Method and system for an X-ray tube with texture

Abstract

The present invention is titled Methods and Systems for an X-ray Tube with Texture. The present invention provides various methods and systems for a cathode cup having surface texturing that aids in adhering an emitter deposition film. In one embodiment, a method may include chemically and / or mechanically texturing a surface of the cathode cup to form a plurality of features, each feature having a depth above a threshold, the surface of the cathode cup facing an emitter coupled to the cathode cup.

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to methods and systems for X-ray systems, and more particularly, to cathode cups having a surface finish or texture to facilitate attachment of an emitter deposition film. Background Art

[0002] Non-invasive imaging modalities can transmit energy in the form of radiation into an imaging subject. Based on the transmitted energy, an image indicative of structural or functional information internal to the imaging subject can then be generated. Electron sources are used in X-ray systems such as computed tomography (CT) and cardiovascular (CV) systems. Electron sources typically include thermionic emitters that emit electrons when reaching a certain temperature. The filaments forming these thermionic emitters can be made of metals (such as tungsten, lanthanum) having a high melting point or their alloys.

[0003] Radiation sources such as X-ray sources typically include an X-ray tube that includes a cathode assembly having an emitter fixed in a cup oriented to face an anode or target, which is typically a metal or composite structure electrically connected to a high-voltage circuit. The space between the cathode and the anode is evacuated. The cathode cup is designed to create a customized potential distribution in a vacuum such that all electron trajectories are redirected from their initial divergent motion towards a focal point on the anode surface. When a circuit generating a potential difference of, for example, 60 kV to 140 kV is energized, electrons are directed from the cathode to the anode. The electrons strike the anode (target) and generate high-frequency electromagnetic waves such as X-rays and residual heat energy. The residual energy is absorbed as heat by components within the X-ray tube.

[0004] During operation of an X-ray system, certain parts of the X-ray tube such as the emitter material can be exposed to high temperatures. Such high temperatures can cause sublimation of the material from the emitter. Reliable methods are employed to contain the sublimated material. Summary of the Invention

[0005] In one embodiment, a method includes: chemically and / or mechanically texturing a surface of a cathode cup to form a plurality of features, each feature having a depth above a threshold and a distance greater than a threshold between two adjacent features, the surface of the cathode cup facing an emitter coupled to the cathode cup.

[0006] It should be understood that the above summary is provided to introduce in a simplified form selected concepts that are further described in the detailed description. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to embodiments that solve any disadvantages noted above or in any part of this disclosure. Brief Description of the Drawings

[0007] The present invention will be better understood by reading the following description of non - limiting embodiments with reference to the accompanying drawings, in which:

[0008] Figure 1 A pictorial view of an imaging system according to one embodiment is shown.

[0009] Figure 2 A block schematic diagram of an exemplary imaging system according to one embodiment is shown.

[0010] Figure 3 A schematic diagram of a radiation source used in the imaging system is shown.

[0011] Figure 4 Is a cross - sectional view of a cathode cup according to an embodiment of the present disclosure.

[0012] Figure 5 An isometric view of the texture on the cathode cup according to the present disclosure is shown.

[0013] Figure 6 A schematic diagram of a cathode cup including a textured surface is shown.

[0014] Figure 7A A first microscopic image of the surface of the cathode cup before texturing is shown.

[0015] Figure 7B A second microscopic image of the surface of the cathode cup before texturing is shown.

[0016] Figure 8A A first optical microscope image of a portion of the cathode cup having a first pattern of chemical etching exposed for a first duration is shown.

[0017] Figure 8B A second optical microscope image of a portion of the cathode cup exposed to chemical etching for a second duration is shown.

[0018] Figure 8C A third optical microscope image of a portion of the cathode cup exposed to chemical etching for a third duration is shown.

[0019] Figure 9A A first electron microscope image of a portion of the cathode cup exposed to chemical etching for a first duration is shown.

[0020] Figure 9B A second electron microscope image of a portion of the cathode cup exposed to chemical etching for a second duration is shown.

[0021] Figure 9C A third electron microscope image of a portion of the cathode cup exposed to chemical etching for a third duration is shown.

[0022] Figure 9D Shows a fourth electron microscope image of the textured cathode cup, which shows the distance between features.

[0023] Figure 10A Shows a first microscope image of a portion of the cathode cup that has a second pattern exposed to chemical etching for a third duration.

[0024] Figure 10B Shows a second microscope image of a portion of the cathode cup that has a second pattern exposed to chemical etching for a third duration.

[0025] Figure 10C Shows a third microscope image of a portion of the cathode cup that has a second pattern exposed to chemical etching for a third duration.

[0026] Figure 11 Shows a flowchart of an exemplary method for texturing a cathode cup via chemical etching.

[0027] Figure 12 Shows a flowchart of an exemplary method for texturing a cathode cup via mechanical sandblasting. Detailed Description

[0028] The following description relates to an X-ray system having a cathode cup with a surface finish that aids in the attachment of a deposited film. The following description relates to various embodiments of a medical imaging system including the X-ray system. In Figure 1 and Figure 2 Examples of CT imaging systems including cathode cups processed according to the techniques of the present invention are provided. Figure 3 An X-ray source including an X-ray tube is shown in, the X-ray tube including a cathode cup and a emitter. Exemplary cathode cups including emitters are shown in Figure 4 and Figure 5 The surface of the cathode cup facing the emitter may be textured to facilitate the attachment of material sublimated from the emitter during operation of the X-ray tube. A schematic diagram of the cathode cup is shown in Figure 6 A portion of the cathode cup may include different patterns. To form a surface texture on the cathode cup, the cathode cup may be exposed to a chemical etching or mechanical sandblasting process, as detailed in the exemplary methods of Figure 11 and Figure 12 In the chemical etching process, the degree of etching implemented to form the desired texture is based on the exposure time to the etchant used. Figures 7A to 10C Shows microscope images of a portion of the cathode cup captured at different durations of exposure to a chemical etchant.

[0029] Although the CT imaging system has been described by way of example, it should be understood that the present technology can also be used to fabricate components in other x-ray imaging systems, such as x-ray tomosynthesis imaging systems, mammography imaging systems, C-arm imaging systems, interventional imaging systems, radiography imaging systems, fluoroscopy imaging systems, etc. This discussion of the CT apparatus is provided only as an example of a suitable imaging technology that uses a radiation shield fabricated via the method described.

[0030] During operation of an x-ray tube at a high temperature typically around 2000 °C, sublimated or evaporated emitter material can deposit onto the cooler surface of the cathode cup. Since the cathode cup is made of an alloy different from the emitter material, there is a thermal expansion mismatch between the deposited material and the material of the cathode cup. For example, the cathode cup can typically be made of nickel, molybdenum, Fe-41.5Ni (Ni42), Fe-29Ni-17Co (Kovar), or niobium, while the deposited emitter material can typically consist of tungsten.

[0031] Due to the high temperature fluctuations that occur during x-ray exposure (which can be 400 °C or higher at the surface of the cathode cup), the difference in the coefficient of thermal expansion (CTE) of the cathode cup and the deposited emitter material can result in unequal thermal expansion of the cathode cup material and the deposited material. The thermomechanical stress caused by the different coefficients of thermal expansion can cause the deposited emitter material to be cut away from the surface of the cathode cup and become loose in the area beneath the emitter and between the sides of the emitter and the surface of the cathode cup. This separation can start at the boundary of the deposited emitter material or in areas of non-uniform deposition.

