Energy transmission window and traveling wave tube including the energy transmission window

Abstract

An embodiment of the present invention discloses an energy transmission window and a traveling wave tube including the energy transmission window. The energy transmission window includes a window frame having a vacuum cavity; the window frame includes a window sealing platform surrounding the vacuum cavity for encapsulating a window sheet, a boss surrounding the outside of the window sealing platform and extending in the axial direction of the window frame, and an encapsulation fixing platform surrounding the outside of the boss for encapsulating the window frame; the window sealing platform, the boss, and the encapsulation fixing platform are arranged at intervals. The present invention provides a boss between the window sealing platform and the encapsulation fixing platform, utilizing the plastic deformation generated by the boss to significantly reduce the stress at the sealing interface between the window sheet and the window frame. As a result, oxygen-free copper can be used as the window frame material in conjunction with a diamond window sheet, thereby reducing the transmission loss of the energy transmission window in the terahertz band and increasing the output power of the traveling wave tube.

Description

Technical Field

[0001] The present invention relates to the field of vacuum electronic devices, and more particularly to an energy transmission window and a traveling wave tube including the energy transmission window. Background Art

[0002] The existing energy transmission window structure in vacuum devices has a sealing stress close to the tensile strength of the energy transmission window component, and the reliability of the energy transmission window is low. The conventional method to reduce the sealing interface stress of the energy transmission window is to use side sealing (sealing the outer diameter side wall of the window piece with the inner diameter side wall of the metal window frame) instead of flat sealing (sealing the window piece surface with one side surface of the metal window frame). However, in the terahertz frequency band, the thickness of the diamond window piece is only tens of microns, and it is impossible to use the outer diameter side wall of the window piece and the inner diameter side wall of the metal window frame for sealing. Under the existing energy transmission window structure, in order to reduce the sealing interface stress, only Kovar alloy with a thermal expansion coefficient close to that of the diamond window piece can be used as the energy transmission window frame material. However, the microwave loss of Kovar alloy is relatively large, which leads to an increase in the insertion loss of the energy transmission window and reduces the output power of the vacuum device. Summary of the Invention

[0003] In view of the above problems, one object of the present invention is to provide an energy transmission window, which can effectively reduce the sealing interface stress between the window sheet and the window frame, has high sealing reliability, and can use low-loss metal as the window frame material, thereby reducing the transmission loss of the energy transmission window and increasing the output power of the device.

[0004] Another object of the present invention is to provide a traveling wave tube comprising the above energy transmission window.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] According to one aspect of the present invention, the present invention provides an energy transmission window, wherein the energy transmission window comprises a window frame having a vacuum cavity;

[0007] The window frame comprises:

[0008] A window sealing station surrounding the vacuum chamber for encapsulating the window;

[0009] a boss surrounding the outer side of the window sheet sealing platform and extending along the axial direction of the window frame; and

[0010] A packaging fixing platform surrounding the outer side of the boss for packaging the window frame;

[0011] The window sealing platform, the boss platform and the packaging fixing platform are arranged at intervals.

[0012] In addition, a preferred solution is that the energy transmission window includes a window piece; the edge of one side surface of the window piece is sealed and fixed to the bottom surface of the window piece sealing platform.

[0013] In addition, a preferred solution is that the material of the window frame is oxygen-free copper, and the material of the window piece is diamond.

[0014] In addition, a preferred solution is that the boss in the circumferential direction is a continuous closed structure or a segmented structure.

[0015] In addition, a preferred solution is that the bottom surface of the window sealing platform is higher than the bottom surface of the boss, and the bottom surface of the packaging and fixing platform is lower than the bottom surface of the boss.

[0016] In addition, a preferred solution is to define the inner diameter of the window sealing platform as D1, the outer diameter of the window sealing platform as D3, the inner diameter of the boss as D4, and the outer diameter of the boss as D2; D3-D1≥0.1mm, D4-D3≥0.3mm; D2-D4≥0.2mm.

[0017] In addition, a preferred solution is that the height difference between the bottom surface of the window sealing platform and the bottom surface of the boss is ≥0.2 mm; the height difference between the bottom surface of the packaging fixing platform and the bottom surface of the boss is ≥0.2 mm.

