X-ray system with field emitters and arc protection

Abstract

To inhibit a field emitter from being deteriorated or broken by arcing in an x-ray tube.SOLUTION: An x-ray tube comprises: a field emitter including an emission surface; an anode; and a focus electrode disposed between the field emitter and the anode. The focus electrode includes: a first surface that is substantially perpendicular to the field emitter emission surface and nearest to the field emitter; a second surface that is axially nearest to the anode, where the field emitter and the anode form an axis; a third surface that extends between the first surface and the second surface; and a first location on the focus electrode between the first surface and the third surface, the first location being farther from the anode than a second location on the focus electrode between the third surface and the second surface.SELECTED DRAWING: None

Description

[Background technology]

[0001] X-ray tubes used within x-ray systems may contain field emitters. Field emitters may be particularly susceptible to arcing due to the structure of the field emitter. Arcing affecting the field emitter can degrade or destroy the structure, ultimately rendering the x-ray tube inoperable. [Brief description of the drawings]

[0002] [Figure 1] FIG. 1 is a block diagram of an x-ray tube according to some embodiments. [Diagram 2] FIG. 1 is a block diagram of an x-ray system in accordance with some embodiments. [Diagram 3] FIG. 1 is a block diagram of an x-ray tube with two surface electrodes according to some embodiments. [Figure 4] FIG. 1 is a block diagram of an x-ray tube with three surface electrodes according to some embodiments. [Diagram 5] FIG. 2 is a block diagram of an x-ray tube with a focusing electrode having protrusions, according to some embodiments. [Figure 6] FIG. 2 is a cutaway view of a focusing electrode according to some embodiments. [Figure 7] FIG. 13 is a cutaway view of a focusing electrode for multiple field emitters according to some embodiments. [Figure 8] 1 is a cross-sectional view of a cathode assembly including a focusing electrode according to some embodiments. [Figure 9] FIG. 1 is a block diagram of an x-ray imaging system in accordance with some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0003] Some embodiments relate to x-ray systems and x-ray tubes with field emitters and arc protection. The field emitter, due to its construction, may be particularly susceptible to arcing and damage. The relative size of the field emitter may result in an increased electric field strength at the field emitter that would normally occur. The increased electric field strength may increase the probability that an arc may occur, which may increase the probability of an arc occurring on the field emitter. As described in more detail below, the location and construction of the focusing electrodes may reduce the probability that an arc may occur on the field emitter and cause damage. Furthermore, if an arc does occur, the location where the arc is likely to occur may be controlled to be far from the field emitter. As a result, there may be an increased probability that the x-ray tube may remain operable after an arc occurs.

[0004] FIG. 1 is a block diagram of an x-ray tube according to some embodiments. The x-ray tube 100a includes an anode 102, a field emitter 104, and a focusing electrode 106a. The anode 102 includes a structure configured to generate x-rays in response to incident electrons. The field emitter 104 is configured to generate an electron beam that can be directed toward the anode 102. The field emitter 104 can include various types of emitters. For example, the field emitter 104 can include a nanotube emitter, a nanowire emitter, a Spindt array, and the like. Conventionally, a nanotube has at least a portion of the structure having a hollow center, while a nanowire or nanorod has a substantially solid core. For ease of use of the terminology, as used herein, nanotubes also refer to nanowires and nanorods. A nanotube refers to a nanometer-scale (nm-scale) tubular structure with an aspect ratio of at least 100:1 (length:width or diameter). Spindt arrays may include individual field emitters with small sharp cone shapes that use electron generating materials such as molybdenum (Mo) or tungsten (W). In some embodiments, the field emitters 104 are made of carbon, metal oxides (e.g., Al), in pure or doped form, etc. 2 O 3 , titanium dioxide (TiO 2), zinc oxide (ZnO), or manganese oxide (Mn x O y , where x and y are integers), formed from conductive or semiconductive materials with high tensile strength and high thermal conductivity, such as metals, sulfides, nitrides, and carbides.

[0005] In some embodiments, the field emitter 104 may include multiple field emitters. For example, the field emitter 104 may include tens to hundreds, or more, of individual field emitters 104. Each field emitter 104 may be configured to generate an electron beam that is directed towards the anode 102. Each field emitter 104 may be associated with a corresponding focusing electrode 106, such as the focusing electrode pair 106a, 106 shown in FIG. 1, or with a corresponding opening in a unitary focusing electrode 106.