[0032] It has now been recognized that there is a need for an improved cathode cup that better adheres sublimated emitter material away from the electron emitter in order to reduce the likelihood of emitter failure due to short circuits caused by loose or flaked sublimated emitter material. It is desirable for the cathode cup to provide improved high voltage stability by reducing the likelihood of loose sublimated emitter material in the high voltage gap between the emitter and the cathode cup.

[0033] For example, one prior art solution includes creating a cavity beneath the emitter to facilitate adhesion between the deposited emitter material and the bottom surface of the cup. However, the present inventors have recognized that this solution alone is not sufficient to inhibit the deposited emitter material from becoming loose. Due to the thermal expansion differences, such as the CTE difference between the deposited emitter material and the cathode, the unmodified surface finish of the cavity can still initiate undesirable flaking because the features of the cavity may not be sufficient to maintain mechanical adhesion of the deposit.

[0034] In one example, the above problem can be solved by developing the cathode cup disclosed in the present invention, which includes a recessed cavity of the cathode cup that is micro-textured. The texturing can be mechanically performed by physical etching with fine media for sandblasting or equivalents. The texturing can also be performed by chemical etching. The chemical etching etches the features of the microstructure to form an irregular texture, which helps the attachment of the deposited emitter film.

[0035] Thus, by forming a microstructure on the surface with features that allow the capture of sublimated emitter material, the deposited material can remain on the cathode cup for a longer duration without flaking. The technical effect of the texturing disclosed in the present invention reduces emitter degradation caused by the layer of flaked material in contact with the emitter. The additional texturing at the microscopic level extends the duration before the deposited emitter material starts to flake. Overall, compared with existing cathode cup embodiments, the texturing cathode cup disclosed in the present invention extends the service life of the emitter.

[0036] Figure 1 An exemplary CT system 100 configured for CT imaging is shown. Specifically, CT system 100 is configured to image a subject 112 (such as a patient, an inanimate object, one or more manufactured parts) and / or a foreign object (such as a dental implant, a stent, and / or a contrast agent present in the body). In one embodiment, CT system 100 includes a gantry 102, which in turn may also include at least one x-ray source 104 configured to project an x-ray radiation beam 106 (see Figure 2 ) for imaging a subject 112 lying on an examination table 114. Specifically, x-ray source 104 is configured to project the x-ray radiation beam 106 towards a detector array 108 positioned on the opposite side of gantry 102. Although Figure 1 only a single x-ray source 104 is depicted, in certain embodiments, multiple x-ray sources and detectors may be employed to project multiple x-ray radiation beams 106 for acquiring projection data at different energy levels corresponding to the patient. In some embodiments, x-ray source 104 can achieve dual-energy gemstone spectral imaging (GSI) through rapid peak kilovoltage (kVp) switching. In some embodiments, the x-ray detector employed is a photon-counting detector capable of distinguishing x-ray photons of different energies. In other embodiments, two sets of x-ray sources and detectors are used to generate dual-energy projections, with one set of x-ray sources and detectors set to a low kVp and the other set set to a high kVp. It should thus be understood that the methods described herein can be implemented using single-energy acquisition techniques as well as dual-energy acquisition techniques.

[0037] In some embodiments, the CT system 100 further includes an image processor unit 110 configured to reconstruct an image of a target volume of the subject 112 using iterative or analytical image reconstruction methods. For example, the image processor unit 110 may use an analytical image reconstruction method such as filtered back projection (FBP) to reconstruct an image of the target volume of the patient. As another example, the image processor unit 110 may use an iterative image reconstruction method (such as advanced statistical iterative reconstruction (ASIR), conjugate gradient (CG), maximum likelihood expectation maximization (MLEM), model-based iterative reconstruction (MBIR), etc.) to reconstruct an image of the target volume of the subject 112. As further described herein, in some examples, in addition to the iterative image reconstruction method, the image processor unit 110 may also use an analytical image reconstruction method (such as FBP).

[0038] In some CT imaging system configurations, the x-ray source projects a cone-shaped x-ray radiation beam that is collimated to lie within the X-Y-Z plane of a Cartesian coordinate system and is commonly referred to as the "imaging plane". The x-ray radiation beam passes through an object being imaged, such as a patient or a subject. The x-ray radiation beam impinges on an array of detector elements after being attenuated by the object. The intensity of the attenuated x-ray radiation beam received at the detector array depends on the attenuation of the radiation beam by the object. Each detector element of the array generates a separate electrical signal that is a measurement of the x-ray beam attenuation at the detector location. The attenuation measurements from all detector elements are acquired separately to generate a transmission profile.

[0039] In some CT systems, a gantry is used to rotate an x-ray source and a detector array around an object to be imaged within an imaging plane, such that the angle at which the radiation beam intersects the object is constantly changing. A set of x-ray radiation attenuation measurements (e.g., projection data) from the detector array at one gantry angle is referred to as a “view”. A “scan” of an object comprises a set of views obtained at different gantry angles or perspectives during one rotation of the x-ray source and detector. It is contemplated that the benefits of the methods described herein are derived from medical imaging modalities other than CT, and thus, as used herein, the term “view” is not limited to the use described above with respect to projection data from one gantry angle. The term “view” is used to mean a data acquisition whenever there are multiple data acquisitions from different angles (whether from CT, positron emission tomography (PET), or single photon emission CT (SPECT) acquisitions), and / or any other modality (including modalities yet to be developed) and combinations thereof in fusion embodiments.

[0040] The projection data is processed to reconstruct an image corresponding to a two-dimensional slice acquired through the object, or in some examples where the projection data includes multiple views or scans, an image corresponding to a three-dimensional rendering of the object. A method for reconstructing an image from a set of projection data is known in the art as filtered backprojection technique. Transmission and emission tomography reconstruction techniques also include statistical iterative methods such as maximum likelihood expectation maximization (MLEM) and ordered subset expectation maximization techniques, and iterative reconstruction techniques. The method converts the attenuation measurements from the scan into an integer called “CT number” or “Hounsfield unit”, which is used to control the brightness of the corresponding pixel on a display device.

[0041] To reduce the total scan time, “helical” scanning may be performed. To perform “helical” scanning, the patient is moved while data for a predefined number of slices is acquired. Such systems produce a single helix from a cone beam helical scan. The helix mapped out by the cone beam generates projection data from which an image in each predefined slice can be reconstructed.

[0042] As used herein, the phrase “reconstructing an image” is not intended to exclude embodiments of the present invention in which data representing an image is generated rather than a visual image. Thus, as used herein, the term “image” broadly refers to both a visual image and data representing a visual image. However, many embodiments generate (or are configured to generate) at least one visual image.

