X-ray cathode shield

Abstract

To provide various systems for a cathode of an X-ray imaging system.SOLUTION: A cathode is configured with shielding elements on exterior surfaces (e.g., electro-polished shields) to maintain high voltage stability. In one example, a shield for a cathode comprises a cathode mask (362) comprising a U-shaped central opening (340) configured to receive a cathode cup (62), where a perimeter (338) of the U-shaped central opening comprises a rounded edge (718).SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In an X-ray tube, ionizing radiation is generated by accelerating electrons from a cathode to an anode in a vacuum by an electric field. The electrons are generated from a filament of the cathode through which an electric current flows. The filament is heated by the flow of an electric current, can release electrons from the cathode, and accelerate the electrons toward the anode. By using additional filaments heated by electric currents of different voltages, an electron beam can be focused toward the anode and the size and position of the X-ray emission spot can be affected. The cathode can be configured to include a shield element (e.g., an electropolished shield, etc.) on its outer surface to maintain high voltage stability.

Summary of the Invention

[0003] In one embodiment, a shield for a cathode includes a cathode mask including a U-shaped central opening configured to receive a cathode cup, and an outer peripheral edge of the U-shaped central opening includes a rounded edge.

[0004] It should be understood that the above summary is provided to introduce in a simplified form concepts further described in the detailed description of the invention. The above summary is not intended to identify key features or essential features of the claimed subject matter, and the scope of the claimed subject matter is defined independently by the claims other than the detailed description of the invention. Further, the claimed subject matter is not limited to embodiments that solve the disadvantages pointed out above or any disadvantages pointed out in any part of this disclosure.

Brief Description of the Drawings

[0005] The present invention can be further understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings.

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Figure 9B

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DETAILED DESCRIPTION OF THE INVENTION

[0006] The following description relates to various embodiments of the cathode of an X-ray tube. The X-ray tube is included in an X-ray imaging system, and an example of its block diagram is shown in FIG. 1. The X-ray imaging system can be an interventional X-ray imaging system, an X-ray fluoroscopy imaging system, a mammography imaging system, a stationary or mobile X-ray radiography (RAD) imaging system, a tomographic imaging system, a computed tomography (CT) imaging system, etc. The X-ray imaging system includes an X-ray source (e.g., an X-ray tube) that generates an irradiation X-ray beam. A schematic cross-sectional view of the X-ray tube is shown in FIG. 2. The X-ray tube of FIG. 2 includes an anode assembly and a cathode assembly housed within a vacuum frame. The cathode assembly includes a cathode cup that houses one or more cathode filaments, a lower extension that mechanically couples the cathode cup to a high-voltage power supply by an electrical lead wire, and a cathode shield, as shown in more detail in FIGS. 3-10.

[0007] FIG. 3 is a perspective view of the cathode and includes a shield assembly. FIG. 4 shows a cross-section of the cathode and shows the position and shape of the shield portion that makes up the shield assembly. The shield assembly includes a first shield portion and a second shield portion. The first shield portion and the second shield portion are spaced apart so that the first shield portion and the second shield portion do not directly physically contact each other. In one embodiment, the first shield portion includes a cathode mask and a disk shield, and the second shield portion surrounds the lower extension of the cathode. FIG. 5 is a rear perspective view of the shield assembly and shows the unshielded portion of the cathode. The rear view shows the rear gap of the cathode shield in the region of low electric field strength, and this gap increases the view factor and reduces the overall temperature of the cathode. FIG. 6 is a perspective view of the shield assembly including an exemplary focusing portion of the cathode mask. FIG. 7 is a cross-sectional perspective view of an example of the disclosed cathode shield assembly. FIG. 8 is a perspective view of an example of the disclosed cathode shield. FIG. 9A shows a cross-section of an example of the disclosed cathode shield. FIG. 9B shows details of the cross-section shown in FIG. 9A. FIG. 10 shows an example of a second shield that can surround the lower extension of the cathode. FIGS. 3-10 are shown at approximately scale, but other relative dimensions may be used.

[0008] In an imaging system (such as an X-ray imaging system), a smart cathode can be used to implement focusing means for a coiled filament, and the functions of the electrodes can be used to realize substantially innumerable focal shapes and sizes. The smart cathode can be configured to provide various imaging services. For example, the smart cathode can be configured for diagnostic applications and interventional applications. In the latter case, current is passed through the coiled filament for a relatively long time. The smart cathode can include one or more coiled filaments, and each coiled filament has a different size so as to be given a current range suitable for the application. Generally, in order to maintain high voltage stability and to reduce the electron emission electric field stress generated in undesirable locations, a cathode shield element is provided. For example, the cathode assembly for the smart cathode can include an integral cathode shield configured to prevent backscattered electrons from reaching the electrical leads, the coiled filament and the focusing element, and other components that are susceptible to the electric field stress of the cathode assembly.

[0009] However, there are problems with conventional smart cathode systems. For example, a large amount of heat is generated when the cathode operates. The components of the cathode include, for example, ceramic insulators and electrical lead wires, which are susceptible to temperature effects and may exceed a temperature threshold at which the components of the cathode may deteriorate sufficiently. In some examples, there is a trade-off between maintaining the output density of the cathode and maintaining an appropriate cathode temperature. In a shield that completely covers the cathode, the problem may be exacerbated by the concentration of waste heat around the components that are susceptible to temperature effects. Over time, thermal stress can lead to component replacement or equipment disposal, increasing inspection time and operator costs. Another problem is that since the smart cathode may include one or more coiled filaments, if the cathode shield is not optimized for the size of each of the one or more coiled filaments, the electric field of one or more of the coiled filaments may be blocked, resulting in a loss of focusing ability. Similarly, if the electric field is overly focused, the image quality may be degraded.

[0010] Accordingly, to at least partially address the above problems, a cathode shield is disclosed herein. In one embodiment, the cathode shield assembly includes a first shield portion and a second shield portion, and the first shield portion and the second shield portion are spaced apart from each other such that the first shield portion and the second shield portion do not physically contact directly. In one example, the first shield portion includes a cathode mask and a disk shield, and the second shield portion surrounds a lower extension. Due to the shape of the disk shield, heat and high voltage generated by the target are blocked from reaching components that are susceptible to being affected (such as ceramic insulators and electrical lead wires). The cathode mask shields components of the cathode cup (such as bolts and welds) or other fastening mechanisms for stabilizing high voltage, and focuses electrons emitted from one or more coiled filaments. The lower extension shield covers components that are susceptible to being affected (such as electrical functional parts and welds), and enables radiative heat transfer through the gap between the second shield portion and the first shield portion. Such a shield assembly guarantees high voltage stability, but allows a large amount of radiative heat to be directly transmitted to the frame. When radiative heat transfer increases, the temperature of the components of the cathode decreases, and the amount of conductive heat transferred to components that are susceptible to temperature effects (such as electrical lead wires and ceramic insulators) decreases. The reduction of heat is particularly valuable in the application of intervention, and can extend the reliability requirements of the HVC and the "energization" time of the filament.

[0011] In another embodiment, a cathode shield is disclosed that includes a cathode mask with a U-shaped central opening configured to receive a cathode cup, and the outer peripheral edge of the U-shaped central opening includes a rounded edge. In one embodiment, the reason for making the central opening of the disclosed cathode mask U-shaped is that the difference between the rounded edge and one or more coiled filaments disposed in the cathode cup is maintained at a similar difference (e.g., generally a similar difference). In one embodiment, the rounded edge is a tip transition portion adjusted to reduce the local electron emission electric field stress at the end of the cathode mask. Such a shield has the advantages of enhancing the high-voltage stability and increasing the focusing field with respect to the size and strength of the coiled filaments that can be included in a smart cathode.

[0012] The technical advantage of the shield for a smart cathode disclosed herein is that the output capacity of the cathode tube can be increased by increasing heat transfer. Another technical advantage of the shield disclosed herein is the improvement of electron focusing ability by adjusting the outer peripheral edge of the cathode mask to the size of the coiled filaments. The shape of the disclosed shield component also contributes to the improvement of high-voltage reliability. Commercial advantages include the possibility of reducing the cost of the cathode tube due to the improvement of the output density and the possibility of miniaturizing the packaging. Other advantages include shortening the inspection time and reducing the associated operator cost.

[0013] Before further describing a smart cathode system having a shield door assembly with a focusing portion while increasing radiative heat transfer between a cathode and a frame, an exemplary imaging system in which a cathode can be implemented is shown. Referring to FIG. 1, a block diagram of one embodiment of an imaging system 10 is shown, and the imaging system 10 is configured to perform both acquiring raw image data and processing the image data so that it can be displayed and / or analyzed according to an exemplary embodiment. It is understood that various embodiments are applicable to a number of X-ray imaging systems (such as X-ray radiography (RAD) imaging systems, X-ray mammography imaging systems, fluoroscopic imaging systems, tomographic imaging systems, or CT imaging systems, etc.) that implement an X-ray tube. The following description of the imaging system 10 is merely an example of such an implementation form and is not intended to be limited with respect to the modality.