[0006] The field emitter 104 may have a larger area compared to other types of emitters. For example, the field emitter 104 may have a length of about 10 millimeters (mm) to about 30 mm and a width of about 2 mm to about 6 mm. In one example, the length of the field emitter 104 is at least 5 times greater than its width. The larger relative area may increase the size of the focal spot on the anode 102. Heating of the anode 102 by incident electrons on the focal spot may spread over its larger area, reducing thermal stress on the anode 102 and allowing for a higher electron flux, etc. Additionally, the field emitter 104 may have a relatively lower current flux compared to other emitters. To compensate for the lower flux, the area of ​​the field emitter 104 may be increased. These aspects result in a larger relative area for the field emitter 104. The larger relative area means that the local electric field strength around the field emitter 104 is more sensitive to the anode 102 or tube voltage.

[0007] The larger the relative area of ​​the field emitter 104, the greater the probability that an arc will occur. As the area of ​​the field emitter 104 increases, other structures that may be subject to arcing are moved farther away from the anode 102, reducing the electric field strength on those structures compared to the electric field strength at the field emitter 104. This may increase the probability that an arc may occur at the field emitter 104. Due to their construction, field emitters 104 may be more susceptible to arcing than other types of emitters, such as thermionic emitters. For example, the field emitter 104 may include relatively small structures, such as thin layers, that may be damaged by arcing.

[0008] Thus, field emitters have contradictory design problems: the field emitter 104 can be large in area, by its nature and because of the desirability of a large focal spot for heating distribution, but as its area increases, the probability of arcing occurring on the field emitter 104 increases.

[0009] The focusing electrode 106a may mitigate the increased probability of arcing on the field emitter 104. As a result, the benefits of a larger area of ​​the field emitter 104 may be realized while reducing the probability of damage to the field emitter 104 due to arcing. The focusing electrode 106a is disposed between the anode 102 and the field emitter 104. The focusing electrode 106a is configured to adjust the size and / or shape of the focal spot on the anode 102. At least a portion of the focusing electrode 106a is closer to the anode 102 than any portion of the field emitter 104. For example, the shortest distance between any portion of the field emitter 104 and any portion of the anode 102 may be distance 108. The shortest distance from a portion of the focusing electrode 106a to the anode 102 may be distance 110. Distance 110 is less than distance 108.

[0010] Because the distance 110 to the focusing electrode 106a is shorter than the distance 108 to the field emitter 104, the electric field strength at the focusing electrode 106a may be higher than the electric field strength at the field emitter 104. As a result, the probability of arcing on the field emitter 104 may be reduced, but the probability of arcing on the focusing electrode 106a may be increased.

[0011] In some embodiments, the focusing electrode 106a is positioned relative to the field emitter 104 and the anode 102 and shaped such that, during operation, the highest point of the electric field strength on the cathode structure is closer to the focusing electrode 106a than to the field emitter 104. The cathode structure may include a structure that is at or near the electric potential of the field emitter 104. For example, the anode 102 may be at about 10 to 50 kilovolts (kV), about 50 to 150 kV, about 50 to 450 kV, etc. (relative to the cathode structure or ground). In some embodiments, these voltages may be associated with specific applications such as mammography, medical imaging, industrial imaging, explosive detection, non-destructive testing (NDT), etc. The cathode structures, such as the field emitter 104, focusing electrode 106a, and grid (not shown), may be at a voltage of about -3 kV to about 1 kV. In general, the higher the electric field strength, the higher the probability of arcing. As a result, the design of the x-ray tube 100a may include minimizing local electric field strength maxima. However, in some embodiments, the electric field strength peak may be generated by design, and may be offset or shifted, particularly away from the field emitter 104. In some embodiments, the electric field strength at the electric field strength peak may be greater than about 8 times the highest electric field strength above the field emitter 104. In some embodiments, the structure of the focusing electrode 106a may result in the electric field strength at the electric field strength peak being at least about 25% higher than the electric field strength at the portion of the focusing electrode 106a closest to the field emitter 104.

[0012] 2 is a block diagram of an x-ray system according to some embodiments. The x-ray system 200 may include an x-ray tube 100b similar to the x-ray tube 100a described above. The x-ray tube 100b may include an evacuated enclosure 212, with the anode 102, field emitter 104, and focusing electrode 106b disposed within an interior 202a of the evacuated enclosure 212.

[0013] The x-ray system 200 may include a voltage source 204 disposed on an exterior 202b of the vacuum enclosure 212. The voltage source 204 may be configured to generate multiple voltages for the x-ray system 200. For example, the voltage source 204 may be configured to generate one or more voltages 206 for the field emitter 104, a high voltage 208 for the anode 102, a focusing electrode voltage 210 for the focusing electrode 106, etc.

[0014] In some embodiments, the focusing electrode 106b may be grounded. That is, the focusing electrode voltage 210 may be 0V or near 0V. A portion of the vacuum enclosure 212, the housing of the x-ray tube 100b, etc. may be grounded. The focusing electrode 106b may share that ground. In some embodiments, the voltage source 204 may share that ground. As a result, the arc may direct charge to ground as it discharges through the focusing electrode 106b.