[0043] Figure 2 An exemplary imaging system 200 similar to Figure 1 is shown. In accordance with aspects of the present disclosure, the imaging system 200 is configured for imaging a subject 204 (e.g., Figure 1Subject 112) is imaged. In one embodiment, the imaging system 200 includes a detector array 108 (see Figure 1 ). The detector array 108 also includes a plurality of detector elements 202 that together sense an x-ray radiation beam 106 passing through a subject 204 (such as a patient) (see Figure 2 ) to acquire corresponding projection data. Thus, in one embodiment, the detector array 108 is fabricated in a multi-slice configuration including multiple rows of cells or detector elements 202. In such a configuration, one or more additional rows of detector elements 202 are arranged in a parallel configuration for acquiring projection data.

[0044] In certain embodiments, the imaging system 200 is configured to traverse different angular positions around the subject 204 to acquire the desired projection data. Thus, the gantry 102 and the components mounted thereon can be configured to rotate about a center of rotation 206 to acquire projection data at different energy levels, for example. Alternatively, in embodiments where the projection angle relative to the subject 204 changes over time, the mounted components can be configured to move along a generally curved path rather than along an arc of a circle.

[0045] Thus, as the x-ray source 104 and the detector array 108 rotate, the detector array 108 collects data on the attenuated x-ray beam. Then, the data collected by the detector array 108 undergoes preprocessing and calibration to condition the data to represent a line integral of the attenuation coefficient of the scanned subject 204. The processed data is commonly referred to as a projection.

[0046] In some examples, individual detectors or detector elements 202 in the detector array 108 can include photon counting detectors that bin the interactions of individual photons into one or more energy bins. It should be understood that the methods described herein can also be implemented using energy integrating detectors.

[0047] The acquired projection data set can be used for basis material decomposition (BMD). During BMD, the measured projections are converted into a set of material density projections. The material density projections can be reconstructed to form a pair or a set of material density maps or images (such as bone, soft tissue, and / or contrast agent maps) for each corresponding basis material. The density maps or images can then be correlated to form a volume rendering of the basis materials (such as bone, soft tissue, and / or contrast agent) in the imaging volume.

[0048] Once reconstructed, the underlying material image generated by the imaging system 200 reveals the internal characteristics of the subject 204 represented by the densities of the two underlying materials. Density images can be displayed to show these characteristics. In traditional methods of diagnosing medical conditions, such as disease states, and more generally medical events, a radiologist or physician would consider a hard copy or display of the density image to discern characteristic features of interest. Such features can include lesions, size, and shape of specific anatomical structures or organs, as well as other features that should be discernible in the image based on the skills and knowledge of the individual practitioner.

[0049] In one embodiment, the imaging system 200 includes a control mechanism 208 to control the movement of components, such as the rotation of the gantry 102 and the operation of the x-ray source 104. In certain embodiments, the control mechanism 208 further includes an x-ray controller 210 that is configured to provide power and timing signals to the x-ray source 104. Additionally, the control mechanism 208 includes a gantry motor controller 212 that is configured to control the rotational speed and / or position of the gantry 102 based on imaging requirements.

[0050] In certain embodiments, the control mechanism 208 further includes a data acquisition system (DAS) 214 that is configured to sample the analog data received from the detector elements 202 and convert the analog data to digital signals for subsequent processing. The DAS 214 can also be configured to selectively aggregate analog data from a subset of the detector elements 202 into so-called macro detectors, as further described herein. The data sampled and digitized by the DAS 214 is transmitted to a computer or computing device 216. In one example, the computing device 216 stores the data in a storage device or mass storage device 218. For example, the storage device 218 can include a hard disk drive, a floppy disk drive, a compact disc-read / write (CD-R / W) drive, a digital versatile disc (DVD) drive, a flash drive, and / or a solid state storage drive.

[0051] Additionally, the computing device 216 provides commands and parameters to one or more of the DAS 214, the x-ray controller 210, and the gantry motor controller 212 to control system operations, such as data acquisition and / or processing. In certain embodiments, the computing device 216 controls system operations based on operator input. The computing device 216 receives operator input via an operator console 220 that is operatively coupled to the computing device 216, the operator input including, for example, commands and / or scan parameters. The operator console 220 can include a keyboard (not shown) or a touch screen to allow the operator to specify commands and / or scan parameters.

[0052] Although Figure 2Only one operator console 220 is shown, but more than one operator console may be coupled to the imaging system 200, for example, for inputting or outputting system parameters, requesting examinations, plotting data, and / or viewing images. Additionally, in some embodiments, the imaging system 200 may be coupled to a plurality of locally or remotely located displays, printers, workstations, and / or similar devices within an institution or hospital or at completely different locations via one or more configurable wired and / or wireless networks (such as the Internet and / or virtual private networks, wireless telephone networks, wireless local area networks, wired local area networks, wireless wide area networks, wired wide area networks, etc.).

[0053] In one embodiment, for example, the imaging system 200 includes a picture archiving and communication system (PACS) 224 or is coupled to a PACS. In an exemplary implementation, the PACS 224 is further coupled to remote systems (such as a radiology information system, a hospital information system) and / or is coupled to an internal or external network (not shown) to allow operators at different locations to supply commands and parameters and / or obtain access to image data.

[0054] The computing device 216 operates the examination table motor controller 226 using operator-supplied and / or system-defined commands and parameters, and the examination table motor controller in turn can control the examination table 114, which may be an electric examination table. Specifically, the examination table motor controller 226 can move the examination table 114 to properly position the subject 204 in the gantry 102 to acquire projection data corresponding to the target volume of the subject 204.

[0055] As previously described, the DAS 214 samples and digitizes the projection data acquired by the detector elements 202. Subsequently, the image reconstructor 230 uses the sampled and digitized x-ray data to perform high-speed reconstruction. Although Figure 2 the image reconstructor 230 is shown as a separate entity, in some embodiments, the image reconstructor 230 may form part of the computing device 216. Alternatively, the image reconstructor 230 may not be present in the imaging system 200, and instead the computing device 216 may perform one or more functions of the image reconstructor 230. Additionally, the image reconstructor 230 may be locally or remotely located and may be operably connected to the imaging system 200 using a wired or wireless network. Specifically, an exemplary embodiment may use computing resources in a "cloud" network cluster for the image reconstructor 230.

[0056] In one embodiment, the image reconstructor 230 stores the reconstructed image in the storage device 218. Alternatively, the image reconstructor 230 may transmit the reconstructed image to the computing device 216 to generate available patient information for diagnosis and evaluation. In certain embodiments, the computing device 216 may transmit the reconstructed image and / or patient information to a monitor or display device 232 that is communicatively coupled to the computing device 216 and / or the image reconstructor 230. In some embodiments, the reconstructed image may be transmitted from the computing device 216 or the image reconstructor 230 to the storage device 218 for short-term or long-term storage.

[0057] The various methods and processes further described herein may be stored as executable instructions in a non-transitory memory on a computing device (or controller) in the imaging system 200. In one embodiment, the image reconstructor 230 may include such executable instructions in the non-transitory memory and may apply the methods described herein to reconstruct an image from the scan data. In another embodiment, the computing device 216 may include instructions in the non-transitory memory and may at least partially apply the methods described herein to the reconstructed image after receiving the reconstructed image from the image reconstructor 230. In another embodiment, the methods and processes described herein may be distributed across the image reconstructor 230 and the computing device 216.

[0058] In one embodiment, the display 232 allows an operator to evaluate the imaged anatomical structure. The display 232 may also allow the operator to select a volume of interest (VOI) and / or request patient information, for example via a graphical user interface (GUI), for subsequent scans or processing.

