A high-power microwave window assembly

Abstract

The invention discloses a high-power microwave window assembly, which includes two protective shells, a cooling diagnosis ring, a cooling ring, two circular waveguide tubes, two copper rings and a window sheet, wherein a first copper ring and a second copper ring are arranged on both sides of the window sheet, a first circular waveguide tube is connected to the first copper ring, and a second circular waveguide tube is connected to the second copper ring respectively, and a gap is left between the first circular waveguide tube, the second circular waveguide tube and the window sheet, and the cooling diagnosis ring, the first copper ring, the second copper ring and the cooling ring constitute a cooling system of the microwave window assembly. The invention reduces the types of materials of the assembly by adopting components of limited materials, and the residual stress after welding with the same material is small, so that the overall structure is more compact; the structure of the ribs is added to the copper ring, so that the heat dissipation performance of the assembly is better, and the overall structure of the assembly is optimized, so that its welds are all fully penetrated welds, and the structure is safer and more reliable.

Description

Technical Field

[0001] The invention relates to the technical field of microwave vacuum devices, in particular to a gyrotron output device, in particular to a novel fusion reactor high-power microwave window assembly. Background Art

[0002] The high-power microwave window is one of the important components of the gyrotron. The quality of the microwave window determines the working efficiency and service life of the gyrotron. In the fusion reactor, microwaves are used to heat the plasma through the window to achieve the purpose of nuclear fusion. The high-energy microwaves pass through the waveguide on one side through the window to the waveguide on the other side, and then transmit the energy to the plasma. The window here is part of the main vacuum boundary of the vacuum chamber of the thermonuclear fusion experimental reactor, which has the function of confining tritium and plays a role of isolation.

[0003] During microwave transmission, if the reflection of the microwave window is too high, the power reflected back to the gyrotron under high output power conditions will also be too high, causing the parasitic mode to self-oscillate in the gyrotron, thereby reducing the output power and mode purity of the gyrotron, and even the gyrotron cannot work normally and stably. The microwave output by the gyrotron needs to play a role in heating the plasma, and the output power of the window needs to be very large. During the transmission process, there is dielectric loss in the waveguide, and loss will also occur on the output window. A relatively high amount of heat will be generated on the waveguide and the window, making the temperature of the waveguide and the window too high, resulting in component failure. The waveguide of the stainless steel material of the third-generation microwave window assembly of ITER (International Thermonuclear Experimental Reactor) has large dielectric loss and insufficient thermal conductivity. The temperature is too high under service conditions, the transmission efficiency is not high, the manufacturing process is numerous, the welding residual stress is large, and the service reliability is not high, which leads to insufficient performance of the gyrotron. Therefore, the development of the fourth-generation new high-power, low-reflection, low-loss, and high-thermal-conductivity microwave window assembly is of great significance for improving the performance of the gyrotron. Summary of the invention

[0004] The present invention provides a design scheme for a fourth-generation high-power microwave window assembly for a fusion reactor, which reduces the loss of a waveguide medium and a window sheet, enhances heat dissipation, and ensures the reliability of the assembly while improving transmission power and efficiency.

[0005] The present invention adopts the following technical solution to solve the above problems:

[0006] A high-power microwave window assembly defined in the present invention comprises a first protective shell, a second protective shell, a cooling diagnostic ring, a cooling ring, a first circular waveguide tube, a second circular waveguide tube, a first copper ring, a second copper ring and a window piece, wherein the first copper ring and the second copper ring are arranged on both sides of the window piece, the first circular waveguide tube is connected to the first copper ring, the second circular waveguide tube is connected to the second copper ring respectively, and a gap is left between the first circular waveguide tube, the second circular waveguide tube and the window piece, and the cooling diagnostic ring, the first copper ring, the second copper ring and the cooling ring constitute a cooling system of the microwave window assembly.

