Cathode heater subassembly for a traveling wave tube and method of manufacture

Abstract

The application provides a cathode heater subassembly for a traveling wave tube and a preparation method, and belongs to the technical field of electric vacuum devices. The cathode heater subassembly comprises a cathode cake, a solid spherical cathode used as an electron source of the traveling wave tube to emit electrons; a heater, a composite structure composed of a boron nitride insulating layer, a graphite electrode layer and a boron nitride covering layer, the graphite electrode layer is located between the boron nitride insulating layer and the boron nitride covering layer, the graphite electrode layer is a single helix structure, the boron nitride insulating layer is brazed to the bottom of the cathode cake, and the heater is used for heating the cathode cake; a heater lead, comprising a first heater lead and a second heater lead, the first heater lead is brazed to a first end of the single helix structure of the graphite electrode layer through the boron nitride covering layer, the second heater lead is brazed to a second end of the single helix structure of the graphite electrode layer through the boron nitride covering layer, the first end is a position away from the center of the single helix structure of the graphite electrode layer, and the second end is a position close to the center of the single helix structure of the graphite electrode layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric vacuum devices, in particular to a cathode heater subassembly for a traveling wave tube and a preparation method thereof. BACKGROUND

[0002] The traveling wave tube is a key component for a satellite. In the traveling wave tube, a cathode generates and emits an electron stream at a specific working temperature. The cathode heater subassembly provides heat for the cathode. The cathode heater subassembly is used to maintain the cathode at the working temperature by heating, so as to continuously generate and emit electrons. In a traditional cathode heater subassembly, a tungsten-rhenium wire is wound into a double helix structure, and then subjected to electrophoresis and sintering. After a tungsten spring is sleeved on the lead, the tungsten-rhenium wire and alumina powder are loaded into a cathode cylinder for sintering together. Then, the cathode is prepared through processes such as salt immersion, ball forming, film coating, and the like, so as to form the cathode heater subassembly.

[0003] However, the traditional cathode heater subassembly is used in a high-temperature environment of 1200℃ for a long time. The alumina is slowly reduced by tungsten at high temperature, which causes the heater in the cathode heater subassembly to be short-circuited, and causes the traveling wave tube to age. In addition, the sintered alumina is loose inside, and is prone to adsorption and desorption. The tungsten-rhenium wire is wound into a double helix structure with a large volume, which causes the cathode heater subassembly to have a large volume and pores, and the heat transfer path to be long, and the heater to have high power consumption, thereby causing the working temperature of the cathode heater subassembly to be too high. SUMMARY

[0004] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present application provides a cathode heater subassembly for a traveling wave tube and a preparation method thereof.

[0005] According to an embodiment of the present application, a cathode heater subassembly for a traveling wave tube is provided, which comprises:

[0006] a cathode cake, the cathode cake being a solid spherical cathode, and being used for emitting electrons as an electron source of the traveling wave tube; a heater, the heater being a composite structure composed of a boron nitride insulation layer, a graphite electrode layer and a boron nitride cover layer, the graphite electrode layer being located between the boron nitride insulation layer and the boron nitride cover layer, the graphite electrode layer being a single helix structure, the boron nitride insulation layer being brazed to the bottom of the cathode cake, and the heater being used for heating the cathode cake; and a heater lead, the heater lead comprising a first heater lead and a second heater lead, the first heater lead being brazed to a first end of the single helix structure on the graphite electrode layer through the boron nitride cover layer, the second heater lead being brazed to a second end of the single helix structure on the graphite electrode layer through the boron nitride cover layer, the first end being a position away from the center of the single helix structure of the graphite electrode layer, and the second end being a position close to the center of the single helix structure of the graphite electrode layer.

[0007] According to an embodiment of the present application, the thickness of the boron nitride insulation layer is 1 mm; and the thickness of the boron nitride cover layer is 1 mm±0.05 mm.