[0015] In some embodiments, the focusing electrode 106b may be at a voltage 210 different from ground. For example, the voltage source 204 may be configured to apply a variable voltage to the focusing electrode 106b. The voltage source 204 may include a spark gap protector or other circuitry to accommodate arcing that may occur while still allowing for the desired variability in the focusing electrode voltage 210.

[0016] 3 is a block diagram of an x-ray tube with two surface electrodes according to some embodiments, where two surfaces 302, 306 of the focusing electrode have a higher electric field strength than the other two surfaces 308, 310 facing away from the anode. The x-ray tube 100c may be similar to the x-ray tubes 100a-b. However, the focusing electrode 106c may have a particular structure.

[0017] The focusing electrode 106c may have a structure relative to an axis 300. The field emitter 104 and the anode 102 may form the axis 300. The axis 300 may be aligned with the general direction of electrons emitted from the field emitter 104 and traveling towards the anode 102. In this example, the axis 300 may extend along the Y-axis. The axially extending components relative to the axis 300 may have some components along the Y-axis. In some embodiments, the axially extending components may extend only axially or only along the Y-axis, while other axially extending components may have some portions extending radially, i.e. perpendicular to the axis 300, or Y-axis parallel to the XZ plane, extending along the X-axis, extending along the Z-axis, etc.

[0018] The focusing electrode 106c includes at least two surfaces. Here, two surfaces 302 and 304 are used as an example. A first surface (or field emitter vertical surface or beam shaping surface) 302 extends substantially parallel to the axis 300, or emission surface of the field emitter 104. The surface 302 may include a beam shaping surface with structures that shape the focal spot on the anode 102 in operation. The surface 302 may contribute a large part of the shaping of the electric field to focus the electrons from the field emitter 104 onto the anode 102. Other surfaces such as the surface 304 may also have some influence, but the relative contribution of the surface 304 is smaller than that of the surface 302.

[0019] The second surface (or the parallel surface facing the anode) 304 of the focusing electrode 106c extends radially away from the axis away from the first surface 302. In some embodiments, the second surface 304 is formed to extend only radially away from the first surface 302 parallel to the XZ plane with substantially no axial component. As a result, the location 306 where the first surface 302 and the second surface join can be at an angle of about 90 degrees. The second surface 304 can be the surface closest to the anode 102. In operation, the highest point of the electric field strength is located at the location where the first surface 302 joins the second surface 304. Because the focusing electrode 106c can be at the same potential, the electric field strength along the surface 302 can necessarily be lower than the electric field strength at the location 306 where the first surface 302 and the second surface 304 join. Furthermore, the relatively sharp feature of the location 306 can result in increased localized electric field strength as the electric field is concentrated around a corner or edge of a conductor within the electric field. As a result, any arcing that may occur may have a higher probability of occurring at location 306 rather than at field emitter 104 .

[0020] Although a 90 degree angle is used as an example, in other embodiments the angle may be different, for example the angle may be larger or smaller within a range such that a local maximum in the electric field strength on the cathode structure occurs at location 306.

[0021] FIG. 4 is a block diagram of an x-ray tube with three surface electrodes according to some embodiments, where three surfaces 402, 404, 406 of the focusing electrode have a higher electric field strength than the other surfaces 414, 416 facing away from the anode. X-ray tube 100d may be similar to x-ray tubes 100a-c. However, focusing electrode 106 may include at least three surfaces with higher electric field strength. First surface (or field emitter vertical surface or beam shaping surface) 402 may be similar to first surface 302 of focusing electrode 106c of x-ray tube 100c. First surface 402 may be a beam shaping surface that affects the focal spot.

[0022] The third surface (or anode-facing surface) 408 may extend radially away from the first surface 402 parallel to the XZ plane and is joined to the first surface 402 at a location (or inner corner or inner corner) 406 similar to the second surface 304 of the focusing electrode 106c. However, the third surface 408 also extends axially away from the first surface 402 with respect to the axis 300 along the Y axis. In this embodiment, the axial extension of the third surface 408 is in a direction toward the anode. As a result, the angle between the first surface 402 and the third surface 408 at the location 406 may be greater than 90 degrees. If the angle at the location 406 is greater, the electric field intensity at the location 406 may be reduced compared to an angle of 90 degrees. Similar to the first surface 402, the third surface 408 is a beam shaping surface and serves to shape the electron beam into a desired cross-section with a desired trajectory on the focal spot of the anode 102 during operation.

