Anti-arcing cathode assembly and x-ray tube

Abstract

An anti-arcing cathode assembly and an X-ray tube. The anti-arcing cathode assembly comprises: a focusing body (1); a mounting plate (2) having a center hole (21); an electron emitter (3), which is located in a cavity (11) and arranged on the mounting plate (2); a shielding tube (4), which is located in the cavity (11); a shielding cup (5), which is located in the shielding tube (4), wherein the rim of the shielding cup (5) sealingly connects to the mounting plate (2) and covers the center hole (21); an insulator (6), which sealingly fills a chamber (52) of the shielding cup (5); and an electrode wire (7), which sealingly penetrates the insulator (6), and penetrates a clearance hole (51) with a clearance. An in-tube triple junction jointly formed by the insulator (6), the electrode wire (7), and an in-tube vacuum area, and an in-tube triple junction (A) jointly formed by the shielding cup (5), the insulator (6), and the in-tube vacuum area are both located in the chamber (52) of the shielding cup (5). The present anti-arcing cathode assembly can effectively inhibit electron emission at the in-tube triple junction (A), and can enhance the connection strength and sealing reliability of a cathode supporting portion, thus helping to enhance the high-voltage stability of a working X-ray tube.

Description

Anti-spark cathode assembly and X-ray tube Technical Field

[0001] The present invention relates to the technical field of X-ray tubes, and in particular to an anti-spark cathode assembly and an X-ray tube. Background Art

[0002] An X-ray tube is a high-voltage, high-vacuum electronic device with an electron emitter. The cathode, where the electron emitter resides, is typically connected via a glass core and several electrode wires, as described in existing patents CN204271034U and CN208674047U. This seal isolates the interior and exterior spaces and provides a seal. The electrode wires both power the electron emitter and support the X-ray tube cathode. The sealed connection between the electrode wires and the glass core is a relatively weak point in the X-ray tube connection. The X-ray tube cathode weighs hundreds of grams, and the vibrations experienced during transportation, operation, and vibration and shock testing can easily damage this sealed connection, leading to leaks. Furthermore, the seal between the multiple electrode wires and the glass core requires a high level of sealing technology and strict requirements for preventing bubbles at the sealing interface, resulting in a relatively high risk of leaks. Furthermore, within the X-ray tube, the junction between the electrode wires, the glass core, and the vacuum chamber is susceptible to electron emission under the influence of the electric field, leading to flashover and sparking, which can cause the X-ray tube to fail reliably or even break down and leak. To address this issue, the existing patent CN111293016A uses a metal shield to surround the cathode assembly to suppress electron emission from the triple junction. However, this method of wrapping the cathode assembly will lead to a reduction in the insulation distance of the tube shell, bringing additional ignition risks.

[0003] Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide an anti-spark cathode assembly and an X-ray tube, which can effectively suppress electron emission at the three-junction joint inside the tube, increase the connection strength and sealing reliability of the cathode support part, and are conducive to enhancing the high-voltage stability of the X-ray tube during operation, and have broad application prospects.

[0005] In order to solve the above technical problems, the present invention provides a spark-proof cathode assembly, comprising:

[0006] A focusing body, wherein the focusing body has a cavity extending through the focusing body along its axial direction;

[0007] a mounting plate having a central hole, the mounting plate being located in the cavity and fixedly connected to the focusing body;

[0008] an electron emitter, the electron emitter being located in the cavity and disposed on the mounting plate;

[0009] a shielding tube, the shielding tube being located in the cavity, one end of the shielding tube being sealed on a side of the mounting plate facing away from the electron emitter and the other end of the shielding tube being used for sealing connection with a vacuum tube shell of an X-ray tube;

[0010] The shielding cup is located in the shielding tube, the bottom of the shielding cup has an avoidance hole, the cup rim of the shielding cup is sealed and connected to the mounting plate and covers the central hole; the avoidance hole has an axial depth of not less than 5 mm, preferably 5-10 mm, 7-15 mm, or 10-20 mm.

[0011] The insulator is sealed and filled in the cup cavity of the shielding cup; the thickness of the insulator filled in the shielding cup is usually not less than 3mm, preferably 3-5mm, 4-6mm, or 3-10mm.