[0014] As shown in FIG. 1, the imaging system 10 includes an X-ray device or X-ray source 12 configured to project an X-ray beam 14 that passes through an object 16. Examples of the object 16 can include a subject, a piece of luggage, or other objects to be scanned. The X-ray source 12 can typically be a conventional X-ray tube that generates X-rays 14 having an energy spectrum in the range of 30 keV to 200 keV. The X-rays 14 pass through the object 16, are attenuated, and then collide with the detector assembly 18. Each detector module of the detector assembly 18 generates an analog electrical signal representing the intensity of the colliding X-ray beam, and thus the attenuated beam when passing through the object 16. In one embodiment, the detector assembly 18 is a detector assembly using a scintillator, but it is also conceivable that a direct conversion type detector (such as a CdTe, CZT, Si detector, etc.) is implemented.

[0015] Processor 20 receives signals from detector assembly 18 and generates an image corresponding to the object 16 being scanned. Computer 22 communicates with processor 20 so that an operator can control the scanning parameters and view the generated image using operator console 24. That is, operator console 24 includes some form of operator interface (such as a keyboard, mouse, voice-activated controller, or other suitable input device, any other suitable input device for allowing the operator to control imaging system 10 and view the reconstructed image or other data from computer 22 on display device 26, etc.). Further, operator console 24 enables the operator to store the generated image in storage device 28 which can include a hard drive, floppy disk, compact disk, etc. The operator can also use operator console 24 to supply commands and instructions to computer 22 for controlling source controller 30 that supplies power and timing signals to x-ray source 12.

[0016] FIG. 2 shows a schematic cross-sectional view of an X-ray device or X-ray source 200 included in the imaging system of FIG. 1. For example, X-ray source 200 is an exemplary embodiment of X-ray source 12 of FIG. 1 and can be formed by an X-ray tube 40 including an anode assembly 42, a cathode assembly 44, and a collector assembly 82. A set of reference axes 201 is illustrated so that comparisons can be made between the multiple figures shown, with the x-axis, y-axis, and z-axis shown. X-ray tube 40 is composed of anode assembly 42, cathode assembly 44, and collector assembly 82 and is supported within a housing or frame 46. The frame houses at least a portion of anode assembly 42, cathode assembly 44, and collector assembly 82. Frame 46 houses an anode 48 having a target 66, a bearing assembly 50, and a cathode 52. Frame 46 defines a region of relatively low pressure (e.g., vacuum) compared to the surroundings, in which a high voltage is generated. Further, frame 46 can be disposed within a casing (not shown) filled with a cooling medium (such as oil), and this casing also includes a high voltage insulator. In the above description, anode 48 that constitutes target 66 was assumed to be a common component of X-ray tube 40, but anode 48 and target 66 may be separate components in an alternative embodiment of the X-ray tube.

[0017] In operation, the electron beam is generated by the cathode assembly 44. In particular, the cathode 52 receives one or more electrical signals through a series of electrical leads 56. The electron beam travels through the space 54 between the cathode 52 and the target 66 of the anode 48. The electrical signal can be a timing / control signal that causes the cathode 52 to emit an electron beam of one or more energies and one or more frequencies. The electrical signal can also at least partially control the potential between the cathode 52 and the anode 48. The cathode 52 includes a central insulating shell 58, and a mask 60 extends from the insulating shell 58. The mask 60 surrounds the electrical lead 56, and this electrical lead 56 extends to a cathode cup 62 attached to the end of the mask 60. In some examples, the cathode cup 62 functions as an electrostatic lens that focuses the electrons emitted from a filament within the cathode cup 62 to form an electron beam.

[0018] The outer surface of the cathode 52 (e.g., the surfaces of the mask 60 and the cathode cup 62) is covered with a shield that can withstand the high electric field stress between the high potential of the cathode 52 and the ground plane of the frame 46. In one embodiment, the shield includes a first shield portion 202 and a second shield portion 204. In this embodiment, the first shield portion 202 and the second shield portion 204 are spaced apart and do not physically contact directly. In one embodiment, the first shield portion 202 can include a disk shield and a cathode mask, and the second shield portion 204 can surround the mask 60. Examples of the first shield portion 202 and the second shield portion 204 are shown in more detail in FIGS. 3-10. In one embodiment, as shown in the schematic diagram of the X-ray source 200, the first shield portion 202 is a single continuous member formed integrally. For example, there can be no weld or joint joining the disk shield and the cathode mask that make up the first shield portion 202. The first shield portion 202 can have a monolithic structure. In other examples, the disk shield and the cathode mask that make up the first shield portion 202 can be formed separately and welded to the cathode assembly.

[0019] The high-speed electrons of the electron beam travel from the cathode 52 toward the target 66 formed on the anode 48 due to the potential difference between the cathode 52 and the target 66 (for example, a potential difference of 60,000 volts or more in the case of CT applications), and when they rapidly decelerate, X-rays 64 are generated. The focusing electrode assembly 82 can include an electron collector 84 and a window 68, and the X-rays 64 generated by the anode assembly 42 are emitted through the window 68. The electron collector 84 holds the window 68 at a predetermined position of the frame 46 and can further absorb backscattered electrons. The X-rays 64 pass through the window 68 formed in the frame 46 and are emitted toward a detector array (such as the detector assembly 18 in FIG. 1).

[0020] The anode assembly 42 includes a rotor 72 and a stator disposed outside the X-ray tube 40 that surrounds the rotor 72 for causing rotation of the anode 48 during operation (not shown). The anode 48 is supported so as to be rotatable by a bearing arm or bearing assembly 50, and when this bearing arm or bearing assembly 50 rotates, the anode 48 rotates about its center line 70. Thus, the center line 70 defines the axis of rotation of the anode 48 and the bearing assembly 50. As shown in the figure, the anode 48 has an annular shape, and a circular opening 74 for receiving the bearing assembly 50 is provided at the center of the anode 48.

[0021] The anode 48 can be manufactured to include a plurality of metals or alloys (such as tungsten, molybdenum, copper, or any material that contributes to bremsstrahlung (for example, deceleration radiation) when electrons collide). The target 66 of the anode 48 can be selected to have a relatively high refractory rate so as to withstand the heat generated by the electrons colliding with the anode 48. Further, the space between the cathode assembly 44 and the anode 48 can be evacuated to minimize electron collisions with other atoms and maximize the potential.

[0022] To avoid overheating of the anode 48 when electrons collide, the rotor 72 rotates the anode 48 at a high speed (e.g., 90 - 250 Hz) about the center line 70. In addition to the rotation of the anode 48 within the frame 46, in the CT application, the entire X-ray tube 40 rotates around an object (such as the object 16 of the imaging system 10 in FIG. 1), typically at a speed of 1 Hz or more.

[0023] Different embodiments of the bearing assembly 50 can be formed of a plurality of suitable ball bearings, etc. In the illustrated exemplary embodiment, the bearing assembly 50 includes a liquid metal hydrodynamic bearing having a load-bearing capacity suitable for operation within the imaging system 10 of FIG. 1 and an acceptable acoustic noise level.

[0024] Generally, the bearing assembly 50 includes a stationary component (such as the central shaft 76) and a rotating part (such as the sleeve 78 to which the anode 48 is attached). The central shaft 76 is described in FIG. 2 as a stationary part of the bearing assembly 50, and the sleeve 78 is described as a rotating part of the bearing assembly 50. However, the embodiments of the present disclosure are also applicable to embodiments where the central shaft 76 is a rotating shaft and the sleeve 78 is a stationary component. In such a configuration, it is considered that when the central shaft 76 rotates, the anode 48 rotates.

[0025] The central shaft 76 can optionally include a cavity or a refrigerant flow path 80. A refrigerant (not shown), such as oil, can flow through the cavity or the refrigerant flow path 80 to cool the bearing assembly 50. In this way, the heat generated at the anode 48 of the X-ray tube 40 can be removed from the anode 48 by the refrigerant and transferred outside the X-ray tube 40. Also, in the configuration of an X-ray tube attached in a straddle form, the refrigerant flow path 80 extends along the longitudinal length of the X-ray tube 40 (e.g., along the center line 70). In an alternative embodiment, in a configuration where the X-ray tube 40 is supported in a cantilever form when the X-ray tube 40 is disposed in the imaging system, the refrigerant flow path 80 can be formed only in a part of the X-ray tube 40.