[0059] Figure 3 Shown in Figure 1 An exemplary x-ray source used in the imaging system of. In one example, the x-ray source 300 may be Figure 1 The x-ray source 105 in. The x-ray source may include an x-ray tube 302 in which an x-ray beam is generated and a collimator 304 in which the x-ray beam is collimated to a desired beam size.

[0060] The x-ray tube 302 may include a cathode 308 and an anode 306 (also referred to herein as a target) that are positioned relative to each other and enclosed within a vacuum container 305. The anode 306 may rotate about the longitudinal axis of a column 315 that supports the anode 306. The cathode 308 may include a cathode cup 352 that encloses an emitter 354. A high-voltage circuit may be electrically coupled to the x-ray tube 302 and configured to power the x-ray tube 302.

[0061] In one example, the high-voltage circuit may include a cathode multiplier electrically coupled to a high-voltage transformer and the cathode 308, and an anode multiplier electrically coupled to the high-voltage transformer and the anode 306. The cathode multiplier may be configured to supply a negative high-voltage DC to the cathode 308, for example, via a high-voltage connection, while the anode multiplier may be configured to supply a positive high-voltage DC to the anode 306, for example, via a high-voltage connection. That is, the cathode 308 and the anode 306 may carry equal voltages of different polarities. In this way, a high potential difference may be generated between the cathode 308 and the anode 206.

[0062] The power supplied to the x-ray tube 302 may create a potential difference of, for example, 60 kV to 140 kV between the emitter 354 of the cathode 308 and the anode 306, causing electrons generated by the emitter 354 to accelerate toward the anode 306. When the electrons collide with the anode 306 at high speed, at least a portion of the kinetic energy of the electrons is converted into high-frequency electromagnetic radiation or x-rays 310.

[0063] In one example, the cathode cup 352 may be made of nickel, molybdenum, Fe-41.5Ni (Ni42), Fe-29Ni-17Co (Kovar), or niobium, the emitter 354 may be made of tungsten, and the anode 306 may be made of tungsten or molybdenum. The cathode cup 352 may include an inner sidewall 358 and an inner base 356 (also referred to herein as an inner bottom surface 356 or simply a bottom surface 356) that directly faces the emitter 354. Specifically, the inner base 356 has a line of sight toward the emitter 354. Due to the high temperature of the emitter 354, the material from the emitter may evaporate and sublime and then deposit on the sidewall 358 and the base 356 of the cathode cup facing the emitter 354. To trap and retain the emitter material on the cathode cup without flaking, the surface of the cathode cup facing the emitter 354 may be engraved to form microstructures.

[0064] The material forming the surface of the cathode cup 352 may be composed of many crystals with various individual orientations. These individual crystals may be referred to as "grains". In any one grain, all the atoms may be arranged in a specific orientation and a specific pattern. The junction between adjacent grains may be referred to as a "grain boundary". A grain boundary is a transition region where some of the atoms are not perfectly aligned with either grain. The orientation mismatch between adjacent grains results in a reduced packing efficiency of the atoms within the grain boundary. Therefore, the atoms in the grain boundary have a more disordered structure and a slightly higher internal energy. Chemical and / or mechanical texturing methods may be used to make the grain boundary atoms dissolve or "etch" more easily and quickly than the atoms within the grains.

[0065] The surfaces of the cathode cup 352 facing the emitter 354, such as the sidewall 358 and the base 356, can be chemically and / or mechanically textured to include a plurality of etched features, where the grain boundaries of the material have a depth above a threshold of 10 μm to trap sublimated material from the emitter. Chemical texturing includes chemically etching the surface, such as by dispensing a quantity of chemical etchant onto the surface and exposing the surface to the chemical etchant for a duration above a threshold. The quantity of chemical etchant dispensed onto the surface can be proportional to the level of texturing to be achieved on the surface, and the quantity of chemical etchant increases as the level of texturing increases. The level of texturing can include the distance between two adjacent features (i.e., the distance between two adjacent features) and the depth of each feature, and the level of texturing increases with each of a decrease in the distance between two adjacent features and an increase in the depth of each feature. The threshold depth of each feature can be 10 μm. In some examples, the threshold depth of each feature can be in the range of 1 μm to 10 μm.

[0066] Mechanical texturing can include sandblasting the surface with a coarse medium for another threshold duration. The blasting can include propelling the coarse medium from a dispenser onto the surface at high pressure for another threshold duration. Each of the threshold duration of the surface being exposed to the chemical etchant and the another threshold duration of the sandblasting can be based on the level of texturing to be achieved on the surface.

[0067] Each feature on the textured surface of the cathode cup can be a grain of the material constituting the surface, the depth of each feature is the depth of the grain boundary, and the distance between two adjacent features is the distance between two adjacent grain boundaries. The depth of each feature is in the range of 10 μm to 1000 μm, and the distance between two adjacent features is in the range of 100 nm to 1000 μm. In one example, the depth of each feature is in the range of 10 μm to 200 μm; and the distance between two adjacent features is in the range of 100 nm to 200 μm. In some examples, such as when heat treatment is employed, the grain coarseness can increase, and thus, the depth of each feature can be in the range of 10 μm to 10 mm, and the distance between adjacent features can be in the range of 100 nm to 10 mm. Additionally, the depth and distance can depend on the initial grain coarseness before etching, which includes the initial grain depth and the initial distance between two adjacent grains.

[0068] The x-ray tube 302 can be encapsulated in a vacuum container 305 including a transmission port 344. For example, the container 305 can include a first radiation shield 330 that is arranged to block x-rays traveling in an undesired direction. The radiation shield can encapsulate the entire x-ray tube except for the transmission port 344. The radiation source can also include a collimator 204 adjacent to the x-ray tube. The x-rays 310 leaving the x-ray tube 202 via the transmission port 344 can enter the collimator. The collimator can include a first collimator blade 318 and a second collimator blade 320 that are coaxially positioned along the longitudinal axis A-A'. The distance between the first collimator blade 218 and the second collimator blade 320 can be adjusted to form an opening or aperture. The first collimator blade 318 and the second collimator blade 320 can be moved relative to each other along the A-A' axis to adjust the size of the aperture 324. Except for the port 316, the collimator 304 can be encapsulated in a second radiation shield 322. A portion of the x-rays 310 can pass through the opening or aperture 324 between the first collimator blade 318 and the second collimator blade 220, and the transmitted x-ray beam 314 can leave the collimator via the port 316. A portion of the x-rays impinging on the first collimator blade 318 or the second collimator blade 320 can be reflected from the respective blade, and the reflected x-rays 312 can be absorbed by the second radiation shield 322. In this way, the reflected light from the collimator blades is restricted from leaving the collimator.

[0069] The x-ray beam 314 leaving the collimator 304 can then be directed to penetrate an object (not shown), such as a human anatomical part for medical examination and diagnostic procedures. The x-rays transmitted through the object are intercepted by a detector (not shown), and an image is formed by the internal anatomical structure. Additionally, industrial x-ray tubes can be used, for example, to inspect metal components for cracks or to examine the contents of airport luggage.