[0012] An electrode wire, the electrode wire is sealed and passed through the insulator and has a gap passed through the avoidance hole, one end of the electrode wire located in the vacuum area inside the tube is electrically connected to the electron emitter, and the other end of the electrode wire located in the non-vacuum area outside the tube is used to electrically connect to the power supply circuit;

[0013] The three-way junction formed by the insulator, the electrode wire and the vacuum zone in the tube and the three-way junction formed by the shielding cup, the insulator and the vacuum zone in the tube are both located in the cup cavity of the shielding cup.

[0014] Preferably, a triple junction formed by the shielding tube, the vacuum tube shell and the non-vacuum area outside the tube is located in the cavity.

[0015] Preferably, the focusing body includes a focusing body portion and a shielding extension portion extending axially along the focusing body portion, the radial spacing W between the shielding extension portion and the shielding tube is not less than 1.5 mm, the axial spacing L between the end face of the shielding extension portion and the outer junction of the tube is not less than 1 mm, and L / W ≥ 2 / 3.

[0016] Preferably, the focusing body further comprises a focusing extension portion, which is coaxially arranged on the focusing body portion, and the focusing extension portion is used to focus the electron beam emitted by the electron emitter.

[0017] Preferably, the focusing body, the shielding tube, the shielding cup and the electrode wire are all made of metal materials, and the insulator and the vacuum tube shell are both made of insulating materials.

[0018] Preferably, the metal material is Kovar alloy, and the insulating material is ceramic or glass whose expansion coefficient matches that of Kovar alloy.

[0019] Preferably, the wall thickness of the shielding tube and the shielding cup is 0.3-1.0 mm, and the diameter of the electrode wire is 0.8-2.0 mm.

[0020] Preferably, the mounting plate has an annular protrusion at a position close to the central hole, and the annular protrusion is sealingly sleeved with the cup edge of the shielding cup.

[0021] The present invention also provides an X-ray tube, comprising:

[0022] vacuum tube shell;

[0023] The anti-spark cathode assembly.

[0024] Preferably, the vacuum tube shell includes a trumpet-shaped connecting tube shell and a main tube shell surrounding the entire anti-spark cathode assembly, the small end of the connecting tube shell is sealed and connected to the shielding tube, and the large end of the connecting tube shell is sealed and connected to the main tube shell.

[0025] The anti-spark cathode assembly is connected to the main tube shell through the connecting tube shell, and the anti-spark cathode assembly is sealed with the connecting tube shell through its own shielding tube. The electrode wire is no longer used to support the entire cathode assembly, but only serves as a connection and sealing function. Compared with the cathode assembly with a glass core column supported by the electrode wire in the prior art, the X-ray tube of the present invention has better supporting strength and sealing reliability.

[0026] As described above, the spark-proof cathode assembly and X-ray tube of the present invention have the following beneficial effects: the spark-proof cathode assembly of the present invention shields the three junctions within the tube within the focusing body, eliminating the need to shield the three junctions outside the vacuum tube shell, thus eliminating the need to sacrifice the insulation distance of the vacuum tube shell. This helps enhance the high-voltage stability of the X-ray tube during operation, suppresses electron emission from the three junctions within the tube, and increases the support strength and sealing reliability of the cathode support portion. Therefore, the spark-proof cathode assembly of the present invention can effectively suppress electron emission from the three junctions within the tube, increase the connection strength and sealing reliability of the cathode support portion, and help enhance the high-voltage stability of the X-ray tube during operation, thus having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic diagram of a first embodiment of an X-ray tube according to the present invention;

[0028] FIG2 is a schematic diagram of a second embodiment of an X-ray tube according to the present invention;

[0029] FIG. 3 is a cross-sectional view of the spark-proof cathode assembly of the present invention.

[0030] Component number description

[0031] 1 Focusing body

[0032] 11 Cavity

[0033] 12 Focus on the main body

[0034] 13 Shield extension

[0035] 14 Focus extension

[0036] 2 Installation disk

[0037] 21 center hole

[0038] 22 Annular protrusion

[0039] 3 Electron emitters

[0040] 31 Transmitter

[0041] 32 Support rod

[0042] 33 Bridge

[0043] 4 shielding tube

[0044] 5 Shielding Cup

[0045] 51 Avoidance hole

[0046] 52 cup cavity

[0047] 6 Insulator

[0048] 7. Wire electrode

[0049] 8 Vacuum tube shell

[0050] 81 Connecting tube and shell

[0051] 82 main tube shell DETAILED DESCRIPTION

[0052] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0053] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0054] As shown in FIG1 , FIG2 and FIG3 , the present invention provides a spark-proof cathode assembly, comprising:

[0055] The focusing body 1 has a cavity 11 extending through the focusing body 1 in its axial direction;

[0056] A mounting plate 2 having a central hole 21, the mounting plate 2 being located within the cavity 11 and being fixedly connected to the focusing body 1 by various means such as welding, riveting, or screw fasteners;

[0057] The electron emitter 3 is located in the cavity 11 and is provided on the mounting plate 2;

[0058] The shielding tube 4 is located in the above-mentioned cavity 11, one end of the shielding tube 4 is vacuum-tightly sealed and arranged on the side of the mounting plate 2 facing away from the electron emitter 3, and the other end of the tube is used for vacuum-tight connection to a vacuum tube shell 8 of an X-ray tube; the vacuum-tight sealing method of the shielding tube 4 and the mounting plate 2 can be brazing, argon arc welding, laser welding and other methods; the sealing method of the shielding tube 4 and the vacuum tube shell 8 can be glass sealing, ceramic brazing sealing and other sealing methods.

[0059] The shielding cup 5 is located inside the shielding tube 4. The bottom of the shielding cup 5 has an escape hole 51. The rim of the shielding cup 5 is vacuum-tightly connected to the mounting plate 2 and covers the central hole 21. The vacuum-tight sealing method between the rim of the shielding cup 5 and the mounting plate can be brazing, argon arc welding, laser welding, etc. The axial depth of the escape hole 51 is not less than 5mm, preferably 5-10mm, 7-15mm, or 10-20mm. The insulator 6 is sealed and filled in the cup cavity 52 of the shielding cup 5. In order to meet the sealing requirements, the thickness of the insulator 6 filled in the shielding cup 5 is usually not less than 3mm, preferably 3-5mm, 4-6mm, or 3-10mm.

[0060] an electrode wire 7 (the number of electrode wires 7 may be one or more), the electrode wire 7 being vacuum-tightly and airtightly passed through the insulator 6 and having a gap passed through the avoidance hole 51; one end of the electrode wire 7 located in the vacuum region inside the tube is electrically connected to the electron emitter 3, and the other end located in the non-vacuum region outside the tube is electrically connected to the power supply circuit;

[0061] The vacuum airtight sealing method of the insulator 6, the electrode wire 7 and the shielding cup 5 can be various methods such as glass sealing, ceramic metallization brazing, etc.

[0062] Among them, the three-joint joint inside the tube formed by the above-mentioned insulator 6, the above-mentioned electrode wire 7 and the vacuum area inside the tube and the three-joint joint inside the tube formed by the shielding cup 5, the insulator 6 and the vacuum area inside the tube are both located in the cup cavity 52 of the above-mentioned shielding cup 5.

[0063] In the present invention, the focusing body 1 has a cavity 11 extending axially through it, which is used to accommodate other components of the anti-spark cathode assembly. Cavity 11 can have a stepped hole structure, which facilitates axial positioning of the mounting plate 2. The mounting plate 2 has a central hole 21 for passing the electrode wire 7. The mounting plate 2 is similar to a flange structure, supporting the electron emitter 3, the shielding cup 5, and the shielding tube 4. To seal the vacuum region within the X-ray tube, the mounting plate 2 is located within the cavity 11 and is fixedly connected to the focusing body 1. One end of the shielding tube 4 is vacuum-tightly sealed on the side of the mounting plate 2 facing away from the electron emitter 3, and the other end is vacuum-tightly connected to the vacuum shell 8 of the X-ray tube. The mouth of the shielding cup 5 is vacuum-tightly connected to the mounting plate 2 and covers the central hole 21. The insulator 6 is vacuum-tightly filled within the cup cavity 52 of the shielding cup 5. The electrode wire 7 is vacuum-tightly passed through the insulator 6, with a gap formed through the avoidance hole 51.

