The present application is related generally to x-ray sources.
X-ray tubes can include an internal vacuum. Maintaining this internal vacuum can be an important consideration in design of the x-ray tube. Cost reduction can also be an important consideration in x-ray tube design. During operation, x-ray tubes generate heat which can damage components if not removed, so heat removal or transfer can also be important. Designing the x-ray tube for appropriately sized electron beam spot and x-ray spot can also be important.
It has been recognized that it would be advantageous to improve x-ray tube design to better maintain an internal vacuum, to reduce cost, to remove heat, and to have an appropriately sized electron beam spot and x-ray spot. The present invention is directed to various embodiments of x-ray tubes that satisfy these needs. Each embodiment may satisfy one, some, or all of these needs.
The x-ray tube can comprise a cathode and an anode electrically insulated from one another. An electron hole can extend from an electron entry at an exterior of the anode into a core of the anode and can be aimed to allow the electrons to pass into the core of the anode. An x-ray hole can extend from an x-ray exit at the exterior of the anode into the core of the anode, intersecting the electron hole at the core of the anode, and aimed for emission of the x-rays from the core of the anode out of the x-ray tube.
In one embodiment, the electron hole and the x-ray hole can form an open, seamless bore from the electron entry to the x-ray exit. In another embodiment, the anode can be a single, integral, monolithic material with a single bore extending therethrough, the single bore comprising the electron hole intersecting the x-ray hole in the core of the anode.
In another embodiment, the core of the anode can include a target material configured for generation of the x-rays in response to the impinging electrons. The target material can be located at, and the electron beam can impinge on, a concave wall of the core of the anode.
As used herein, the terms “adjoin”, “adjoins”, and “adjoining” mean direct and immediate contact.
As used herein, the term “mm” means millimeter(s).
As used herein, the term “parallel” means exactly parallel, parallel within normal manufacturing tolerances, or nearly parallel, such that any deviation from exactly parallel would have negligible effect for ordinary use of the device.
As used herein, the term “perpendicular” means exactly perpendicular or within 15° of exactly perpendicular. The term “perpendicular” can mean within 0.1°, within 1°, within 5°, or within 10° of exactly perpendicular if explicitly so stated in the claims.
As used herein, “same distance” or similar phrases means exactly the same distance, the same distance within normal manufacturing tolerances, or nearly the same distance, such that any deviation from exactly the same distance would have negligible effect for ordinary use of the device.
As used herein, the term “K*m2/W” means degrees Kelvin times meters squared divided by watts.
As used herein, the term “W/(m*K)” means watts divided by meters and degrees Kelvin.
As used herein, the term “x-ray tube” means a device for producing x-rays, and which is traditionally referred to as a “tube”, but need not be tubular in shape.
As illustrated in
The anode 12 can be optimized for maintaining an internal vacuum, for low cost, and for electron beam spot and x-ray spot size. A hole, defining an electron hole 14, can extend from an electron entry 21 at an exterior 12E of the anode 12 into a core 16 of the anode 12. The electron hole 14 can be aimed to allow the electrons to pass into the core 16 of the anode 12. Another hole, defining an x-ray hole 19, can extend from an x-ray exit 22 at the exterior 12E of the anode 12 into the core 16 of the anode 12, intersecting the electron hole 14 at the core 16 of the anode 12. The x-ray hole 19 can be aimed for emission of the x-rays 18 from the core 16 of the anode 12 out of the x-ray tube 10 or 20. The electron entry 21 and the x-ray exit 22 can be located on different sides of the anode 12. The electron hole 14 and the x-ray hole 19 can form an open bore from the electron entry 21 to the x-ray exit 22. Thus, the bore can be an unobstructed, uninterrupted path from the electron entry 21 to the x-ray exit 22 without passing through any solid materials. The entire bore from the electron entry 21 to the x-ray exit 22 can be exposed to the internal vacuum of the x-ray tube 10 or 20.
In order to minimize electron backscatter from edges and to avoid additional holes for gas leakage, the electron hole 14 and the x-ray hole 19 can form a single bore from the electron entry 21 to the x-ray exit 22. Thus, the only holes into the core 16 of the anode 12 can be the electron hole 14 and the x-ray hole 19. The single bore can comprise, consist essentially of, or consist of the electron hole 14 intersecting with the x-ray exit 22 in the core 16 of the anode 12. The single bore can be seamless. A single, integral, monolithic anode material can form walls of the electron hole 14, the x-ray hole 19, and the core 16.
In contrast, the anode 12 of
The electron hole 14, the x-ray hole 19, or both can have concave walls. The electron hole 14, the x-ray hole 19, or both can have a cylindrical shape. The bore in the anode 12 can be manufactured by boring (e.g. drilling, laser cutting, etc.) two intersecting holes in a block of material.