[0018] In addition, a preferred solution is that the inner side wall surface of the boss is opposite to the side wall surface of the window piece, and the side wall surface of the window piece is fitted and fixed to the inner side wall surface of the boss.

[0019] In addition, a preferred solution is that a surface of the window facing away from the window sealing platform is higher than the bottom surface of the boss.

[0020] According to another aspect of the present invention, the present invention further provides a traveling wave tube, comprising:

[0021] A high-frequency system having an electromagnetic wave input structure and an electromagnetic wave output structure;

[0022] an electron gun located at one end of the high frequency system; and

[0023] A collecting electrode located at an end of the high-frequency system away from the electron gun;

[0024] At least one of the electromagnetic wave input structure and the electromagnetic wave output structure includes the energy transmission window as described above.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention sets a boss between the window sealing platform and the packaging fixing platform, and uses the boss to generate plastic deformation to significantly reduce the stress at the sealing interface between the window and the window frame. As a result, oxygen-free copper can be used as the window frame material in combination with the diamond window, reducing the transmission loss of the energy transmission window in the terahertz band and improving the output power of the traveling wave tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Figure 1 A schematic diagram of the existing energy transmission window structure is shown.

[0029] Figure 2 A comparison of transmission loss between oxygen-free copper window frames and Kovar (nickel-cobalt) window frames is shown.

[0030] Figure 3 A three-dimensional cross-sectional view of the existing oxygen-free copper window frame structure and the diamond window sheet matching structure is shown.

[0031] Figure 4 Show Figure 3 The figure shows the stress distribution diagram of the sealing between the existing oxygen-free copper window frame and the diamond window.

[0032] Figure 5a A cross-sectional view showing a window frame in an energy transmission window structure provided by the present invention.

[0033] Figure 5b A cross-sectional view showing the cooperation between the window frame and the window sheet in the energy transmission window structure provided by the present invention is shown.

[0034] Figure 6 A three-dimensional cross-sectional view of the cooperation structure of the window frame and the window sheet in the energy transmission window structure provided by the present invention is shown.

[0035] Figure 7 Show Figure 6 The present invention provides a sealing stress distribution diagram of an oxygen-free copper window frame and a diamond window.

[0036] Figure 8 A transmission loss comparison diagram is shown for a window frame provided by the present invention when oxygen-free copper is used and when Kovar is used. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0038] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0039] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0040] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0041] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0042] A traveling wave tube (TWT) is a microwave electron tube that achieves amplification by continuously modulating the speed of an electron beam. The electron gun, high-frequency system, and collector are responsible for emission, transmission, and collection of electrons, respectively. The slow-wave structure provides electromagnetic waves for interaction with the electrons, and the energy window facilitates the transmission of electromagnetic waves within and outside the device. Besides optimizing the slow-wave structure and enhancing the beam-wave interaction, another important approach to increasing the output power of a TWT is to reduce transmission losses in the energy window. Figure 1 Shows a schematic diagram of the existing energy transmission window structure, Figure 1 The energy window structure shown is a diamond box-type energy window, primarily composed of a straight waveguide 100, a circular waveguide 200, and a diamond window 300. Currently, in the short millimeter wave and terahertz frequency bands, the frame material for diamond energy windows is typically iron-nickel-cobalt ceramic sealing alloy (Kovar). Kovar is chosen as the frame material for diamond energy windows because, among the metal materials commonly used in vacuum devices, Kovar and diamond have the closest thermal expansion coefficients. When the two are fixed together using a flat seal, the sealing stress at the interface is minimized at high temperatures, as shown in Table 1. However, in the terahertz band, Kovar's equivalent electrical conductivity is only one-twentieth that of oxygen-free copper, resulting in significant microwave losses. Figure 2 A comparison chart of transmission loss between oxygen-free copper and Kovar window frames is shown. The transmission loss of the energy transmission window is calculated for Kovar and oxygen-free copper window frames, respectively. When the Kovar window frame is made of Kovar, the calculated S21 (transmission loss of the energy transmission window) is approximately -2.5dB, which agrees with the measured data (-2.5dB to -3dB). When oxygen-free copper is used as the window frame material, the calculated S21 (transmission loss of the energy transmission window) is approximately -0.5dB within the 310-390GHz frequency band. This represents a 2dB reduction in transmission loss, resulting in a 60% increase in the output power of the traveling wave tube, significantly improving the device's output power.