[0008] According to an embodiment of the present application, the boron nitride cover layer has a first hole and a second hole, the first hole corresponds to the first end of the single helix structure on the graphite electrode layer, and the second hole corresponds to the second end of the single helix structure on the graphite electrode layer, and the diameters of the first hole and the second hole are both 0.5mm-0.8mm.

[0009] According to an embodiment of the present application, the first thermal sub-lead is brazed to the first end of the single helix structure on the graphite electrode layer through the first hole, and the second thermal sub-lead is brazed to the second end of the single helix structure on the graphite electrode layer through the second hole.

[0010] According to an embodiment of the present application, the length of the graphite electrode layer is 15mm, the width is 0.2mm, and the thickness is 0.2mm; and the thermal conductivity of the graphite electrode layer is greater than or equal to 2000W / (m·K).

[0011] According to an embodiment of the present application, the material of the thermal sub-lead includes molybdenum-rhenium alloy and nickel wire, and the thermal sub-lead is prepared by wrapping the nickel wire with the molybdenum-rhenium alloy belt.

[0012] According to an embodiment of another aspect of the present application, a preparation method of a cathode thermal sub-assembly is provided, and the method comprises:

[0013] The boron nitride insulation layer is deposited on the isostatic pressing graphite mold by chemical vapor deposition of boron chloride and ammonia; the graphite electrode layer is prepared on the boron nitride insulation layer; the graphite electrode layer is laser processed to obtain a graphite electrode layer with a single helix structure, the first end of the single helix structure of the graphite electrode layer is a position away from the center of the single helix structure of the graphite electrode layer, and the second end of the single helix structure of the graphite electrode layer is a position close to the center of the single helix structure of the graphite electrode layer; the boron nitride cover layer is prepared on the graphite electrode layer with the single helix structure, and the thermal sub-lead hole is processed on the boron nitride cover layer to obtain the thermal sub; the graphite electrode layer with the single helix structure of the thermal sub is vacuum brazed with the thermal sub-lead through the thermal sub-lead hole, and the boron nitride insulation layer of the thermal sub is brazed with the bottom of the cathode cake to obtain the cathode thermal sub-assembly.

[0014] According to an embodiment of the present application, after the boron nitride insulation layer of the thermal sub is brazed with the bottom of the cathode cake, the method further comprises: surface film coating of the cathode cake.

[0015] According to an embodiment of the present application, brazing the boron nitride insulation layer of the thermal sub with the bottom of the cathode cake comprises:

[0016] The solder is added between the thermal sub and the bottom of the cathode cake, and the boron nitride insulation layer of the thermal sub is connected to the bottom of the cathode cake by the solder.

[0017] According to the embodiment of the present application, the hot sub lead wire comprises a first hot sub lead wire and a second hot sub lead wire, both of which are composed of molybdenum-rhenium alloy and nickel wire, and the hot sub lead wire hole comprises a first hole and a second hole, the first hole corresponding to the first end of the single helix structure on the graphite electrode layer, and the second hole corresponding to the second end of the single helix structure on the graphite electrode layer.

[0018] According to the embodiment of the present application, the vacuum brazing of the hot sub graphite electrode layer with single helix structure and the hot sub lead wire through the hot sub lead wire hole comprises:

[0019] The vacuum brazing of the first end of the single helix structure on the graphite electrode layer and the molybdenum-rhenium alloy belt through the first hole of the hot sub lead wire hole, and the vacuum brazing after the nickel wire is wrapped with the molybdenum-rhenium alloy belt, to obtain the first hot sub lead wire.

[0020] The vacuum brazing of the second end of the single helix structure on the graphite electrode layer and the molybdenum-rhenium alloy belt through the second hole of the hot sub lead wire hole, and the vacuum brazing after the nickel wire is wrapped with the molybdenum-rhenium alloy belt, to obtain the second hot sub lead wire.