[0026] As described above, a cathode shield that maintains high voltage stability, increases the heat transferred to the frame, and optimizes the focusing of the electron field for one or more coiled filaments with different strengths is desired. The shield described herein can improve high voltage stability and increase the usable life compared to conventional smart cathodes. In one example, the cathode shield assembly includes a first shield portion and a second shield portion, and the first shield portion and the second shield portion are spaced apart so that the first shield portion and the second shield portion do not physically contact directly. Such a cathode shield shields the high electric field stress region while increasing the radiative heat transfer from the cathode region that is susceptible to low electric field stress and high heat. In one embodiment, the first shield portion includes a cathode mask and a disk shield, and the second shield portion surrounds the lower extension of the cathode. In one embodiment, the disk shield is a substantially concave disk having a curved lip and a cutout, and a portion of the cathode (e.g., the cathode cup) protrudes from the cutout. The cutout can be a substantially rectangular cutout offset from the center of the disk shield. The cathode mask includes a U-shaped central opening configured to receive the cathode cup. In one embodiment, the outer peripheral edge of the U-shaped central opening includes a rounded edge. The U-shaped central opening can include a plurality of radiused curved portions formed to focus one or more coiled filaments of the cathode. The rounded edge can have a bend angle formed to reduce the electric field stress at the outer peripheral edge of the central opening.

[0027] Depending on the position and shape of the shield part, the view factor is increased in the region where the electron emission electric field stress is low, while contributing to the stability of high voltage, achieving a balance between the optical and electrostatic viewpoints. For example, depending on the shape of the first shield part, the electric field stress is concentrated on the OD of the shield, and the low electric field stress part of the cathode can be exposed by the gap interval between the first shield part and the second shield part. Therefore, in the system described in this specification, compared with the conventional cathode having a completely covered shield, a cathode with a reduced temperature of the components can be obtained, the stability of high voltage is improved, and the image quality is improved by adjusting the electric field focusing. Accordingly, the usable life of the cathode is relatively increased, and the component replacement and inspection time can be shortened.

[0028] Figure 3 shows a perspective view of the cathode assembly 300, which can be an embodiment of the cathode assembly 44 in Figure 2. In the cathode assembly 300, components equivalent to those of the X-ray tube 40 in Figure 2 are given the same reference numerals. A set of reference axes 301 is shown for comparison between the figures shown, with the x-axis, y-axis, and z-axis shown. The x-axis may be referred to as the lateral axis, the z-axis may be referred to as the vertical axis, and the y-axis may be referred to as the longitudinal axis.

[0029] As described above, the cathode assembly 300 emits electrons from the cathode, and the electrons are received by the anode assembly (e.g., the anode assembly 42 in Figure 2) to generate X-rays. The cathode assembly 300 can include a large insulator 358, a lower extension 405 (see Figure 4), and a cathode 52 including a cathode cup 62. The large insulator 358 can be equivalent to the central insulating shell 58, and the lower extension 405 can be equivalent to the mask 60 as described with reference to Figure 3.

[0030] The cathode cup 62 can include a focusing element and one or more coiled filaments. In one embodiment, the focusing element can be a single continuous structure having at least one channel sized such that a thermionic filament can be disposed in the channel, and at least one focusing portion positioned laterally of the at least one channel. In one embodiment, the focusing portion and the channel of the focusing element can have rounded corners and edges and a smooth geometry as opposed to corners that contact at a linear angle. In one embodiment, the focusing element can have a plurality of coiled filaments. In the illustrated example, the focusing element 375 is shown schematically in FIGS. 3-4 and in detail in FIGS. 6-7, and the focusing element 375 can be configured as a grid electrode of a continuous single structure (e.g., a monolithic structure) in which electron emission filaments are disposed in each of at least three channels having a geometry that focuses the emitted electrons into a single electron beam. The focusing element 375 incorporates a first filament 376, a second filament 378, and a third filament 380. The spacing between the three filaments can be adjusted based on the size and strength of each of these filaments. In one example, the focusing element 375 has a substantially rectangular shape (e.g., when viewed from above the Y-axis) taking into account the spacing between the three filaments. The focusing element 375 may have a U-shape or a bowl shape (e.g., when viewed from above the z-axis) such that the sides of the focusing element are higher compared to the central portion of the focusing element. As previously described with reference to FIG. 2, the cathode assembly 300 can direct electrons at various energy levels from each of the one or more coiled filaments to a target (e.g., target 66 in FIG. 2). The cathode cup 62 is partially surrounded by a cathode shield assembly.

[0031] In one embodiment, the cathode shield assembly includes a first shield portion 302 and a second shield portion 304. The first shield portion 302 is disposed at a distance from the second shield portion 304, and the first shield portion 302 and the second shield portion 304 are not in contact. The first shield portion 302 can be the same as or similar to the first shield portion 202, and the second shield portion 304 can be the same as or similar to the second shield portion 204 (described with reference to FIG. 2). The first shield portion 302 and the second shield portion 304 can be separated by a gap interval between the first shield portion 302 and the second shield portion 304, and this will be described with reference to FIG. 4 described later. As will be described in more detail below, the first shield portion 302 has a disk shield 365 and a cathode mask 362. The second shield portion 304 surrounds a lower extension 405. The second shield portion 304 can be ring-shaped. In one embodiment, the disk shield 365 includes a cutout or opening for receiving the cathode cup 62, and a part of the disk shield 365 is mechanically and securely coupled to the lower extension 405. The cathode cup 62 is partially surrounded by the cathode mask 362. The first shield portion 302 and the second shield portion 304 cooperate to protect the components (filament, focusing element, electrical lead wire, etc.) of the cathode 52 from high temperature and backscattered electrons, achieve high voltage stability, and at the same time, can increase the radiative heat transfer to the frame 46.

[0032] The disk shield 365 can be substantially concave and substantially disk-shaped. The disk shield 365 can have a first outer surface 322. The first outer surface 322 can include a curved lip 310, a flat region 312, and an inclined transition portion 314 between the curved lip 310 and the flat region 312. In one example, the curved lip 310 and the inclined transition portion 314 are inclined downward with respect to the z-axis toward the flat region 312. Also, the curved lip 310 can progress downward with respect to the z-axis and form a surface 316. The surface 316 is part of the curved lip 310 and extends radially around the central axis 317. The first outer surface 322 can be a plane centered on the central axis 317. In one embodiment, the disk shield 365 can include a first cutout, which can be defined by an opening in the first outer surface 322, an opening in the first inner surface 404 (see FIG. 4), and a first cut surface 324. In one embodiment, the first cutout can be a substantially rectangular cutout offset from the center of the disk shield 365. For example, the first cutout can be located above a first center line 315 that bisects the cathode assembly 300 longitudinally. The shape of the disk shield 365 is described in further detail below with reference to FIGS. 4-7.

[0033] In one embodiment, the cathode cup 62 can project through the first cutout portion, and the cathode mask 362 can receive the cathode cup 62. The cathode mask 362 can have a substantially columnar shape with a rectangular extension 326. The cathode mask 362 includes a second outer surface 330 and a second inner surface 434 (see FIG. 4). In one embodiment, the second outer surface 330 and the first outer surface 322 form a continuous and integral surface of the first shield portion 302. In one embodiment, the substantially columnar and rectangular extension 326 includes a plurality of side walls 328 disposed perpendicular to the front panel 332, and the side walls 328 and the front panel 332 are in contact so as not to form sharp edges. In other words, the shape of the cathode mask has a rounded edge at the transition between the side walls, the front panel, and the rectangular extension. The cathode mask 362 has a central opening 340 defined by an opening in the second outer surface 330, an opening in the second inner surface 434 (see FIG. 4), and a lip or outer peripheral edge 338.

[0034] In one embodiment, the cathode mask 362 is formed to accommodate the focusing element 375 of the cathode cup 62 and the coiled filaments. For example, the rectangular extension 326 surrounds the focusing element 375. The cathode mask 362 can be formed to maintain an equal distance between each coiled filament of a plurality of coiled filaments (such as the first filament 376, the second filament 378, and the third filament 380, etc.) disposed on the focusing element 375 and the outer peripheral edge 338 of the central opening 340. In one embodiment, the central opening 340 is configured in a U-shape (when viewed from above the z-axis, for example), and the outer peripheral edge 338 can form a rounded edge. The U-shape and the rounded edge are an example of the focusing portion of the cathode mask 362 that can be adjusted to balance optics and electrostatics. The shape and focusing portion of the cathode mask 362 will be described in more detail below with reference to FIGS. 4 to 9B.

[0035] FIG. 4 shows a cross-sectional view 400 of the cathode assembly 300 of FIG. 3, the shape of which is shown by a lateral cut along the dashed line 4-4 of FIG. 3. Similar components are labeled with the same reference numerals as in FIG. 3. A set of reference axes 401 is illustrated to enable comparison between the multiple figures shown, with the x-axis, y-axis, and z-axis shown.

[0036] The cross-sectional view 400 shows a cathode cup 62, a large insulator 358, a lower extension 405, and a cathode shield that partially surrounds the cathode 52 and includes a first shield portion 302 and a second shield portion 304. The cathode cup 62 includes a plurality of electrical leads (not shown). The lower extension 405 couples the cathode cup 62 to the large insulator 358 and surrounds a plurality of high-voltage cables 56 (shown schematically). The plurality of high-voltage cables 56 couple a plurality of electrical lead wires to a high-voltage power source. A disk shield 365 can be coupled to the surface 462 of the lower extension 405, and a cathode mask 362 can be coupled to the cathode cup 62 and can partially shield the cathode cup 62. The second shield portion 304 can form a sleeve or ring around the lower extension 405.

