Cathode device and x-ray tube
By designing a tapered section of the emitter well and a gate cutoff contact in the cathode device, the influence of Coulomb force on the electron emitter is reduced, solving the problem of shortened lifespan caused by electron emitter bending and improving the reliability and stability of the X-ray tube.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SIEMENS HEALTHINEERS AG
- Filing Date
- 2025-03-07
- Publication Date
- 2026-05-26
Smart Images
Figure CN224288230U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a cathode device and an X-ray tube. Background Technology
[0002] Conventional cathode devices are used to provide electrons, which are typically generated on the cathode side by means of an electron emitter within the vacuum-sealed housing of the X-ray tube, so that they are accelerated from there toward the anode. In interaction with the anode, X-ray radiation is produced.
[0003] DE 2020 21 103 476U1 discloses a modular cathode device for an X-ray tube, the modular cathode device having a focusing head with a well for focusing emitted electrons and an electron emitter at least partially disposed in the well, characterized by having a well plate for influencing focusing, the well plate being connected to the focusing head and partially covering the well to limit the emission window through which the emitted electrons pass.
[0004] To accelerate electrons from the electron emitter toward the anode, a high voltage is typically applied between the cathode and the anode as an accelerating voltage. This accelerating voltage is commonly referred to as the tube high voltage. Depending on the X-ray tube design, the cathode and anode can be at high voltage potentials, for example, in the case of a bipolar X-ray tube. In the case of a monopolar X-ray tube, either the cathode or anode is at a high voltage potential, while the other electrode is at a constant ground potential.
[0005] In conventional cathode devices, an electron emitter is typically inserted into a focusing head. The focusing head may be electrically insulated from the electron emitter. In this case, it is conceivable that the focusing head and the electron emitter have different potentials. Here, one of the two potentials of the focusing head and the electron emitter may be ground potential, or both potentials may be high voltage potentials. This high voltage on the cathode side, or this high voltage potential difference on the cathode side, between the focusing head and the electron emitter can typically be used for various functions, such as for grid cutoff and / or electrostatic focusing. Typically, the high voltage potential difference on the cathode side is smaller during electrostatic focusing than during grid cutoff.
[0006] In electrostatic focusing, the focusing head is typically configured to shape, in particular focus, defocus, or deflect the emitted electron beam by means of a high-voltage potential difference on the cathode side. Here, the high-voltage potential difference on the cathode side is typically in the low kV range. During electrostatic focusing, the high-voltage potential of the focusing head can be more positive or more negative than the high-voltage potential of the electron emitter. For example, in a monopolar X-ray tube, during electrostatic focusing, the high-voltage potential of the anode can be +80 kV, and the high-voltage potential of the electron emitter can be up to -5 kV, especially -100 V, while the focusing head has a ground potential.
[0007] Conversely, when the grid is cut off, a high voltage potential typically exists at the electron emitter, which is more positive than the high voltage potential of the focusing head in the low kV range. This allows electron emission to be blocked, preferably by using the focusing head as a cutoff grid. This grid cutoff, for example, enables the faster clamping of electron emission toward the anode compared to cutting off the heating current of the electron emitter or applying a high tube voltage between the anode and cathode. For example, in a monopolar X-ray tube, when the grid is cut off, the high voltage potential of the anode can be +80 kV, and the high voltage potential of the electron emitter can be +(1 to 5) kV, for example, 2 kV, while the focusing head has a ground potential.
