X-RAY MACHINE
20220285120 · 2022-09-08
Assignee
Inventors
- Karl E. Swanson (Davenport, IA, US)
- John Charles Drenter (Davenport, IA, US)
- Paul Michael Fletcher (Chelmsford, MA, US)
Cpc classification
International classification
Abstract
An x-ray apparatus includes a vacuum chamber that includes a window for exit of x-rays. Electrons are generated at a cathode within the vacuum chamber and accelerated toward a target anode associated with the window. An x-ray generating layer is included as a surface of the target anode to receive the electrons emitted by the cathode and to create x-rays. A blocking path blocks over 70% of the free electrons reaching said target anode from continuing on to exit through the window, while allowing x-rays leaving the x-ray generating layer to continue along the selectively blocking path to exit through the window. The x-ray apparatus is capable of operating at low voltage and relatively high power to reduce the necessary shielding and the corresponding weight of the apparatus yet allow more ready absorption of x-rays by items being irradiated.
Claims
1. An x-ray apparatus, comprising: a vacuum chamber having a window for exit of x-rays, said window having an exterior surface outside of the vacuum in the vacuum chamber; a cathode within said vacuum chamber; a target anode associated with said window, said target anode having an interior surface within said vacuum chamber; a less than 400 kV but more than 80 kW power supply connected between said cathode and target anode whereby free electrons are accelerated in their flow from said cathode to said target anode within said vacuum chamber; said interior surface of said target anode comprising an associated x-ray generating layer comprising one or more of an element with an atomic number equal to or greater than 73; a selectively blocking path beginning at the x-ray generating layer and continuing through the remaining portion of said target anode where said selectively blocking path blocks over 70% of the free electrons reaching said target anode from continuing on to exit through the window, while allowing x-rays leaving the x-ray generating layer to continue along the selectively blocking path to exit through the window; and a liquid cooling pathway associated with said target anode between said x-ray generating layer and the exterior surface of the window for heat transfer from the target anode.
2. The x-ray apparatus of claim 1, in which said cathode comprises at least 4 separate and non-collinear filaments.
3. The x-ray apparatus of claim 1, in which said target anode has a solid structure, the majority of which comprises aluminum, wherein the liquid in the cooling pathway comprises water, and wherein the x-ray generating layer comprises gold.
4. The x-ray apparatus of claim 1, in which said selectively blocking path beginning at the x-ray generating layer and continuing through the remaining portion of said target anode blocks over 95% of the free electrons reaching said target anode from continuing on to exit through the window, while allowing x-rays leaving the x-ray generating layer to continue to exit through the window.
5. The x-ray apparatus of claim 1, in which over 60% of the x-rays generated in said x-ray generating layer proceed in a path within 30° of a line through the nearest point on the cathode and a point of generation of the x-ray, as measured with a vertex of the 30° measurement at the point of generation and extending outward through the window.
6. An x-ray apparatus, comprising: a vacuum chamber having a wall and a window in said wall to allow exit of x-rays with a vacuum existing in said vacuum chamber; a cathode assembly housed within said vacuum chamber, wherein said cathode assembly includes at least four non-contiguous filaments; a liquid cooled window anode that incorporates a cooling path in which sides of the cooling path provide structural support for the window to keep a vacuum in said chamber; a power supply connected between said cathode assembly and window anode, whereby free electrons are accelerated in their flow from said cathode assembly to said window anode within said vacuum chamber; and said window anode containing a thin layer of a target material that has an atomic number equal to or greater than 73, whereby the thin layer is of sufficient thickness that a majority of electrons reaching the window anode will be absorbed by said thin layer and whereby the thin layer is of sufficient thinness that resulting x-rays can exit the other side of said thin layer and thereafter exit from the window anode through the window.
7. The x-ray apparatus of claim 6, further comprising: a reaction chamber having one or more shielded sides, said reaction chamber being configured to hold a product to be treated; and positioned to receive x-rays passing through said window and into said reaction chamber for irradiation of a product to be treated in said reaction chamber.
