing element is welded to the base assembly after cleaning of the base assembly and electropolishing of the focusing element. This allows for cleaning of the insulators of the base assembly, as well as the upper and lower extensions, which can increase the cathode's service life. Additionally, machining the focusing element separately from the machined base assembly allows for a focusing element geometry that can increase the focusing of electrons emitted from the filament into a single electron beam. Electropolishing the focusing element improves the high-voltage stability of the focusing element, further increasing the cathode's service life and enhancing the focusing of emitted electrons. Welding the focusing element to the base assembly at weld features along the first, second, third, and fourth edges, rather than at the bends between the weld features, allows for stress relief. For example, the bends between the weld features allow the welded parts and other metallic features of the cathode to expand when heated during welding of the focusing element to the base assembly and during operation of the cathode (e.g., emitting electrons from the filament), reducing the likelihood of breakage due to stress.

[0075] The technical effects of the cathode used in the imaging system as described herein are increased electron focusing capability of the cathode, high voltage stability of the cathode, and increased yield of manufactured cathodes, wherein the cathode includes multiple focusing features on a focusing element, and the focusing element is welded to a base assembly including an insulator.

[0076] This disclosure also provides support for a method of manufacturing a cathode for an X-ray imaging system, the method comprising machining a plurality of focusing features on a focusing element and welding the focusing element to a base assembly. In a first example of the method, the method further comprises brazing an upper extension and a lower extension to a pad to form a base assembly, wherein a first face of the upper extension is coupled to a first face of the pad using filler metal and the lower extension is coupled to an opposite second face of the pad using filler metal. In a second example of the method, optionally including the first example, the method further comprises machining a local reference and a weld feature on the upper extension of the base assembly. In a third example of the method, optionally including one or both of the first and second examples, the local reference and weld feature are machined using electrical discharge machining (EDM). In a fourth example of the method, optionally including one or more of the first to third examples, or each of them, the weld feature is machined on each of a first, second, third, and fourth edge of a second face of the upper extension, with a bending space between each of the weld features. In a fifth example of the method, optionally including one or more of the first to fourth examples, the focusing element is welded to the base assembly at welding features, and the welding stops at each of the following: a first bending space between the first and second edges, a second bending space between the second and third edges, a third bending space between the third and fourth edges, and a fourth bending space between the fourth and first edges. In a sixth example of the method, optionally including one or more of the first to fifth examples, the focusing element is welded to the upper extension using laser welding. In a seventh example of the method, optionally including one or more of the first to sixth examples, the method further includes cleaning the base assembly. In an eighth example of the method, optionally including one or more of the first to seventh examples, cleaning the base assembly includes sandblasting the base assembly. In a ninth example of the method, optionally including one or more of the first to eighth examples, multiple focusing features are machined on the focusing element using electrical discharge machining and five-axis milling, such that the multiple focusing features have rounded corners and smooth geometry. In a tenth example of the method, which optionally includes one or more or each of the first to ninth examples, the method further includes: an electropolishing focusing element.

[0077] This disclosure also provides support for a cathode for an X-ray imaging system, the cathode including: a base assembly, a plurality of focusing features on a focusing element, and a welded coupling, wherein the focusing element is coupled to the base assembly via the welded coupling. In a first example of the system, the system further includes: a cathode cup circumferentially surrounding the base assembly and the focusing element, wherein the focusing element extends above the height of the cathode cup. In a second example of the system optionally including the first example, the base assembly comprises a lower extension brazed to a first side of an insulator using filler metal, and an upper extension brazed to an opposite second side of the insulator using filler metal. In a third example of the system optionally including one or both of the first and second examples, the lower extension has a stepped architecture, wherein a second level extends vertically from a portion of the first level such that the height of the second level is at least partially circumferentially surrounded by the insulator. In a fourth example of a system that optionally includes one or more of the first to third examples, the system further includes: a first lateral gap having a first width around the circumference of the second layer between the second layer and the insulator, and a second lateral gap having a second width equal to the first lateral gap between the second layer and the upper extension. In a fifth example of a system that optionally includes one or more of the first to fourth examples, the system further includes: a distance greater than or equal to the height of the insulator between a first surface of the upper extension and an upper surface of the first layer of the lower extension. In a sixth example of a system that optionally includes one or more of the first to fifth examples, a welded coupling attaches a focusing element to a base assembly along a welded feature positioned along a first edge, a second edge, a third edge, and a fourth edge of the upper extension. In a seventh example of the system that optionally includes one or more or each of the first to sixth examples, each of the first bending space between the first and second edges, the second bending space between the second and third edges, the third bending space between the third and fourth edges, and the fourth bending space between the fourth edge and the first edge is in a gap present in the welded joint.

[0078] This disclosure also provides support for a method for manufacturing a cathode, the method comprising: manufacturing a base assembly, including: brazing a first face of an upper extension to a first face of an insulator using filler metal; brazing a lower extension to a second face of the insulator opposite to the first face of the insulator using filler metal; machining welding features on each of a first edge, a second edge, a third edge, and a fourth edge of the second face of the upper extension opposite to the first face of the upper extension using electrical discharge machining, each of the welding features having a bending space; machining a reference on the base assembly; cleaning the base assembly by sandblasting; machining a focusing element having a plurality of focusing features and at least one channel; electropolishing the focusing element; positioning a thermionic filament in each of the at least one channel; welding the first face of the focusing element to the second face of the upper extension at each of the welding features along the first edge, the second edge, the third edge, and the fourth edge; and stopping welding at each of a first bending space between the first edge and the second edge, a second bending space between the second edge and the third edge, a third bending space between the third edge and the fourth edge, and a fourth bending space between the fourth edge and the first edge.