[0070] Figure 4 A cross-section 400 of an exemplary cathode 308 of an x-ray system is shown. The cathode 308 includes a emitter 354 and a cathode cup 352 that holds the emitter 354. In some examples, the emitter 354 can be coupled to a surface (such as the bottom surface 356) of the cathode cup 352 via one or more support arms (not shown). The cathode cup can be made of any material, such as nickel, molybdenum, Ni42, kovar, or niobium. The emitter 354 is positioned within a recess 332 such that the cathode cup 352 acts as an electron focusing element to direct electrons from the emitter 354 towards the anode. In various embodiments, the emitter 354 can be a plate, a coil, a filament, or other types of emission devices known in the art. The emitter 354 can be parallel to the bottom surface 356 of the recessed cavity 332 or can be angled relative to the bottom surface 356 at any angle.

[0071] A recessed cavity 332 is formed in the material of the cathode cup 352. The cathode cup 352 includes an inner bottom surface 356 facing the emitter 354 (that is, the bottom surface 356 has a line of sight towards the emitter 354). The cathode cup 352 may have one or more sidewalls 358 that may be perpendicular to the bottom surface 356 or at any angle thereto. Alternatively, the cathode cup 352 may be bowl-shaped or otherwise have a curved bottom surface 356.

[0072] Figure 5 An isometric view 500 of the cathode cup 352 with a textured surface is shown. Texturing may be applied to the bottom surface 356 and the side surface 358 of the cathode cup 352. Texturing means that all surfaces may have a deposited emitter material due to exposure to high voltage at the emitter 354 and sublimation of the emitter material during electron emission. For example, the sidewalls 358 and the bottom surface 356 of the cathode cup 352 may be textured. In various embodiments, the recessed cavity micro-texturing may be performed by mechanical or chemical methods. Texturing at the micro level allows the emitter material to be deposited and retained on the surface of the cathode cup.

[0073] Figure 6 A schematic view 600 of the cathode cup 352 including a textured surface is shown. The cathode cup 352 may include a patterned portion disposed within a cavity formed within the cathode cup 352. The cathode cup 352 may include sidewalls 358 located on each side of the bottom surface 356. The bottom surface 356 may include a cavity 614 having a patterned surface 610. In this example, the cavity may be rectangular, having non-patterned walls 615 on each side of the patterned surface 610. The patterned surface 610 may include a plurality of protrusions 612 forming a pattern. In this example, each protrusion 612 may be rectangular. Each protrusion 612 may include a flat upper surface, with angled walls attached to the patterned surface 610. In one example, the size and shape of each protrusion may be the same. In another example, there may be differences between the protrusions. The protrusions may cover the entire patterned surface 610 within the cavity formed on the bottom surface 356 of the cathode cup 352. The pattern disrupts the flat surface of the cathode cup and reduces the spalling of the deposited emitter material.

[0074] In one example, the pattern may be formed by an end milling process. Other processes such as electrical discharge milling (EDM), traverse feed EDM, knurling, etc. may be used to form the pattern and are within the scope of the present disclosure.

[0075] The bottom surface 356 of the cathode cup including the patterned surface 610 can face the emitter. During the operation of the x-ray tube, due to the high operating temperature, the material from the emitter can sublime and deposit on the surface of the cathode cup, including the bottom surface 356, the patterned surface 610, the sidewall 358, and other surfaces of the cavity 614 (such as the wall 615). To retain the deposited material on the surface of the cathode cup, the surfaces exposed to the emitter material can be engraved to form microstructures. In other words, the surfaces of the cathode cup that receive the sublimed emitter material (including the bottom surface 356, the patterned surface 610, the sidewall 358, and other surfaces of the cavity) can be etched to form microstructures (features) having a depth and a spacing between adjacent microstructures. Even during temperature cycling, the microstructures facilitate the mechanical attachment of the deposited material on the surface, thereby reducing the likelihood that the material flakes off the surface and disrupts the operation of the cathode cup. The micro-texturing of the cathode cup surface can extend the duration before the deposited emitter material begins to flake off.

[0076] For example, since different surfaces of the cathode cup may be exposed to different degrees of emitter material deposition, the degree of micro-texturing performed on different surfaces of the cathode cup can vary. In one example, since the bottom surface 356 including the patterned surface 610 has a higher exposure relative to the sidewall 358 of the cathode cup, an increased level of texturing can be imparted to the bottom surface 356 including the patterned surface 610 relative to the sidewall 358. Methods for texturing the surface of the cathode cup via chemical etching and mechanical sandblasting are described in detail Figure 11 and Figure 12 are provided.

[0077] Figure 11 An exemplary method 1100 for texturing a cathode cup (such as Figure 6 the cathode cup 352 therein) via chemical etching is shown. Specifically, etching can be utilized to preferentially attack grains, grain boundaries, or specific phases, thereby producing a roughening effect. One or more surfaces of the cathode cup exposed to the deposits from the emitter can be textured at the micro level. The textured cathode cup surface can include the bottom surface (such as Figure 6 the bottom surface 356 therein), the sidewall (such as Figure 6 the sidewall 358 therein), and the patterned surface including protrusions on the cathode cup (such as Figure 6 the surface 610 therein).

[0078] At 1102, the surface of the cathode cup can be prepared for etching. Preparing the surface for etching can include cleaning the surface. Preparing the surface can also include masking selected areas that do not need to be textured. For example, a mask material made of a material resistant to the selected etchant can be applied to the selected areas to protect the selected areas from the etchant.

[0079] At 1104, etchant chemicals can be dispensed onto the surface to be etched. Specifically, the etchant chemicals are selected to preferentially etch grains, grain boundaries, and / or specific phases. A pipette, syringe, dropper, or similar dispenser can be used to add the etchant. The etchant can be a liquid chemical that completely covers the surface to be textured. Exemplary chemical etchants can be acids or bases. Exemplary acidic compounds include hydrofluoric acid (HF), sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), ferric chloride, or any combination thereof. Exemplary basic compounds that can be used for chemical etching include sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), or any combination thereof. Texturing the surface includes etching away material from the grain boundaries to increase the roughness of the surface. The degree of texturing can be based on features on the material on the surface such as the size of the grains. Specifically, the degree of texturing can be based on the initial depth of the features and the initial spacing between two adjacent features (before etching).

[0080] In one example, after etching, the distance between features can be in the range of 100 nm to 10 mm, and the depth of the features can be in the range of 10 μm to 10 mm. In another example, after etching, the distance between features can be in the range of 100 nm to 1000 μm, and the depth of the features can be in the range of 10 μm to 1000 μm. In yet another example, after etching, the distance between features can be in the range of 100 nm to 200 μm, and the depth of the features can be in the range of 10 μm to 200 μm. It should be understood that the depth of the features and the distance between adjacent features can vary proportionally depending on the type of process and the initial roughness of the features.

[0081] The distance between features can be the distance between two adjacent grain boundaries. For example, a first level of texturing can include a distance between features in the range of 100 nm to 2 μm, and the depth of the features in the range of 10 μm to 20 μm. As another example, a second level of texturing can include a distance between features in the range of 2 μm to 200 μm, and the depth of the features in the range of 20 μm to 200 μm. A first higher degree of texturing (higher exposure to sublimation from the emitter) can be applied to the surface directly facing the emitter (such as the bottom surface of the patterned surface including the cathode cup). A second lower degree of texturing (lower exposure to sublimation from the emitter) can be applied to the surface not directly facing the emitter (such as the sidewall of the cathode cup).