[0021] According to the embodiment of the present application, the hot sub, the hot sub lead wire and the cathode cake adopting the composite structure of the boron nitride insulation layer, the graphite electrode layer and the boron nitride cover layer form the cathode hot sub assembly, since the insulation layer of the hot sub adopts the boron nitride with high thermal conductivity, and the electrode layer adopts the pyrolytic graphite with high density and low outgassing rate, the technical problems of the short circuit of the hot sub caused by the low thermal conductivity of the traditional alumina ceramic and the high power consumption of the large volume hot sub caused by the loose internal structure of the traditional alumina ceramic after sintering, the easy absorption and outgassing, are solved, so that the light weight, low outgassing rate and high reliability cathode hot sub assembly is realized. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application taken in conjunction with the accompanying drawings, in which:

[0023] Figure 1 FIG. 1 is a schematic diagram of the cathode hot sub assembly for the traveling wave tube according to the embodiment of the present application;

[0024] FIG. 2(a) is a schematic diagram of the boron nitride insulation layer and the graphite electrode layer in the hot sub according to the embodiment of the present application;

[0025] FIG. 2(b) is a schematic diagram of the hot sub according to the embodiment of the present application;

[0026] Figure 3 FIG. 3 is a schematic diagram of the hole on the boron nitride cover layer;

[0027] FIG. 4(a) is a direct schematic diagram of the hot sub lead wire brazed to the graphite electrode layer;

[0028] Figure 4(b) Schematic diagram of the thermal lead being brazed to the graphite electrode layer through the boron nitride capping layer;

[0029] Figure 5 This is a flowchart of a method for preparing a cathode thermal component according to an embodiment of the present invention. Detailed Implementation

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0032] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0033] Figure 1 This is a schematic diagram of a cathode thermal assembly for a traveling wave tube according to an embodiment of the present invention.

[0034] like Figure 1 As shown, the cathode thermal assembly includes a cathode disc 1, a thermal element 2, and thermal leads 3. The thermal leads 3 include a first thermal lead 3-1 and a second thermal lead 3-2.

[0035] According to an embodiment of the present application, the cathode cake 1 can be a solid spherical cathode for emitting electrons as a traveling wave tube electron source. The cathode 1 can be a salt-impregnated cathode prepared by impregnating aluminate into a porous tungsten sponge structure and then turning the structure into a spherical surface. The salt-impregnated cathode cake has the characteristics of high emission current density, long service life, and electron bombardment, and is widely used in electric vacuum devices.

[0036] According to an embodiment of the present application, the heat sub 2 is used to heat the cathode cake and is arranged at the bottom of the cathode cake 1. The heat sub 2 is brazed to the cathode cake 1 by using TiCr 20 Mn7Ni3 high-temperature active solder at a temperature of 1350°C. For example, FIG. 2(a) is a schematic view of a boron nitride insulation layer and a graphite electrode layer in a heat sub according to an embodiment of the present application; and FIG. 2(b) is a schematic view of a heat sub according to an embodiment of the present application.

[0037] According to an embodiment of the present application, in combination with FIGS. 2(a) and 2(b), the heat sub 2 is a composite structure composed of a boron nitride insulation layer 2-1, a graphite electrode layer 2-2, and a boron nitride cover layer 2-3. The heat sub 2 is prepared by sequentially depositing the boron nitride insulation layer 2-1, the graphite electrode layer 2-2, and the boron nitride cover layer 2-3 in a deposition mold (not shown in the figure).

[0038] According to an embodiment of the present application, the graphite electrode layer 2-2 is located between the boron nitride insulation layer 2-1 and the boron nitride cover layer 2-3. After the graphite electrode layer 2-2 is deposited, the graphite electrode layer can be processed to form a single helix structure and a planar structure.

[0039] According to an embodiment of the present application, since the graphite electrode layer is a planar single helix structure, compared with a heat sub prepared by conventionally winding a double helix tungsten-rhenium wire in an axial direction, the cathode heat sub assembly can be made smaller and lighter.