[0079] As used herein, elements or steps listed in the singular and beginning with the word "a" or "an" should be understood to not exclude a plurality of said elements or steps unless such exclusion is explicitly stated. Furthermore, references to "one embodiment" of the invention are not intended to be construed as excluding the existence of additional embodiments that also include the referenced features. Moreover, unless explicitly stated to the contrary, embodiments that "comprise," "include," or "have" elements or multiple elements having a particular characteristic may include additional such elements that do not have that characteristic. The terms "comprise" and "in..." are used as concise linguistic equivalents to the corresponding terms "comprising" and "wherein". Furthermore, the terms "first," "second," and "third," etc., are used merely as notations and are not intended to impose numerical requirements or a particular order of position on their objects.

[0080] This written description uses examples to disclose the invention, including the best mode, and also enables those skilled in the art to practice the invention, including making and using any device or system and performing any included methods. The scope of patentability of the invention is defined by the claims and may include other examples that would occur to those skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that have minor differences from the literal language of the claims.

Claims

1. A method for manufacturing a cathode for an X-ray imaging system, the method comprising: Multiple focusing features are machined onto the focusing element; The upper and lower extensions are brazed to the pads to form the base assembly; as well as The focusing element is welded to the base assembly. The welding features are machined on each of the first, second, third, and fourth edges of the second surface of the upper extension, and there is a bending space between each of the welding features. The focusing element is welded to the base assembly at a welding feature, and the welding stops at each of the following: a first bending space between the first edge and the second edge, a second bending space between the second edge and the third edge, a third bending space between the third edge and the fourth edge, and a fourth bending space between the fourth edge and the first edge.

2. The method of claim 1, wherein the first surface of the upper extension is coupled to the first surface of the solder pad using filler metal and the lower extension is coupled to the opposite second surface of the solder pad using filler metal.

3. The method of claim 1, wherein the focusing element is welded to the upper extension using laser welding.

4. The method of claim 1, further comprising cleaning the base assembly.

5. The method of claim 4, wherein cleaning the base assembly comprises sandblasting the base assembly.

6. The method of claim 1, wherein the plurality of focusing features are machined on the focusing element using electrical discharge machining and five-axis milling, such that the plurality of focusing features have rounded corners and smooth geometry.

7. The method of claim 1, further comprising electropolishing the focusing element.

8. A cathode for an X-ray imaging system, the cathode comprising: Base assembly; Multiple focusing features on the focusing element; as well as Welded connectors; in The focusing element is connected to the base assembly via the welded connector. The base assembly comprises a lower extension brazed to a first side of an insulator using filler metal, and an upper extension brazed to the opposite second side of the insulator using the filler metal. The welded connector links the focusing element to the base assembly along a welded feature positioned along the first, second, third, and fourth edges of the upper extension. Each of the following: a first bending space between the first edge and the second edge, a second bending space between the second edge and the third edge, a third bending space between the third edge and the fourth edge, and a fourth bending space between the fourth edge and the first edge, is located in the welded joint and there is a gap therein.

9. The cathode according to claim 8, further comprising: A cathode cup circumferentially surrounds the base assembly and the focusing element, wherein the focusing element extends above the height of the cathode cup.

10. The cathode of claim 8, wherein the lower extension has a stepped structure including a first level and a second level, wherein the second level extends vertically from a portion of the first level such that the height of the second level is at least partially surrounded circumferentially by the insulator.

11. The cathode of claim 10, further comprising a first lateral gap having a first width around the circumference of the second layer between the second layer and the insulator, and a second lateral gap having a second width equal to the first width of the first lateral gap between the second layer and the upper extension.

12. The cathode of claim 10, further comprising a distance between the first surface of the upper extension and the upper surface of the first layer of the lower extension that is greater than or equal to the height of the insulator.

13. A method for manufacturing a cathode, the method comprising: Manufacturing the base assembly, including: The first side of the upper extension is brazed to the first side of the insulator using filler metal; The lower extension is brazed to the second side of the insulator opposite to the first side of the insulator using filler metal; Welding features are machined on each of the first, second, third, and fourth edges of the second surface of the upper extension opposite to the first surface of the upper extension using an electrical discharge machine, with a bending space between each of the welding features; and Machining references on the base assembly; The base assembly is cleaned by sandblasting. Machining a focusing element with multiple focusing features and at least one channel; Electropolishing of the focusing element; Position the thermal ionization filament in each of the at least one channel; Welding the first face of the focusing element to the second face of the upper extension at each of the first edge, the second edge, the third edge, and the fourth edge in each of the welding features; and Welding is stopped at each of the following: a first bending space between the first edge and the second edge, a second bending space between the second edge and the third edge, a third bending space between the third edge and the fourth edge, and a fourth bending space between the fourth edge and the first edge.

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