[0008] Coulomb forces often act significantly on the electron emitter, especially when a non-zero high voltage is applied between the electron emitter and the focusing head, creating a high-voltage potential difference. These forces often occur independently of the electron emission that actually occurs with the electron emitter. The Coulomb forces cause bending of the electron emitter, particularly when it is typically not 100% precisely symmetrically inserted into the emitter well of the focusing head, but only to a certain extent asymmetrically within a predetermined installation tolerance. In principle, such Coulomb forces can also occur even with 100% precisely symmetrical insertion. The bending of the electron emitter typically increases over time and, in particular, reduces the distance between the electron emitter and the focusing head. Therefore, the bending of the electron emitter can eventually cause arcing between the electron emitter and the focusing head, which often results in X-ray tube malfunction as a faulty image grid failure. Alternatively or additionally, the bending of the electron emitter can cause a downward bulge of the electron emitter, which can cause anode overload, especially in the case of a small focal spot. Another sign of a malfunction when an electron transmitter is bent is a lateral bulge, which can occur particularly in parallel-plane transmitters. Utility Model Content
[0009] The purpose of this invention is to provide a cathode device and X-ray tube with an improved service life.
[0010] The objective is achieved through the features of this invention. Advantageous design solutions are described herein.
[0011] The cathode device for an X-ray tube according to this invention includes a focusing head and a focusing head.
[0012] -Electron transmitter,
[0013] -High voltage can be applied between the focusing head and the electron transmitter.
[0014] -The focusing head has at least one transmitter well.
[0015] -The electronic transmitter is centrally located above or inside the transmitter well.
[0016] -The transmitter well tapering section, which is part of the focusing head, makes the width of the transmitter well at the height of the electron transmitter smaller than its width below the transmitter well tapering section.
[0017] -The varying cross-sectional configuration of the transmitter well is used to reduce the Coulomb force acting on the electron transmitter due to the applied high voltage.
[0018] The X-ray tube according to this utility model has
[0019] - Cathode device
[0020] - Anode, and
[0021] -A vacuum-sealed casing
[0022] -The cathode and anode are installed inside the vacuum-sealed housing.
[0023] According to one implementation, the electron emitter is a parallel flachemitter, a single-branch parallel flachemitter, or a helical emitter.
[0024] According to one embodiment, a gate cut-off patch is provided at the center of the bottom of the transmitter well, wherein the depth of the transmitter well substantially corresponds to the height of the gate cut-off patch.
[0025] According to one embodiment, the gate cutoff patch tapers toward the well opening.
[0026] According to one implementation, the width of the transmitter well corresponds substantially to twice the height of the gate cutoff patch.
[0027] According to one embodiment, the width of the transmitter well at the height of the electronic transmitter is at least 5% smaller than the width below the tapered portion of the transmitter well.
[0028] According to one embodiment, the well wall below the tapered section of the transmitter well and the well bottom located between the well walls together have a U-shaped cross-section.
[0029] According to one embodiment, the transmitter well tapered section is formed in a tabular shape.
[0030] According to one embodiment, the lower side of the tapered portion of the transmitter well has a rounded transition portion to the well wall.
[0031] According to one embodiment, the transmitter well is triangularly tapered.
[0032] According to one embodiment, the shape of the tapered portion of the transmitter well is a right-angled triangle, with the longest side of the right-angled triangle facing the transmitter well.
[0033] According to one embodiment, the depth of the transmitter well is greater than 0.1 mm and less than 10 mm.
[0034] According to one implementation, the depth of the transmitter well is between 1 mm and 2 mm.
[0035] According to one embodiment, the width of the transmitter well at the height of the electronic transmitter is greater than 1 mm and less than 15 mm.
[0036] According to one embodiment, the width of the transmitter well at the height of the electronic transmitter is between 4 mm and 5 mm.
[0037] The cathode device or X-ray tube according to this invention has the following advantages:
[0038] Due to the varying cross-section of the transmitter well, the electron transmitter experiences a reduced Coulomb force. In other words, advantageously, the electron transmitter is less likely to bend due to the Coulomb force. This preferably extends the lifespan of the electron transmitter. Attached Figure Description
[0039] The present invention will now be described and illustrated in detail with reference to the embodiments shown in the accompanying drawings. In principle, the same structures and units will be maintained substantially in the following description of the drawings, using the same reference numerals as when the corresponding structures or units first appear.