8. The x-ray apparatus of claim 6, in which the thin layer is gold or platinum.
9. The x-ray apparatus of claim 8, in which the thin layer is gold.
10. The x-ray apparatus of claim 8, in which the thin layer is on adjacent curved surfaces made of aluminum or copper.
11. The x-ray apparatus of claim 10, wherein said window anode has a base plate formed from aluminum.
12. The x-ray apparatus of claim 11, wherein said base plate includes stepped surfaces in which risers of said stepped surfaces have sides perpendicular to parallel surfaces of said stepped surfaces.
13. The x-ray apparatus of claim 6, wherein said cooling path is between a base plate with stepped surfaces and curved segments coated with the target material.
14. The x-ray apparatus of claim 6, wherein a voltage difference between said cathode assembly and said target material is less than 400 kV.
15. The x-ray apparatus of claim 14, in which the voltage difference between said cathode assembly and said target material is between 200 kV and 320 kV.
16. The x-ray apparatus of claim 6, wherein a majority of sides of said reaction chamber average shielding of less than the equivalent of 2.0 inches of lead shielding.
17. The x-ray apparatus of claim 6, wherein a majority of sides of said reaction chamber average shielding of less than the equivalent of 1.5 inches of lead shielding.
18. The x-ray apparatus of claim 17, in which the lead shielding is no more than 1.25 inches.
19. An x-ray apparatus with modular cathodes and modular anodes within one vacuum chamber, comprising: a vacuum chamber; a cathode assembly housed within said vacuum chamber, wherein said cathode assembly includes at least four modular filaments units, each containing a separate filament; a liquid cooling source; an anode target assembly, including a plurality of modular anode target units each a. containing a material that generates x-rays when struck by free electrons, b. containing a cooling pathway which couples to the cooling pathway in an adjacent modular anode target unit, with said cooling liquid source connected to these pathways; and a window configured to allow passage of the x-rays generated by said anode target assembly to create a radiation zone outside of said vacuum chamber.
20. The x-ray apparatus of claim 19 in which said modular target anode units are arranged in a parallel linear array.
21. The x-ray apparatus of claim 20, in which said modular filament units have filaments that resemble a straight line, and are arranged with the filament in each modular filament unit being parallel to the filament in another modular filament unit.
22. The x-ray apparatus of claim 21, in which there are at least 4 modular filament units and 4 modular target units.
23. The x-ray apparatus of claim 22, in which there are at least 10 modular filament units and 10 modular target units.
24. The x-ray apparatus of claim 20, in which said window comprises adjacent modular anode assemblies.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
DESCRIPTION OF THE SELECTED EMBODIMENTS
[0022] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates. One embodiment of the invention is shown in great detail, although it will be apparent to those skilled in the relevant art that some features that are not relevant to the present invention may not be shown for the sake of clarity.
[0023]
[0024] A cross-sectional front view of the x-ray apparatus 10 is illustrated in
[0025] In the embodiments shown in
[0026] The walls 22 of the reaction chamber 20 have a thickness that may include shielding to prevent x-rays that are introduced into the reaction chamber from escaping into the environment exterior to the reaction chamber. The thickness of the walls 22 may be modified to increase or decrease the amount of shielding as desired. In some embodiments, the majority of the walls 22 of the reaction chamber comprise average shielding of less than the equivalent of 2.0 inches of lead shielding. In other embodiments, the majority of area of the walls 22 of the reaction chamber comprise average shielding of less than the equivalent of 1.5 inches of lead shielding. In one example, the shielding is no more than the equivalent of 1.25 inches of lead. As an alternative, the reaction chamber may not be the only component with substantial shielding, but the entire unit itself, including the x-ray generating portion as well as the reaction chamber and pathways leading to and from it, may be shielded by side walls of comparable thickness to those described above for the reaction chamber, as schematically depicted in
[0027] A cross-sectional perspective view of some components within the vacuum chamber 15 is shown in
[0028] The form grid 34 has a semi-circular shape that surrounds a portion of the filament 32. In other embodiments, different shapes may be used for the form grid 34. Additionally, in other embodiments, the form grid 34 may surround more or less of the filament 32, including the possibility of having no form grid. As shown in
[0029] In the embodiment shown, the cathode assembly 30 is arranged horizontally within the vacuum chamber 15. However, in other embodiments, the cathode assembly 30 may be arranged in a different orientation depending on the orientation of the vacuum chamber 15. As an example, the cathode assembly 30 may be arranged vertically or in an angled orientation. The reaction chamber 20 may be positioned accordingly to receive radiation created in the vacuum chamber 15 and exiting through the window 50.