Smooth and concave walls of the bore can improve transmission of electrons to the target and can improve transmission of x-rays out of the x-ray tube. For example, ≥50%, ≥70%, ≥80%, ≥90%, ≥95%, ≥99%, or all of walls of the bore can be concave. The target material can be located at, and the electron beam can impinge on, a concave wall of the core 16 of the anode 12. This concave wall can be shaped, such as by selection of drill bit size or by other method of forming the bore, for optimal shape of the electron beam 17 spot size on the target material and thus for optimal shape of the x-ray spot size.
A diameter De of the electron hole 14 and a diameter Dx, of the x-ray hole 19 can be similar in size for ease of manufacturing and for improved shaping of the electron beam 17 and the x-ray beam. For example, DS/DL≥0.3, DS/DL≥0.5, DS/DL≥0.7, DS/DL≥0.9, DS/DL≥0.95, or DS/DL≥0.98; where DS is a smallest diameter of one of the electron hole 14 or the x-ray hole 19 and DL is a largest diameter of the other of the electron hole 14 or the x-ray hole 19.
For improved shaping of the electron beam 17, a diameter De of the electron hole 14, measured perpendicular to a longitudinal axis of the electron hole 14, can be sized in relation to a width of an electron spot. The electron spot is an area on the wall of the core 16 of the anode 12 upon which ≥85% of the electron beam 17 impinges. The electron spot can have a length (longest dimension) and a width (longest distance perpendicular to the length). For example, the width of the electron spot can be ≤75% or ≤50% of the diameter De of the electron hole 14.
As shown in
A relationship between a size of the anode 12 and a size of the electron hole 14 can be optimized for improved generation of x-rays, heat transfer, and x-ray emission shape. For example, LA/Le≥1.3, LA/Le1.5, or LA/Le≥1.8 and LA/Le≤2.2, LA/Le≤2.5, or LA/Le≤3; where LA is a length of the anode 12 and Le is a length of the electron hole 14, both lengths parallel to a longitudinal axis of the electron hole 14 (parallel to the first vector V1). For example, DA/De≥1.5, DA/De≥2, or DA/De≥2.5 and DA/De≥3, DA/De≤3.5, or DA/De≤5; where DA is a diameter of the anode 12 and De is a diameter of the electron hole 14, both diameters perpendicular to the longitudinal axis of the electron hole 14. Other relationships between the size of the anode 12 and the size of the electron hole 14 are within the scope of this invention.
The core 16 of the anode 12 can include a target material configured for generation of the x-rays 18 in response to the impinging electrons. The target material can be aligned to face the electron emitter. For simplicity of manufacture, the target material can be integral and monolithic with the anode 12. Material of the anode 12 surrounding the bore can be the target material. A composition of the target material can be the same as a composition of the anode 12. The anode 12 can be the target material. Alternatively, a material composition of the target material can be different from a material composition of the anode 12, allowing more variety of target materials to be used, and saving cost if the material composition of the target material is expensive.
The anode 12 can comprise a material with high atomic number for blocking x-rays from emitting from the x-ray tube 10 or 20 in undesirable directions. For example, the anode 12 can comprise ≥50, ≥75, ≥90, or ≥98 weight percent of materials with atomic number ρ26, ≥29, or ≥74. It can also be helpful for the anode to have relatively high thermal conductivity to conduct heat away from the target material.
One possible composition of the target material and the anode 12 is tungsten and lanthanum oxide. For example, the target material and the anode 12 can each comprise one or more of the following: ≥90, ≥95, ≥97, ≥98, or ≥98.5 weight percent tungsten; ≤99, ≤99.5, ≤99.75, or ≤99.9 weight percent tungsten; ≥0.01, ≥0.05, ≥0.25, ≥0.5, or ≥0.95 weight percent lanthanum oxide; and ≤1, ≤3, or ≤5 weight percent lanthanum oxide. As used herein, the term lanthanum oxide means a chemical compound of lanthanum and oxygen in any ratio, including La2O3 and non-stoichiometric combinations of lanthanum and oxygen.
An electrically-insulative enclosure 13 can be attached or sealed to the cathode 11 and the anode 12, can electrically insulate the cathode 11 from the anode 12, and can have an interior through which the electron beam can pass. Examples of material composition of the electrically-insulative enclosure 13 include ceramic, glass, or combinations thereof.