[0040] According to an embodiment of the present application, the boron nitride cover layer 2-3 is located on the graphite electrode layer 2-2. Since the thickness of the boron nitride cover layer 2-3 is 1 mm ± 0.05 mm, the single helix structure of the graphite electrode layer 2-2 can be observed through the boron nitride cover layer 2-3, so that a hole corresponding to the two ends of the single helix structure can be processed on the boron nitride cover layer in the future. In the present application, in order to better reflect the boron nitride cover layer 2-3, the graphite electrode layer 2-2 under the boron nitride cover layer 2-3 is not visualized in FIG. 2(b).

[0041] According to an embodiment of the present application, the single helix structure of the graphite electrode layer 2-2 includes a first end a and a second end b. The boron nitride covering layer 2-3 includes a first hole 2-31 and a second hole 2-32. The first hole 2-31 can correspond to the first end a of the single helix structure of the graphite electrode layer 2-2, and the second hole 2-32 can correspond to the second end b of the single helix structure of the graphite electrode layer 2-2. As shown in FIG. 4 (a) and FIG. 4 (b), the first heat sub 3-1 is soldered on the first end a of the single helix structure of the graphite electrode layer 2-2 through the first hole 2-31 of the boron nitride covering layer 2-3, and the second heat sub 3-2 is soldered on the second end b of the single helix structure of the graphite electrode layer 2-2 through the second hole 2-32 of the boron nitride covering layer 2-3. Figure 3 Schematic diagram of the holes on the boron nitride covering layer.

[0042] According to an embodiment of the present application, the first hole 2-31 on the boron nitride covering layer 2-3 corresponds to the first end a of the single helix structure of the graphite electrode layer 2-2, and the second hole 2-32 corresponds to the second end b of the single helix structure of the graphite electrode layer 2-2, so as to solder the heat sub lead through the holes of the boron nitride covering layer to the positions of the first end and the second end of the corresponding graphite electrode layer.

[0043] For example, FIG. 4 (a) is a schematic diagram of soldering the heat sub lead to the graphite electrode layer; FIG. 4 (b) is a schematic diagram of soldering the heat sub lead to the graphite electrode layer through the boron nitride covering layer.

[0044] As shown in FIG. 4 (a) and FIG. 4 (b), the first heat sub 3-1 is soldered on the first end a of the single helix structure of the graphite electrode layer 2-2 through the first hole 2-31 on the boron nitride covering layer 2-3, and the second heat sub 3-2 is soldered on the second end b of the single helix structure of the graphite electrode layer 2-2 through the second hole 2-32 on the boron nitride covering layer 2-3.

[0045] According to an embodiment of the present application, as shown in FIG. 2 (a), the first end a can be a position away from the center of the single helix structure of the graphite electrode layer, and the second end b can be a position close to the center of the single helix structure of the graphite electrode layer.

[0046] According to an embodiment of the present application, as shown in FIG. 2 (a), the first end a can be a position away from the center of the single helix structure of the graphite electrode layer, and the second end b can be a position close to the center of the single helix structure of the graphite electrode layer. Figure 1 As shown in FIG. 5, the boron nitride covering layer 2-3 in the heat sub 2 is soldered to the bottom of the cathode cake to form a cathode heat sub assembly.

[0047] According to an embodiment of the present application, the thickness of the boron nitride insulating layer can be 1 mm, and the thickness of the boron nitride covering layer can be 1 mm ± 0.05 mm.

[0048] According to an embodiment of the present application, the thermal conductivity of the boron nitride insulating layer is 3 times higher than that of the traditional aluminum oxide, and the material is dense and has low outgassing rate.

[0049] According to the embodiment of the present application, the length of the graphite electrode layer 2-2 deposited on the boron nitride insulation layer 2-1 is 15 mm, the width is 0.2 mm, and the thickness is 0.2 mm. It can be processed into an electrode layer with a single helical planar structure, which has a thermal conductivity greater than or equal to 2000 W / (m·K), and has the characteristics of material density and low outgassing rate.

[0050] According to the embodiment of the present application, the size of the first hole 2-31 and the second hole 2-32 on the boron nitride cover layer 2-3 can be 0.5 mm-0.8 mm, so that the thermal sub-lead can be brazed to the graphite electrode layer.