[0023] The focusing electrode further includes a second surface (or parallel surface facing the anode) 404. The second surface 404 joins with a third surface 408 at a location (or outer corner or outer corner) 410. The second surface 404 extends away from the third surface 408 relative to the axis 300. The resulting structure allows for control of the focal spot through the surface 402 as well as positioning of points of higher electric field strength further away from the field emitter 104 by the angle at location 406, the length of the third surface 404, and the angle at location 410.

[0024] For example, line 412 is a point that is equidistant from the anode 102. A location 410 where the third surface 408 joins the second surface 404 may be at the equidistant line 412. However, a location 406 may be farther from the anode 102 than the equidistant line 412. As a result, the electric field strength at location 406 may be lower than the electric field strength at location 410. The highest point of electric field strength may be located at location 410 where the third surface 408 joins the second surface 404.

[0025] Additionally, the angle of the second surface 404 relative to the third surface 408 at location 410 may be determined such that other points along the second surface 404 are farther from the anode 102 than point 410. As a result, the electric field intensity along the surface 404 may be lower than the electric field intensity at location 410. The electric field intensity along the focusing electrode 106d may be at a local maximum at location 410. Any arcing may occur at location 410 rather than other locations along the focusing electrode 106d, including those closer to the field emitter 104. Due to the close proximity of location 306 (FIG. 3) to the field emitter, arcing at location 306, where the electric field intensity is highest, may still leak or occur to surrounding features such as the field emitter 104 and cause damage to the field emitter 104. Moving the highest electric field strength to a location 410 (FIG. 4) away from the field emitter 104 reduces the likelihood that arcing at the location 410 of highest electric field strength will leak or occur to the field emitter 104, thereby reducing the likelihood of damage to the field emitter 104 due to arcing. For similarly sized focusing electrodes 106c, 106d at similar distances away from the anode 102, the location 306 (FIG. 3) with the sharp or narrow angle may be closer to the anode 102 where the electric field strength is higher than the location 410 (FIG. 4) with the wider angle. Thus, the focusing electrode 106c may have improved beam shaping and focusing characteristics, but with a higher likelihood of arcing and arc-induced damage to cathode structures such as the field emitter 104.

[0026] In some embodiments, a portion or location (e.g., 410) of the focusing electrode 106d that is closer to the anode 102 (e.g., has the highest electric field strength) than any portion of the field emitter 104 will be farther from the center of the field emitter 104 than another portion of the focusing electrode 106d (e.g., 402, 406, 408). For example, a beam shaping surface of the focusing electrode 106d, such as surface 402 facing the electron beam, may be closer to the center of the field emitter 104 than that portion or location (e.g., 410) of the focusing electrode 106d (where the electric field strength is highest). Because the focusing electrode 106d may be at a single potential, the electric field strength will be higher at the portion or location (e.g., 410) of the focusing electrode 106d that is closer to the anode 102 than the beam shaping surface (e.g., 402, 404, 408).

[0027] 5 is a block diagram of an x-ray tube with a focusing electrode having protrusions, according to some embodiments. X-ray tube 100e may be similar to x-ray tubes 100a-d described above. Focusing electrode 106e may include surfaces 502, 504, and 508 having corresponding locations 506 and 510 that are similar to surfaces 402, 404, and 408, and locations 406 and 410.

[0028] In some embodiments, the focusing electrode 106e includes a protrusion 514. The protrusion extends from the third surface 508 toward the anode 102. The protrusion 514 comprises a portion of the focusing electrode 106e that is closer to the anode 102 than any portion of the field emitter 104. The portion of the protrusion 514 lies on a line 512 that is equidistant from the anode 102. All other portions of the focusing electrode 106e are farther from the anode 102 than the portion of the protrusion 514.

[0029] In some embodiments, the protrusion 514 is associated with a local minimum radius. As the radius R at the corner of the protrusion 514, shown in FIG. 5, decreases, the particular feature becomes sharper. The local radius R may approach zero or approach a sharp corner. The sharper the feature, the smaller the radius, etc., the more concentrated the electric field may be in that area. The protrusion 514 may be offset from a portion of the focusing electrode 106e that is closer to the field emitter 104. As a result, the location of the higher electric field intensity may be offset from the field emitter 104. The location of the protrusion 514 provides control of the location of the higher electric field intensity and therefore the location where arcing may occur.

[0030] In some embodiments, protrusion 514 may be located at or nearer location 510 than location 506. Thus, protrusion 514, which is prone to arcing, may be further away from field emitter 104.

[0031] In some embodiments, points across the third surface 508 other than the protrusions 514 are substantially equidistant from the anode 102. As a result, the electric field strength along these points may be substantially the same. However, because the protrusions 514 are at the same potential as the surface 504, the electric field strength at the protrusions 514 may necessarily be higher.