[0037] The cathode cup 62 can further include a base 444, an insulator 446, and a welding pad 448. The cathode cup 62 can include one or more brazing foils used to couple the insulator 446 to the base 444 and the welding pad 448 respectively (e.g., by brazing). In one embodiment, the insulator 446 can be a ceramic insulator (e.g., an insulator formed of ceramic). In other examples, the insulator 446 can be formed of a material that sufficiently insulates the base 444 from the welding pad 448. The insulator 446 can have a rectangular ring shape with a cavity in the center. For example, the insulator 446 can have a rectangular shape with curved edges and can have a rectangular cutout with curved edges at the center of the insulator 446. The base 444 can be formed of a metal (e.g., nickel, steel, kovar, or niobium, etc.) and can have a continuous stepped structure including a first level 444a and a second level 444b. A plurality of electrical lead wires are coupled to the rear surface 426 of the base 444. The welding pad 448 can have a ring shape with rounded corners connecting straight edges and a hollow portion. The welding pad 448 can also be formed of a metal (e.g., nickel, steel, kovar, or niobium, etc.). Due to the ring-shaped structures of the insulator 446 and the welding pad 448, the second level 444b of the base 444 can penetrate through the central portions of the insulator 446 and the welding pad 448. The insulator 446 can circumferentially surround the second level 444b of the base 444.

[0038] The welding pad 448, the base 444, the brazing foil, and the insulator 446 can be brazed together using torch brazing, induction brazing, resistance brazing, or another brazing method in which the welding pad 448, the base 444, and the insulator are joined by a filler material (e.g., brazing foil). For example, a filler material can be used to couple the insulator to the base 444 and the welding pad 448 by brazing.

[0039] In one embodiment, the base 444 of the cathode cup 62 can be coupled to the mounting wall 460 of the lower extension 405 in an inclined state. For example, the mounting wall 460 of the lower extension 405 can be arranged substantially perpendicular to the second center line 458. The second center line 458 may be substantially collinear with the central axis 317 or may be formed from the central axis 317. The second center line 458 bisects the cathode assembly 300 longitudinally. The second dashed line 464 indicates that the mounting wall 460 is substantially perpendicular. The rear surface 426 of the cathode cup 62 can be inclined at an inclination angle 466 with respect to the second dashed line 464. In one embodiment, the cathode cup 62 and the lower extension 405 have a tolerance that controls the inclination angle to + / -0.25°.

[0040] In one example, the lower extension 405 can include one or more windows 450, which are defined by an opening in the outer surface 452 of the lower extension, an opening in the inner surface 454 of the lower extension, and a window surface 456 of the lower extension. The window 450 can contribute to the cooling of cathode components such as a plurality of electrical leads (e.g., ribbons, wires, cables, pins, or other electrical connection components) arranged on the rear surface 426 of the cathode cup that couple one or more of the coiled filaments (e.g., the third filament 380) of the plurality of coiled filaments housed in the cathode cup 62 to the high voltage cable 56. A sleeve component 468 can be interposed between the lower extension 405 and the small insulator 428.

[0041] In the illustrated example, the disk shield 365 has an outer portion 406 and an inner portion 408. The distance between the outer portion 406 and the inner portion 408 can define the disk shield width 412 with respect to the y-axis. The curved lip 310 can define an arcuate surface integral with the disk shield 365. The curved lip 310 extends between the outer portion 406 of the disk shield 365 and the outer peripheral edge 416. The curved lip 310 can have a plurality of curvature change points on the cross-sectional view 400 of line 4-4. One curvature change point can be located on the surface 316, and the curved lip 310 can curve towards the outer portion 406 or the outer peripheral edge. Another curvature change point can be located near the outer portion 406, at which the curved lip 310 can bend in the direction of the outer peripheral edge 416 to form the inclined transition portion 314. Another curvature change point can be located near the outer peripheral edge 416, at which the curved lip 310 can curve in the direction of the outer portion 406. After curving at the aforementioned curvature change points, the curved lip 310 has a termination portion in the axial region between the outer portion 406 and the outer peripheral edge 416 and can radially expand about the second center line 458. The aforementioned plurality of curvature change points can be reflected in the portion of the curved lip 310 on the opposite side of the second center line 458. The aforementioned plurality of curvature change points can be part of a ring or other function arranged radially with respect to the second center line 458 when projected onto the three-dimensional space of the curved lip 310.

[0042] The inclined transition portion 314 extends between the outer portion 406 and the flat region 312. The inclined transition portion 314 is inclined at an inclination angle 418 with respect to the axial length 420 over the portion 422 with a changing radius. The flat region 312 is offset from the inner portion 408 by a first offset 424. In one embodiment, the disk shield 365 can be welded to the lower extension 405. For example, the flat region 312 can be laser welded to the surface 462 of the mounting wall 460.

[0043] In one embodiment, the cathode cup 62 protrudes through the first cutout of the disk shield 365. The cathode mask 362 is configured to receive the cathode cup 62. The central opening 340 is disposed on the side opposite to the opening surface 480 of the cathode mask 362. The cathode cup 62 can be received at the opening surface 480. In one embodiment, the second inner surface 434 can be in face-sharing contact with the base 444 of the cathode cup 62, and an air gap 440 can be formed between the second inner surface 434 and the focusing element 375, the insulator 446, and the welding pad 448 of the cathode cup 62. In one embodiment, the cathode mask 362 can be welded to the cathode cup 62. For example, the cathode mask 362 can be laser welded to the base 444. The focusing element 375 of the cathode cup 62 can be partially exposed by the central opening 340 of the cathode mask 362, and the plurality of side walls 328 and the outer peripheral edge 338 surround the focusing element 375 and the filament (e.g., the third filament 380) disposed in the cathode cup 62. The rear surface 426 of the cathode cup 62 can be exposed (or partially exposed) by the opening surface 480 of the cathode mask 362. The curved lip 310 of the disk shield 365 can partially shield the rear surface 426 of the cathode cup 62. For example, the curved lip 310 can shield the portion of the rear surface 426 having a high electric field strength (e.g., near the contact portion between the cathode mask 362 and the first level 444a).

[0044] Due to the shape of the first shield portion 302, electric field stress concentrates on the first outer surface 322 and the second outer surface 330, preventing the heat generated at the anode target (e.g., the target 66 of the anode 48 in FIG. 2) from reaching components that are susceptible to temperature effects, such as the large insulator 358, the small insulator 428, and the plurality of electrical leads. Also, the first shield portion 302 improves the high voltage stability. For example, the cathode mask 362 contributes to the high voltage stability by shielding the welded portion (e.g., the welding pad 448), the brazed portion, the fastening portion, or other types of fastening mechanisms that make up the cathode cup 62. In addition, the shape with a smoothly rounded transition between the plurality of side walls 328 and the front panel 332 contributes to the high voltage stability. In addition, the shape of the central opening 340 can reduce the electric field stress at the end of the cathode mask 362 and increase the focusing field of the coiled filament. This will be described in more detail below. As another example, the shape of the disk shield 365 contributes to the high voltage stability. For example, the inclined transition portion 314 becomes a curved lip 310 with a smooth transition without sharp corners, reducing the electric field stress at the outer peripheral edge 416. For example, by shielding components that are susceptible to temperature effects with the first shield portion 302, the rear surface 426 of the cathode cup 62 can be exposed (e.g., without shielding). The opening surface 480 of the cathode mask 362 can transfer more radiant heat from the cathode cup 62 to the frame 46 without impairing the high voltage stability.

[0045] By preventing the electric field stress from concentrating on the first outer surface 322 and the second outer surface 330 of the first shield portion 302 and exposing the components that are susceptible to the influence of temperature to the high temperature generated at the anode, the disclosed cathode shield can simultaneously expose the previously surrounded portion of the cathode 52. For example, the disclosed cathode shield exposes the portion of the cathode 52 where the electric field strength is low, the temperature is high, and the view factor with respect to the frame 46. By selectively shielding in this way, the temperature of the cathode components can be sufficiently reduced, and the amount of heat transferred to the plurality of high-voltage cables 56 can be decreased. The first shield portion 302 will be described in more detail below.

[0046] The second shield portion 304 is a cylinder or ring-shaped member having an opening that surrounds the lower extension 405. The second shield portion 304 has an annular inner surface 430 and an annular outer surface 432. In one embodiment, the annular inner surface 430 is in surface contact with the outer surface 452 of the lower extension. In one embodiment, the second shield portion 304 can be welded to the outer surface 452 of the lower extension. In one embodiment, the second shield portion 304 can have a flare-shaped lip 472 on the side of the first circular opening and a flat rim 474 on the side of the second circular opening on the opposite side. The flare-shaped lip 472 can contact the small insulator 428. In one embodiment, the second shield portion 304 can have a third length 476 with respect to the y-axis. In one embodiment, the second shield portion 304 can be arranged at a gap distance 478 from the first shield portion 302 with respect to the y-axis. The third length 476 and the gap distance 478 can be in the axial direction with respect to the second center line 458.