[0043] Commonly used materials in vacuum devices <![CDATA[Coefficient of thermal expansion (×10 -6 K -1 )]]> <![CDATA[Equivalent conductivity (×10 6 S / m)]]> Nickel-copper alloy 15.3 0.74 pure iron 12.1 8.7 Iron-cobalt-nickel ceramic seal alloy (Kovar) 6.9 1 oxygen-free copper 16.5 20 diamond 2.3 —

[0044] Table 1

[0045] If using Figure 1 The original energy transmission window structure shown in the figure is replaced with oxygen-free copper by the window frame material from Kovar alloy. The sealing stress between the diamond window and the energy transmission window is calculated, as shown in the figure below. Figure 3 、 4 As shown. Figure 4 It is not difficult to see that the maximum principal stress in the diamond window surface sealing area is 210MPa, which is greater than the average sealing strength of 116.2MPa for the diamond and oxygen-free copper tensile member. Therefore, the existing energy transmission window frame structure cannot meet the design requirements. A new energy transmission window structure is needed to reduce the sealing stress at the interface between the window and the window frame at high temperatures.

[0046] In order to solve the above technical problems, according to one aspect of the present invention, the present invention first provides an energy transmission window, combined with Figure 5a 、 Figure 5b 、 Figure 6 As shown, specifically, the energy transmission window includes a window frame 1 having a vacuum cavity 10. The window frame 1 is made of oxygen-free copper. The window frame 1 includes a window sealing platform 11 surrounding the vacuum cavity 10 for encapsulating the window 2, a boss 12 surrounding the window sealing platform 11 and extending along the axial direction of the window frame 1, and an encapsulation and fixing platform 13 surrounding the boss 12 for encapsulating the window frame. The window sealing platform 11, boss 12, and encapsulation and fixing platform 13 are spaced apart, i.e., a first groove structure 14 is formed between the window sealing platform 11 and the boss 12, and a second groove structure 15 is formed between the boss 12 and the encapsulation and fixing platform 13. Optionally, the boss 12 is a continuous closed structure or a segmented structure in the circumferential direction. Compared with the existing window frame structure, when the oxygen-free copper window sealing platform is sealed with the diamond window, the sealing stress at the interface will be blocked by the first groove structure 14 and will not be directly transmitted along the radial direction of the window frame, thereby attenuating the sealing stress at the interface. In addition, the provision of the second groove structure 15 can ensure that the boss 12 has space for radial plastic deformation relative to the packaging fixing platform 13, so that the boss 12 can have a better ability to release the sealing stress at the interface. The present invention, by providing the boss 12 between the window sealing platform 11 and the packaging fixing platform 13, utilizes the boss 12 to generate plastic deformation, thereby significantly reducing the sealing stress at the packaging interface between the window 2 and the window frame 1. As a result, oxygen-free copper can be used as the window frame material in conjunction with the diamond window, reducing the transmission loss of the energy transmission window in the terahertz band and improving the output power of the traveling wave tube.

[0047] Optionally, the window frame 1 is an integrated structure, and the window frame 1 further comprises a plurality of flange holes for connecting components, and the plurality of flange holes are arranged circumferentially along the window frame 1, which belongs to conventional technology and is not limited in this embodiment. Figure 5a 、 Figure 5b as well as Figure 6 The perspective shown in the figure is the use state of the energy transmission window. In this view, the surface of the window sealing platform used for fixing the window package is the bottom surface of the window sealing platform. It can be understood that the bottom surface described in this embodiment is the perspective shown in the reference figure and is non-restrictive.

