Cathode stack including consolidated layers and x-ray tubes including the same

Abstract

Cathode stacks including joined or co-formed layers and x-ray tubes including the same are disclosed. A cathode stack can include a plurality of functional layers including an emitter substrate, a gate, a gap spacer between the gate and the emitter substrate, and a gate frame proximate the gate opposite the gap spacer. At least two proximate layers of the plurality of functional layers can be formed from a single material or can be joined together by at least one of brazing, welding, metal-to-metal bonding, or adhesive bonding.

Description

CATHODE STACK INCLUDING CONSOLIDATED LAYERS AND X-RAYTUBES INCLUDING THE SAMECROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of priority pursuant to 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63 / 626,316, filed 29 January 2024, and entitled “Consolidated Cathode Stack,” which is hereby incorporated by reference in its entirety.BACKGROUND

[0002] X-ray sources can include cold cathode stacks, which can be used to emit electrons that are then used to generate x-rays. Cold cathode stacks can include flat layers of metal and ceramic, which can be stacked and held together by bolts and nuts. Each layer of a cold cathode stack can have a significant amount of surface area in contact with adjacent layers. The surface areas between layers of the cold cathode stack can create virtual leaks in a vacuum chamber or evacuated enclosure of an x-ray source (e.g, an x-ray tube), which can reduce the vacuum in the vacuum chamber over time. In addition, there can be a tolerance allowed in the stack-up of the cold cathode from layer to layer that can offset a critical quality gap distance, such as a gap between a cold cathode emitter and a gate of the cold cathode stack.SUMMARY

[0003] An aspect of the present disclosure relates to a cathode stack including a plurality of functional layers including an emitter substrate, a gate, a gap spacer between the gate and the emitter substrate, and a gate frame proximate the gate opposite the gap spacer. At least two proximate layers of the plurality of functional layers can be formed from a single material or can be joined together by at least one of brazing, welding, metal-to-metal bonding, or adhesive bonding.

[0004] In one or all examples, the at least two proximate layers of the plurality of functional layers can include ceramic materials. The at least two proximate layers of the plurality of functional layers can be joined together by brazing or adhesive bonding. In one or all examples, the at least two proximate layers of the plurality of functional layers can include a ceramic material and a metal material. The at least two proximate layers of the plurality of functional layers can be joined together by brazing. In one or all examples, the at least twoproximate layers of the plurality of functional layers can include two different metal materials. The at least two proximate layers of the plurality of functional layers can be joined together by brazing or metal-to-metal bonding. In one or all examples, the at least two proximate layers of the plurality of functional layers can include a same metal material. The at least two proximate layers of the plurality of functional layers can be joined together by brazing or welding.

[0005] In one or all examples, the at least two proximate layers can be formed from a single continuous material. In one or all examples, each of the layers of the plurality of functional layers can be formed from single materials or are joined together with proximate layers of the plurality of functional layers. In one or all examples, the cathode stack can further include a fastener coupled to the cathode stack and configured to retain the layers of the plurality of functional layers relative to one another.

[0006] Another aspect of the present disclosure relates to a method of forming a cathode stack for an x-ray tube, the method including providing at least three functional layers, the at least three functional layers including a gap spacer including a cavity configured to receive a field emitter, a gate proximate the gap spacer, the gap spacer being configured to space the gate from the field emitter, and a gate frame proximate the gate. Providing the at least three functional layers can include at least one of joining at least two proximate layers of the at least three functional layers together or machining the at least two proximate layers of the at least three functional layers from a single material.

[0007] In one or all examples, the at least three functional layers can further include an isolation spacer between the gate frame and a focus electrode. The gate frame and the isolation spacer can be joined together or machined from the single material. In one or all examples, the at least three functional layers can further include an emitter substrate configured to receive the field emitter on a surface thereof. The emitter substrate and the gap spacer can be joined together or machined from the single material.

[0008] In one or all examples, the at least two proximate layers of the at least three functional layers can be machined from the single material. Machining the at least two proximate layers can include machining a cavity in the single material to define the gap spacer or the gate frame and machining a grid in the single material to define the gate. The grid can be machined by energetic beam machining.

[0009] In one or all examples, the at least two proximate layers of the at least three functional layers can include a metal material and a ceramic material. The at least two proximate layers of the at least three functional layers can be joined together by at least one of brazing or adhesive bonding. In one or all examples, the at least two proximate layers of the at least three functional layers can include two different metal materials. The at least two proximate layers of the at least three functional layers can be joined together by at least one of brazing or metal - to-metal bonding. In one or all examples, the at least two proximate layers of the at least three functional layers can include a same metal material. The at least two proximate layers of the at least three functional layers can be joined together by at least one of brazing or welding.

[0010] Yet another aspect of the present disclosure relates to a cathode stack including an emitter substrate configured to receive an electron emitter, a gate, a gap spacer between the emitter substrate and the gate, and a gate frame proximate the gate opposite the gap spacer. At least one of the emitter substrate and the gap spacer can be formed from a first single continuous material, the gap spacer and the gate can be formed from a second single continuous material, or the gate and the gate frame can be formed from a third single continuous material.

[0011] In one or all examples, the emitter substrate and the gap spacer can be formed from the first single continuous material including a ceramic material. In one or all examples, the gap spacer and the gate can be formed from the second single continuous material including a metal. In one or all examples, the gate and the gate frame can be formed from the third single continuous material including a metal.

[0012] In one or all examples, the cathode stack can further include a focus electrode and an isolation spacer between the gate frame and the focus electrode. The isolation spacer and the gate frame can be formed from a fourth single continuous material including a ceramic material.

[0013] An aspect of the present disclosure relates to a cathode stack including at least three functional layers including a gap spacer with a cavity with a field emitter to emit electrons, a gate proximate the gap spacer, spaced from the field emitter by the gap spacer, and configured to be electrically isolated and at a different electric potential from the field emitter, and a gate frame proximate the gate and configured to retain the gate. At least two proximate functional layers of the at least three functional layers can be joined together by brazing or can share a common monolithic body of the same material that is continuous through the body.