[0064] The main innovation of the present invention lies in: the opening of the shielding cup 5 faces the electron emitter 3, the rim of the shielding cup 5 vacuum-tightly covers the central hole 21, the cup cavity 52 of the shielding cup 5 is filled with an insulator 6, and the inner wall of the shielding cup 5 and the insulator 6 are in vacuum-tight contact, and the electrode wire 7 is vacuum-tightly inserted through the insulator 6, and the electrode wire 7 and the shielding cup 5 are insulated. In this arrangement, the insulator 6, the electrode wire 7, and the vacuum region within the tube form a triple junction A within the tube cavity 52. ​​The shielding cup 5 and the electrode wire 7 serve as an electrode connection, through which the power supply circuit of the X-ray tube is electrically connected to the electron emitter 3, the focusing body 1, and the mounting plate 2 within the tube. When voltage is applied to the anti-spark cathode assembly of the X-ray tube, for example, a voltage of tens or hundreds of kV, the three junctions A in the tube (the common contact area of ​​the shielding cup 5, the insulator 6 and the vacuum area in the tube, and the common contact area of ​​the electrode wire 7, the insulator 6 and the vacuum area in the tube) are located in the cup cavity 51 of the shielding cup 5, and are then shielded from the electric field by the shielding cup 5. The electric field strength of the three junctions A in the tube is zero, thereby suppressing the emission of electrons at the three junctions A in the tube, and avoiding sparks at the three junctions A in the tube, which may cause breakdown of the seal and leakage.

[0065] Another important point is that since the outer surface of the shielding cup 5 is in direct contact with the non-vacuum area outside the tube, and since the X-ray tube is usually immersed in insulating oil for heat dissipation, the three-junction A inside the tube dissipates heat to the outside through the shielding cup 5, and the heat dissipation path is very short. In this way, the temperature of the three-junction A inside the tube will be relatively low, which will further suppress electron emission and more effectively prevent the three-junction A inside the tube from igniting and causing the seal to break down and leak.

[0066] In addition, the anti-spark cathode assembly is sealed and connected to the vacuum tube shell 8 of an X-ray tube through its own shielding tube 4, rather than relying solely on the electrode wire 7 being semi-suspended at one end of the vacuum tube shell 8. This greatly improves the connection strength and sealing reliability between the anti-spark cathode assembly and the vacuum tube shell 8, and prevents the X-ray tube from being damaged due to vibration during transportation, use, and vibration shock testing.

[0067] Therefore, the spark-proof cathode assembly of the present invention shields the three junctions within the tube within the focusing body 1, eliminating the need to shield the three junctions outside the vacuum tube shell 8, thereby eliminating the need to sacrifice the insulation distance of the vacuum tube shell 8. This helps enhance the high-voltage stability of the X-ray tube during operation, suppresses electron emission from the three junctions within the tube, and increases the support strength and sealing reliability of the cathode support. Therefore, the spark-proof cathode assembly of the present invention can effectively suppress electron emission from the three junctions within the tube, increase the connection strength and sealing reliability of the cathode support, and help enhance the high-voltage stability of the X-ray tube during operation, thus having broad application prospects.

[0068] The electron emitter 3 includes two support rods 32 and an emission end 31. The emission end 31 is electrically connected to the two support rods 32 at the same time. One of the support rods 32 is insulated and arranged on the mounting plate 2 and is electrically connected to the electrode wire 7 through the bridge portion 33. The other support rod 32 is electrically connected to the mounting plate 2.

[0069] In order to effectively seal and connect the shielding cup 5 and the mounting plate 2, the shielding cup 5 is sealed and connected to the end surface of the mounting plate 2 by laser welding, argon arc welding or brazing.

[0070] To effectively suppress electron emission from the X-ray tube's outer triple junction B, the triple junction formed by the shielding tube 4, the vacuum tube shell 8, and the non-vacuum region outside the tube is located within the aforementioned cavity 11. Specifically, the entire shielding tube 4 is located within the cavity 11 of the focusing body 1, and the sealed connection between the shielding tube 4 and the vacuum tube shell 8 is also located within the cavity 11 of the focusing body 1. This arrangement allows the triple junction B, formed by the vacuum tube shell 8, the shielding tube 4, and the non-vacuum region outside the tube, to be located within the cavity 11 of the focusing body 1. When the anti-spark cathode assembly is operating with voltage applied, the triple junction B is shielded by the focusing body 1, and the electric field strength at the triple junction B is zero. This suppresses electron emission from the triple junction B and prevents sparks from occurring at the triple junction B, which could lead to breakdown of the seal and leakage.

[0071] In order to better shield the triple junction B on the shielding tube 4, the focusing body 1 includes a focusing main body 12 and a shielding extension portion 13 extending along the vacuum-tight axial direction. The radial spacing W between the shielding extension portion 13 and the shielding tube 4 is not less than 1.5 mm, and the axial spacing L between the end face of the shielding extension portion 13 and the triple junction B is not less than 1 mm, that is, the shielding extension portion 13 is higher than the triple junction B, and L / W ≥ 2 / 3.