[0047] In one embodiment, the second shield portion 304 is formed to shield components that are housed within the lower extension 405 and would otherwise increase high voltage instability, while allowing as much radiative heat transfer as possible. For example, the third length 476 and the gap spacing 478 of the second shield portion 304 can be optimized to cover the weld, be close to ground, the temperature of the cathode components, and the balance of the view factor with respect to the frame 46. In one embodiment, the gap spacing 478 can be between 25 mm and 30 mm. The second shield portion 304 will be described in more detail below.

[0048] In one embodiment, the disk shield 365 and the cathode mask 362 of the first shield portion 302 are a single, integrally formed, continuous member as described with reference to FIG. 2. In another embodiment, the disk shield 365 and the cathode mask 362 are formed as separate elements. The first shield portion 302 and the second shield portion 304 can be formed of a metal (e.g., nickel, steel, kovar, or niobium, etc.). The shield surface may be given an electropolished finish. In one example, the first shield portion 302 and the second shield portion 304 can be made of nickel, and the first outer surface 322, the second outer surface 330, and the annular inner surface 430 can be electropolished nickel.

[0049] FIG. 5 shows a rear view 500 of the cathode assembly 300 of FIG. 3. Components similar to those in FIG. 3 are given similar numbers, and similar components include the first shield portion 302, the second shield portion 304, the cathode cup 62, and the frame 46. A set of reference axes 501 is shown to enable comparison between the multiple figures shown, with the x-axis, y-axis, and z-axis shown.

[0050] Depending on the positions and shapes of the first shield portion 302 and the second shield portion 304, the electric field stress in the open view factor region is reduced. For example, the dotted line 502 indicates the curvature of the first shield portion 302 that shields the high electric field stress region of the cathode cup 62. In one example, the curvature and the highly polished nickel surface can shield an electric field strength as high as about 1×10 7 volts per meter (V / m). The electric field strength in the unshielded regions of the gap spacing 478 and the rear surface 426 can be made sufficiently low (e.g., in the range of 0 to 2.5×10 6 V / m). In one embodiment, the view factor with respect to the frame 46 in the unshielded regions of the gap spacing 478 and the rear surface 426 can have an emissivity in the range of 0.4 to 0.7. In one embodiment, the first shield portion 302 and the second shield portion 304 expose a portion of the cathode cup 62 where the electric field stress intensity is less than the intensity threshold (e.g., less than 2.5×10 6 V / m) and the view factor with respect to the frame is greater than the emissivity threshold (e.g., greater than an emissivity of 0.4).

[0051] The open portion of the shield increases the view factor and the corresponding radiative heat transfer from the cathode 52 to the frame 46. In addition, the gap spacing 478 between the second shield portion 304 and the first shield portion 302 can enhance the cooling of the components while leaving the window 450 of the lower extension 405 unshielded. As a result, the overall temperature of the cathode decreases. For example, components that are susceptible to the effects of high temperature (such as a plurality of electrical lead wires (not shown) that pass current through the coiled filament and a cathode cup insulator (e.g., insulator 446 in FIG. 4)) are sufficiently cooled, and the reliability of the components can be improved.

[0052] FIG. 6 shows a front view 600 of the cathode assembly 300 of FIG. 3. Similar components are numbered as in FIG. 3, and the cathode mask 362, the disk shield 365, the cathode cup 62, and the second shield portion 304 that constitute the first shield portion 302 are shown. A set of reference axes 601 is illustrated so that comparisons can be made between the multiple figures shown, with the x-axis, y-axis, and z-axis shown.

[0053] In one example, the cathode cup 62 can include a medium filament disposed in a first channel 602, a small filament disposed in a second channel 604, and a large filament disposed in a third channel 606. The filaments can be the first filament 376, the second filament 378, and the third filament 380 described with reference to FIG. 3. In other examples, these filaments may be of the same size or different sizes. The filaments can be disposed at different heights within their respective channels relative to the back surface of the base 444 (see FIG. 4). Each of the filaments in the first channel 602, the second channel 604, and the third channel 606 can have a lateral spacing relative to an adjacent filament, and the lateral spacing is defined as the lateral distance with respect to a horizontal axis (e.g., the x-axis) between the center point of the diameter of the first filament and the center point of the diameter of the second filament.

[0054] To conform to the lateral spacing, size, and relative height of each filament, the cathode mask 362 can be configured to have a shape that focuses the electrons emitted from the filaments into a single electron beam. In one embodiment, the central opening 340 and the outer peripheral edge 338 of the central opening 340 can include various curved portions. For example, the central opening 340 can have a U shape, and the outer peripheral edge 338 can include a rounded edge. Such curved portions can maintain a similar distance between the outer peripheral edge and each filament, and can increase the electric field strength. For example, the curved portions can include a plurality of curved portions, a plurality of curved portions with various bending radii, and a plurality of curved portions with various dimensions.

[0055] As a first example of the bent portion, the first bent portion 680 includes a first axis 608 and a second axis 610 arranged parallel to the x-axis, and the second bent portion 682 includes a third axis 612 and a fourth axis 614 arranged parallel to the y-axis. The outer peripheral edge 338 converges to the first axis 608 up to the first bent portion 680. In one example, the first bent portion 680 can have a first bending radius in the range of 2 millimeters (mm) to 6 mm and a first bending dimension 676 in the range of 4.1 mm to 4.7 mm. The first bent portion 680 can be a longitudinal bend in the y-axis direction. The outer peripheral edge 338 converges to the second axis 610 at the second bent portion 682. The second bent portion 682 can have a second bending radius. In one example, the first bending radius of the first bent portion 680 and the second bending radius of the second bent portion 682 can have different dimensions. For example, the second bent portion 682 can have a second bending radius in the range of 12 mm to 14 mm and a second bending dimension 674 in the range of 3 mm to 5 mm. The second bent portion can be a lateral bend in the x-axis direction. In the illustrated example, the outer peripheral edge 338 includes a third bent portion 684 reflecting the second bent portion 682 and a fourth bent portion 686 reflecting the first bent portion 680. The first bent portion 680, the second bent portion 682, the third bent portion 684, and the fourth bent portion 686 form a U-shape when viewed from the z-axis. In one embodiment, the first bent portion 680, the second bent portion 682, the third bent portion 684, and the fourth bent portion 686 have profile tolerances based on dimensions and radii. In one example, the profile tolerance is ±1 mm.

[0056] As disclosed herein, by incorporating a bent portion into the central opening of the cathode mask and adjusting the focusing field with respect to the size, intensity, and position of each filament of one or more filaments, the X-ray image quality is improved. As another advantage, the bent portion reduces the electric field stress at the end of the cathode cup, and thus, correspondingly, improves the high voltage stability. Another example of the bent portion will be described in detail below.

[0057] FIG. 7 shows a cross-sectional view 700 of the cathode assembly 300 of FIG. 3 shown by a lateral cut along the dashed line 7-7 of FIG. 6. Similar components are numbered the same as in FIG. 3. A set of reference axes 701 is shown so that comparisons can be made between the multiple figures shown, with the x-axis, y-axis, and z-axis shown.

[0058] The cross-sectional view 700 shows the height of the first filament 376 of the first channel 602 and the second filament 378 of the second channel 604 relative to the rear surface 426 of the cathode cup 62. The U-shaped bent portion as described with reference to FIG. 6 can maintain the same distance between the outer peripheral edge and the filament. Conversely, assuming that a conventional circular cathode cup shield (or cathode mask) or a uniform rectangular shield was used, the electric field strength around the filament could potentially be minimized (especially around the smallest filament and / or the filament farthest from the uniform outer peripheral edge).

[0059] In the illustrated example, the first plane 702 shows the y-z plane that cuts the outer peripheral edge 338 of the central opening 340 and the second filament 378 of the second channel 604. With respect to the rear surface 426, the height of the second filament 378 indicated by the dashed arrow 710 and the height of the outer peripheral edge 338 indicated by the dashed arrow 708 have a first difference indicated by the dashed arrow 712. The first difference is the depth measured in the first plane 702, and can be the depth between the x-z plane corresponding to the second filament 378 and the x-z plane corresponding to the outer peripheral edge 338. The second plane 704 shows the y-z plane that cuts the outer peripheral edge 338 and the first filament 376 of the first channel 602. With respect to the rear surface 426, the height of the first filament 376 indicated by the dashed arrow 706 and the height of the outer peripheral edge 338 indicated by the dashed arrow 714 have a second difference indicated by the dashed arrow 716. Similarly, the second difference is the depth measured in the second plane 704, and can be the depth between the x-z plane parallel to the first filament 376 and the x-z plane parallel to the outer peripheral edge 338. Note that the dashed arrow 714 and the dashed arrow 706 extend to the rear surface 426 but are only partially shown. In one embodiment, the first difference and the second difference may be the same. In one embodiment, the first difference and the second difference may differ by only a threshold value. In other words, each coiled filament can be arranged at a depth within the threshold from the rounded edge of the cathode mask. In one embodiment, the factor determining the shape of the disclosed cathode mask is to maintain the difference between the outer peripheral edge of the central opening and each filament of one or more coiled filaments to be generally the same difference.