[0051] According to the embodiment of the present application, the material of the thermal sub-lead is molybdenum-rhenium alloy and nickel wire, which is brazed to the first end a and the second end b of the graphite electrode layer by using TiCr 20 Mn7Ni3 high-temperature active solder, and the molybdenum-rhenium alloy is clamped and brazed with the nickel wire.

[0052] According to the embodiment of the present application, brazing the molybdenum-rhenium alloy to the first end a of the graphite electrode layer can include brazing the molybdenum-rhenium alloy to the first end a of the graphite electrode layer by using TiCr 20 Mn7Ni3 high-temperature active solder, and the molybdenum-rhenium alloy is clamped and brazed with the nickel wire.

[0053] According to the embodiment of the present application, the cathode thermal sub-assembly is formed by adopting the composite structure of the thermal sub-lead, the thermal sub-lead, and the cathode cake composed of the boron nitride insulation layer, the graphite electrode layer, and the boron nitride cover layer. Since the insulation layer of the thermal sub-lead adopts boron nitride with high thermal conductivity, and the electrode layer adopts pyrolytic graphite with high density and low outgassing rate, the technical problems of short circuit of the thermal sub-lead caused by low thermal conductivity of traditional alumina ceramic and high power consumption of the thermal sub-assembly caused by large volume due to easy absorption and outgassing of traditional alumina ceramic after sintering are solved, so that the cathode thermal sub-assembly with light weight, low outgassing rate, and high reliability is realized.

[0054] Figure 5 The flowchart of the preparation method of the cathode thermal sub-assembly according to the embodiment of the present application.

[0055] As shown in Figure 5 , the method comprises operations S510-S550.

[0056] In operation 510, a boron nitride insulation layer is deposited on an isostatic pressing graphite mold by chemical vapor deposition of boron chloride and ammonia.

[0057] In operation 520, a graphite electrode layer is prepared on the boron nitride insulation layer.

[0058] At operation 530, laser processing is performed on the graphite electrode layer to obtain a graphite electrode layer with a single helix structure, a first end of the graphite electrode layer with the single helix structure being a position away from a center of the single helix structure of the graphite electrode layer, and a second end of the graphite electrode layer with the single helix structure being a position close to the center of the single helix structure of the graphite electrode layer.

[0059] At operation 540, a boron nitride cover layer is prepared on the graphite electrode layer with the single helix structure, and two hot sub-lead holes are processed on the boron nitride cover layer to obtain a hot sub, wherein the two hot sub-lead holes correspond to the first end and the second end, respectively.

[0060] At operation 550, the graphite electrode layer with the single helix structure of the hot sub is vacuum brazed with the hot sub-lead through the hot sub-lead holes, and the boron nitride insulating layer of the hot sub is brazed with the bottom of the cathode cake to obtain a cathode hot sub assembly.

[0061] According to the embodiment of the present application, high-purity boron chloride (BCl3) and ammonia gas (NH3) can be used to deposit high-purity and high-density hexagonal pyrolytic boron nitride h-BN on an isostatic pressing graphite mill under a certain furnace pressure and at a high temperature of 2100°C by a chemical vapor deposition method to form a boron nitride insulating layer with a thickness of 1mm.

[0062] According to the embodiment of the present application, the deposited boron nitride insulating layer has a thermal conductivity 3 times higher than that of traditional aluminum oxide and has good density and low outgassing rate.

[0063] According to the embodiment of the present application, high-purity and high-density pyrolytic graphite can be deposited on the boron nitride insulating layer by a chemical vapor deposition method under an atmosphere of high-purity CH4 at a high temperature of 2000°C±20°C to form a graphite electrode layer, and the deposited graphite electrode layer is processed in a structure by high-speed milling or laser processing to form a planar single helix structure, thereby completing the composite structure of the boron nitride insulating layer and the graphite electrode layer.