As illustrated in
As illustrated in
Material of construction of the x-ray window 23 in
Thickness Th23 of the x-ray window 23 in
As illustrated in
The heat sink 35 can be thermally coupled to the anode 12. As used herein, the term “thermally coupled” means that the coupled devices are joined by materials or methods for reducing resistance to heat transfer. The heat sink 35 can be in thermal contact with the anode 12. As used herein, the term “thermal contact” means that the devices in thermal contact with each other are (a) directly touching; or (b) not directly touching but all material(s) between the devices have a coefficient of thermal conductivity of at least 1 W/(m*K). The term “thermal contact” can mean not directly touching but connected by material(s) having a coefficient of thermal conductivity of ≥2 W/(m*K), ≥20 W/(m*K), ≥50 W/(m*K), ≥100 W/(m*K), or ≥200 W/(m*K) if explicitly so stated in the claims. For example, a thermal grease or thermal paste can adjoin the heat sink 35 and the anode 12. Thus, for example, thermal resistance for conduction times area of heat transfer between target material of the anode 12 and the heat sink 35 can be ≤0.01 K*m2/W, ≤0.001 K*m2/W, or ≤0.0005 K*m2/W.
The heat sink 35 can extend away from the anode 12 towards the cathode 11 along a heat sink longitudinal axis 33. The heat sink 35 can have a base 31 and a fin 34 extending from the base 31. The fin 34 can be a single continuous fin wrapping multiple times around the base 31. The fin 34 can be a plurality of wires extending away from the base 31.
The fin 34 can comprise an array of fins 36, which can be arrayed along the heat sink longitudinal axis 33. Fins 34 of the array of fins 36 can be parallel with respect to each other. Each fin 34 of the array of fins 36 can extend from the base 31 in a direction perpendicular to or parallel to the heat sink longitudinal axis 33 (i.e. a plane of each fin 34 can be perpendicular to or parallel to the heat sink longitudinal axis 33) depending on direction of air flow. For example, the fins 34 of x-ray sources 30, 40, 50, and 70 extend from the base 31 in a direction perpendicular to the heat sink longitudinal axis 33. As another example, the fins 34 of x-ray source 90 extend from the base 31 in a direction parallel to the heat sink longitudinal axis 33, as shown in
As illustrated in
Outermost fins 34o can be wider than inner fins 34i (fins 34 between the two outermost fins 34o). The inner fins 34i (
A maximum width WG (
As shown in
As illustrated in
As illustrated in
The array of fins 36 can include two opposite flat sides F at the outer perimeter 72 facing in opposite directions and located between the convex shapes of the fins. Each opposite flat side F can provide a surface for mounting a fan 71. As illustrated in
The fins 34 at the two opposite flat sides F at a location closest to the base 31 can have a small maximum height H or can be completely removed. For example, a maximum height H of each of the fins at the two opposite flat sides can be ≤0.5 mm, ≤1 mm, or ≤3 mm.
For improved heat transfer, the base 31 can have a tapered increase in thermal resistance for conduction moving away from the anode 12. For example, the thermal resistance for conduction of the base farthest from the anode 12 can be ≥1.5 times, ≥2 times, ≥3 times, or ≥5 times the thermal resistance for conduction of the base nearest the anode 12.
Referring again to
A hole or bore can extend through the base 31. This bore can be aligned with the heat sink longitudinal axis 33. The bore can have opposite ends with the x-ray tube 10, 20, 42, or 51 mounted at one of the ends. The x-ray tube, cables 32 for providing electrical power to the x-ray tube, or both, can pass through the bore.
As illustrated in
The method can further comprise inserting target material 101 through the electron hole 14, the x-ray hole, or both into the core. The target material 101 can then be brazed, pressed, or both onto a wall of the core 16. A material composition of the target material 101 can be different from a material composition of the anode 12. An order of steps of the method can be boring the electron hole 14; inserting the target material 101; brazing the target material 101, pressing the target material 101, or both onto the wall of the core 16; then boring the x-ray hole 19. An alternative order of steps of the method can be boring the x-ray hole 19; inserting the target material 101; brazing the target material 101, pressing the target material 101, or both onto the wall of the core 16; then boring the electron hole 14.
As illustrated in
Following are additional, possible variations of the method. The following variations can be combined in any order. Material composition of the anode 12 can be as described above. The anode 12 can be a single, integral, monolithic material. The electron hole 14 and the x-ray hole 19 can form a seamless bore from the electron entry 21 to the x-ray exit 22. Part or all of the walls of the electron hole 14, the x-ray hole 19, or both can be concave, such as with percentages described above. An angle A1 between a first vector V1 and a second vector V2 can have values as described above. Length LA of the anode 12, diameter DA of the anode 12, length Le of the electron hole 14, diameter De of the electron hole 14, and DS/DL, can have values and relationships as described above.
Priority is claimed to co-pending U.S. Provisional Patent Application Ser. No. 62/667,721, filed May 7, 2018, which is hereby incorporated herein by reference.
Number | Date | Country | |
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62667721 | May 2018 | US |