[0060] Cross-sectional view 700 shows a rounded edge 718. The rounded edge 718 can be adjusted to reduce the local electron emission electric field stress at the end of the cathode mask (e.g., the outer peripheral edge 338 of the central opening 340). In one example, the rounded edge can be bent perpendicular to the z-axis. An example of a cathode mask including the shape of the rounded edge will be described in more detail with reference to FIGS. 8 and 9A - 9B.

[0061] FIG. 8 shows a perspective view of an example of a cathode mask 800, which is part of a cathode shield assembly for a cathode. The cathode mask 800 can be the same as or similar to the cathode mask 362 described with reference to FIGS. 3 - 7. A set of reference axes 801 is illustrated to enable comparison between the multiple figures shown, with the x-axis, y-axis, and z-axis shown.

[0062] In one embodiment of the disclosed cathode shield assembly, the cathode mask 800 is columnar in shape and has a rectangular extension 811. The cathode mask 800 is mirror symmetric with respect to a lateral symmetry line 802. In other embodiments of the disclosed cathode shield assembly, the cathode mask may not be laterally symmetric. The cathode mask 800 has a first side wall 804, a second side wall 806, and a third side wall 808. The first side wall 804 faces the second side wall 806, and the third side wall 808 is disposed perpendicular to the first side wall 804 and the second side wall 806 and is located between the first side wall 804 and the second side wall 806. The cathode mask 800 has a front panel 812 disposed perpendicular to the first side wall 804, the second side wall 806, and the third side wall 808. The cathode mask 800 has a short extension 810 extending from the front panel 812 and parallel to the third side wall 808. The first side wall 804, the second side wall 806, the third side wall 808, and the front panel 812 are in contact without forming an acute angle. For example, the transition surface 814 from the first side wall 804 to the front panel 812 may be smoothly rounded or chamfered from the x - z extent of the front panel 812 to the y - z extent of the first side wall 804.

[0063] In the illustrated example, excluding the rectangular extension 811, the overall dimensions of the cathode mask 800 are a first height 822, a first depth 826, and a first width 838. The front panel 812 extends to a second depth 840 that is shorter than the first depth 826 and can be approximately half of the first depth 826. The short extension 810 has a second height 846 that is shorter than the first height 822.

[0064] The rectangular extension 811 is disposed in the upper half with respect to the horizontal center line 803 of the cathode mask 800. The rectangular extension 811 can have a first segment 816, a second segment 818, a third segment 832, and a fourth segment 834. The first segment 816 is an extension of the first side wall 804, the second segment 818 is an extension of the second side wall 806, and the third segment 832 is an extension of the third side wall 808. The fourth segment 834 intersects the front panel 812 substantially perpendicularly, thus forming a short wall. The first segment 816 and the second segment 818 can have a third length 830 that is shorter than the first depth 826. The third segment 832 and the fourth segment 834 can have a length substantially the same as the first width 838 of the overall dimensions of the cathode mask 800.

[0065] The rectangular extension 811 can be substantially U-shaped with respect to the lateral symmetry line 802. For example, the rectangular extension 811 can have a high side portion with a second height 842 and a low central portion with a third height 844. The first segment 816 and the second segment 818 can be substantially the second height 842. The third segment 832 and the fourth segment 834 can be substantially the second height 842 near the ends of the first segment 816 and the second segment 818, and decrease to the third height 844 in the direction of the lateral symmetry line 802. The shape of the rectangular extension is affected by the dimensions of the focusing element and the arrangement of the coiled filament of the focusing element.

[0066] The first segment 816, the second segment 818, the third segment 832, and the fourth segment 834 can have an extension surface 848. The extension surface 848 can be part of the outer shield surface 850. The first side wall 804, the second side wall 806, the third side wall 808, and the short extension 810 can have a columnar outer peripheral surface 825. The central opening of the cathode mask 800 can be defined by the opening of the extension surface 848, the opening of the inner shield surface 852, and the outer peripheral surface 824. In this way, the extension surface 848 can form the outer peripheral edge or the frame portion of the central opening.

[0067] In one embodiment, the extension surface 848 has a rounded edge. For example, the extension surface 848 bends or curls inwardly toward the inner shield surface 852 to form a curved end transition portion around the opening. For example, the extension surface 848 can bend from a plane substantially perpendicular to the x-y plane of the cathode mask 800 in the embodiment to a plane substantially parallel to the x-y plane. When the cathode assembly is assembled, the central opening can receive the cathode cup, the columnar outer peripheral surface 825 can be substantially flush with the rear surface of the cathode cup, and the extension surface 848 can surround the focusing elements (such as the rear surface 426 of the cathode cup 62 and the focusing element 375 described with reference to FIGS. 2-7).

[0068] FIG. 9A shows a cross-sectional view 900 of the cathode mask 800 of FIG. 8 shown by a lateral cut along the dashed line 9-9 of FIG. 8. The cross-sectional view 900 shows an example of the focusing portion of the cathode mask 800. The focusing portion is the end transition portion of the central opening of the cathode mask. In this example, the end transition portion can be an outer peripheral edge including a rounded edge. FIG. 9B is a detailed view 950 of the cross-section shown in FIG. 9A. Similar components are labeled with the same numbers as in FIG. 8. A set of reference axes 901 is shown so that comparisons can be made between FIGS. 9A and 9B, with the x-axis, y-axis, and z-axis shown.

[0069] Cross-sectional view 900 traverses the third segment 832 of the third side wall 808 and the fourth segment 834 of the front panel 812, and shows a rounded edge 902. The wall 904 of the cathode mask 800 can be bent so that the rounded edge 902 is formed. For example, the wall 904 within the region of the rectangular extension 811 can be formed to be bent perpendicular to the z-axis, and the inner portion is directed towards the center line 911 of the central opening. The bent portion of the wall 904 can be made sufficiently rounded along the longitudinal axis. The rounded edge 902 can include a substantially round extension surface 848 and an outer peripheral edge 906 facing the center line 911.

[0070] The bent portion of the rounded edge 902 can be made the same way at each end of the rectangular extension 811, and the first segment 816, the second segment 818 (see FIG. 8), the third segment 832, and the fourth segment 834 can be bent with the same dimensions. The rounded edge 902 protects the outer peripheral edge 906 from electric field stress, and one or more coiled filaments can achieve a sufficient focusing field.

[0071] FIG. 9B shows in detail an example of the dimensions of the rounded edge 902. The rounded edge 902 is electrostatically advantageous and limits the kV / mm in the shield region. Due to the rounded feature, the same kV / mm as a larger radius is provided without extending "further downwards" towards the grid electrode (e.g., the focusing element 375). By not extending further downwards, the opening can be enlarged, thus increasing the focusing field and the electron emission.

[0072] In the illustrated example, the rounded edge 902 can be substantially parallel to the first axis 908 over the first length 910. The intersecting second axis 914 and the first axis 908 are perpendicular. The third axis 916 intersects the outer peripheral edge 906, the first axis 908, and the second axis 914. The intersecting third axis 916 and the second axis 914 form a bending angle 912. In one embodiment, the bending angle 912 can have a lower threshold angle of 69° and an upper threshold angle of 75°.

[0073] The first bent portion 918 has a first bending radius 920. In one embodiment, the first bending radius 920 can have a lower threshold radius of 1.5 mm and an upper threshold radius of 2.5 mm. The second bent portion 922 has a second bending radius 924. In one example, the second bending radius 924 can have a lower threshold radius of 1.9 mm and an upper threshold radius of 2.5 mm. In one embodiment, the first bending radius 920 and the second bending radius 924 may have different dimensions. The rounded edge 902 includes a first bending length 928 that is the length of the first bent portion 918 and the second bent portion 922 with respect to the y-axis between the second axis 914 and the fourth axis 926. The rounded edge 902 includes a second bending length 930 that is the length of the first bent portion 918 and the second bent portion 922 with respect to the z-axis. In one embodiment, the first bending length 928 can be longer than the second bending length 930.

[0074] Thus, in at least some embodiments, the cathode mask disclosed herein can include various bent portions. That is, the bent portions of the edge transition portion (e.g., the rounded edge 902) and the U-shaped bent portion of the central opening (e.g., the central opening 340). Such focusing portions of the cathode mask (e.g., the cathode mask 800) can cooperate as a whole to increase the focusing field of one or more coiled filaments having different intensities and / or different dimensions and reduce high voltage instability.