[0014] In one or all examples, the at least two proximate function layers can be without an abutting surface interface of opposing surfaces forming a virtual leak surface area. In one or all examples, the at least two proximate function layers can be without a mechanical fastener spanning the at least two proximate function layers.

[0015] In one or all examples, the at least two proximate function layers can include the gap spacer and the gate formed as the common monolithic body. The common monolithic body can include metal. In one or all examples, the at least two proximate function layers can include the gate and the gate frame formed as the common monolithic body. The common monolithic body can include metal. In one or all examples, the at least two proximate function layers can include the gap spacer and the gate formed as the common monolithic body. The common monolithic body can include metal. The at least two proximate function layers can further include the gate and the gate frame formed as the common monolithic body. The common monolithic body can include metal.

[0016] In one or all examples, the at least three functional layers can further include an emitter substrate proximate the gap spacer and configured to carry the field emitter. In one or all examples, the at least two proximate function layers can include the emitter substrate and the gap spacer formed as the common monolithic body. The common monolithic body can include ceramic.

[0017] In one or all examples, the cathode stack can further include a focus electrode coupled to the cathode stack and configured to focus electrons from the field emitter. The at least three functional layers can further include an isolation spacer proximate the gate frame and configured to electrically isolate the gate frame from the focus electrode. In one or all examples, the at least two proximate function layers can include the gate frame and isolation spacer formed as the common monolithic body. The common monolithic body can include ceramic. In one or all examples, the at least two proximate function layers can further include the gap spacer and the gate formed as another common monolithic body of metal.

[0018] In one or all examples, the cathode stack can be included in an x-ray source having a vacuum enclosure. The cathode stack can contact the vacuum enclosure.

[0019] Another aspect of the present disclosure relates to a method for emitting electrons for an x-ray tube, the method including providing a cathode stack with at least three functional layers including a gap spacer with a cavity with a field emitter to emit electrons, a gate proximate the gap spacer, spaced from the field emitter by the gap spacer, and configured to beelectrically isolated and at a different electric potential from the field emitter, and a gate frame proximate the gate and configured to retain the gate. The method can further include combining at least two proximate functional layers of the at least three functional layers by joining the at least two proximate functional layers together by brazing or forming the at least two proximate functional layers in a common monolithic body of the same material that is continuous through the body.

[0020] In one or all examples, the method can further include forming the gap spacer and the gate as the common monolithic body from metal. In one or all examples, the method can further include forming the gate and the gate frame as the common monolithic body from metal.

[0021] In one or all examples, the method can further include providing the at least three functional layers of the cathode stack with an emitter substrate proximate the gap spacer, the emitter substrate being configured to carry the field emitter and forming the emitter substrate and the gap spacer as the common monolithic body from ceramic.

[0022] In one or all examples, the method can further include providing a focus electrode coupled to the cathode stack, the focus electrode being configured to focus electrons from the field emitter, providing the at least three functional layers of the cathode stack with an isolation spacer proximate the gate frame and configured to electrically isolate gate frame from focus electrode, and forming the gate frame and isolation spacer as the common monolithic body from ceramic.

[0023] Yet another aspect of the present disclosure relates to a cathode stack including means for emitting electrons, means for controlling field emission from the means for emitting electrons, means for spacing the means for controlling field emissions from the means for emitting electrons, means for supporting the means for controlling field emissions, and means for combining at least two of the means for controlling field emissions, means for spacing, and means for supporting without a virtual leak surface area.

[0024] In one or all examples, the means for combining can further include means for forming the at least two of the means for controlling field emissions, means for spacing, and means for supporting in a common monolithic body of the same material that is continuous through the body. In one or all examples, the means for combining can further include means for joining the at least two of the means for controlling field emissions, means for spacing, and means for supporting.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:

[0026] FIG. 1 is a cross-sectional schematic diagram of an x-ray tube including a cathode stack.

[0027] FIG. 2 is a cross-sectional schematic diagram of an x-ray tube including a cathode stack.

[0028] FIG. 3 is a cross-sectional schematic diagram of functional layers of a cathode stack.

[0029] FIG. 4 is a cross-sectional schematic diagram of a cathode stack including consolidated layers.

[0030] FIG. 5 is a cross-sectional schematic diagram of a cathode stack including consolidated layers.DETAILED DESCRIPTION

[0031] Reference will now be made to the examples illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended. Alterations and further modifications of the features illustrated herein, and additional applications of the examples as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the description.

[0032] The following disclosure relates to x-ray sources, such as x-ray tubes, which can be used to generate x-rays. X-ray sources and x-ray tubes can be used in a variety of contexts, including medical imaging, diagnostics, radiotherapy, non-destructive testing, materials detection or analysis, security inspection, sanitation, sterilization, materials alteration, and the like. More specifically, the following disclosure relates to cathode stacks that can be included in an x-ray source, such as an x-ray tube. The cathode stack can include consolidated parts or layers. For example, adjacent layers in the cathode stack can be consolidated or combined into a single, unitary component or layer. This can reduce a number of virtual leak areas in the cathode stack, decrease part variation in the cathode stack, decrease a part count of the cathode stack, and tighten tolerances in a stack-up or manufacturing process of the cathode stack.

[0033] As will be described in detail below, the present disclosure can combine adjacent layers of the cathode stack into a single piece, component, or layer; instead of using multiple parts or layers. In one or all examples, metal and ceramic layers can be combined. In one or all examples, adjacent layers that are combined can both include metal layers or ceramic layers. In one or all examples, two sets of layers can be combined in a cathode stack to reduce four layers to two layers or components. This can reduce a number of interfaces in the cathode stack between adjacent layers by two, which can reduce virtual leak surfaces in the cathode stack, decrease part variation in the cathode stack, decrease a part count of the cathode stack, and tighten tolerances in the manufacturing of the cathode stack. The adjacent parts or layers can be combined by forming the two parts or layers from a single piece of material, joining the adjacent parts or layers together, or the like. Thus, the cathode stack or layers thereof can be consolidated.