[0064] According to the embodiment of the present application, the graphite electrode layer has a graphite length of 15mm, a width of 0.2mm, a thickness of 0.2mm, a cold resistance of 15.3Ω±0.5Ω, a resistance of 7.5Ω±0.3Ω under a hot state, and a power consumption of about 3.1W.

[0065] According to the embodiment of the present application, the thermal conductivity of the deposited graphite electrode layer can be greater than or equal to 2000W / (m·K), which is ten times that of isostatic pressing graphite, the material is dense, and the outgassing rate is low.

[0066] According to the embodiment of the present application, the first end of the graphite electrode layer with the single helix structure is a position away from a center of the single helix structure of the graphite electrode layer, and the second end of the graphite electrode layer with the single helix structure is a position close to the center of the single helix structure of the graphite electrode layer.

[0067] According to the embodiment of the present application, high-purity high-density pyrolytic boron nitride can be deposited on the graphite electrode layer of the composite structure of the boron nitride insulation layer and the graphite electrode layer by using the chemical vapor deposition method under the atmosphere of high-purity CH4 at a high temperature of 2000℃±20℃, to form a boron nitride covering layer with a thickness of 1mm±0.05mm.

[0068] According to the embodiment of the present application, the boron nitride insulation layer, the graphite electrode layer and the boron nitride covering layer form a hot sub with a composite structure, and two hot sub lead holes, i.e., a first hole and a second hole, are processed on the boron nitride covering layer, wherein the first hole is located at a position corresponding to the first end of the single helix structure of the graphite electrode layer, and the second hole is located at a position corresponding to the second end of the single helix structure of the graphite electrode layer.

[0069] According to the embodiment of the present application, the first hot sub lead can be vacuum brazed with the first end of the graphite electrode layer through the first hole, and the second hot sub lead can be vacuum brazed with the second end of the graphite electrode layer through the second hole, to form a hot sub with hot sub leads.

[0070] According to the embodiment of the present application, the boron nitride insulation layer of the hot sub with hot sub leads can be brazed with the cathode cake at a temperature of 1350℃ by using TiCr 20 Mn7Ni3 high-temperature active solder, to form a cathode hot sub assembly.

[0071] According to the embodiment of the present application, the brazing of the boron nitride insulation layer of the hot sub with hot sub leads and the cathode cake can be performed in a vacuum protection furnace, specifically: heating to 1250℃±10℃ at a heating rate of not more than 15℃ / min and maintaining for 25-35min; then heating to 1350℃±10℃ at a heating rate of not more than 20℃ / min and maintaining for 3-5min, so that the TiCr 20 Mn7Ni3 high-temperature active solder starts to dissolve; cooling to 800℃±10℃ within 30min; cooling to 400℃±10℃ within 30min, and then cooling to room temperature with the furnace, so that the solder solidifies, thereby brazing, and the cathode hot sub assembly is obtained after the brazing is completed.

[0072] According to the embodiment of the present application, the cathode hot sub assembly is formed by using the hot sub with a composite structure composed of the boron nitride insulation layer, the graphite electrode layer and the boron nitride covering layer, the hot sub leads and the cathode cake, since the insulation layer of the hot sub adopts high-thermal-conductivity boron nitride and the electrode layer adopts high-density and low-outgassing-rate pyrolytic graphite, the technical problems of short circuit of the hot sub caused by low thermal conductivity of the traditional alumina ceramic and high power consumption of the hot sub caused by large volume of the hot sub due to outgassing of the traditional alumina ceramic after sintering are solved, thereby realizing the cathode hot sub assembly with light weight, low outgassing rate and high reliability.

[0073] According to the embodiment of the present application, after brazing the boron nitride insulating layer of the hot element to the bottom of the cathode cake, a film coating treatment is needed on the surface of the cathode cake.

[0074] According to the embodiment of the present application, brazing the boron nitride insulating layer of the hot element to the bottom of the cathode cake comprises: adding solder between the hot element and the bottom of the cathode cake, and using the solder to connect the boron nitride insulating layer of the hot element to the bottom of the cathode cake.