[0032] Although focusing electrode 106e, similar to focusing electrode 106d, has been used as an example of a focusing electrode 106 including a protrusion 514, in other embodiments, other focusing electrodes 106 may include a protrusion 514. For example, focusing electrode 106e may include a structure similar to focusing electrode 106c of FIG. 3, but with a protrusion 514 extending from a surface of focusing electrode 106e toward the anode 102.

[0033] 6 is a cutaway view of a focusing electrode according to some embodiments. As described above, there may be multiple field emitters 104. The focusing electrode 106f includes multiple openings 620. Each opening 620 is associated with one of the multiple field emitters 104. For each of the field emitters 104, a point on the focusing electrode 106f is closer to the anode 102 than that field emitter 104. The openings 620 may have a first surface 602 similar to the first surfaces 302, 402, 502, etc. described above. The focusing electrode 106f may include a second surface 604 similar to the second surfaces 304, 404, and 504 described above.

[0034] Although the apertures 620 are described as being associated one-to-one with the field emitters, in other embodiments, each aperture 620 may be associated with multiple field emitters. However, the focusing electrode 106f may nevertheless have a point that is closer to an anode, such as the anode 102 of Figures 1-5, than any of the field emitters 104.

[0035] 7 is a cutaway view of a focusing electrode for multiple field emitters according to some embodiments. Focusing electrode 106g includes a single opening 702 formed between portions 106g-1 and 106g-2. Multiple field emitters 104 are disposed within the single opening 702. In some embodiments, a frame 704 may be disposed between the field emitters 104. In some embodiments, the frame 704 may be grounded or at the same potential as focusing electrode 106g. Focusing electrode 106g may have a cross-section similar to focusing electrode 106 described above. For example, focusing electrode 106g may have a cross-section, include protrusions, etc., similar to focusing electrodes 106a-e described above.

[0036] FIG. 8 is a cross-sectional view of a cathode assembly including a focusing electrode according to some embodiments. The cathode assembly 800 includes a substrate 830. The substrate 830 may include a ceramic substrate or other insulating substrate. A conductive layer 836, such as a copper layer, is disposed on the substrate 830. An emitter 844, such as a carbon nanotube, nanowire, nanorod, or the like as described above, may be disposed on the conductive layer 836. Although one emitter 844 is shown, there may be multiple emitters 844, similar to the field emitter 104 of FIG. 7. A grid 834 may be disposed over the emitter 844. A voltage may be applied between the conductive layer 836 and the grid 834 to generate electrons from the emitter 844. The grid 834 may be of a shielded type, in which the electrons pass through a grid, such as a mesh, as shown, or may be of a non-shielded type (not shown), in which the electrons pass through an open aperture.

[0037] A frame 838, similar to frame 704 of FIG. 7, may be disposed over substrate 830. Frame 838 may also contribute to focusing the electron beam. Frame 838 may provide structural support to other components, such as grid 834. A spacer (not shown) may separate frame 838 and grid 834, and the spacer may be conductive or insulating. Frame 838 may include a plurality of openings 838′ associated with a plurality of emitters 844.

[0038] A spacer 840 may separate the frame 838 and the substrate 830. The spacer 840 may be conductive or insulating. The frame 838 may include a conductive material. A second spacer 842 is disposed on the frame 838. The second spacer 842 may be conductive or insulating. A focusing electrode 106h is disposed on the second spacer 842. The focusing electrode 106h may be similar to the focusing electrodes 106a-g described above.

[0039] In some embodiments, the focusing electrode may include a first portion 106h-1 and a second portion 106h-2 similar to portions 106g-1 and 106g-2 of FIG. 7. The plurality of openings 838' may be disposed between portions 106h-1 and 106h-2. The portions 106h-1 and 106h-2 may extend parallel to the emitter 844, for example in the Z direction.

[0040] The spacer 842 may be insulating, but in some embodiments the spacer 842 may be conductive or may be omitted. Thus, the focusing electrode 106h and the frame 838 may be at the same potential.

[0041] The grid 834 or frame 838 may provide some protection to the emitter 844 from damage due to arcing. However, because the grid 834 and frame 838 are relatively close to the emitter 844 and the potential of the arc is high, the protection may be minimal. For example, the frame 838 may be about 200 micrometers (μm) away from the emitter 844. Due to its close proximity to the emitter 838, the frame 838 or an attached grid will not be able to mitigate any molten metal or metal vapor damage caused by the arc. Furthermore, if an arc occurs near the frame 838, the material of the spacer 842 or other structures may be damaged. Therefore, by moving the location where an arc may occur further away from the emitter 844 and frame 838 on the focusing electrode 106h, the damage that may occur to the emitter 844, frame 838, spacer 842, or other similar structures due to an arc may be reduced.