[0075] FIG. 10 shows a perspective view of an example of a second shield portion 1000 that is part of a cathode shield assembly for a cathode. The second shield portion 1000 can be the same as or similar to the second shield portion 304 described with reference to FIGS. 3 - 7. A set of reference axes 1001 is illustrated so as to be comparable among the plurality of figures shown, with an x-axis, a y-axis, and a z-axis shown.

[0076] In one embodiment of the disclosed cathode shield assembly, the second shield portion 1000 can be substantially ring-shaped. The second shield portion 1000 is radially symmetric about a radial symmetry line 1002. The second shield portion 1000 has an annular wall 1004. The annular wall 1004 has an annular outer surface 1006 and an annular inner surface 1008. The second shield portion 1000 has a central hollow portion that is defined by a first circular opening of the inner surface 1014, a second circular opening of the outer surface 1016, and the annular inner surface 1008. In one example, the second shield portion 1000 can have a flat rim 1012 on the inner surface 1014 and a flare lip 1010 on the outer surface 1016. When assembled to the cathode assembly, the central hollow portion can surround a lower extension (such as the lower extension 405 in FIG. 4). The flare lip 1010 can contact a ceramic insulator (such as the small insulator 428 in FIG. 4). The flat rim 1012 can be provided at a mating portion of the lower extension. In one example, the annular inner surface 1008 of the flat rim 1012 can be in surface contact with the surface of one or more windows of the lower extension (such as the lower extension window surface 456 of the window 450 in FIG. 4).

[0077] The second shield portion 1000 can have a ring length 1018 with respect to the y-axis. The second shield portion can have a first inner diameter 1020 and a second inner diameter 1022 with respect to the radial symmetry line 1002. The first inner diameter 1020 can be determined, for example, based on the dimensions of the lower extension body (e.g., the lower extension body 405). The second inner diameter 1022 can be determined based on the shape of the flare lip 1010 (e.g., the angle opening outward). The ring length 1018 can be determined based on several factors. For example, by keeping the gap space (e.g., the gap interval 478 shown in FIG. 4) between the first shield portion (e.g., the first shield portion 302) and the second shield portion 1000 as wide as possible, radiant heat transfer can be increased. However, if the length of the second shield is made too short, the shielding effect of the grounded cathode component will decrease. In addition, if the effect of shielding the low-temperature components decreases, it may not contribute sufficiently to cooling. To determine the appropriate length, a trade-off can be considered between covering the weld that hinders the high-voltage stability and enabling as much radiant heat transfer as possible.

[0078] In contrast to the integrated cathode shielding common in X-ray systems, by separating the shield into a first shield portion and a second shield portion, the disclosed shield promotes radiant heat transfer to the frame and reduces the overall cathode temperature. The disclosed curved portion of the cathode mask has the additional advantage of increasing the focusing force of one or more coiled filaments (e.g., the exemplary three-filament configuration shown in FIGS. 3-7) and reducing the electric field stress at the end portion of the cathode mask. When used in a smart cathode system, the cathode shield assembly can improve the high-voltage stability, extend the life of the X-ray tube, and improve the resolution and accuracy for various X-ray applications.

[0079] In some examples, the disclosed cathode shield can include a cathode mask having a central opening and an outer periphery of another shape. As an example, the cathode assembly can include a cathode cup having only a single coiled filament. In such a cathode assembly, as an example, the cathode mask can have a square extension instead of a rectangular extension, and the outer periphery of the central opening can include a rounded edge. Alternatively, the extension can be oval or circular, and the outer periphery can have a curved end transition. As another example, the cathode assembly can include a coiled filament disposed within the cathode cup such that the side surfaces are linear rather than the exemplary U - shape, which is suitable for electric field focusing. In such an example, the cathode shield including the opening can provide the advantage of promoting radiative heat transfer while supporting various configurations of the cathode cup and the coiled filament (e.g., by the gap spacing and the large view factor).

[0080] In other embodiments, the disclosed cathode shield can include a cathode mask (e.g., cathode mask 800) having a central opening and an outer periphery with one or more curved portions, which can be used in combination with complementary shield portions of different configurations. As an example, a cathode mask having a U - shaped central opening and a rounded edge can be used together with a disk shield of another shape. For example, the disk shield can be shaped differently to increase the view factor to another shaped frame and / or to shield a larger or differently positioned insulator. In such an example, the cathode mask incorporating the disclosed curved portions of the central opening and the outer periphery can enlarge the focusing field of a smart cathode having one or more coiled filaments while supporting various x - ray tube designs.

[0081] In this way, by using a selective shield in a region with high electric field stress and keeping other regions open, heat conduction and heat concentration to the cathode components susceptible to temperature influence and their surroundings can be reduced. By forming a cathode mask shield such that the focusing by one or more coiled filaments is adjusted, the smart cathode can achieve a current range suitable for diagnostic applications and interventional applications without losing the focusing force. This technical effect is that the lifespan of the X-ray tube is extended, the reliability of the X-ray tube is improved, and the emission performance of the X-ray beam is improved.

[0082] Further, the present disclosure provides support for a cathode shield. The cathode shield includes a cathode mask having a U-shaped central opening configured to receive a cathode cup, and an outer peripheral edge of the U-shaped central opening includes a rounded edge. In a first embodiment of the system, the U-shaped central opening maintains a similar distance between each coiled filament of a plurality of coiled filaments and the rounded edge. In a second embodiment of the system, optionally including the first embodiment, the U-shaped central opening includes a first bent portion having a first bending radius and a second bent portion having a second bending radius, and the first bending radius and the second bending radius are of different dimensions. In a third embodiment of the system, including one or both of the first and second embodiments, the rounded edge includes a portion bent perpendicularly toward a center line of the U-shaped central opening. In a fourth embodiment of the system, optionally including one or more of the first to third embodiments or each embodiment, the rounded edge includes a first bent portion having a first bending radius and a second bent portion having a second bending radius, and the first bending radius and the second bending radius are of different dimensions. In a fifth embodiment of the system, optionally including one or more of the first to fourth embodiments or each embodiment, the rounded edge consists of a first bent portion having a first bending radius and a second bent portion having a second bending radius, and the first bending radius and the second bending radius are of similar dimensions. In a sixth embodiment of the system, optionally including one or more of the first to fifth embodiments or each embodiment, the rounded edge has a bending angle, and the bending angle has a similar angle at each end of the outer peripheral edge of the U-shaped central opening.

[0083] The present disclosure also provides a support for a cathode assembly for an X-ray device. The cathode assembly for an X-ray device includes a cathode cup that houses a focusing element, a plurality of coiled filaments disposed on the focusing element, and a cathode shield including a cathode mask having a U-shaped central opening configured to receive the cathode cup, wherein an outer peripheral edge of the U-shaped central opening includes a rounded edge. In a first embodiment of the system, the focusing element is U-shaped. In a second embodiment of the system, optionally including the first embodiment, the cathode mask includes a rectangular extension that surrounds the focusing element. In a third embodiment of the system, optionally including one or both of the first and second embodiments, the focusing element includes two or more coiled filaments, and each coiled filament is disposed at a depth within a threshold from a surface corresponding to the rounded edge of the cathode mask. In a fourth embodiment of the system, optionally including one or more or each of the first to third embodiments, the cathode mask is welded to a base of the cathode cup. In a fifth embodiment of the system, optionally including one or more or each of the first to fourth embodiments, the cathode mask is formed from electropolished nickel.

[0084] Also, the present disclosure provides support for an imaging system. The imaging system includes a collector assembly, an anode assembly, and a cathode assembly configured to focus an electron beam onto the anode assembly. The cathode assembly includes a cathode cup and a cathode shield. The cathode shield includes a cathode mask having a U-shaped central opening configured to receive the cathode cup. The outer peripheral edge of the U-shaped central opening includes a rounded edge. In a first embodiment of the system, the collector assembly includes a window through which X-rays generated by the anode assembly are emitted, and an electron collector for absorbing backscattered electrons within the imaging system. In a second embodiment of the system, optionally including the first embodiment, the system includes a target onto which the electron beam is focused, a rotor, and a bearing arm. In a third embodiment of the system, optionally including one or both of the first and second embodiments, the cathode cup includes two or more coiled filaments disposed in the focusing element of the cathode cup. In a fourth embodiment of the system, optionally including one or more or each of the first through third embodiments, the U-shaped central opening includes a first bent portion having a first bending radius and a second bent portion having a second bending radius, and the first bending radius and the second bending radius are different dimensions. In a fifth embodiment of the system, optionally including one or more or each of the first through third embodiments, and optionally including one or more or each of the first through fourth embodiments, the rolled-over edge is bent perpendicular to the centerline of the U-shaped central opening. In a sixth embodiment of the system, optionally including one or more or each of the first through third embodiments, and optionally including one or more or each of the first through fifth embodiments, the rolled-over edge consists of a bending angle, and the bending angle is the same on each side of the outer periphery of the U-shaped central opening.