[0034] In one or all examples, the parts or layers of a cathode stack can be combined by machining two layers of the cathode stack from a single piece or component, or by joining two pieces or components together. The machining can be any suitable machining processes, suchas wet etching, milling, turning, polishing, energetic beam machining, or the like. The joining can be any suitable joining process, such as brazing, welding, metal -to-metal bonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like), adhesive bonding (e.g., a ceramic paste), gluing or the like. In one or all examples, a gate and a gap spacer of the cathode stack can be formed together as a single part or joined to one another and can be formed of metal. For example, a recess can be machined in a component to form the gap spacer and a grid pattern can be cut in the component to form the gate. In one or all examples, a gate frame and an isolation spacer of the cathode stack can be formed together as a single part or joined to one another and can be formed of ceramic. The gate frame and the isolation ceramic can both be machined from a single component. By combining the gate and the gap spacer and combining the gate frame and the isolation spacer, a part count for the cathode stack can be reduced by two parts (e.g., the portion of the cathode stack including the gate, the gap spacer, the gate frame, and the isolation spacer can be reduced from four parts to two). Production costs may be lowered by the reduced part count. Reliability and longevity of an x-ray tube including the cathode stack can be increased because there is less surface area available for virtual leaks to degrade the vacuum levels in the x-ray tube over the lifetime of the x-ray tube. Further, part variation can be reduced, and tighter tolerances can be achieved in the cathode stack.

[0035] These and other examples are discussed below with reference to FIGS. Ithrough 5. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. Furthermore, as used herein, a system, a method, an article, a component, a feature, or a sub-feature including at least one of a first option, a second option, or a third option should be understood as referring to a system, a method, an article, a component, a feature, or a sub-feature that can include one of each listed option (e.g., only one of the first option, only one of the second option, or only one of the third option), multiple of a single listed option (e.g., two or more of the first option), two options simultaneously (e.g., one of the first option and one of the second option), or combination thereof (e.g., two of the first option and one of the second option).

[0036] FIG. 1 is a cross-sectional schematic diagram illustrating an example of an x-ray tube 100 with a cathode stack 110. The x-ray tube 100 can be a transmission target x-ray tube. The x-ray tube 100 can be an x-ray source.

[0037] The x-ray tube 100 can include a cathode, e.g., the cathode stack 110, and an anode 114 separated from one another, such as by an insulative tube 118. The cathode stack 110, the anode 114 and the insulative tube 118 may form a vacuum enclosure 122 or evacuated enclosure and may be configured to maintain a substantial vacuum, a negative pressure, or otherwise be evacuated. The cathode stack 110 can include an electron emitter, such as a field emitter 126, to generate an electron beam. The anode 114 may include a target 130 to generate x-rays from impact of the electron beam. The anode 114 may have a window 134 to allow the x-rays to pass out of the x-ray tube 100 and the vacuum enclosure 122 in the case of a transmission target x-ray tube. The cathode stack 110 can be in contact with or can form part of the vacuum enclosure 122.

[0038] The field emitter 126 can generate electrons or an electron beam that may be directed towards the anode 1 14 and / or the target 130. The field emitter 126 may include a variety of types of emitters. For example, the field emitter 126 may include a nanotube emitter, a nanowire emitter, a Spindt array, or the like. The nanotubes can have at least a portion of the structure that has a hollow center, where nanowires or nanorods can have a substantially solid core. For simplicity in use of terminology, as used herein, a nanotube refers to a nanometerscale (nm-scale) tube-like structure with an aspect ratio of at least 100: 1 (length: width or diameter). A Spindt array may include individual field emitters with small sharp cones using an electron generating material, such as molybdenum (Mo) or Tungsten (W). In one or all examples, the field emitter 126 can be formed of an electrically conductive or semi-conductive material with a high tensile strength and high thermal conductivity such as carbon, metal oxides e.g., AI2O3, titanium oxide (TiCh), zinc oxide (ZnO), or manganese oxide (MnxOy, where x and y are integers)), metals, sulfides, nitrides, and carbides, either in pure or in doped form, or the like.

[0039] In one or all examples, the field emitter 126 may include multiple field emitters. For example, the field emitter 126 may include tens to hundreds or more of individual field emitters. Each field emitter 126 may be configured to generate an electron beam directed towards the anode 114.

[0040] Field emitters 126 may have areas that are larger relative to other types of emitters. For example, a field emitter 126 may have a length of about 10 micrometers (pm) to about 30 pm and a width from about 2 nanometers (nm) to about 6 nm. In one or all examples, the length of the field emitter can be at least 5,000 times larger than the width. The larger relative area thanother emitters may result in a larger size of a focal spot on the anode. Heating of the anode due to incident electrons on the focal spot may be spread over that larger area, decreasing the thermal stress on the anode, while permitting a higher electron flux, or the like. In addition, field emitters 126 may have a relatively lower current flux as compared to other emitters. To compensate for the lower flux, the area of the field emitter may be increased. These aspects lead to larger relative areas for field emitters. The larger relative area means that the local electric field strength around the field emitter 126 can be more sensitive to the anode or tube voltage.

[0041] A voltage source 136 can generate multiple voltages for the x-ray tube 100 and can be coupled to or associated with one or more of the x-ray tube 100, the cathode stack 110, the field emitter 126 or the anode 114. For example, the voltage source 136 may be configured to generate one or more voltages for the field emitter 126 and a high voltage for the anode 114.