[0042] 9 is a block diagram of a radiography system according to some embodiments. The radiography system 900 includes an x-ray source 902 and a detector 910. The x-ray source 902 may be similar to the x-ray tubes 100a-e as described above. The x-ray source 902 is positioned relative to the detector 910 such that x-rays 920 may be generated to pass through a specimen 922 and be detected by the detector 910. In some embodiments, the detector 910 is part of a medical imaging system, a non-destructive testing system, or the like. In other embodiments, the radiography system 900 may include a portable vehicle scanning system as part of a cargo scanning system.

[0043] Some embodiments include an x-ray tube, the x-ray tube including a field emitter 104 having an emitting surface, an anode 102, and focusing electrodes 106, 106a-h disposed between the field emitter 104 and the anode 102, the focusing electrodes 106, 106a-h being substantially perpendicular to the emitting surface of the field emitter 104, a first surface 302, 402, 502, 602 closest to the field emitter 104, and a second surface 304, 404, 504, 604 axially closest to the anode 102, where the field emitter 104 and the anode 102 form an axis, 4, 504, 604, a third surface 308, 408, 508 extending between the first surface 302, 402, 502, 602 and the second surface 304, 404, 504, 604, and a first location 406, 506 on the focusing electrode 106, 106a-h between the first surface 302, 402, 502, 602 and the third surface 308, 408, 508, the first location 406, 506 being farther from the anode 102 than a second location 410, 510 on the focusing electrode 106, 106a-h between the third surface 308, 408, 508 and the second surface 304, 404, 504, 604.

[0044] In some embodiments, the second location 410, 510 on the focusing electrode 106, 106a-h is further from the center of the field emitter 104 than another portion of the focusing electrode 106, 106a-h.

[0045] In some embodiments, the focusing electrodes 106, 106a-h are grounded.

[0046] In some embodiments, the focusing electrodes 106, 106a-h further include a protrusion 514 that extends toward the anode 102.

[0047] In some embodiments, the protrusion 514 is closer to the second location 410, 510 on the focusing electrodes 106, 106a-h and the anode 102 than the first location 406, 506 on the focusing electrodes 106, 106a-h.

[0048] In some embodiments, the focusing electrodes 106, 106a-h are shaped such that during operation, the highest point of electric field strength is located at the second location 410, 510.

[0049] In some embodiments, the second surface 304, 404, 504, 604 extends radially and axially away from the first surface 302, 402, 502, 602 relative to the axis.

[0050] In some embodiments, the x-ray tube further includes a cathode structure including a substrate on which the field emitter 104 is disposed, a frame disposed on the substrate above the field emitter 104, and focusing electrodes 106, 106a-h disposed on the frame.

[0051] In some embodiments, the field emitter 104 is one of a plurality of field emitters 104s disposed on a substrate, the frame includes a plurality of openings, each opening corresponding to one of the plurality of field emitters 104s, the focusing electrodes 106, 106a-h include a first portion and a second portion, and the opening in the frame is disposed between the first portion and the second portion.

[0052] In some embodiments, points across the second surface 304 , 404 , 504 , 604 are substantially equidistant from the anode 102 .

[0053] Some embodiments include an x-ray tube comprising a cathode structure 800 having a field emitter 104, an anode 102, and focusing electrodes 106, 106a-h disposed between the field emitter 104 and the anode 102, the focusing electrodes 106, 106a-h disposed relative to the field emitter 104 and the anode 102, and the focusing electrodes 106, 106a-h shaped such that, during operation, the highest point of electric field intensity on the cathode structure is closer to the focusing electrodes 106, 106a-h than to the field emitter 104.

[0054] In some embodiments, the highest point of the electric field intensity is further from the center of the field emitter 104 than another portion of the focusing electrodes 106, 106a-h.

[0055] In some embodiments, the focusing electrodes 106, 106a-h are grounded.

[0056] In some embodiments, the field emitter 104 and the anode 102 form an axis, and the focusing electrodes 106, 106a-h include a first surface 302, 402, 502, 602 extending substantially parallel to the axis, and a second surface 304, 404, 504, 604 extending radially away from the first surface 302, 402, 502, 602 relative to the axis.

[0057] In some embodiments, a first location on the focusing electrodes 106, 106a-h is between the first surface 302, 402, 502, 602 and the second surface 304, 404, 504, 604, and the focusing electrodes 106, 106a-h are shaped such that, during operation, the highest point of electric field strength is located at the first location.

