Patent Application
20240021400
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 the 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 “on”, “located on”, “located at”, and “located over” mean located directly on or located over with some other solid material between. The terms “located directly on”, “adjoin”, “adjoins”, and “adjoining” mean direct and immediate contact.
As used herein, the term “same cross-sectional area” means exactly the same wire cross-sectional area; the same wire cross-sectional area within normal manufacturing tolerances; or almost exactly the same wire cross-sectional area, such that any deviation from exactly the same wire cross-sectional area would have negligible effect for ordinary use of the device.
As used herein, the term “same thickness” means exactly the same thickness; the same thickness within normal manufacturing tolerances; or almost exactly the same thickness, such that any deviation from exactly the same thickness would have negligible effect for ordinary use of the device.
As used herein, the term “same width” means exactly the same width; the same width within normal manufacturing tolerances; or almost exactly the same width, such that any deviation from exactly the same width would have negligible effect for ordinary use of the device.
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.
In comparison of thicknesses, if the region has multiple thicknesses, then the largest thickness in the region is used for the comparison. In comparison of widths, if the region has multiple widths, then the largest width in the region is used for the comparison.
There are advantages to having a different filament cross-sectional area at different locations, including (a) focused and increased emission of electrons from a center of the filament, (b) increased rate of filament temperature rise, and (c) stabilization of vulnerable locations of the filament.
In regions of smaller cross-sectional area, there can be higher current density, and thus increased heating of the wire. In regions of larger cross-sectional area, there can be lower current density, and thus decreased heating of the wire. This increased and decreased heating affects overall wire temperature. By adjusting the cross-sectional area of the wire at different locations, electron emission can be largely confined to preferential region(s), such as a center of the filament. For example, ≥50% or ≥90% of electrons can be emitted from a central 25% of the filament.
A center-region 14 of the filament can be wider, to increase area for electron emission. The center-region 14 can also be thinner, to increase current density and heating at the center. Thus, a wider and thinner center-region 14 of the filament can work together to increase electron emission from this center-region 14. This wider and thinner center-region 14 can also increase the rate of temperature rise in the filament, allowing more rapid pulses of electron emission. The center-region 14 of the filament can be wider, thinner, or both than any other part of the filament.
Typically, a filament has a higher temperature at its center-region 14. As a result of this higher temperature, grain structure can be different at the center-region than at outer ends. The filament can prematurely cleave at a transition between these locations of different grain structure. It can be beneficial to strengthen this location by increasing the filament's cross-sectional area at such location. An area of the filament with increased cross-sectional area can have more grains and more grain boundaries, and thus can be stronger.
The filaments herein can be planar and spiral. These filaments can include an elongated wire extending non-linearly in a plane 31 (see
One benefit of a spiral shape can be avoiding corners of a zig-zag shape. Another benefit can be a central, circular region of electron emission, resulting in a central, circular region of x-ray emission at the target 104 (
The filament can include a spiral segment with the elongated wire forming at least one complete revolution about an axis 16 at a center-region 14, on both sides of the axis 16. Thus, the filament can form a double spiral shape oriented parallel to the plane 31.
As illustrated in
As illustrated in
As illustrated in
For the filaments herein, different regions can have different cross-sectional areas (A12, A11, A13) relative to each other, and thus different current density relative to each other, for shaping of the electron beam and/or strengthening selected regions of the filament. The cross-sectional area (A12, A11, A13) can be the wire width times thickness for a square or rectangular wire.
For example, the low-region 12 can have a wire cross-sectional area A12 that is larger than a wire cross-sectional area A11 of an adjacent outer-high-region 11. Here are example relationships between the cross-sectional area. A12 of the wire in the low-region 12 compared to the cross-sectional area A11 of the wire in the outer-high-region 11: A12>A11, A12/A11≥1.05, A12/A11≥1.1, A12/A11≥1.2, A12/A11≥1.5, A12/A11≥2, A12/A11≥3, or A12/A11≥4.
Due to this difference in wire cross-sectional area A12 and A11, the low-region 12 can have lower current density than a current density of the adjacent outer-high-region 11. For example, each low-region 12 can have at least 10% less, at least 15% less, at least 25% less, or at least 50% less current density during operation as in the adjacent outer-high-region 11.