[0042] The cathode stack 110 may include structures that are at or near the potential of the field emitter 126. The anode 114 may be at a voltage in a range from about 10 kilovolts (kV) to about 50 kV, from about 50 kV to about 150 kV, from about 50 kV to about 450 kV, or the like (relative to the cathode stack 110 or ground). In one or all examples, these voltages may be associated with particular applications, such as mammography, medical diagnostic imaging, industrial imaging, explosive detection, non-destructive testing (NDT), or the like. The cathode stack 110, such as the field emitter 126, a grid, or the like, may be at voltages in a range from about -3 kV to about 1 kV.

[0043] Generally, a higher electric field strength may increase the probability of an arc. As a result, the design of the x-ray tube 100 may include minimizing local electric field strength maxima. However, in one or all examples, the point of highest electric field strength can be created by design and offset or shifted away from the field emitter 126. In one or all examples, the electric field strength at the point of highest electric field strength may be greater than about 8 times the highest electric field strength on the field emitter 126.

[0044] In one or all examples, the x-ray tube 100 can have a focus electrode 138 coupled to the cathode stack 110 to focus electrons from the field emitter 126. The focus electrode 138 can be coupled to the voltage source 136. The focus electrode 138 can be an optional component of the x-ray tube 100.

[0045] In one or all examples, the x-ray tube 100 can have a getter 142 located in the vacuum enclosure 122. The getter 142 can absorb gas molecules that can permeate into the vacuum enclosure 122 over time.

[0046] FIG. 2 is a cross-sectional schematic diagram illustrating an example of an x-ray tube 200 including a cathode stack 110. The x-ray tube 200 can be a reflection target x-ray tube. The x-ray tube 200 can include components that are the same as or similar to components of the x- ray tube 100, and like components of the x-ray tube 200 can be named the same as or similar to components of the x-ray tube 100. The x-ray tube 200 is similar in many aspects to the x-ray tube 100 of FIG. 1, and such description will not be repeated. The x-ray tube 200 can include an anode 114 with a target 130 disposed within an insulative tube 118. The insulative tube 118, the anode 114, and / or the cathode stack 110 can define a vacuum enclosure 122 (e.g., an evacuated enclosure). The cathode stack 110 can include a field emitter 126 and a focus electrode 138 can be provided for the cathode stack 110. A voltage source 136 can be applied to the anode 114 and / or the cathode stack 110. A getter 142 can be included in the vacuum enclosure 122 (e.g., on a sidewall of the insulative tube 118). In the example of FIG. 2, the anode 114 can be angled and can include an angled target 130. The insulative tube 118 may have a window 234 to allow the x-rays generated from the target 130 to pass out of the x-ray tube 200 in the case of the reflection target x-ray tube.

[0047] In one or all examples, the x-ray tube can be a bell jar x-ray tube. The cathode stack 110 and the anode 114 may be disposed inside a vacuum enclosure in the case of a bell jar tube, and the x-rays may reflect off of a target of the anode and pass out of a side of the enclosure.

[0048] FIG. 3 is a detailed cross-sectional schematic diagram illustrating an example of functional layers of the cathode stack 110. The functional layers can be layers of the cathode stack 110 with a function or purpose that may be distinct from the function or purpose of other or proximate layers. The cathode stack 110 can include at least three functional layers. The functional layers of the cathode stack 110 can include: an emitter substrate 342, a gap spacer 346, a gate 350 (also referred to or including a grid), a gate frame 3 4, and an isolation spacer 358. The emitter substrate 342 can be located proximate the gap spacer 346 and can carry the field emitter 126.

[0049] The gap spacer 346 can be located proximate the emitter substrate 342 and can have a cavity 362 with the field emitter 126 located therein. In other words, the cavity 362 can be configured to receive the field emitter 126. The cavity 362 can be an aperture extendingthrough the gap spacer 346, or from the field emitter 126 to the gate 350, for passage of electrons.

[0050] The gate 350 can be located proximate the gap spacer 346 and spaced from the field emitter 126 by the gap spacer 346. The gate 350 can have a grid 366 to control field emission from the field emitter 126. The gate 350 can be electrically isolated and at a different electric potential from the field emitter 126. The gap spacer 346 and the aperture thereof can be sized to position the grid 366 apart from the field emitter 126. The grid 366 and the gate 350 can have openings therethrough for passage of electrons. The gate 350 can be located proximate the gate frame 354.

[0051] The gate frame 354 can be located proximate the gate 350 and can retain the gate 350. In one aspect, the gate frame 354 can help retain the gate 350 in a flat configuration. The gate frame 354 can have a thickness to retain the gate 350 and the grid 366 in a flat configuration. The gate frame 354 can have an aperture therethrough for passage of electrons. The gate frame 354 can also space the focus electrode 138 apart from the gate 350 by a desired distance. The gate frame 354 can be located proximate the isolation spacer 358.

[0052] The isolation spacer 358 can be located proximate the gate frame 354 and can electrically isolate gate frame 354 from the focus electrode 138. The isolation spacer 358 can have a thickness to electrically isolate and resist arcing between the gate frame 354 and the focus electrode 138. The isolation spacer 358 can also space the focus electrode 138 apart from the gate 350 by a desired distance and can prevent any electrical breakdown, arcing, or the like between the focus electrode 138 and the gate 350. The focus electrode 138 and the isolation spacer 358 can be optional. The isolation spacer 358 can have an aperture therethrough for passage of electrons. The focus electrode 138 can have an aperture therethrough that is sized and shaped to focus electrons.

[0053] At least two proximate functional layers of the at least three functional layers can be combined. In one or all examples, the two proximate functional layers can be joined together by brazing. In one or all examples, the two proximate functional layers can share a common monolithic body of the same material that is continuous through the body. Thus, the two proximate functional layers can be without an abutting surface interface of opposing surfaces forming a virtual leak surface area. In addition, the two proximate functional layers can be without a mechanical fastener spanning the at least two proximate functional layers. Combiningthe two proximate functional layers can reduce virtual leaks, increase reliability and life of the x-ray tube, reduce gap distance, and reduce part count.