[0085] Figures 2 to 10 show exemplary configurations of the relative positional relationships of various elements. When elements are illustrated as being in direct contact with each other or directly coupled to each other, these elements can be referred to, in at least one embodiment, as elements in direct contact or directly coupled elements, respectively. Similarly, elements shown as being contiguous or adjacent to each other can be referred to, in at least one embodiment, as contiguous elements or adjacent elements to each other, respectively. As an example, elements in surface contact with each other can be referred to as elements in surface contact. As another example, when elements arranged apart from each other have a space between the elements but no other elements, in at least one example, they can be referred to as elements apart from each other. Also, as another example, elements shown as being above and below each other, opposite each other, or left and right of each other can be referred to as elements above and below each other, opposite elements, or left and right elements, respectively. Further, as shown in the figures, in at least one example, the uppermost element or the uppermost point of an element can be referred to as the "upper part" of the element, and the lowermost element or the lowermost point of an element can be referred to as the "lower part" of the element. In this specification, upper / bottom, upper side / lower side, and up / down represent relative to the vertical axis of the figure and are used to explain the relative positions of the elements of the figure with respect to each other. Thus, an element shown above another element is, in one example, vertically arranged above the other element. As yet another example, it can be said that the elements shown in the figures have their shapes (e.g., circular, straight, planar, curved, rounded, chamfered, angled, etc.). Further, elements shown as intersecting each other can be referred to, in at least one example, as intersecting elements or elements intersecting each other. Further, an element shown within another element or outside another element can be referred to, in one example, as an element shown within another element or outside another element.

[0086] In this specification, elements or steps described in the singular and preceded by the words "a" or "an" are to be understood as not excluding a plurality of such elements or steps, unless explicitly stated otherwise. Further, reference to "an embodiment" of the present invention is not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features. Further, unless explicitly stated to the contrary, an embodiment "comprising", "including", or "having" one or more elements having a particular characteristic can include additional elements not having that characteristic. The terms "including" and "in which" are used as plain language equivalents of the respective terms "comprising" and "wherein". Further, terms such as "first", "second", and "third" are used merely as labels and are not intended to impose numerical requirements or a particular positional ranking on the items to which they refer.

[0087] In this specification, the term "about" is to be construed as meaning ±5% of the range, unless otherwise specified, and the term "substantially concave" means that the element has a shape that is sufficient for a person skilled in the art to consider it concave, even if it is not a perfect concave. The term "substantially rectangular" in this specification means that the element has a shape that is sufficient for a person skilled in the art to consider it rectangular, even if it is not a perfect rectangle. The term "substantially columnar" in this specification means that the element has a shape that is sufficient for a person skilled in the art to consider it columnar, even if it is not a perfect column.

[0088] The description provided herein discloses the present invention (including the best mode) using examples, and enables those skilled in the art to practice the present invention (including manufacturing and using any device or system, and performing any incorporated method). The patentable scope of the present invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be included in the claims if they include structural elements that do not differ from the language of the claims, or equivalent structural elements that do not differ substantially from the language of the claims.

Explanation of Signs

[0089] 10 Imaging system 12 X-ray source 14 X-ray beam 16 Object 18 Detector assembly 20 Processor 22 Computer 24 Operator console 26 Display device 28 Storage device 30 Source controller 40 X-ray tube 42 Anode assembly 44 Cathode assembly 46 Frame 48 Anode 50 Bearing assembly 52 Cathode 54 Space 58 Central insulating shell 60 Mask 62 Cathode cup 64 X-ray 66 Target 68 Window 70 Center line 72 Rotor 74 Opening 76 Central shaft 78 Sleeve 80 Refrigerant flow path 82 Focusing electrode assembly 84 Electron collector 200 X-ray source 202 First shield part 204 Second shield part 300 Cathode assembly 302 First shield part 304 Second shield part 310 Lip 312 Flat area 314 Tapered transition part 315 First center line 316 Surface 317 Central axis 322 First outer surface 324 Surface 326 Extension part 328 Side wall 330 Second outer surface 332 Front panel 338 Outer periphery 340 Central opening 358 Large insulator 362 Cathode mask 365 Disk shield 375 Focusing element 376 First filament 378 Second filament 380 Third filament 404 First inner surface 405 Lower extension body 406 Outer part 408 Inner part 412 Disk shield width 416 Outer periphery 418 Taper angle 420 Length 424 First offset 426 Rear surface 428 Small insulator 440 Air gap 444 Base 446 Insulator 448 Welding pad 460 Mounting wall 462 Surface 464 Second dashed line 466 Inclination angle 468 Sleeve part 472 Flared lip 474 Rim 476 Third length 478 Gap interval 480 Opening surface 502 Dashed line 602 First channel 604 Second channel 606 Third channel 608 First axis 610 Second axis 612 Third axis 614 Fourth axis 674 Second bending dimension 676 First bending dimension 702 First surface 704 Second surface 718 Edge 800 Cathode mask 802 Symmetry line 803 Horizontal center line 804 First side wall 806 Second side wall 808 Third side wall 810 Extension 811 Rectangular extension 812 Front panel 814 Transition surface 816 First segment 818 Second segment 822 First height 824 Peripheral surface 825 Outer peripheral surface 826 First depth 830 Third length 832 Third segment 834 Fourth segment 838 First width 840 Second depth 842 Second height 844 Third height 846 Second height 848 Extension surface 850 Outer shield surface 852 Inner shield surface 852 Internal shield surface 904 Wall 906 Outer periphery 908 First axis 910 First length 911 Center line 912 Bending angle 914 Second axis 916 Third axis 920 First bending radius 924 Second bending radius 926 Fourth axis 928 First bending length 930 Second bending length 1000 Second shield part 1002 Radial symmetry line 1004 Annular wall 1006 Annular outer surface 1008 Annular inner surface 1010 Flared lip 1012 Edge 1014 Inner surface 1016 Outer surface 1018 Annular length 1020 First inner diameter 1022 Second inner diameter

Claims

1. A cathode shield, comprising: a cathode mask (362) including a U-shaped central opening (340) configured to receive a cathode cup (62), wherein an outer peripheral edge (338) of the U-shaped central opening includes a rounded edge (718).

2. The cathode shield according to claim 1, wherein the U-shaped central opening (340) maintains a similar distance between each coiled filament of a plurality of coiled filaments (376, 378, 380) and the rounded edge (718).

3. The cathode shield according to claim 1, wherein the U-shaped central opening (340) includes a first bent portion (680) having a first bending radius and a second bent portion (682) having a second bending radius, and the first bending radius and the second bending radius are of different dimensions.

4. The cathode shield according to claim 1, wherein the rounded edge (902) includes a portion bent perpendicular to a center line (911) of the U-shaped central opening.

5. The cathode shield according to claim 1, wherein the rounded edge includes a first bent portion (918) having a first bending radius (920) and a second bent portion (922) having a second bending radius (924), and the first bending radius and the second bending radius are of different dimensions.

6. The cathode shield according to claim 1, wherein the rounded edge consists of a first bent portion (918) having a first bending radius (920) and a second bent portion (922) having a second bending radius (924), and the first bending radius and the second bending radius are of similar dimensions.

7. The cathode shield according to claim 1, wherein the rounded edge has a bending angle (912), and the bending angle has a similar angle at each end of an outer peripheral edge (906) of the U-shaped central opening.

8. A cathode assembly for an X-ray device, comprising: a cathode cup (62) for accommodating a focusing element (375), a plurality of coiled filaments (376, 378, 380) disposed on the focusing element, and a cathode shield including a cathode mask (362) including a U-shaped central opening (340) configured to receive the cathode cup, wherein an outer peripheral edge (338) of the U-shaped central opening includes a rounded edge (718), the cathode assembly including the cathode shield.

9. The cathode assembly according to claim 8, wherein the focusing element (375) is U-shaped. **Claim 10** The cathode assembly according to claim 8, wherein the cathode mask (362) includes a rectangular extension (326), and the rectangular extension surrounds the focusing element. **Claim 11** The cathode assembly according to claim 8, wherein the focusing element (375) includes two or more coiled filaments, and each coiled filament is disposed at a depth within a threshold (712, 716) from a plane corresponding to the rounded edge (338) of the cathode mask. **Claim 12** The cathode assembly according to claim 8, wherein the cathode mask (362) is welded to a base (444) of the cathode cup (62). **Claim 13** The cathode assembly according to claim 8, wherein the cathode mask (362) is formed of electropolished nickel. **Claim 14** The U-shaped central opening (340) includes a first bent portion (680) having a first bending radius and a second bent portion (682) having a second bending radius, and the first bending radius and the second bending radius have different dimensions. The cathode assembly according to claim 8. **Claim 15** The cathode assembly according to claim 8, wherein the rounded edge (902) includes a portion bent perpendicularly toward a center line (911) of the U-shaped central opening. **Claim 16** The U-shaped central opening is disposed centered on a lateral symmetry line of the cathode mask. The cathode assembly according to claim 8.

Images