The low-region 12 can have a wire cross-sectional area A12 that is larger than a wire cross-sectional area A13 of an adjacent central-high-region 13. Here are example relationships between the cross-sectional area A12 of the wire in the low-region 12 compared to the cross-sectional area. A13 of the wire in the central-high-region 13: A12>A13, A12/A13≥1.05, A12/A13≥1.1, A12/A13≥1.2, A12/A13≥1.5, A12/A13≥2, A12/A13≥3, or A12/A1.3≥4.
Due to this difference in wire cross-sectional area A12 and A13, the low-region 12 can have lower current density than a current density of the adjacent central-high-region 13. For example, each low-region 12 can have at least 10% less, at least 15% less, at least 25% less, or at least 50% less current density during operation as in the adjacent central-high-region 13.
The center-region 14 can have a wire cross-sectional area A14 that is larger than a wire cross-sectional area A13 of adjacent central-high-regions 13. Here are example relationships between the cross-sectional area. A14 of the wire in the center-region 14 compared to the cross-sectional area A13 of the wire in the central-high-region 13: A14<A13, A14/A13≥1.05, A14/A13≥1.1, A14/A13≥1.2, A14/A13≥1.5, A14/A13≥2, A14/A13≥3, or A14/A13≥4.
Due to this difference in wire cross-sectional area A14 and A13, the center-region 14 can have lower current density than a current density of the adjacent central-high-regions 13. For example, the center-region 14 can have at least 10% less, at least 15% less, at least 25% less, or at least 50% less current density during operation as in the adjacent central-high-region(s) 13.
Each central-high-region 13 can have ≥1.05 times, ≥1.1 times, ≥1.2 times, ≥1.5 times, ≥2 times, or ≥4 times as much current density during operation as in the low-region 12 and/or in the center-region 14 adjacent to the central-high-region 13.
The above relationships, of different area values of different regions, can be due to different widths, different thicknesses, or both. Different widths are illustrated in
Here are example relationships between the width W12 of the wire in the low-region 12 compared to the width W11 of the wire in the outer-high-region 11: W12>W11, W12/W11≥1.05, W12/W1≥1.1, W12/W11≥1.2, W12/W11≥1.5, W12/W11≥2, W12/W11>3, or W12/W11≥4. Here are example relationships between the width W12 of the wire in the low-region 12 compared to the width W13 of the wire in the central-high-region 13: W12>W13, W12/W13≥1.05, W12/W13≥1.1, W12≥W13≥1.2, W12/W13≥1.5, W12/W13, W12/W13≥3, or W12/W13≥4. Here are example relationships between the width W14 of the wire in the center-region 14 compared to the width W13 of the wire in the central-high-region 13: W14>W13, W14/W13≥1.05, W14/W13≥1.1, W14/W13≥1.2, W14/W13≥1.5, W14/W13≥2, W4/W13≥3, or W14/W13≥4.
Here are example relationships between the thickness T12 of the wire in the low-region 12 compared to the thickness T11 of the wire in the outer-high-region 11: T12>T11, T12/T11≥1.05, T12/T11≥1.1, T12/T11≥1.2, T12/T11≥1.5, T12/T1≥2, T12/T11≥3, or T12/T11≥4. Here are example relationships between the thickness T12 of the wire in the low-region 12 compared to the thickness T13 of the wire in the central-high-region 13: T12>T13, T12/T13≥1.05, T12/T13≥1.1, T12/T13≥1.2, T12/T13≥1.5, T12/T13≥2, T12/T13≥3, or T12/T13≥4. Here are example relationships between the thickness 114 of the wire in the center-region 14 compared to the thickness T13 of the wire in the central-high-region 13: T14>T13, T14/T13≥1.05, T14/T13≥1.1, T14/T13≥1.2, T14/T13≥1.5, T14/T13≥2, T14/T13≥3, or T14/T13≥4.