[0054] In one or all examples, the emitter substrate 342 can be formed from an insulative material, such as a ceramic material. The gate 350 can be formed from a conductive material, such as a metal. The gate 350 can be formed from a material having a high melting temperature (e.g., refractory metals), such as tungsten, molybdenum, or the like. The isolation spacer 358 can be formed from an insulative material, such as a ceramic material. The focus electrode 138 can be formed from a conductive material, such as a metal. The gap spacer 346 and the gate frame 354 can be formed from either insulative or conductive materials, which can include ceramic materials, metals, or the like.

[0055] The gap spacer 346 and the gate frame 354 and can be formed from the same, similar, or like materials to proximate layers of the cathode stack 110. In examples in which the gap spacer 346 and / or the gate frame 354 are formed from like materials to proximate layers of the cathode stack 110, both of the proximate layers can be formed from conductive materials or insulative materials. As an example, the gap spacer 346 can be formed from the same or similar materials as the emitter substrate 342 or the gate 350. The gate frame 354 can be formed from the same or similar materials as the gate 350 or the isolation spacer 358. Both the gap spacer 346 and the gate frame 354 can be formed form the same or similar materials to the gate 350. In examples in which the gap spacer 346 and / or the gate frame 354 are formed from the same materials as proximate layers of the cathode stack 110, the proximate layers can be formed from a single piece of material or can be joined to one another. Forming the proximate layers from the same or similar materials can allow a broader range of joining processes to be used. For example, welding can be used when two proximate layers are both formed from the same metal; ceramic paste can be used when two proximate layers are both formed from ceramics; and metal-to-metal bonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like) can be used when two proximate layers are both formed from metals.

[0056] Proximate layers of the cathode stack 110 can be formed from a single piece of material or otherwise formed as single, unitary components through any suitable processes. For example, proximate layers of the cathode stack 110 can be machined from a single piece of material. The machining can be any suitable machining processes, such as wet etching, milling, turning, polishing, energetic beam machining, or the like. Additive manufacturingprocesses, such as molding {e.g., including sintering), 3D printing, or the like can be used to form the proximate layers. The additive manufacturing processes can be followed by machining processes. In examples in which the proximate layers of the cathode stack 110 are joined to one another, the joining can be any suitable joining process, such as brazing, welding, metal -to-metal bonding {e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like), adhesive bonding e.g., a ceramic paste), gluing or the like. After proximate layers are combined, additional processing, such as polishing or the like can be used to reduce variation throughout the cathode stack 110, tighten tolerances, and the like. For each pair of proximate layers in the cathode stack 110 that are combined (e. ., joined or formed as a single component), a part count for the cathode stack 110 can be reduced, production costs can be lowered, reliability and longevity for the cathode stack 110 can be increased, a number of virtual leak areas can be reduced, part variation can be decreased, and tighter tolerances can be achieved.

[0057] Any of the layers of the cathode stack 110 can be joined with proximate layers of the cathode stack 110, even when the proximate layers are formed from different materials or unlike materials {e.g., materials having different conductivities or in cases where one layer is formed from conductive materials and a proximate layer is formed from insulative materials). For example, brazing, adhesives, or the like can be used to join proximate layers of the cathode stack 110, regardless of the materials used to form the layers of the cathode stack 110. Each pair of proximate layers of the cathode stack 110 that is joined can reduce a number of virtual leak areas in the cathode stack 110, decrease part variation in the cathode stack 110, decrease a part count of the cathode stack 110, and tighten tolerances in a stack-up or manufacturing process of the cathode stack 110.

[0058] In one or all examples, fasteners can be provided for the cathode stack 110 to join or fasten any layers of the cathode stack 110 to one another that are not otherwise combined {e.g., through joining or being formed as single components). The fasteners can include bolts, pins, screws, or the like that pass through at least a portion of the cathode stack 110. For example, threaded openings can be formed in the focus electrode 138, and bolts can pass through openings in the emitter substrate 342, the gap spacer 346, the gate 350, the gate frame 354, and the isolation spacer 358 and can be threaded into the threaded openings to hold any un-joined layers of the cathode stack 110 together. In one or all examples, exterior fasteners, such as clips or clamps, can be fastened around exterior surfaces of the cathode stack 110, such asbetween opposite surfaces of the emitter substrate 342 and the focus electrode 138, in order to hold any un-joined layers of the cathode stack 1 10 together. In one or all examples, each of the layers of the cathode stack 110 can be combined with proximate layers of the cathode stack 110, such that no additional fasteners are used to hold the layers of the cathode stack 110 together.

[0059] FIG. 4 is a detailed cross-sectional schematic diagram illustrating an example of a cathode stack 410. The cathode stack 410 can be the same as or similar to the cathode stack 110, discussed above in reference to FIGS. 1 through 3, except that proximate layers of the cathode stack 410 are combined (e.g, as single components, through joining, or the like). In the example of FIG. 4, the cathode stack 410 can include two combined layers: the gap spacer 346 and the gate 350 can be combined in a first combined layer and the gate frame 354 and the isolation spacer 358 can be combined in a second combined layer.

[0060] As illustrated in FIG. 4, two proximate functional layers, namely the gap spacer 346 and the gate 350, can be combined. In one or all examples, the gap spacer 346 and the gate 350 can be formed as a common monolithic body 470. The common monolithic body 470 can include a conductive material, such as a metal, which can include tungsten, molybdenum, or the like. The gap spacer 346 and the gate 350 can be formed from a single piece of material that is machined. The machining can be any suitable machining processes, such as wet etching, milling, turning, polishing, energetic beam machining, or the like. As an example, a cavity for the gap spacer 346 can be machined in the single piece of material and can have a depth equal to the thickness of the gap spacer 346. A grid can then be machined into the single piece of material through a process such as energetic beam machining in order to define the gate 350. Thus, the single material can be continuous through the common monolithic body 470, which can define the gap spacer 346 and the gate 350.