[0082] The concentration and / or contact duration of the etchant dispensed on the surface can be proportional to the degree of texturing desired to be obtained on the surface. In one example, for a surface to be textured at a first higher level of texturing (i.e., as the depth of the features increases and / or the spacing between the features increases), a first higher concentration of the etchant can be dispensed on the surface. In another example, for a surface to be textured at a second lower level of texturing (i.e., as the depth of the features decreases and / or the spacing between the features decreases), a second lower concentration of the etchant can be dispensed on the surface. In addition or alternatively, the contact duration of the etchant can be varied to achieve the desired degree of texturing. For example, the contact duration of the etchant can be increased to increase the degree of texturing and vice versa.

[0083] At 1106, additional surfaces not yet covered with the etchant chemical can be wiped with the etchant chemical. The etchant chemical can be soaked in an applicator (such as a swab) and foamed on the surface to be etched. Once each of the surfaces to be textured has been covered with the chemical etchant, a timer can be started. The chemical reaction between the etchant and the surface material causes the material to be removed along the grain boundaries, thereby highlighting the grain boundaries and creating a texture of the desired feature size.

[0084] At 1108, the routine includes determining whether a threshold time has elapsed since the deposition of the chemical etchant on the surface. Over time, the etching action occurs. The threshold duration of etching can be pre-calibrated based on the desired level of texturing on the surface to be etched and the type of chemical used. For example, if a higher level of texturing is required, the threshold duration can be increased. If it is determined at 1109 that the threshold time has not elapsed since the deposition of the chemical etchant on the surface, the routine can wait until the threshold time has elapsed. It can be inferred that the desired level of texturing has not been obtained and more time or continuation of the chemical reaction causing the etching is required.

[0085] If it is determined that the threshold time has elapsed since the deposition of the chemical etchant on the surface, it can be inferred that the desired level of etching has been obtained. At 1110, the timer can be stopped and the remaining etchant chemical can be discarded. Discarding the etchant can include wiping the surface with an appropriate solution, neutralizing, and / or removing the chemical depending on the etchant chemical used.

[0086] At 1112, the textured cathode cup surface can be cleaned with water / cleaning solution and then the surface can be dried at room temperature to remove all traces of water / solution.

[0087] Once the texturing is complete, the surface can be characterized. The surface topography (quantification of surface roughness) of the surface can be determined via a surface measurement instrument. In one example, a standard optical profilometer such as an interferometer can be used to determine the surface roughness. In this non-contact profilometry method, the surface is scanned with a light beam, and the reflection of the light beam from the surface is quantified to determine the roughness of the surface. For example, the depth of the feature (surface texture) can be estimated to be about 10 μm with a deviation of ±3 μm.

[0088] To further determine the texture of the surface, the surface of the cathode cup can be examined via optical and electron microscopy before and after texturing. Figures 7A to 7B A microscopic image of the surface of the cathode cup before texturing is shown. The imaged surface of the cathode cup can be a patterned surface including protrusions on the cathode cup (such as Figure 6 the surface 610 in).

[0089] Figure 7A The first image 700 in can be captured via a scanning electron microscope (SEM). The patterned surface 702 can be Figure 6 the patterned surface 610 in, which can include a plurality of repeating symmetric protrusions 703 that form a pattern. In this example, each protrusion 703 is a tapered rectangular protrusion. Each protrusion 703 can include a wider base and a narrower top surface, such as a flat rectangular upper surface 712, where the angled walls on each side are attached to the base of the patterned surface 702. The walls can include two longer sidewalls 706 and 708 adjacent to the flat upper surface 712 and two shorter sidewalls 704 and 710. From this image, it can be seen that the length of the shorter sidewalls 704 and 710 at the base can be about 2 μm (with a tolerance of 10%), while the length of the longer sidewalls 706 and 708 at the base can be about 2.5 μm (where the walls intersect the surface 702).

[0090] The flat upper surface 712 of one of the protrusions is magnified in the Figure 7B second SEM image 720 in. In this image, it can be seen that the surface 712 is largely smooth, without any significant texture / pattern / undulation / microstructure. Even if the sublimated material from the emitter is deposited and trapped in the protrusion due to the smooth upper surface of the protrusion, the deposited material can be peeled off. The thermal expansion mismatch between the surface and the deposited material can cause the deposited material to be more easily removed from the smooth surface. As previously detailed, to keep the deposited material on the surface of the cathode cup for a longer time, the surface of the cathode cup facing the emitter can be textured.

[0091] During etching, the changes in the etched cathode surface can be imaged at different stages of the etching process. Figures 8A to 8COptical microscope images of the cathode cup surface with a first pattern exposed to chemical etching for a first duration, a second duration, and a third duration are shown respectively. Figures 9A to 9C SEM images of the cathode cup surface with a first pattern exposed to chemical etching for a first duration, a second duration, and a third duration are shown respectively.

[0092] Figure 8A A first optical microscope image 820 of the surface 802 of the cathode cup is shown, which surface has a first pattern exposed to chemical etching for a first duration. The imaged surface 802 can be Figure 7A the patterned surface 702 in. The patterned surface 802 can include a plurality of repeating symmetric protrusions 703 that form the pattern. Each protrusion 703 can include a flat rectangular upper surface 712 having angled walls 822. The pattern can include flat raised surfaces 712 separated by the walls 822, thereby forming a lattice pattern. During chemical etching, the entire surface 802 can be covered with a chemical etchant, and the etchant can be allowed to react with the surface for a pre-calibrated duration to form the desired pattern. In this example, the surface has been exposed to a chemical etchant such as iron chloride for 5 minutes (the first duration).

[0093] Figure 9A A first scanning electron microscope image 920 of the surface 802 of the cathode cup is shown, which surface has a first pattern exposed to chemical etching for a first duration. For example, the flat raised surface 826 of one of the protrusions 703 as seen in the image 820 can be magnified in the image 920. As seen from the images 820 and 920, due to etching on the surface, textures (such as lines 922) are visible on the surface in the form of lines. The material at the grain boundaries of the material of the surface is etched away (eroded) to form a rough surface. The lines 922 can represent magnified grain boundaries. The texture can constitute a series of peaks and valleys along the grain boundaries. The width of the lines 922 can represent the magnification level of the grain boundaries obtained through the etching process. When etching continues, the lines 922 can widen and newer features can be formed, thereby increasing the surface roughness.

[0094] Figure 8B A second optical microscope image 840 of the surface 802 of the cathode cup is shown, which surface has a first pattern exposed to chemical etching for a second duration. The second duration can be longer than the first duration such that the image 840 of the same surface 820 can be captured after the first optical microscope image 820 is captured (as the etching process progresses). For example, the first duration of chemical etchant exposure can be 5 minutes, and the second duration of chemical etchant exposure can be 10 minutes, and the chemical etchant to which the surface is exposed is iron chloride.