[0048] In one embodiment, the energy transmission window includes a window 2, and the material of the window 2 is diamond. Generally, the thickness of the diamond window in the terahertz band is 60 microns to 200 microns, and it is impossible to seal through the side wall of the window, and it is necessary to seal with the bottom surface of the window sealing platform. In one embodiment provided by the present invention, referring to Figure 5a 、 Figure 5b As shown, the edge of one side surface of the window 2 is sealed and fixed to the bottom surface of the window sealing platform 11, that is, the window 2 and the window sealing platform 11 are sealed and fixed using a flat seal method. Of course, thicker diamond windows can also be used in other frequency bands. Such windows can be sealed and fixed to the inner wall of the window sealing platform using a side seal method, and the present invention does not limit this.

[0049] Reference Figure 5a 、 Figure 5b 、 Figure 6 As shown, in this embodiment, the bottom surface of the window sealing platform 11 is higher than the bottom surface of the boss 12, and the bottom surface of the packaging fixing platform 13 is lower than the bottom surface of the boss 12. Optionally, the height difference between the bottom surface of the window sealing platform 11 and the bottom surface of the boss 12 is ≥0.2mm. The height difference between the bottom surface of the packaging fixing platform 13 and the bottom surface of the boss 12 is ≥0.2mm. The bottom surface of the packaging fixing platform is used to fix with the external waveguide structure to fix the energy transmission window. The inner side wall surface of the edge of the packaging fixing platform and the inner side wall surface of the edge of the boss can provide guidance and fixation for the insertion of the waveguide structure, which is easy to assemble and convenient to process.

[0050] Specifically, combined Figure 5a 、 Figure 5b As shown, it is defined that the inner diameter of the window sealing platform 11 is D1, the outer diameter of the window sealing platform 11 is D3, the inner diameter of the boss 12 is D4, the outer diameter of the boss 12 is D2, the height of the window sealing platform 11 is FD2, the height of the boss 12 is FD1, and the height of the packaging fixing platform 13 is FD3.

[0051] Taking a 340 GHz energy transmission window as an example, the inner diameter D1 of the window sealing platform 11, the inner diameter D4 of the protrusion 12 (equivalent to the diameter of the diamond window), and the height FD2 of the window sealing platform 11 are structural parameters of the energy transmission window and are determined when designing the electrical performance of the energy transmission window. The remaining dimensions, the outer diameter D2 of the protrusion 12, the outer diameter D3 of the window sealing platform 11, and the height FD1 of the protrusion 12, determine the sealing surface area and the protrusion size for releasing sealing stress. The numerical relationship is as follows:

[0052] FD1: FD3-0.2mm≥FD1≥FD2+0.2mm;

[0053] D3: D3-D1≥0.1mm, D4-D3≥0.3mm;

[0054] D2: D2-D4 ≥ 0.2 mm;

[0055] That is, D3-D1 ≥ 0.1mm, D4-D3 ≥ 0.3mm, and D2-D4 ≥ 0.2mm. The bottom surface of the window sealing platform 11 forms the sealing surface for securing the window. If the width of the sealing surface is too small, the uniformity of the sealing compound between the window and the sealing surface will be poor, and the window will be prone to leakage after sealing, affecting the airtightness of the energy transmission window.

[0056] Among the various parameters used to evaluate the sealing stress of the energy transmission window, the principal stress parameter perpendicular to the diamond window surface is the most critical. Using ANSYS Workbench, the maximum principal stress in the diamond window surface sealing area was used as the target driving parameter to optimize the key structural parameters of the window frame. Ultimately, the structural parameters were obtained when the diamond window surface sealing stress was minimized. The minimum value of the maximum principal stress on the diamond window surface was 50 MPa (i.e., at the sealing interface between window 2 and window frame 1). Figure 7 As shown in the figure, this value is less than the average sealing strength of the diamond and oxygen-free copper combined tensile member of 116.2 MPa, which meets the design requirements.