[0061] In one or all examples, the gap spacer 346 and the gate 350 can be formed separately and joined together by any suitable joining process. Suitable joining processes can include brazing, welding, metal -to-metal bonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like), adhesive bonding (e.g., a ceramic paste), gluing or the like. The gap spacer 346 and the gate 350 can be joined to one another at an interface 474. In examples in which the gap spacer 346 and the gate 350 are joined to one another, the gap spacer 346 and the gate 350 can be formed from the same, similar, like, or unlike materials, and suitable joining processes can be selected depending on the materials usedto form the gap spacer 346 and the gate 350. As examples, the gap spacer 346 and the gate 350 can both be formed from the same metal and can be joined by welding; the gap spacer 346 and the gate 350 can be formed from different metals and can be joined by metal-to-metal bonding ( .g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like); or the gap spacer 346 can be formed from ceramic and the gate 350 can be formed from metal and the proximate layers can be joined by brazing.

[0062] As illustrated in FIG. 4, another two proximate functional layers, namely the gate frame 354 and the isolation spacer 358, can be combined. In one or all examples, the gate frame 354 and the isolation spacer 358 can be formed as a common monolithic body 478. The common monolithic body 478 can include an insulative material, such as a ceramic. Thus, the gate frame 354 and the isolation spacer 358 can electrically isolate the focus electrode 138 from the gate 350. The gate frame 354 and the isolation spacer 358 can be formed from a single piece of material that is machined. The machining can be any suitable machining processes, such as wet etching, milling, turning, polishing, energetic beam machining, or the like. Thus, the single material can be continuous through the common monolithic body 478, which can define the gate frame 354 and the isolation spacer 358.

[0063] In one or all examples, the gate frame 354 and the isolation spacer 358 can be formed separately and joined together by any suitable joining process. Suitable joining processes can include brazing, adhesive bonding (e. , a ceramic paste), gluing or the like. The gate frame 354 and the isolation spacer 358 can be joined to one another at an interface 482. In examples in which the gate frame 354 and the isolation spacer 358 are joined to one another, the gate frame 354 and the isolation spacer 358 can be formed from the same, similar, like, or unlike materials, and suitable joining processes can be selected depending on the materials used to form the gate frame 354 and the isolation spacer 358. As examples, the gate frame 354 and the isolation spacer 358 can both be formed from ceramics and can be joined by adhesives (e.g., a ceramic paste), brazing or the like or the isolation spacer 358 can be formed from ceramic and the gate frame 354 can be formed from metal and the proximate layers can be joined by brazing.

[0064] The cathode stack 410 can be part of an x-ray source or x-ray tube, e.g., the x-ray tube 100 or the x-ray tube 200 discussed above with respect to FIGS. 1 and 2, with a vacuum enclosure 122. The cathode stack 410 can contact or define the vacuum enclosure 122. Forexample, the cathode stack 410 can be located in the vacuum enclosure 122, and / or can form part of the vacuum enclosure 122, as shown in FIG. 1 and FIG. 2.

[0065] FIG. 5 is a detailed cross-sectional schematic diagram illustrating an example of a cathode stack 510. The cathode stack 510 can be the same as or similar to the cathode stack 110, discussed above in reference to FIGS. 1 through 3, except that proximate layers of the cathode stack 510 are combined (e.g., as single components, through joining, or the like). In the example of FIG. 5, the cathode stack 510 can include two combined layers: the emitter substrate 342 and the gap spacer 346 can be combined in a first combined layer and the gate 350 and the gate frame 354 can be combined in a second combined layer.

[0066] As illustrated in FIG. 5, two proximate functional layers, namely the gate 350 and the gate frame 354, can be combined. In one or all examples, the gate 350 and the gate frame 354 can be formed as a common monolithic body 586. The common monolithic body 586 can include a conductive material, such as a metal, which can include tungsten, molybdenum, or the like. The gate 350 and the gate frame 354 can be formed from a single piece of material that is machined. The machining can be any suitable machining processes, such as wet etching, milling, turning, polishing, energetic beam machining, or the like. As an example, a cavity for the gate frame 354 can be machined in the single piece of material and can have a depth equal to the thickness of the gate frame 354. A grid can then be machined into the single piece of material through a process such as energetic beam machining in order to define the gate 350. Thus, the single material can be continuous through the common monolithic body 586, which can define the gate frame 354 and the gate 350.

[0067] In one or all examples, the gate 350 and the gate frame 354 can be formed separately and joined together by any suitable joining process. Suitable joining processes can include brazing, welding, metal -to-metal bonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like), adhesive bonding (e.g., a ceramic paste), gluing or the like. The gate 350 and the gate frame 354 can be joined to one another at an interface 590. In examples in which the gate 350 and the gate frame 354 are joined to one another, the gate 350 and the gate frame 354 can be formed from the same, similar, like, or unlike materials, and suitable joining processes can be selected depending on the materials used to form the gate 350 and the gate frame 354. As examples, the gate 350 and the gate frame 354 can both be formed from the same metal and can be joined by welding; the gate 350 and the gate frame 354 can be formed from different metals and can be joined by metal -to-metalbonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like); or the gate frame 354 can be formed from ceramic and the gate 350 can be formed from metal and the proximate layers can be joined by brazing.