[0095] Figure 9BShows a second scanning electron microscope image 940 of the surface 802 of the cathode cup, which surface has a first pattern exposed to chemical etching for a second duration. For example, the flat raised surface 828 of one of the protrusions 703 as seen in image 840 can be magnified in image 940. As seen from images 840 and 940, due to the continued etching on the surface, textures (such as line 922) become more prominent compared to the textures in image 920. The width of line 922 increases and grain boundaries become visible, thus increasing the level of surface texturing.

[0096] Figure 8B Shows a second optical microscope image 840 of the surface 802 of the cathode cup, which surface has a first pattern exposed to chemical etching for a second duration. The second duration can be longer than the first duration such that an image 840 of the same surface 820 can be captured after the first optical microscope image 820 has been captured (as the etching process progresses). For example, the first duration of chemical etchant exposure can be 5 minutes and the second duration of chemical etchant exposure can be 10 minutes, and the chemical etchant to which the surface is exposed is ferric chloride.

[0097] Figure 9B Shows a second scanning electron microscope image 940 of the surface 802 of the cathode cup, which surface has a first pattern exposed to chemical etching for a second duration. For example, the flat raised surface 828 of one of the protrusions 703 as seen in image 840 can be magnified in image 940. As seen from images 840 and 940, due to the continued etching on the surface, textures (such as line 922) become more prominent compared to the textures in image 920. The width of line 922 increases and grain boundaries become visible, thus increasing the level of surface texturing.

[0098] Figure 8C Shows a third optical microscope image 860 of the surface 802 of the cathode cup, which surface has a first pattern exposed to chemical etching for a third duration. The third duration can be longer than each of the first duration and the second duration such that an image 860 of the same surface 820 can be captured after each of the first optical microscope image 820 and the second optical microscope image 840 have been captured (as the etching process progresses). For example, the first duration of chemical etchant exposure can be 5 minutes, the second duration of chemical etchant exposure can be 10 minutes, and the third duration of chemical etchant exposure can be 15 minutes, and the chemical etchant to which the surface is exposed is ferric chloride.

[0099] Figure 9CShows a third scanning electron microscope image 960 of the surface 802 of the cathode cup, which surface has a first pattern exposed to chemical etching for a third duration. For example, the flat raised surface 830 of one of the protrusions 703 as seen in image 860 can be magnified in image 940. As seen from images 860 and 960, due to the continuous etching on the surface, textures (such as lines 922) become coarser and grain boundaries become more prominent, thereby increasing the level of surface texturing. Grains are visible as features on the textured surface.

[0100] Figure 9D Shows a fourth electron microscope image 980 of the textured cathode cup, which shows the distance between enhanced features 984 captured after exposing the surface to a chemical etchant for at least a third duration. It can be seen from the microscope image that after exposing the cathode cup surface to the chemical etchant for a third duration, the distance between features (such as adjacent grains) can be in the range of 100 nm to 200 μm. The grain boundaries can have a depth in the range of 10 μm to 200 μm. In this way, texturing can be enhanced at the micro level to form a surface capable of holding sublimated material deposited thereon.

[0101] Figures 10A to 10C Shows a microscope image of a portion of the cathode cup that has a second pattern exposed to chemical etching for a third duration. In one example, the third duration can be 15 minutes, and the chemical etchant used to etch the surface can be ferric chloride. The second pattern can include pyramidal protrusions 1022 formed on the surface (such as Figure 6 the patterned surface 610 in Figure 6 the cathode cup 352) of the cathode cup. Each pyramidal protrusion 1022 can include angled walls 1044 leading to the tip 1046. The protrusions 1022 can be symmetrically distributed on the surface 1010 of the cathode cup.

[0102] As Figure 10A shown, the first image 1020 is captured via a scanning electron microscope (SEM) at a first magnification. As Figure 10B shown, the second image 1040 is captured via SEM at a second magnification, and as Figure 10CThe third image 1060 shown is captured via SEM at a third magnification. The third magnification may be higher than each of the first and second magnifications, and the second magnification may be higher than the first magnification. As can be seen from the image, texture 1042 is formed on the protrusion 1022 and the surface 1010 when exposed to the chemical etchant for a third duration. Material at the grain boundaries of the material of the surface is etched away (eroded) to form a rougher surface. The distance between features (such as adjacent grains) may be in the range of 100nm to 200μm, and the grain boundaries may have a depth in the range of 10μm to 200μm. The texture provides microscopic edges and cavities where sublimated material from the emitter can be trapped and retained for longer durations. Texturing on the cathode cup surface may also be obtained via a mechanical process such as sandblasting. Figure 12 The cathode cup (such as Figure 6 Example method 1200 for texturing a cathode cup 352 in a cathode cup. One or more surfaces of the cathode cup exposed to deposits from the emitter can be textured at a microscopic level. The textured cathode cup surface can include a bottom surface (such as Figure 6 The bottom surface 356 in the sidewalls (such as Figure 6 The sidewalls 358 in the cathode cup and the patterned surface including the protrusions of the cathode cup (such as Figure 6 Surface 610 in.

[0103] At 1202, the surface of the cathode cup may be prepared for sandblasting. Preparing the surface for sandblasting may include cleaning the surface with water and / or a cleaning solution and drying the surface. Preparing the cathode surface may also include providing a mask for shielded areas that are not to be textured.

[0104] At 1204, the surface to be textured can be sandblasted with abrasive for a threshold duration. The abrasive stream can be forced under high pressure from a dispenser and, upon encountering the surface to be textured, can remove material from the surface, thereby increasing its surface roughness. The abrasive can etch the grains on the surface of the cathode cup, highlighting the grain boundaries and causing non-uniformity. Exemplary abrasives for sandblasting can include metal grit, sand, glass beads, and plastic beads. In one example, the entire surface area can be sandblasted in one pass by directing the abrasive to the entire surface to be textured. In another example, the dispenser of the abrasive can scan the entire surface area and advance the abrasive over a smaller area each time. The travel path of the dispenser can be programmed such that the entire surface area is covered. The level of micro-texturing (engraving) obtained can be based on the abrasive used and the duration of sandblasting, and the level of texturing increases with the duration of sandblasting. The desired amount of engraving on the surface can include a threshold distance between adjacent grain boundaries and a threshold depth of the grain boundaries. For example, the threshold distance can be in the range of 100 nm to 10 mm, and the threshold depth is in the range of 10 μm to 10 mm. In one example, the threshold distance can be in the range of 100 nm to 1000 μm, and the threshold depth is in the range of 10 μm to 1000 μm. As another example, the threshold distance can be in the range of 100 nm to 200 μm, and the threshold depth is in the range of 10 μm to 200 μm.

[0105] When the desired amount of engraving has been achieved, sandblasting the surface with abrasive can be stopped, and at 1206, the surface of the cathode cup being textured can be cleaned, and all remaining abrasive can be removed from the surface. The surface can be wiped with water or a cleaning solution.

[0106] In this way, the surface of the cathode cup can be chemically and / or mechanically engraved to have a microstructure, forming multiple features, each feature having a depth above the threshold, and the surface of the cathode cup faces the emitter coupled to the cathode cup. Although the above embodiments illustrate chemical and mechanical etching processes for engraving the surface of the cathode cup, in addition or alternatively, heat treatment can be employed, for example, to further increase the coarseness of the microstructure / features.