[0040] The attached diagram shows:
[0041] Figure 1 A cathode device according to the prior art is shown.
[0042] Figure 2 The cathode device according to the present invention is shown.
[0043] Figure 3 A first embodiment of the cathode device is shown.
[0044] Figure 4 A second embodiment of the cathode device is shown.
[0045] Figure 5 A third embodiment of the cathode device is shown.
[0046] Figure 6 A first embodiment of an electron transmitter is shown, and
[0047] Figure 7An X-ray tube according to the present invention is shown. Detailed Implementation
[0048] Figure 1 A cross-section through the cathode device 10 according to the prior art is shown.
[0049] The cathode device 10 has a focusing head 11 and an electron emitter 12. A high voltage can be applied between the focusing head 11 and the electron emitter 12. The focusing head 11 has at least one emitter well 13. The emitter well 13 has well walls that are parallel to each other and perpendicular to the bottom of the well. The electron emitter 12 is centrally located in the emitter well 13, thus partially covering the emitter well 13. The electron emitter 12 is a single-branch planar emitter.
[0050] Figure 2 The cross-section of the cathode device 20 according to the present invention is shown.
[0051] The cathode device 20 has a focusing head 21 and an electron emitter 22. The electron emitter 22 is an electron emitter that can be activated by a heating current, and is therefore a thermionic emitter. Alternatively, in principle, it is conceivable to combine a cold emitter as the electron emitter with the emitter well tapered section according to the present invention, instead of a thermionic emitter. The cold emitter can in particular be a field-effect emitter.
[0052] The electron transmitter 22 can be fastened to Figure 2 At the two heating current delivery support rods (not shown), fastening is achieved, for example, by welding or a detachable connection. The two heating current delivery support rods specifically guide the heating current. In this case, the heating current delivery support rods are electrically insulated from the focusing head 21 and enable energizing the electron transmitter 22 with the heating current. Alternatively, the electron transmitter 22 can be fastened to a non-current-guiding fastening mechanism, wherein the electron transmitter can be heated by means of another heating current delivery device.
[0053] Figure 2 The electron emitter 22 is a single-branch planar emitter. Alternatively, the electron emitter may be a parallel planar emitter or a spiral emitter. A single-branch planar emitter is characterized in that it is typically elongated and / or constitutes a thin sheet with lateral cuts, and the two ends of the planar emitter are connected to each other by a single current path. In particular, a single-branch planar emitter has a branch through which only one heating current can flow.
[0054] A high voltage can be applied between the focusing head 21 and the electron emitter 22. The high voltage on the cathode side, or the high voltage potential difference on the cathode side, can be, for example, between 0 kV and 20 kV, particularly between 1 kV and 5 kV, preferably 2 kV or 100 V. In principle, the focusing head can be configured to be at ground potential in the case of a monopolar X-ray tube or at a high voltage potential in the case of a bipolar X-ray tube.
[0055] exist Figure 2 In the focal head 21, there is a transmitter well 23. Alternatively, the focal head 21 may have multiple transmitter wells. An electronic transmitter 22 is centrally positioned in the transmitter well 23, thereby partially covering the transmitter well 23.
[0056] As part of the focusing head 21, a transmitter well tapered section 25 is formed, such that the width of the transmitter well 23 at the height of the electron transmitter 22 is smaller than its width below the transmitter well tapered section 25. The transmitter well tapered section 25 and the remaining sections of the focusing head 21 are particularly constructed as a single piece or integral component, for example, by casting.
[0057] The varying cross-sectional configuration of the transmitter well 23 is used to reduce the Coulomb force acting on the electron transmitter 22 due to the applied high voltage. The varying cross-section of the transmitter well 23 particularly compensates for the Coulomb force, allowing the electron transmitter 22 to bend more advantageously and less frequently.