As illustrated in
The thin-region 72 can be thinner than the pair of thick-regions 71. This can increase current density in the thin region 72, which can be located at a center of the wire. This increased current density can increase wire temperature in this region of desired electron emission. For example, T71/T72≥1.05, T71/T72≥1.1, T71/T72≥1.2, T71/T72≥1.5, T71/T72≥2, T71/T72≥3, or T71/T72≥4. T71 is a thickness of the wire in the pair of thick-regions 71. T72 is a thickness of the wire in the thin-region 72.
The thin-region 72 can be wider than the pair of thick-regions 71. This can increase area for electron emission. For example, W72/W71≥1.05, W72/W71≥1.1, W72/W71≥1.2, W72/W71≥1.5, W72/W71≥2, W72/W71≥3, or W72/W71≥4. W72 is a width of the wire in the thin-region 72. W71 is a width of the wire in the pair of thick-regions 71.
Junctions between each thick-region 71 and the thin-region 72 can be located in a central 25% of a length of the wire. The thin-region 72 can be located entirely in a central 25% of a length of the wire.
Thus, making the wire thinner (to increase current density) and making the wire wider (to increase area for electron emission) can greatly increase electron emission at a center of the filament. This can result in a small, focused electron spot at the target.
In any filament described herein, to avoid sharp electrical field gradients, there can be a smooth transition of cross-sectional area of the wire between regions.
As illustrated in
As illustrated in
This smooth transition of width, thickness, or both can be any non-abrupt transition. The transition can be linear, a chamfer, curved, etc. A transition length L can be at least 30% of a transition height H (L≥0.3*H). See
A junction between each low-region 12 and the central-high-region 13 it is adjacent to can be located in a central 25% of a length of the wire. The pair of low-regions 12 can be located in a central 25% of a length of the wire.
The wire can have the same cross-sectional area throughout the outer-high-regions 11. The wire can have the same cross-sectional area throughout the central-high-region 13. Thus, there can be substantially uniform heating throughout each of these regions.
X-ray tubes 100, 110, and 120 are illustrated in
Each x-ray tube can include a cathode 101 and an anode 102 electrically insulated from one another. An electrically-insulative enclosure 105 can insulate the cathode 101 from the anode 102. The cathode 101 can include the filament 101F. The filament 101F can be configured to emit electrons towards the anode 102. The anode 102 can include a target 104 which is configured to generate x-rays. The x-rays can emit through an x-ray window 103 and out of the x-ray tube in response to the impinging electrons from the filament 101F.
Following are methods of making a spiral filament with multiple, different thicknesses. Steps of the methods can be performed in the order shown. The spiral filament can have properties as described above.
A method of making a spiral filament with multiple, different thicknesses can include the following steps, which can be performed in the following order:
In the above method, providing the sheet of metal 131 with the multiple, different thicknesses Th can include applying a mask 142 on a planned thicker region of a sheet of metal 131, then etching outside of the mask 142, to form the multiple, different thicknesses Th (see
In the above method, cutting the elongated shape 151 of the spiral filament can include applying a mask 142 on a planned location of the elongated shape 151, on the sheet of metal 131, then etching outside of the mask 142 to form the elongated shape 151. See
In the above method, culling the elongated shape can include using a laser 161. This can further comprise tapering laser settings between the different thicknesses to produce smooth transitions of thickness between the different thicknesses. See
Another method for making a spiral filament with multiple, different thicknesses can include the following steps, which can be performed in the following order:
(a) cutting an elongated shape 151 of the spiral filament in a sheet of metal with a laser 161 (
(b) applying a mask 142 on a planned thicker region of the elongated shape 151 (
The mask 142 may then be removed chemically following step (b). This step (b) can be repeated, with the mask 142 in different locations, for more than two different thicknesses Th.
Another method for making a spiral filament with multiple, different thicknesses can include cutting an elongated shape 151 of the spiral filament in a sheet of metal with a laser 161 and using a different amount of laser cutting, in different regions with respect to each other, to form the multiple, different thicknesses. The method can further comprise tapering laser settings between the different regions to produce smooth transitions of thickness between the different regions.
This application claims priority to US Provisional Patent Application Number U.S. 63/388,306, filed on Jul. 12, 2022, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63388306 | Jul 2022 | US |