[0075] According to the embodiment of the present application, the hot element and the cathode cake can be welded by using solder, and the cathode cake and the hot element with the hot element lead form a cathode hot element assembly.

[0076] According to the embodiment of the present application, the hot element lead comprises a first hot element lead and a second hot element lead, both of which are composed of molybdenum-rhenium alloy and nickel wire, and the hot element lead hole comprises a first hole and a second hole, the first hole corresponding to the first end of the single helix structure on the graphite electrode layer, and the second hole corresponding to the second end of the single helix structure on the graphite electrode layer.

[0077] According to the embodiment of the present application, the single helix structure of the graphite electrode layer can be observed through the boron nitride covering layer, the first hole can be processed at the position of the boron nitride covering layer corresponding to the first end of the single helix structure until the first end of the single helix structure is exposed, and the second hole can be processed at the position of the boron nitride covering layer corresponding to the second end of the single helix structure until the second end of the single helix structure is exposed.

[0078] According to the embodiment of the present application, the first end of the single helix structure of the graphite electrode layer can be vacuum brazed to the molybdenum-rhenium alloy strip through the first hole, and after the welding is completed, the nickel wire is wrapped with the molybdenum-rhenium alloy strip and then brazed, so that the first hot element lead is obtained and brazed to the graphite electrode layer.

[0079] According to the embodiment of the present application, the second end of the single helix structure of the graphite electrode layer can be vacuum brazed to the molybdenum-rhenium alloy strip through the second hole, and after the welding is completed, the nickel wire is wrapped with the molybdenum-rhenium alloy strip and then brazed, so that the second hot element lead is obtained and brazed to the graphite electrode layer.

[0080] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above are only specific embodiments of the present application and are not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A cathode heater subassembly for a traveling wave tube, characterized by, The application relates to a solid-sphere cathode for a traveling wave tube electron source, which comprises the following components: a cathode cake (1), which is a solid-sphere cathode used for emitting electrons as a traveling wave tube electron source; a hot sub (2), which is a composite structure composed of a boron nitride insulating layer (2-1), a graphite electrode layer (2-2) and a boron nitride covering layer (2-3), the graphite electrode layer (2-2) is located between the boron nitride insulating layer (2-1) and the boron nitride covering layer (2-3), after the graphite electrode layer (2-2) is deposited, the graphite electrode layer is processed to form a single helix structure and a plane structure, the boron nitride insulating layer (2-1) is brazed to the bottom of the cathode cake (1), and the hot sub (2) is used for heating the cathode cake (1); a hot sub lead (3), which comprises a first hot sub lead (3-1) and a second hot sub lead (3-2), the first hot sub lead (3-1) is brazed to a first end (a) of the single helix structure of the graphite electrode layer (2-2) through the boron nitride covering layer (2-3), the second hot sub lead (3-2) is brazed to a second end (b) of the single helix structure of the graphite electrode layer (2-2) through the boron nitride covering layer (2-3), the first end (a) is a position away from the center of the single helix structure of the graphite electrode layer (2-2), and the second end (b) is a position close to the center of the single helix structure of the graphite electrode layer (2-2).

2. The cathode thermal subassembly of claim 1, wherein, The thickness of the boron nitride insulating layer (2-1) is 1 mm; and the thickness of the boron nitride covering layer (2-3) is 1 mm+ / -0.05 mm.

3. The cathode thermal subassembly of claim 2, wherein, The boron nitride covering layer (2-3) is provided with a first hole (2-31) and a second hole (2-32), the first hole (2-31) corresponds to the first end (a) of the single helix structure of the graphite electrode layer (2-2), the second hole (2-32) corresponds to the second end (b) of the single helix structure of the graphite electrode layer (2-2), and the diameters of the first hole (2-31) and the second hole (2-32) are both 0.5 mm-0.8 mm.