[0058] The width of the transmitter well 23 at the height of the electronic transmitter 22 is at least 5% smaller than its width below the transmitter well taper 25. The well wall below the transmitter well taper 25 and the well bottom located between the well walls together have a U-shaped cross-section. The transmitter well 23 has well walls below the transmitter well taper 25 that are parallel to each other and perpendicular to the well bottom. (According to...) Figure 1 Compared to transmitter well 13, the width and depth of transmitter well 23 are enlarged.
[0059] The transmitter well tapering section 25 closes the well wall of the transmitter well 23 towards the well opening. The transmitter well tapering section 25 is formed particularly on both sides of the transmitter well 23. The transmitter well tapering section 25 is typically formed symmetrically. The transmitter well tapering section 25 may be provided only on two opposite sides of the transmitter well 23 or on all four sides of the transmitter well 23. In the latter case, the transmitter well tapering section 25 is a surrounding section that encloses the transmitter well 23.
[0060] The transmitter well tapering 25 typically partially covers the bottom of the well. The transmitter well tapering 25 is particularly a protrusion. The transmitter well tapering 25 particularly reduces the volume of the transmitter well 23. The upper side of the transmitter well tapering 25 is particularly flat and flush with the rest of the focusing head 21.
[0061] Figure 3 A detailed view showing a cross-section through the cathode device 20 according to the first embodiment is shown.
[0062] A gate cutoff tab 24 is centrally located at the bottom of the transmitter well 23. "Center" means that the gate cutoff tab 24 preferably divides the transmitter well 23 into two identical halves. The arrangement of the gate cutoff tab 24 and the electron transmitter 22 is T-shaped in cross-section.
[0063] The gate cutoff tab 24 is specifically formed as part of the focusing head 21. Alternatively, the gate cutoff tab 24 can be implemented as a separate component disposed in the transmitter well 23. The gate cutoff tab 24 is at the potential of the focusing head 21. Therefore, the gate cutoff tab 24 advantageously contributes to gate cutoff, particularly for the remaining areas of the focusing head 21.
[0064] The depth of the emitter well 23 substantially corresponds to the height of the gate cut-off patch 24. This essentially means that the height of the gate cut-off patch 24 can exceed or fall below the depth of the emitter well 23 by up to 10% and / or several mm. The gate cut-off patch 24 can be flush with the upper edge of the emitter well 23.
[0065] The width of the transmitter well 23 is approximately twice the height of the gate cutoff patch 24. The ratio of the width of the transmitter well 23 to the height of the gate cutoff patch 24 can be a multiple greater than or less than 2.
[0066] Figure 3 It is also shown that the electron emitter 22 is a parallel planar emitter. Parallel planar emitters are particularly thermionic sheet emitters. A parallel planar emitter comprises two sheet branches, typically of the same size and / or symmetrically configured, connected at their ends and separated from each other between their ends. The sheet branches may in particular be tab halves of the electron emitter 22 and / or form two parallel current paths. The branches of a parallel planar emitter are typically elongated and / or configured with lateral cutouts. The width of the gap between the two sheet branches is typically such that the gate cutoff tab 24 can extend through the gap between the two sheet branches. Therefore… Figure 3 The cross-section of the two thin-film branches through the electron emitter 22 and through the gate cut-off patch 24 is shown.
[0067] The gate cutoff patch 24 tapers toward the well opening. The tapered gate cutoff patch 24 specifically includes two segments of different thicknesses, which are connected to each other by a transition segment. Figure 3 The transition section is approximately rounded.
[0068] The transmitter well tapered section 25 is configured in a tab-like shape. The tab-like shape means that the transmitter well tapered section 25 has a substantially rectangular cross-section. Furthermore, the embodiment also shows that the lower side of the tab-shaped transmitter well tapered section 25 has a rounded transition to the well wall. Therefore, the stability of the transmitter well tapered section 25 can be advantageously improved.
[0069] Figure 4 A detailed view showing a cross-section through the cathode device 20 according to the second embodiment is shown.