[0068] As illustrated in FIG. 5, another two proximate functional layers, namely the emitter substrate 342 and the gap spacer 346, can be combined. In one or all examples, the emitter substrate 342 and the gap spacer 346 can be formed as a common monolithic body 594. The common monolithic body 594 can include an insulative material, such as a ceramic. Thus, a field emitter 126 disposed on the emitter substrate 342 can be electrically isolated from the gate 350. The emitter substrate 342 and the gap spacer 346 can be formed from a single piece of material that is machined. The machining can be any suitable machining processes, such as wet etching, milling, turning, polishing, energetic beam machining, or the like. As an example, a cavity for the gap spacer 346 can be machined in the single piece of material and can have a depth equal to the thickness of the gap spacer 346. The emitter substrate 342 can be defined as a lower surface of the cavity. The field emitter 126 can be deposited or otherwise attached to the emitter substrate 342 in the cavity. For example, the field emitter 126 can include carbon nanotubes, which can be deposited on the emitter substrate 342 within the cavity defined by the gap spacer 346. Thus, the single material can be continuous through the common monolithic body 594, which can define the emitter substrate 342 and the gap spacer 346.

[0069] In one or all examples, the emitter substrate 342 and the gap spacer 346 can be formed separately and joined together by any suitable joining process. Suitable joining processes can include brazing, adhesive bonding (e.g., a ceramic paste), gluing or the like. The emitter substrate 342 and the gap spacer 346 can be joined to one another at an interface 598. In examples in which the emitter substrate 342 and the gap spacer 346 are joined to one another, the emitter substrate 342 and the gap spacer 346 can be formed from the same, similar, like, or unlike materials, and suitable joining processes can be selected depending on the materials used to form the emitter substrate 342 and the gap spacer 346. As examples, the emitter substrate 342 and the gap spacer 346 can both be formed from ceramics and can be joined by adhesives (e.g., a ceramic paste), brazing or the like or the emitter substrate 342 can be formed from ceramic and the gap spacer 346 can be formed from metal and the proximate layers can be joined by brazing.

[0070] The cathode stack 510 can be part of an x-ray source or x-ray tube, e.g., the x-ray tube 100 or the x-ray tube 200 discussed above with respect to FIGS. 1 and 2, with a vacuumenclosure 122. The cathode stack 510 can contact or define the vacuum enclosure 122. For example, the cathode stack 510 can be located in the vacuum enclosure 122, and / or can form part of the vacuum enclosure 122, as shown in FIG. 1 and FIG. 2.

[0071] Although FIGS. 4 and 5 are discussed in the context of specific layers of the cathode stacks 410, 510 being combined, any number of layers of a cathode stack can be combined according to the methods and processes disclosed herein in order to achieve the benefits described herein. Moreover, FIGS. 4 and 5 discuss two pairs of proximate layers being combined, however, more than two layers can be combined and any of the proximate layers can be combined. For example, in one or all example, the gap spacer 346, the gate 350, and the gate frame 354 can be formed as a common monolithic body from a single material, and any of the proximate layers in a cathode stack can be combined through the joining processes discussed herein.

[0072] One or all examples can include a method for emitting electrons for an x-ray tube and / or for forming or providing a cathode stack 110, 410, 510. The method can include providing a cathode stack 110, 410, 510 with at least three functional layers. The functional layers can include a gap spacer 346 that can define a cavity 362 in which a field emitter 126 to emit electrons can be positioned; a gate 350 proximate the gap spacer 346, spaced from the field emitter 126 by the gap spacer 346, configured to control field emission from the field emitter 126, and configured to be electrically isolated and at a different electric potential from the field emitter 126; and a gate frame 354 proximate the gate 350 and configured to retain the gate 350. The method can include combining at least two proximate functional layers of the at least three functional layers. The proximate layers can be combined through joining or by forming the layers as a common monolithic body from a same material that is continuous through the body. Joining techniques for proximate layers can include brazing, welding, metal- to-metal bonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like), adhesive bonding (e.g, a ceramic paste), gluing or the like.

[0073] In one or all examples, the method can further include forming the gap spacer 346 and the gate 350 as a common monolithic body 470, such as from metal, as shown in FIG. 4.

[0074] In one or all examples, the method can further include forming the gate 350 and the gate frame 354 as a common monolithic body 586, such as from metal, as shown in FIG. 5.

[0075] In one or all examples, the method can further include providing the at least three functional layers of the cathode stack 110, 410, 510 with an emitter substrate 342 proximate thegap spacer 346. The emitter substrate 342 can be configured to carry the field emitter 126. The method can further include forming the emitter substrate 342 and the gap spacer 346 as a common monolithic body 594, such as from ceramic, as shown in FIG. 5.

[0076] In one or all examples, the method can further include providing a focus electrode 138 coupled to the cathode stack 110, 410, 510. The focus electrode 138 can be configured to focus electrons emitted from the field emitter 126. The method can further include providing the at least three functional layers of the cathode stack 110, 410, 510 with an isolation spacer 358 proximate the gate frame 354 and configured to electrically isolate gate frame 354 from focus electrode 138. The method can further include forming the gate frame 354 and the isolation spacer 358 as a common monolithic body 478, such as from ceramic, as shown in FIG. 4.

[0077] One or all examples can include a cathode stack 110, 410, 510 that can include: a means for emitting electrons; a means for controlling field emission from the means for emitting electrons; a means for spacing the means for controlling field emissions from the means for emitting electrons; a means for supporting the means for controlling field emissions; and a means for combining at least two of the means for controlling field emissions, the means for spacing and the means for supporting without a virtual leak surface area.

[0078] An example of the means for emitting electrons can include the field emitter 126. An example of the means for controlling field emission from the means for emitting electrons can include the gate 350. An example of the means for spacing the means for controlling field emissions from the means for emitting electrons can include the gap spacer 346. An example of the means for supporting the means for controlling field emissions can include the gate frame 354.

[0079] In one or all examples, the means for combining at least two of the means for controlling field emissions, the means for spacing and the means for supporting without a virtual leak surface area can include combining the gate 350 and the gap spacer 346 (FIG. 4) and / or the gate frame 354 and the gate 350 (FIG. 5).

