Patent Application
20240120167
The present application is related to x-ray sources.
X-rays have many uses, including imaging, x-ray fluorescence analysis, x-ray diffraction analysis, and electrostatic dissipation. A large voltage between a cathode and an anode of an x-ray tube, and sometimes a heated filament, can cause electrons to emit from the cathode to the anode. The anode can include a target material. The target material can generate x-rays in response to impinging electrons from the cathode.
As used herein, the terms “adjacent, “on”, “located on”, “located at”, and “located over” mean on or nearby. The terms “located directly on”, “adjoin”, “adjoins”, and ˜adjoining” mean direct and immediate contact.
As used herein, the term “x-ray tube” is not limited to tubular/cylindrical shaped devices. The term “tube” is used because this is the standard term used for x-ray emitting devices.
As used herein, the term “+/−” means plus or minus. Thus, “53+/−5” means 48-58.
Unless explicitly noted otherwise herein, all temperature-dependent values are such values at 25° C.
X-rays, generated in an x-ray tube, can emit in all directions. It is normally desirable to block x-rays emitted in undesirable directions, and allow x-rays to emit only in a desired direction. Material used for blocking these x-rays can be heavy. The weight of the shielding materials can be particularly problematic for hand-held x-ray sources. The invention herein improves x-ray tube shielding with less weight, which is ergonomically advantageous.
X-ray tubes can be hermetically-sealed with an internal vacuum. As the x-ray tube expands and contracts during heating and cooling, the hermetic seal can be damaged, thus causing the x-ray tube to lose vacuum and fail. This heating and cooling can occur during manufacturing braze sealing or during operation of the x-ray tube. The invention herein provides a more robust hermetic seal, particularly as the x-ray tube is heated and cooled. Thus, the x-ray tube designs herein can have a longer life, which saves cost and minimizes adverse impact on the environment, due to less waste.
As illustrated in
The x-ray tubes 10, 20, and 30 can include a proximal-housing 13 and a distal-housing 14. The proximal-housing 13 can be located closer to the cathode 11, and the distal-housing 14 can be located farther from the cathode 11. The proximal-housing 13 and the distal-housing 14 can be separate components, spaced apart from each other.
An internal-cavity 17 can extend through a core of the proximal-housing 13 and the distal-housing 14. The internal-cavity 17 can be aligned for a straight-line-axis 18 to extend from an electron-emitter at the cathode 11, through the internal-cavity 17, to a target 21 at the anode 12. The internal-cavity 17 can be unobstructed by any solid material along the straight-line-axis 18.
The proximal-housing 13 can have a far-end 13f that is farthest from the cathode 11. The distal-housing 14 can have a near-end 14n that is nearest to the cathode 11. The proximal-housing 13 and the distal-housing 14 can be connected to each other by a hermetic-seal 25 at the far-end 13f of the proximal-housing 13 and the near-end 14n of the distal-housing 14.
The hermetic-seal 25 can include an interface-ring 15 bonded to and between the proximal-housing 13 and the distal-housing 14. The interface-ring 15 can have a coefficient of thermal expansion (CTEr) that is similar to a coefficient of thermal expansion (CTEp) of the proximal-housing 13 and/or that is similar to a coefficient of thermal expansion (CTEd) of the distal-housing 14. Thus, the interface-ring 15 can expand and contract with the proximal-housing 13 and the distal-housing 14 during heating and cooling. This can reduce failure of the hermetic-seal 25.
For example, 0.3≤CTEr/CTEp, 0.5≤CTEr/CTEp, or 0.7≤CTEr/CTEp; CTEr/CTEp≤1.4, CTEr/CTEp≤2, or CTEr/CTEp≤3.3; 0.3≤CTEr/CTEd, 0.5≤CTEr/CTEd, or 0.7≤CTEr/CTEd; and/or CTEr/CTEd≤1.4, CTEr/CTEd≤2, or CTEr/CTEd≤3.3.
The proximal-housing 13 and the distal-housing 14 can be made of glass or ceramic. The interface-ring 15 can include at least 95 weight percent iron, nickel, and cobalt. The interface-ring 15 can include 53+/−5 weight percent iron, 29+/−5 weight percent nickel, 17+/−5 weight percent cobalt, and total weight percent of all chemical elements equal to 100%. Other materials, such as copper or nickel can have a compatible coefficient of thermal expansion and other acceptable physical characteristics. The interface-ring 15 can include copper, nickel, or both.