[0030] In some embodiments, rather than having an array of multiple filaments, a single, large filament may be included in cathode assembly 30. The single filament may be used to heat either a single cathode or multiple cathodes that radiate electrons that may be used to create x-rays. Having multiple cathodes covering a larger area in a non-collinear manner may have an advantage in creating a more uniform distribution of electrons that may provide a more desirable and more uniform pattern of resulting x-rays. Ideally, the multiple cathodes are made of many similar modules placed in a line or in an array, with each module containing a filament that is positioned in a non-collinear orientation to another filament in another module, with all of these multiple cathode modules being in the same vacuum chamber.
[0031] In the embodiment shown in
[0032] A target assembly 60 is supported by the window 50 and positioned within the vacuum cavity 18. The target assembly 60 includes an array of targets 62 (see
[0033] The cooling fluid may be provided to the cooling passage 68 from a cooling source 14 (see
[0034] The target sheet 64 is made from a base material and plated with an x-ray generating layer 65 that is suitable for generation of x-rays upon impingement of electrons produced by the cathode assembly 30. The x-ray generating layer 65 may be added electro-chemically, mechanically, vapor depositing, sputtering, or by any other suitable process. Typically, the base material of the target sheet 64 is a metal that has a lower atomic number (a low Z material) such as aluminum, beryllium, or another suitable metal. The plating material is typically a material that has a high atomic number such as tungsten, gold, rhenium, platinum, iridium, lead or other similar materials. In some embodiments, the target sheet 64 is plated with a material that has an atomic number that is equal to or greater than 73. Using a thin layer of a relatively high atomic number material as the plating material increases the x-ray dose rate that is applied to the product in the reaction chamber 20 and minimizes the absorption of the x-rays as they are transmitted from the vacuum chamber 15 to the reaction chamber 20.
[0035] As shown in
[0036] Each target sheet 64 is associated with a corresponding target anode module that has a cooling passage, structural support and an inner x-ray generating layer. By using such a modular approach, machines of different capacity can readily be made by changing the number of modules for both the cathodes and anodes, as the modules for each can be made the same width. The top surface 67 of the base plate 66 may be a stepped surface. The top surface 67 is formed by several parallel surfaces such as 67a, 67b, and 67c of varying heights. The parallel surfaces are connected to adjacent parallel sides by risers 67x, 67y, and 67z that are perpendicular to the parallel surfaces. The stepped top surface 67 helps to distribute the cooling fluid evenly over the width of the base plate 66 to increase the cooling effect of the cooling fluid. However, in other embodiments, the top surface 67 may have any other desired shape that still allows for a cooling passage 68 between the target sheet 64 and the base plate. As an example, the top surface 67 may be curved to match the arch of the target sheet 64, or the top surface 67 of the base plate 66 may be flat. The entire array may be unitary and may be cast, extruded, or drilled or otherwise machined as desired, to provide the desired cooling fluid passages, while being coated on the inner side that is in the vacuum chamber with a thin layer of x-ray generating material.
[0037] The target assembly 60 in combination with the window 50 acts as an anode for operation with the cathode assembly 30. The power supply 12 connected between the cathode assembly 30 and the target assembly 60, provides a voltage difference between them so that electrons generated at the filaments 32 of the cathode assembly 30 are accelerated toward the target assembly 60 and impinge on the targets 62 to generate x-rays. In some embodiments, a negative voltage is generated at the cathode assembly 30 and the target assembly 60 may be grounded or given a positive voltage to create the voltage difference between the cathode assembly 30 and the target assembly 60. The electron accelerating voltage and current may be selected to achieve the highest x-ray dose rate for the product to be irradiated while staying within the limitations of the high voltage power source and shielding limitations.