[0080] In one or all examples, the means for combining can further include a means for forming the at least two of the means for controlling field emissions, the means for spacing and the means for supporting in a common monolithic body of the same material that is continuous through the common monolithic body. An example of the means for forming can include machining and / or laser cutting.

[0081] In one or all examples, the means for combining can further include a means for joining the at least two of the means for controlling field emissions, the means for spacing and the means for supporting. An example of the means for joining can include brazing, welding, metal -to-metal bonding (e.g., diffusion bonding, explosion bonding, ultrasonic welding, friction welding, or the like), adhesive bonding (e.g., a ceramic paste), gluing or the like.

[0082] Although the structures, devices, methods, and systems have been described in accordance with particular embodiments, one of ordinary skill in the art will readily recognize that many variations to the particular embodiments are possible, and any variations should therefore be considered to be within the scope disclosed herein. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the scope of the appended claims.

[0083] Recitation in the claims of the term “first” with respect to a feature or element does not necessarily imply the existence of a second or additional such feature or element.

[0084] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more examples. In the preceding description, numerous specific details were provided, such as examples of various configurations to provide a thorough understanding of examples of the described technology. One skilled in the relevant art will recognize, however, that the technology can be practiced without one or more of the specific details, or with other methods, components, devices, etc. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring aspects of the technology.

[0085] Although the subject matter has been described in language specific to structural features and / or operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features and operations described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Numerous modifications and alternative arrangements can be devised without departing from the scope of the described technology.

Claims

CLAIMSWhat is claimed is:

1. A cathode stack comprising: a plurality of functional layers including: an emitter substrate; a gate; a gap spacer between the gate and the emitter substrate; and a gate frame proximate the gate opposite the gap spacer; wherein: at least two proximate layers of the plurality of functional layers are formed from a single material or are joined together by at least one of brazing, welding, metal -to-metal bonding, or adhesive bonding.

2. The cathode stack of claim 1, wherein: the at least two proximate layers of the plurality of functional layers comprise ceramic materials; and the at least two proximate layers of the plurality of functional layers are joined together by brazing or adhesive bonding.

3. The cathode stack of claim 1, wherein: the at least two proximate layers of the plurality of functional layers comprise a ceramic material and a metal material; and the at least two proximate layers of the plurality of functional layers are joined together by brazing.

4. The cathode stack of claim 1, wherein: the at least two proximate layers of the plurality of functional layers comprise two different metal materials; and the at least two proximate layers of the plurality of functional layers are joined together by brazing or metal-to-metal bonding.

5. The cathode stack of claim 1, wherein: the at least two proximate layers of the plurality of functional layers comprise a same metal material; and the at least two proximate layers of the plurality of functional layers are joined together by brazing or welding.

6. The cathode stack of claim 1, wherein the at least two proximate layers are formed from a single continuous material.

7. The cathode stack of claim 1, wherein each of the layers of the plurality of functional layers are formed from single materials or are joined together with proximate layers of the plurality of functional layers.

8. The cathode stack of claim 1, further comprising a fastener coupled to the cathode stack and configured to retain the layers of the plurality of functional layers relative to one another.

9. A method of forming a cathode stack for an x-ray tube, the method comprising: providing at least three functional layers, the at least three functional layers comprising: a gap spacer comprising a cavity configured to receive a field emitter; a gate proximate the gap spacer, the gap spacer being configured to space the gate from the field emitter; and a gate frame proximate the gate; wherein providing the at least three functional layers comprises at least one of: joining at least two proximate layers of the at least three functional layers together, or machining the at least two proximate layers of the at least three functional layers from a single material.

10. The method of claim 9, wherein:the at least three functional layers further comprise an isolation spacer between the gate frame and a focus electrode; and the gate frame and the isolation spacer are joined together or machined from the single material.

11. The method of claim 9, wherein: the at least three functional layers further comprise an emitter substrate including a surface, the emitter substrate configured to receive the field emitter on the surface; and the emitter substrate and the gap spacer are joined together or machined from the single material.

12. The method of claim 9, wherein: the at least two proximate layers of the at least three functional layers are machined from the single material; and machining the at least two proximate layers comprises: machining a cavity in the single material to define the gap spacer or the gate frame; and machining a grid in the single material to define the gate, wherein the grid is machined by energetic beam machining.

13. The method of claim 9, wherein: the at least two proximate layers of the at least three functional layers comprise a metal material and a ceramic material; and the at least two proximate layers of the at least three functional layers are joined together by at least one of brazing or adhesive bonding.

14. The method of claim 9, wherein: the at least two proximate layers of the at least three functional layers comprise two different metal materials; and the at least two proximate layers of the at least three functional layers are joined together by at least one of brazing or metal -to-metal bonding.

15. The method of claim 9, wherein: the at least two proximate layers of the at least three functional layers comprise a same metal material; and the at least two proximate layers of the at least three functional layers are joined together by at least one of brazing or welding.

16. A cathode stack comprising: an emitter substrate configured to receive an electron emitter; a gate; a gap spacer between the emitter substrate and the gate; and a gate frame proximate the gate opposite the gap spacer; wherein at least one of: the emitter substrate and the gap spacer are formed from a first single continuous material; the gap spacer and the gate are formed from a second single continuous material; or the gate and the gate frame are formed from a third single continuous material.

17. The cathode stack of claim 16, wherein the emitter substrate and the gap spacer are formed from the first single continuous material comprising a ceramic material.

18. The cathode stack of claim 16, wherein the gap spacer and the gate are formed from the second single continuous material comprising a metal.

19. The cathode stack of claim 16, wherein the gate and the gate frame are formed from the third single continuous material comprising a metal.

20. The cathode stack of claim 16, further comprising: a focus electrode; and an isolation spacer between the gate frame and the focus electrode; wherein the isolation spacer and the gate frame are formed from a fourth single continuous material comprising a ceramic material.

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