[0058] In some embodiments, the field emitter 104 and the anode 102 form an axis, and the focusing electrodes 106, 106a-h have a first surface 302, 402, 502, 602 extending substantially parallel to the axis, a second surface 304, 404, 504, 604 extending radially away from the first surface 302, 402, 502, 602 relative to the axis, and a second surface 304, 404, 504, 604 extending radially away from the first surface 302, 402, 502, 602 relative to the axis. a third surface 308, 408, 508 extending radially and axially toward 504, 604, a first location 306, 406, 506 on the focusing electrode 106, 106a-h between the first surface 302, 402, 502, 602 and the third surface 308, 408, 508, and a second location 410, 510 on the focusing electrode 106, 106a-h and between the third surface 308, 408, 508 and the second surface 304, 404, 504, 604.

[0059] In some embodiments, the focusing electrodes 106, 106a-h are shaped such that during operation, the highest point of electric field strength is located at the second location 410, 510.

[0060] In some embodiments, points across the second surface 304 , 404 , 504 , 604 are substantially equidistant from the anode 102 .

[0061] Some embodiments include an x-ray tube comprising a means for emitting electrons toward an anode and a means for focusing electrons emitted from the means for emitting electrons toward the anode, the means for focusing the electrons comprising means for increasing an electric field strength at the means for focusing the electrons beyond an electric field strength at the means for emitting electrons.

[0062] Examples of the means for emitting electrons towards the anode include the cathode structure 800, the field emitter 104, the grid 834, etc. In one example, the means for emitting electrons towards the anode can include at least three field emitters 104.

[0063] Examples of the means for focusing electrons emitted from the means for emitting electrons towards the anode include focusing electrodes 106, 106a-h and frames 704, 838.

[0064] Examples of the means for increasing the electric field strength at the means for focusing electrons beyond the electric field strength at the means for emitting electrons include surfaces 302, 402, 502, 602, 408, 508, locations or edges 406, 506, protrusions 514, and the like.

[0065] In some embodiments, the means for focusing electrons further includes means for positioning a maximum point of electric field strength on the means for focusing electrons further from the means for emitting electrons than the nearest portion of the means for focusing electrons to the means for emitting electrons. Examples of means for positioning a maximum point of electric field strength on the means for focusing electrons further from the means for emitting electrons than the nearest portion of the means for focusing electrons to the means for emitting electrons include positions 410 and 510, protrusion 514, etc.

[0066] Some embodiments include a method that includes emitting electrons from a cathode 800 toward an anode 102, focusing the emitted electrons toward the anode 102 with a focusing electrode 106, and increasing the electric field strength at the focusing electrode 106 beyond the electric field strength at the cathode 800.

[0067] In some embodiments, the maximum point of electric field strength is located on the focusing electrode 106 further from the cathode 800 than the closest portion of the focusing electrode 106 to the cathode 800 .

[0068] Although the structures, devices, methods, and systems have been described in accordance with specific embodiments, one skilled in the art will readily recognize that many variations to the specific embodiments are possible, and therefore any variations should be considered within the spirit and scope of the disclosure herein. Accordingly, many modifications may be made by one skilled in the art without departing from the spirit and scope of the appended claims.

[0069] The claims following this written disclosure are hereby expressly incorporated into the disclosure herein, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of independent claims with dependent claims. Furthermore, additional embodiments that may be derived from the following independent and dependent claims are also expressly incorporated into the description herein. These additional embodiments are determined by replacing the dependency of a given dependent claim with the phrase "any of the claims beginning with claim [x] and ending with the claim immediately preceding this claim," where the bracketed term "[x]" is replaced with the number of the most recently described independent claim. For example, for the first set of claims beginning with independent claim 1, claim 4 depends on any of claims 1 and 3, and these separate dependencies can result in two different embodiments; claim 5 depends on any one of claims 1, 3, or 4, and these separate dependencies can result in three different embodiments; claim 6 depends on any one of claims 1, 3, 4, or 5, and these separate dependencies can result in four different embodiments, etc.

[0070] The recitation in a claim of the term "first" with respect to a feature or element does not necessarily imply the presence of a second or additional such feature or element. When present, elements specifically recited in means-plus-function form are intended to be construed to cover the corresponding structure, material, or acts described herein, and their equivalents, pursuant to 35 U.S.C. §112(f). The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Claims

1. A field emitter having an emission surface, A-scatter, A focusing electrode is disposed between the field emitter and the anode, An X-ray tube including, The aforementioned focusing electrode is The first surface is substantially perpendicular to the emission surface of the field emitter and is closest to the field emitter, The second surface is the closest to the anode in the axial direction, and the field emitter and the anode form an axis with respect to the second surface, A third surface extending between the first surface and the second surface, A first position on the focusing electrode between the first surface and the third surface, which is further from the anode than a second position on the focusing electrode between the third surface and the second surface, Includes, The focusing electrode further includes a projection extending toward the anode. x-ray tube.