[0107] In one example, a method includes: chemically and / or mechanically texturing a surface of a cathode cup to form a plurality of features, each feature having a depth above a threshold and a distance greater than a threshold between two adjacent features, the surface of the cathode cup facing an emitter coupled to the cathode cup. In the foregoing example, in addition or alternatively, the chemical texturing includes chemically etching the surface with a chemical etchant. In any or all of the foregoing examples, in addition or alternatively, the chemical etching includes dispensing an amount of the chemical etchant onto the surface and exposing the surface to the chemical etchant for a duration above a threshold. In any or all of the foregoing examples, in addition or alternatively, dispensing the chemical etchant includes adding the chemical etchant to the surface via one or more of a pipette, a syringe, and a dropper. In any or all of the foregoing examples, in addition or alternatively, dispensing the chemical etchant further includes dipping the chemical etchant in a swab and foaming the chemical etchant on the surface with the swab. In any or all of the foregoing examples, in addition or alternatively, one or more of the concentration of the chemical etchant dispensed on the surface and the contact duration of the chemical etchant with the surface is proportional to the level of texturing to be obtained on the surface, and one or more of the concentration of the chemical etchant and the contact duration increases as the level of texturing increases. In any or all of the foregoing examples, in addition or alternatively, the level of texturing includes the distance between two adjacent features and the depth of each feature, and the level of texturing increases with each of a decrease in the distance between two adjacent features and an increase in the depth of each feature. In any or all of the foregoing examples, in addition or alternatively, each feature is any one of a grain, a grain boundary, and a material phase constituting the surface. In any or all of the foregoing examples, in addition or alternatively, the depth of each feature is in the range of 10 μm to 10 mm, and the distance between two adjacent features is in the range of 100 nm to 10 mm. In any or all of the foregoing examples, in addition or alternatively, the mechanical texturing includes sandblasting the surface with a medium for another threshold duration. In any or all of the foregoing examples, in addition or alternatively, the sandblasting includes propelling the medium from a dispenser onto the surface at high pressure for another threshold duration. In any or all of the foregoing examples, in addition or alternatively, each of the threshold duration of exposing the surface to the chemical etchant and the another threshold duration of sandblasting is based on the level of texturing to be obtained on the surface. In any or all of the foregoing examples, in addition or alternatively, the threshold depth of each feature is in the range of 1 μm to 10 μm.

[0108] Another manufacturing method includes: engraving the surface of the cathode cup of an x-ray tube with microstructures, including: coating the surface with a chemical etchant; and exposing the surface to the chemical etchant for a threshold duration to etch the grain boundaries of the material of the surface, the threshold duration being based on the desired amount of engraving. In the foregoing example, the method further includes (in addition to or optionally) sandblasting the surface with an abrasive to obtain a microstructure having a surface roughness proportional to the particle size of the abrasive. In any or all of the foregoing examples, in addition to or optionally, the abrasive includes one or more of metallic grains, sand, glass beads, ceramic beads, and plastic beads, and wherein the chemical etchant includes either an acidic compound or a basic compound, the acidic compound including any one of hydrofluoric acid (HF), sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), ferric chloride, or any combination thereof, and the basic compound including any one of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), or any combination thereof. In any or all of the foregoing examples, in addition to or optionally, the desired amount of engraving is a threshold distance between adjacent grain boundaries and a threshold depth of the grain boundaries, the threshold distance being in the range of 100 nm to 10 mm, and the threshold depth being in the range of 10 μm to 10 mm.

[0109] In yet another example, a system includes: the surface of the cathode cup of an x-ray tube facing an emitter formed of a material; the surface includes a plurality of etched features, and the grain boundaries of the material have a depth above a threshold of 1 μm to trap sublimated material from the emitter. In the foregoing example, in addition to or optionally, the distance between two adjacent features of the plurality of etched features is in the range of 100 nm to 10 mm. In any or all of the foregoing examples, in addition to or optionally, the material forming the surface of the cathode cup is one of nickel, molybdenum, Fe-41.5Ni (Ni42), Fe-29Ni-17Co (Kovar), or niobium, and wherein the emitter is made of tungsten.

[0110] As used herein, an element or step recited in the singular and preceded by the word "a" or "an" should be understood as not excluding a plurality of the recited elements or steps, unless expressly stated to the contrary. Moreover, a reference to "one embodiment" of the present invention is not to be construed as excluding the existence of additional embodiments that also incorporate the recited features. Further, unless expressly stated to the contrary, an embodiment that "comprises," "includes," or "has" an element or elements with a particular property may include additional such elements that do not have that property. The terms "comprising" and "in" are used as concise verbal equivalents of the corresponding terms "including" and "wherein." Further, the terms "first," "second," and "third," etc. are used merely as labels and are not intended to impose numerical requirements or a particular positional order on their objects.

[0111] The written description uses examples to disclose the invention, including the best mode, and also enables one of ordinary skill in the relevant art to practice the invention, including making and using any device or system and performing any included method. Certain terms are used for brevity, clarity, and ease of understanding. No unnecessary limitations should be inferred therefrom, other than as required by the prior art, as such terms are used for descriptive purposes only and are intended to be broadly construed. The scope of the patentable invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A method for an X-ray system, comprising: chemically and / or mechanically texturing a surface of a cathode cup to form a plurality of features in a microscopic form, each feature having a depth above a threshold and a distance greater than a threshold between two adjacent features, the surface of the cathode cup facing a emitter coupled to the cathode cup, wherein the depth and the distance are related to a size of grains of a material of the surface.

2. The method according to claim 1, wherein the chemical texturing comprises chemically etching the surface with a chemical etchant.

3. The method according to claim 2, wherein the chemical etching comprises dispensing an amount of the chemical etchant onto the surface and exposing the surface to the chemical etchant for a duration above a threshold.

4. The method according to claim 3, wherein one or more of a concentration of the chemical etchant dispensed onto the surface and a contact duration of the chemical etchant with the surface is proportional to a level of texturing to be obtained on the surface, and the one or more of the concentration of the chemical etchant and the contact duration increases as the level of texturing increases.

5. The method according to claim 3, wherein the mechanical texturing comprises sandblasting the surface with a medium for another threshold duration.

6. The method according to claim 5, wherein the sandblasting comprises propelling the medium from a dispenser onto the surface at a high pressure for the another threshold duration.

7. The method according to claim 6, wherein each of the threshold duration for which the surface is exposed to the chemical etchant and the another threshold duration for sandblasting is based on the level of texturing to be obtained on the surface.

8. A manufacturing method, comprising: engraving a surface of a cathode cup of an X-ray tube having a microstructure, comprising: coating the surface with a chemical etchant; and exposing the surface to the chemical etchant for a threshold duration to etch grain boundaries of a material of the surface, the threshold duration being based on a desired amount of engraving, wherein a degree of the engraving is related to a size of grains of the material of the surface.

9. The method according to claim 8, further comprising sandblasting the surface with an abrasive to obtain the microstructure having a surface roughness proportional to a particle size of the abrasive.

10. A system for an X-ray tube, comprising: a surface of a cathode cup of the X-ray tube facing an emitter formed of a material; the surface comprising a plurality of etched features and grain boundaries of the material having a depth above a threshold of 1 μm to trap sublimated material from the emitter, wherein a degree of texturing of the plurality of etched features is related to a size of grains of the material.

Images