[0057] The present invention can metallize the diamond window by using a multi-layer composite thin film metallization method, and then seal it after precise assembly with the oxygen-free copper window frame. After sealing, the airtightness test is performed using a helium chamber leak detector, and the helium leakage rate is ≤1×10 -11 Pa·m 3 / s, achieving airtight sealing. The transmission characteristics of the airtight diamond-oxygen-free copper energy transmission window were measured, and the test results are shown in Figure 8 At 320-355 GHz, the average measured S21 (transmission loss of the energy transmission window) is -0.7 dB, which is close to the calculated transmission loss of the oxygen-free copper window frame. Compared with the diamond-Kovar energy transmission window, the measured transmission loss is reduced by about 2 dB, and the corresponding output power can be increased by 60%.

[0058] In one embodiment, the inner sidewall of the boss 12 faces the sidewall of the window 2, and the sidewall of the window 2 is fixedly attached to the inner sidewall of the boss 12. The surface of the window 2 facing away from the window sealing platform 11 is higher than the bottom surface of the boss 12. This design facilitates the external waveguide structure to act on the window after assembly.

[0059] According to another aspect of the present invention, the present invention further provides a traveling wave tube, which includes a high-frequency system having an electromagnetic wave input structure and an electromagnetic wave output structure, an electron gun located at one end of the high-frequency system, and a collector located at the end of the high-frequency system away from the electron gun. At least one of the electromagnetic wave input structure and the electromagnetic wave output structure includes an energy transmission window as described above. That is, the energy transmission window provided by the present invention can be used for the electromagnetic wave input structure, can also be used for the electromagnetic wave output structure, and can also be applied to the electromagnetic wave input structure and the electromagnetic wave output structure at the same time. As for the advantages of the traveling wave tube including the energy transmission window provided by the present invention compared with the prior art, it should be said that they are roughly the same as the advantages of the energy transmission window provided by the present invention compared with the prior art, and will not be repeated here.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. An energy transmission window, characterized in that: The energy transmission window includes a window frame having a vacuum cavity; The window frame comprises: A window sealing station surrounding the vacuum chamber for encapsulating the window; a boss surrounding the outer side of the window sheet sealing platform and extending along the axial direction of the window frame; and A packaging fixing platform surrounding the outer side of the boss for packaging the window frame; The window sealing platform, the boss and the packaging fixing platform are arranged at intervals; the boss can be plastically deformed; The energy transmission window comprises a window piece; an edge of a surface on one side of the window piece is sealed and fixed to the bottom surface of the window piece sealing platform.

2. The energy transmission window according to claim 1, characterized in that: The material of the window frame is oxygen-free copper, and the material of the window piece is diamond.

3. The energy transmission window according to claim 1, characterized in that: The boss in the circumferential direction is a continuous closed structure or a segmented structure.

4. The energy transmission window according to claim 1, characterized in that: The bottom surface of the window sealing platform is higher than the bottom surface of the boss, and the bottom surface of the packaging and fixing platform is lower than the bottom surface of the boss.

5. The energy transmission window according to claim 1, characterized in that: Definition: the inner diameter of the window sealing platform is D1, the outer diameter of the window sealing platform is D3, the inner diameter of the boss is D4, and the outer diameter of the boss is D2; D3-D1≥0.1mm, D4-D3≥0.3mm; D2-D4≥0.2mm.

6. The energy transmission window according to claim 4, characterized in that: The height difference between the bottom surface of the window sealing platform and the bottom surface of the boss is ≥0.2 mm; the height difference between the bottom surface of the packaging fixing platform and the bottom surface of the boss is ≥0.2 mm.

7. The energy transmission window according to claim 1, characterized in that: The inner side wall surface of the boss is opposite to the side wall surface of the window piece, and the side wall surface of the window piece is fitted and fixed to the inner side wall surface of the boss.

8. The energy transmission window according to claim 1, characterized in that: The surface of the window facing away from the window sealing platform is higher than the bottom surface of the boss.

9. A traveling wave tube, characterized in that: The traveling wave tube comprises: A high-frequency system having an electromagnetic wave input structure and an electromagnetic wave output structure; an electron gun located at one end of the high frequency system; and A collecting electrode located at an end of the high-frequency system away from the electron gun; At least one of the electromagnetic wave input structure and the electromagnetic wave output structure includes the energy transmission window according to any one of claims 1 to 8.

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