[0072] In order to focus the electron beam, the focusing body 1 further includes a focusing extension portion 14, which is coaxially arranged on the focusing body 12 and is used to focus the electron beam emitted by the electron emitter 3. Specifically, a focusing concave hole needs to be formed at one end of the focusing body 1.

[0073] To enable the electron emitter 3 to emit electrons, the focusing body 1, shielding tube 4, shielding cup 5, and electrode wire 7 are all made of metal materials, and the insulator 6 and vacuum tube shell 8 are also made of insulating materials. The electrode wire 7 can serve as a power supply electrode at one end of the electron emitter 3, while the shielding cup 5 and mounting plate 2 can function as electrodes. Furthermore, they can serve as a power supply electrode at the other end of the electron emitter 3, or as a gate electrode that is not electrically connected to the electron emitter 3.

[0074] For ease of manufacturing, the metal material can be Kovar alloy, and the insulating material can be ceramic or glass with a coefficient of expansion that matches Kovar alloy. A molten glass insulator can be hermetically connected to the pre-oxidized shield cup 5, while a metallized ceramic insulator can be brazed and hermetically connected to the shield cup 5.

[0075] In order to achieve a better sealing and matching effect, the wall thickness of the shielding tube 4 and the shielding cup 5 is 0.3-1.0 mm, and the diameter of the electrode wire 7 is 0.8-2.0 mm.

[0076] In order to improve the sealing reliability between the mounting plate 2 and the shielding cup 5 , the mounting plate 2 has an annular protrusion 22 near the center hole 21 , and the annular protrusion 22 is sealingly sleeved with the cup edge of the shielding cup 5 .

[0077] The present invention also provides an X-ray tube, comprising:

[0078] Vacuum tube shell 8;

[0079] The above-mentioned anti-spark cathode assembly.

[0080] With this arrangement, the weight of several hundred grams of the entire anti-spark cathode assembly is supported by the entire circle of shielding tube 4, which is then sealed and connected to the connecting tube shell 81 of the vacuum tube shell 8. The electrode wire 7 only serves as an electrode connection and does not need to support the weight of several hundred grams of the entire anti-spark cathode assembly. Compared with the existing glass flat core column that supports the entire cathode through the sealed connection between several electrode wires and the glass, the X-ray tube of the present invention can enhance the supporting strength of its own cathode part, thereby preventing the X-ray tube from being damaged by vibration during transportation, use and vibration shock testing.

[0081] Therefore, the X-ray tube of the present invention can suppress electron emission at the three junctions of the cathode part, increase the support strength of the cathode support part, improve the reliability of the X-ray tube during operation, and has good application prospects.

[0082] To enhance the connection strength between the vacuum tube shell 8 and the anti-spark cathode assembly, the vacuum tube shell 8 comprises a trumpet-shaped connecting tube shell 81 and a main tube shell 82 that encloses the entire anti-spark cathode assembly. The small end of the connecting tube shell 81 is sealed to the shielding tube 4, while the large end of the connecting tube shell 81 is sealed to the main tube shell 82. Specifically, the connecting tube shell 81 and the main tube shell 82 can be integrally formed and then hermetically connected to the shielding tube 5. Alternatively, the connecting tube shell 81 can be hermetically connected to the shielding tube 5 first and then to the main tube shell 82. One end of the shielding tube 4 is hermetically connected to the mounting plate 2 via laser welding, argon arc welding, or brazing. The vacuum tube shell 8 of the X-ray tube not only supports and seals the X-ray tube, but also insulates the cathode and anode high voltages of the X-ray tube. Preferably, the shielding tube 4 is made of Kovar alloy, and the connecting tube shell 81 and the main tube shell 82 are made of ceramic or glass with a coefficient of expansion matching that of the shielding tube 4.

[0083] In addition, the difference between the X-ray tube shown in FIG. 1 and the X-ray tube shown in FIG. 2 is that the height H of the shielding cup 5 is different, which is suitable for different connection modes between the shielding cup 5 and the mounting plate 2 .