[0038] The combination of the target assembly 60 and the window 50 forms an electron blocking path that begins at the x-ray generating layer 65 and continues through the window 50 to the exterior of the vacuum chamber 15. This electron blocking path includes the base material of the target sheet 64 as well as the base plate 66 and the window. The blocking path blocks at least 70% of the free electrons that are generated at the cathode assembly 30 and reach the target assembly 60 from continuing through the window 50 and exiting into the reaction chamber 20. However, the electron blocking path allows x-rays that are generated at the x-ray generating layer 65 of the target 62 to continue along the blocking path and to exit through the window 50 into the reaction chamber 20. The materials used for the target sheet 64, the base plate 66, and the window 50 may be chosen to maximize the number of electrons that are blocked and to maximize the number of x-rays that are allowed to pass through to the reaction chamber 20. In other embodiments, more or fewer free electrons may be blocked by the blocking path. For example, in some embodiments, the selectively blocking path blocks over 95% of the free electrons reaching the target assembly 60 from continuing on to exit through the window 50.
[0039]
[0040] In some embodiments, the electron accelerating voltage between the cathode and the anode may be less than 400 kV and more preferably less than 320 kV, while the power provided by the power supply 12 is greater than 80 kW and more preferably greater than 120 kW and most preferably at about 200 kW or greater. In other embodiments, the voltage may be in a range between 200 kV and 320 kV. The combination of relatively low voltage and relatively high power allows for several benefits with respect to irradiation, curing, inactivation, disinfection, or sterilization of the products that are inserted into the reaction chamber 20. The low voltage allows treatment of smaller boxes and packages. Higher energy x-rays would have a tendency to pass through these smaller boxes and packages without providing sufficient radiation to sterilize the products within the box or package in a short enough time. The use of a lower voltage produces lower energy x-rays that will be absorbed more readily by a smaller box.
[0041] The use of lower voltages that create lower energy x-rays also reduces the amount of shielding that is needed to prevent exposure to the x-rays in the environment exterior to the reaction chamber 20. Reduced shielding decreases the cost of the x-ray apparatus 10 and decreases the weight and size of the x-ray apparatus 10. The decreased size and weight of the x-ray apparatus 10 makes the x-ray apparatus 10 more suitable for inclusion on an assembly line with other processing machines. The large, wide array created by having multiple filaments 32 and multiple targets 62 enables the x-ray apparatus 10 to provide high power with relatively lower energy x-rays to irradiate more material with reduced shielding and lower cost.
[0042] The arrangement of the window 50 and the target assembly 60 shown in
[0043] The dimensions of the x-ray apparatus 10 shown in
[0044] Although reaction chamber 20 is shown as a singular chamber useful for batch processing in
[0045] In this embodiment, the reaction chamber 120 surrounds a portion of the conveyor system 110. The walls 122 of the reaction chamber 120 provide shielding that prevent harmful x-ray radiation from escaping to the surrounding environment. As shown, in some embodiments, the reaction chamber 120 may have an input path 124 and an output path 126. The reaction chamber 120 input and output paths may also include turns or 90 degree angles that aid in shielding the radiation produced by the x-ray apparatus 10. As with the reaction chamber 20 already described, the low voltage, high power characteristics of the x-ray apparatus 10 helps to minimize the amount of shielding necessary and can increase the rate of absorption of the x-rays in small products being irradiated. Reduced shielding decreases the weight and cost of the reaction chamber 120 and allows for greater portability and reduces the footprint of the x-ray apparatus 10 and the reaction chamber 120 to allow for efficient placement on the conveyor system 110.
[0046] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the inventions defined by following claims are desired to be protected. All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference and set forth in its entirety herein.