The x-ray tubes 10, 20, and 30 can further comprise a blocking-ring 16. The blocking-ring 16 can be proximate to, adjacent to, or can adjoin, the interface-ring 15. For better blocking of x-rays, the blocking-ring 16 can be closer to the cathode 11 than the interface-ring 15. Alternatively, the interface-ring 15 can be closer to the cathode 11 than the blocking-ring 16. The blocking-ring 16 can be encircled by the proximal-housing 13, by the distal-housing 14, or by both. As illustrated in
The blocking-ring 16 can include a material with a high atomic number, such as for example at least 72. It is preferable that the blocking-ring 16 includes tungsten, because tungsten is effective at blocking x-rays, and is also compatible with the vacuum within the x-ray tube. It is preferable that the blocking-ring 16 does not include lead because lead can be incompatible with the internal vacuum of the x-ray tube. For X-ray tubes which operate at intermediate energy levels, the blocking ring could be made from lower atomic number materials, such as molybdenum or niobium. For X-ray tubes which operate at even lower energies, the blocking-ring 16 can include a material with a lower atomic number, such as for example at least 21 or at least 30.
There can be a hole 22 extending through the interface-ring 15 and the blocking-ring 16. The hole 22 can be aligned to allow electrons from the electron-emitter to pass through the hole 22 to the target 21. The straight-line-axis 18 can extend through the hole 22.
The x-ray tubes 10, 20, and 30 can also include a blocking-enclosure 23. The blocking-enclosure 23 can surround the distal-housing 14 except at its near-end 14n, at an opening 24 aligned for intended emission of x-rays, and at an entrance for a wire 27 for providing voltage to the anode 12 (
The distal-housing 14 can have a distal-end 14d farthest from the cathode 11 and a midpoint 14m that is half-way between the near-end 14n and the distal-end 14d of the distal-housing 14. The blocking-enclosure 23 can be spaced apart from the distal-housing 14 from the midpoint 14m to the distal-end 14d of the distal-housing 14. The blocking-enclosure 23 can adjoin the distal-housing 14 at its near-end 14n.
The blocking-enclosure 23 can be configured to block x-rays in undesirable directions. Thus, the blocking-enclosure 23 can include a material with an atomic number of at least 72. Example materials of the blocking-enclosure 23 include lead, tungsten, or both. The lead and/or tungsten can be suspended in a carrier material such as a polymer or metal matrix for casting or molding of the blocking-enclosure 23. The blocking-enclosure 23 can be electrically insulative or can be electrically conductive.
As illustrated in
Example preferred relationships between the maximum outer diameter Dp of the proximal-housing 13 and the maximum outer diameter Dd of the distal-housing 14 include the following: Dp/Dd≥1.1, Dp/Dd≥1.25, or Dp/Dd≥1.5; and/or Dp/Dd≤2.5, Dp/Dd≤4, or Dp/Dd≤10.
For improved blocking of x-rays, it is preferable for a minimum inner diameter Di of the proximal-housing 13 to be greater than the maximum outer diameter Dd of the distal-housing 14 (Di>Dd).
Example preferred relationships between the minimum inner diameter Di of the proximal-housing 13 and the maximum outer diameter Dd of the distal-housing 14 include the following: Di/Dd≥1.05, Dp/Dd≥1.15, or Dp/Dd≥1.25.
Due to the overall configuration of the x-ray tube, with a smaller outer diameter Dp of the proximal-housing 13, and with the blocking-enclosure 23, a large percent of x-rays can be blocked, except those emitted through the opening 24. For example, at least 75%, at least 90%, or at least 99% of x-rays generated in the target can be blocked from escaping the x-ray tube except through the opening 24.
The cathode 11 and the anode 12 can be electrically insulated from one another by the proximal-housing 13 and by the distal-housing 14. Thus, the proximal-housing 13 and the distal-housing 14 can be electrically insulative. The proximal-housing 13 and the distal-housing 14 can be ceramic or glass. In this example, structure 26 can be part of the cathode, structure 28 can be part of the anode, and both can be electrically conductive.
Alternatively, the proximal-housing 13 and the distal-housing 14 can be electrically conductive. The proximal-housing 13 and the distal-housing 14 can be metallic. In this example, structure 26 and structure 28 can be electrically insulative.
This application claims priority to U.S. Provisional Patent Application No. 63/415,195, filed on Oct. 11, 2022, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63415195 | Oct 2022 | US |