[0084] In summary, the present invention, by providing the aforementioned spark-proof cathode assembly, can shield the triple junction within focusing body 1 and reduce the temperature of the triple junction, thereby suppressing electron emission from the triple junction and improving the stability and reliability of the X-ray tube during operation. By providing the aforementioned spark-proof cathode assembly, the weight of the cathode in the X-ray tube of the present invention is supported by the entire sealed joint surface of shielding tube 4, significantly increasing the support area and thereby enhancing the reliability of the X-ray tube when subjected to vibration and shock. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial value.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A spark-proof cathode assembly, characterized in that: include: A focusing body (1), wherein the focusing body (1) has a cavity (11) that penetrates the focusing body along its axial direction; A mounting plate (2) having a central hole (21), the mounting plate (2) being located in the cavity (11) and being fixedly connected to the focusing body (1); An electron emitter (3), the electron emitter (3) being located in the cavity (11) and arranged on the mounting plate (2); A shielding tube (4), the shielding tube (4) being located in the cavity (11), one end of the shielding tube (4) being sealed and arranged on a side of the mounting plate (2) facing away from the electron emitter (3), and the other end of the shielding tube being used for sealing and connecting to a vacuum tube shell (8) of an X-ray tube; A shielding cup (5), the shielding cup (5) is located in the shielding tube (4), the bottom of the shielding cup (5) is provided with an avoidance hole (51), the mouth of the shielding cup (5) is sealedly connected to the mounting plate (2) and covers the central hole (21); An insulator (6), the insulator (6) is sealed and filled in the cup cavity (52) of the shielding cup (5); An electrode wire (7), the electrode wire (7) is sealed and penetrated through the insulator (6) and has a gap penetrated through the avoidance hole (51), one end of the electrode wire (7) located in the vacuum area inside the tube is electrically connected to the electron emitter (3) and the other end of the electrode wire (7) located in the non-vacuum area outside the tube is used to be electrically connected to the power supply circuit; The insulator (6), the electrode wire (7) and the vacuum zone in the tube jointly formed a three-way junction in the tube and the shielding cup (5), the insulator (6) and the vacuum zone in the tube jointly formed a three-way junction in the tube both located in the cup cavity (52) of the shielding cup (5).

2. The spark-proof cathode assembly according to claim 1, characterized in that: The triple junction formed by the shielding tube (4), the vacuum tube shell (8) and the non-vacuum area outside the tube is located in the cavity (11).

3. The spark-proof cathode assembly according to claim 2, characterized in that: The focusing body (1) comprises a focusing body portion (12) and a shielding extension portion (13) extending axially along the focusing body portion (12); a radial spacing W between the shielding extension portion (13) and the shielding tube (4) is not less than 1.5 mm; an axial spacing L between the end face of the shielding extension portion (13) and the outer junction of the tube is not less than 1 mm; and L / W is ≥ 2 / 3.

4. The spark-proof cathode assembly according to claim 3, characterized in that: The focusing body (1) further comprises a focusing extension portion (14), which is coaxially arranged on the focusing body portion (12), and the focusing extension portion (14) is used to focus the electron beam emitted by the electron emitter (3).

5. The spark-proof cathode assembly according to claim 1, characterized in that: The focusing body (1), the shielding tube (4), the shielding cup (5) and the electrode wire (7) are all made of metal materials, and the insulator (6) and the vacuum tube shell (8) are all made of insulating materials.

6. The spark-proof cathode assembly according to claim 5, characterized in that: The metal material is Kovar alloy, and the insulating material is ceramic or glass whose expansion coefficient matches that of Kovar alloy.

7. The spark-proof cathode assembly according to claim 1, characterized in that: The wall thickness of the shielding tube (4) and the shielding cup (5) is 0.3-1.0 mm, and the diameter of the electrode wire (7) is 0.8-2.0 mm.

8. The spark-proof cathode assembly according to claim 1, characterized in that: The mounting plate (2) has an annular protrusion (22) at a position close to the central hole (21), and the annular protrusion (22) is sealingly sleeved with the cup mouth of the shielding cup (5).

9. The spark-proof cathode assembly according to claim 1, characterized in that: The hole depth of the avoidance hole (51) along its axial direction is not less than 5 mm.

10. The spark-proof cathode assembly according to claim 1, characterized in that: The thickness of the insulator (6) filled in the shielding cup (5) is not less than 3 mm.

11. An X-ray tube, characterized in that: include: Vacuum tube shell (8); The spark-proof cathode assembly according to any one of claims 1 to 10.

12. The X-ray tube according to claim 11, characterized in that: The vacuum tube shell (8) comprises a trumpet-shaped connecting tube shell (81) and a main tube shell (82) surrounding the entire anti-spark cathode assembly, the small end of the connecting tube shell (81) is sealed and connected to the shielding tube (4), and the large end of the connecting tube shell (81) is sealed and connected to the main tube shell (82).

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