4. The cathode thermal sub-assembly of claim 3, wherein, The first hot sub lead (3-1) is brazed to the first end (a) of the single helix structure of the graphite electrode layer (2-2) through the first hole (2-31), and the second hot sub lead (3-2) is brazed to the second end (b) of the single helix structure of the graphite electrode layer (2-2) through the second hole (2-32).

5. The cathode thermal subassembly of claim 1, wherein, The length of the graphite electrode layer (2-2) is 15 mm, the width is 0.2 mm, and the thickness is 0.2 mm; and the thermal conductivity of the graphite electrode layer (2-2) is greater than or equal to 3000 W / (m*K).

6. The cathode thermal subassembly of claim 1, wherein, The material of the hot sub lead (3) comprises molybdenum-rhenium alloy and nickel wire, and is prepared by wrapping the nickel wire with the molybdenum-rhenium alloy belt.

7. A method of manufacturing a cathode thermal sub-assembly according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: depositing a boron nitride insulating layer (2-1) on an isostatic pressing graphite mold by using boron chloride and ammonia gas for chemical vapor deposition; preparing a graphite electrode layer (2-2) on the boron nitride insulating layer (2-1); The graphite electrode layer (2-2) is laser processed to obtain a graphite electrode layer (2-2) with a single helix structure, wherein a first end (a) of the graphite electrode layer (2-2) with the single helix structure is a position away from the center of the single helix structure of the graphite electrode layer (2-2), and a second end (b) of the graphite electrode layer (2-2) with the single helix structure is a position close to the center of the single helix structure of the graphite electrode layer (2-2); A boron nitride covering layer (2-3) is prepared on the graphite electrode layer (2-2) with the single helix structure, and two thermal sub-lead holes are processed on the boron nitride covering layer (2-3) to obtain a thermal sub, wherein the two thermal sub-lead holes correspond to the first end (a) and the second end (b) respectively; The graphite electrode layer (2-2) with the single helix structure of the thermal sub (2) is vacuum brazed with a thermal sub-lead (3) through the thermal sub-lead holes, and the boron nitride insulating layer (2-1) of the thermal sub is brazed with the bottom of a cathode cake (1) to obtain a cathode thermal sub assembly.

8. The method of claim 7, wherein, After brazing the boron nitride insulating layer (2-1) of the thermal sub (2) with the bottom of the cathode cake (1), the surface of the cathode cake (1) is coated.

9. The method of claim 7, wherein, The brazing of the boron nitride insulating layer (2-1) of the thermal sub (2) with the bottom of the cathode cake (1) comprises: Solder is added between the thermal sub (2) and the bottom of the cathode cake (1), and the boron nitride insulating layer (2-1) of the thermal sub (2) is connected to the bottom of the cathode cake (1) by using the solder.

10. The method of claim 7, wherein, The thermal sub-lead (3) comprises a first thermal sub-lead (3-1) and a second thermal sub-lead (3-2), both of which are composed of molybdenum-rhenium alloy and nickel wire, and the thermal sub-lead holes comprise a first hole (2-31) and a second hole (2-32), the first hole (2-31) corresponds to the first end (a) of the single helix structure of the graphite electrode layer (2-2), and the second hole (2-32) corresponds to the second end (b) of the single helix structure of the graphite electrode layer (2-2); The vacuum brazing of the graphite electrode layer (2-2) with the single helix structure of the thermal sub (2) with the thermal sub-lead (3) through the thermal sub-lead holes comprises: The first end (a) of the single helix structure of the graphite electrode layer (2-2) is vacuum brazed with a molybdenum-rhenium alloy strip through the first hole (2-31) of the thermal sub-lead hole, and then vacuum brazed after wrapping the nickel wire with the molybdenum-rhenium alloy strip to obtain the first thermal sub-lead (3-1); The second end (b) of the single helix structure of the graphite electrode layer (2-2) is vacuum brazed with the molybdenum-rhenium alloy strip through the second hole (2-32) of the thermal sub-lead hole, and then vacuum brazed after wrapping the nickel wire with the molybdenum-rhenium alloy strip to obtain the second thermal sub-lead (3-2).

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