[0070] The transmitter well tapering section 25 is triangularly constructed. Triangular means that the transmitter well tapering section 25 has a substantially triangular cross-section. The term triangular should be specifically included. Figure 4 The trapezoid shown has a maximum of two inner right angles.
[0071] Figure 4 The transmitter well tapering 25 is shown to be a right-angled triangle, with its longest side facing the transmitter well 23. The longest side is particularly an extension of the well wall below the transmitter well tapering 25. The longest side forms part of the well wall.
[0072] like Figure 4 As shown, the triangle specifically includes a cross-section in which the transition from the transmitter well taper 25 to the corresponding well wall is maximized. Therefore, the stability and / or manufacturability of the transmitter well taper 25 can be advantageously improved.
[0073] Preferably, the depth of the transmitter well 23 is greater than 0.1 mm and less than 10 mm. The depth of the transmitter well 23 is particularly advantageously between 1 mm and 2 mm.
[0074] Preferably, the width of the transmitter well 23 at the height of the electronic transmitter 22 is greater than 1 mm and less than 15 mm. Particularly advantageously, the width of the transmitter well 23 at the height of the electronic transmitter 22 is between 4 mm and 5 mm.
[0075] and Figure 3 In contrast, the transition section of the tapered gate cutoff patch 24 is trapezoidally formed. It is conceivable that... Figure 4 The upper portion of the gate cutoff patch 24 can be replaced by a trapezoidal or triangular transition portion. The transition portion is advantageously configured to be less sharp.
[0076] Figure 5 A cross-section through the cathode device 20 according to the third embodiment is shown.
[0077] Figure 5 The focusing head 21 has another transmitter well 26. In principle, it is conceivable that the focusing head 21 has more than two, for example three transmitter wells in total.
[0078] Another transmitter well 26 can, in principle, be constructed in the same manner as transmitter well 23. In this case, typically, another gate cutoff contact is the same as gate cutoff contact 24 and / or another electron transmitter 28 is the same as electron transmitter 22.
[0079] On the contrary, Figure 5 The transmitter well 26 has no gate cut-off contact at the center of its bottom. Another electronic transmitter 28 is disposed in another transmitter well 26. A tapered section 29 of the other transmitter well causes the transmitter well 26 to taper. The other electronic transmitter 28... Figure 5 The electron emitter is configured as a single-branch planar emitter. Alternatively, the electron emitters 22, 28, and especially the other electron emitter 28, can be configured as a helical emitter.
[0080] The other transmitter well 26 may, in principle, have the same dimensions as transmitter well 23. Alternatively, transmitter well 26 may have a smaller width and / or a smaller depth compared to transmitter well 23, or vice versa. In this case, the other electronic transmitter 28 is typically configured to be smaller in width than electronic transmitter 22.
[0081] The other transmitter well tapered section 29 can, in principle, be constructed in the same manner as the transmitter well tapered section 25. Alternatively, the other transmitter well tapered section 29 may have a smaller and / or different shape compared to the transmitter well tapered section 25.
[0082] Figure 5 The focusing head 21 is configured as a flat focusing head with a flat surface, such that the two regions having a transmitter well 23, 26 and the associated electron transmitters 22, 28 are aligned in a straight line. Alternatively, the focusing head may have a particularly V-shaped or U-shaped surface, which causes the electron transmitter 22 and its transmitter well 23 to share an angle similar to the surface of the focusing head, and the other electron transmitter 28 and its other transmitter well 26 to share an angle.
[0083] Figure 6 A first embodiment of the electron transmitter is shown in a bird's-eye view.
[0084] Electron emitter 22 is a parallel planar emitter and can be connected, for example, to two heating current delivery devices. Electron emitter 22 has two branches with lateral cutouts, for each branch the cutouts forming a meandering current path. The two current paths are centrally separated from each other, with gate cut-off tabs 24 extending into the gaps. Electron emitter 22 partially covers emitter well 23.
[0085] Figure 7 The cross-section of the X-ray tube 30 according to the present invention is shown.