2. The X-ray tube according to claim 1, wherein the second position on the focusing electrode is further from the center of the field emitter than another portion of the focusing electrode.

3. The X-ray tube according to claim 1, wherein the focusing electrode is grounded.

4. The X-ray tube according to claim 1, wherein the protrusion is closer to the second position on the focusing electrode and the anode than to the first position on the focusing electrode.

5. The X-ray tube according to claim 1, wherein the focusing electrode is shaped such that the point of maximum electric field strength is located at the second position during operation.

6. The X-ray tube according to claim 1, wherein the second surface extends radially and axially away from the first surface with respect to the axis.

7. The substrate on which the field emitter is arranged, A frame disposed on the substrate on the field emitter, The focusing electrode is positioned on the frame, An X-ray tube according to any one of claims 1 to 6, further comprising a cathode structure having the

8. The field emitter is one of a plurality of field emitters arranged on the substrate, The frame includes a plurality of openings, each opening corresponding to one of the plurality of field emitters, The focusing electrode includes a first part and a second part, The X-ray tube according to claim 7, wherein the opening of the frame is positioned between the first portion and the second portion.

9. The X-ray tube according to claim 1, wherein the points on the second surface are substantially equidistant from the anode.

10. A cathode structure having an electric field emitter, A-scatter, A focusing electrode is positioned between the field emitter and the anode and includes a projection extending toward the anode, An X-ray tube including, An X-ray tube in which the focusing electrode is positioned relative to the field emitter and the anode, and the focusing electrode is shaped such that, during operation, the highest point of the electric field strength on the cathode structure becomes closer to the focusing electrode than to the field emitter and is positioned on the protruding portion of the focusing electrode.

11. The X-ray tube according to claim 10, wherein the point of maximum electric field strength is located further from the center of the field emitter than another part of the focusing electrode.

12. The X-ray tube according to claim 10, wherein the focusing electrode is grounded.

13. The field emitter and the anode form an axis, The aforementioned focusing electrode is A first surface extending substantially parallel to the aforementioned axis, A second surface extending radially away from the first surface with respect to the axis, An X-ray tube according to any one of claims 10 to 12, including the X-ray tube according to any one of claims 10 to 12.

14. The first position on the focusing electrode is located between the first surface and the second surface. The X-ray tube according to claim 13, wherein the focusing electrode is shaped such that the point of maximum electric field strength is located at the first position during operation.

15. The field emitter and the anode form an axis, The aforementioned focusing electrode is A first surface extending substantially parallel to the aforementioned axis, A second surface extending radially away from the first surface with respect to the axis, A third surface extending radially and axially toward the second surface, away from the first surface with respect to the axis, A first position on the focusing electrode located between the first surface and the third surface, A second position on the focusing electrode located between the third surface and the second surface, An X-ray tube according to any one of claims 10 to 12, including the X-ray tube according to any one of claims 10 to 12.

16. The X-ray tube according to claim 15, wherein the focusing electrode is shaped such that the point of maximum electric field strength is located at the second position during operation.

17. The X-ray tube according to claim 13, wherein the points on the second surface are substantially equidistant from the anode.

18. A means for emitting electrons toward the anode, A means for focusing electrons emitted from the means for emitting electrons toward the anode, A means for increasing the electric field strength in the means for focusing the electrons to exceed the electric field strength in the means for emitting the electrons, the means including a projection extending toward the anode, The means for focusing the electrons, including X-ray tubes, including one.

19. The X-ray tube according to claim 18, wherein the means for focusing electrons further includes means for positioning a point of maximum electric field strength on the means for focusing electrons that is further away from the means for emitting electrons than the portion of the means for focusing electrons that is closest to the means for emitting electrons.

20. Each field emitter has an emission surface, and comprises a plurality of field emitters, A-scatter, A focusing electrode is disposed between at least one of the plurality of field emitters and the anode, A substrate on which at least one of the plurality of field emitters is disposed, A frame disposed on the substrate on at least one of the plurality of field emitters, Includes, The focusing electrode is positioned on the frame, Cathode structure and An X-ray tube including, The aforementioned focusing electrode is The first surface is substantially perpendicular to the emission surface of at least one of the plurality of field emitters and is closest to at least one of the plurality of field emitters, The second surface is the closest in the axial direction to the anode, and at least one of the plurality of field emitters and the anode form an axis with respect to the second surface, A third surface extending between the first surface and the second surface, A first position on the focusing electrode between the first surface and the third surface, which is further from the anode than a second position on the focusing electrode between the third surface and the second surface, Includes, The frame includes a plurality of openings, each opening corresponding to one of the plurality of field emitters, The focusing electrode includes a first part and a second part, The opening of the frame is located between the first portion and the second portion. x-ray tube.

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