[0086] The X-ray tube 30 has a cathode device 20, an anode 31, and a vacuum-sealed housing 32. Inside the vacuum-sealed housing 32, the cathode device 20 is arranged opposite to the anode 31.
[0087] The X-ray tube 30 is specifically configured to generate X-ray radiation. The generated X-ray radiation can be used, in particular, for imaging and / or treatment. Imaging includes, in particular, diagnostic applications such as angiography, computed tomography, mammography, and / or radiography. Alternatively or additionally, imaging may include materials inspection and / or security checks.
[0088] Although the details of the present invention have been described and illustrated with reference to preferred embodiments, the present invention is not limited to the disclosed examples and other variations can be derived by those skilled in the art without departing from the protection scope of the present invention.
Claims
1. A cathode device (20) for use in an X-ray tube (30). Its features are, The cathode device (20) has - Focusing head (21), and - Electron transmitter (22). - Wherein a high voltage can be applied between the focusing head (21) and the electron transmitter (22), - The focusing head (21) has at least one transmitter well (23). - The electronic transmitter (22) is centrally located above or within the transmitter well (23). - Wherein, as part of the focusing head (21), a transmitter well tapering section (25) is formed, such that the width of the transmitter well (23) at the height of the electron transmitter (22) is smaller than the width below the transmitter well tapering section (25). - The varying cross-sectional configuration of the transmitter well (23) is used to reduce the Coulomb force acting on the electron transmitter due to the applied high voltage.
2. The cathode device (20) according to claim 1. A gate cutoff patch (24) is provided at the center of the bottom of the transmitter well (23), and the depth of the transmitter well (23) corresponds to the height of the gate cutoff patch (24).
3. The cathode device (20) according to claim 2. The gate cutoff patch (24) therein tapers toward the well opening.
4. The cathode device (20) according to any one of claims 2 or 3. The width of the transmitter well (23) corresponds to twice the height of the gate cut-off patch (24).
5. The cathode device (20) according to any one of claims 1 to 3. The width of the transmitter well (23) at the height of the electronic transmitter (22) is at least 5% smaller than the width below the tapered portion (25) of the transmitter well.
6. The cathode device (20) according to any one of claims 1 to 3. The well wall below the tapered section (25) of the transmitter well and the well bottom located between the well walls have a U-shaped cross-section.
7. The cathode device (20) according to any one of claims 1 to 3. The transmitter well tapered section (25) is formed in a tab-like shape.
8. The cathode device (20) according to claim 7. The lower side of the tapered portion (25) of the transmitter well has a rounded transition portion to the well wall.
9. The cathode device (20) according to any one of claims 1 to 3. The transmitter well tapering section (25) is triangular in shape.
10. The cathode device (20) according to claim 9. The transmitter well tapering section (25) is shaped like a right triangle, with the longest side of the right triangle facing the transmitter well (23).
11. The cathode device (20) according to any one of claims 1 to 3. The depth of the transmitter well (23) is greater than 0.1 mm and less than 10 mm.
12. The cathode device (20) according to claim 11. The depth of the transmitter well (23) is between 1 mm and 2 mm.
13. The cathode device (20) according to any one of claims 1 to 3. The transmitter well (23) has a width greater than 1 mm and less than 15 mm at the height of the electronic transmitter (22).
14. The cathode device (20) according to claim 13. The width of the transmitter well (23) at the height of the electronic transmitter (22) is between 4 mm and 5 mm.
15. The cathode device (20) according to any one of claims 1 to 3. The electron transmitter is a parallel planar transmitter, a single-branch planar transmitter, or a spiral transmitter.
16. An X-ray tube (30). Its features are, The X-ray tube (30) has - Cathode device (20) according to any one of claims 1 to 15. - Anode (31), and - Vacuum-sealed shell (32). - The cathode device (20) and the anode (31) are provided inside the vacuum-evacuated housing (32).