[0007] Furthermore, for better heat transfer and welding, the window plate of the present invention is made of diamond, and the cooling diagnosis ring, cooling ring, first circular waveguide tube and second circular waveguide tube are made of copper-chromium-zirconium alloy, which can better connect with the copper ring.

[0008] Furthermore, the present invention also defines that the first copper ring, the second copper ring and the window plate are connected by brazing, and the first circular waveguide and the first copper ring, and the second circular waveguide and the second copper ring are connected by electron beam welding.

[0009] Furthermore, the present invention also defines that the gap between the first circular waveguide tube, the second circular waveguide tube and the window piece is 50-100 μm.

[0010] Furthermore, the present invention also defines that a cooling channel and four diagnostic holes are provided on the cooling diagnostic ring, and the cooling channel is provided on the cooling ring.

[0011] Furthermore, the present invention also defines that the cooling channel on the same side of the cooling diagnosis ring and the cooling ring is connected through a three-way pipe for passing cooling water.

[0012] Furthermore, the present invention also defines that a plurality of ribs are provided on the first copper ring and the second copper ring.

[0013] Furthermore, the present invention also defines that when microwaves pass through the window without reflection, the thickness d of the window is calculated as follows:

[0014]

[0015] Where π is the circumference of a circle, ε is the r is the dielectric constant of the window, c is the speed of light, f is the frequency of the electromagnetic wave, μ mn is the nth zero point of the derivative of the m-th order Bessel function, and R is half of the inner diameter of the waveguide.

[0016] Furthermore, the present invention also stipulates that the components corresponding to the electron beam welding connection are all provided with protrusions.

[0017] Furthermore, the outer side of the waveguide of the present invention is connected to other waveguides by a flange, and a protrusion is also provided at the connection.

[0018] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1) The present invention reduces the types of materials of the components by using components of limited materials, reduces the residual stress after welding of the same materials, and eliminates the spacer ring between the microwave window waveguide and the copper ring of the previous generation, making the overall structure more compact;

[0020] 2) The present invention adopts a waveguide made of a copper-chromium-zirconium alloy material, and utilizes the alloy's better electrical conductivity and higher thermal conductivity, thereby effectively reducing the temperature level of the component during service;

[0021] 3) The present invention adds a fin structure to the copper ring, so that the heat dissipation performance of the component is better;

[0022] 4) The present invention optimizes the overall structure of the assembly so that all welds are fully penetrated, making the structure safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of the structure of a microwave window assembly;

[0024] Figure 2 is a front view of a microwave window assembly;

[0025] Figure 3 is a front cross-sectional view of a microwave window assembly;

[0026] Figure 4 This is the loss distribution diagram of the 1 / 4 window.

[0027] In the figure: 1. cooling diagnostic ring; 2. first protective shell; 3. first circular waveguide; 4. cooling ring; 5. second circular waveguide; 6. second protective shell; 7. first copper ring; 8. second copper ring; 9. window. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0029] like Figure 1-3As shown, a high-power microwave window assembly of the present invention comprises a first protective shell 2, a second protective shell 6, a cooling diagnostic ring 1, a cooling ring 4, a first circular waveguide tube 3, a second circular waveguide tube 5, a first copper ring 7, a second copper ring 8 and a window piece 9, wherein the first copper ring 7 and the second copper ring 8 are arranged on both sides of the window piece 9, the first circular waveguide tube 3 and the first copper ring 7, the second circular waveguide tube 5 and the second copper ring 8 are connected respectively, and a gap is left between the first circular waveguide tube 3, the second circular waveguide tube 5 and the window piece 9. In the embodiment of the present invention, the gap is preferably 50-100 μm; the cooling diagnostic ring 1, the first copper ring 7, the second copper ring 8 and the cooling ring 4 constitute the cooling system of the microwave window assembly. The first circular waveguide tube 3 and the second circular waveguide tube 5 can be connected to other waveguide tubes through flanges, the first circular waveguide tube 3 and the cooling diagnostic ring 1 are connected to the first protective shell 2, the second circular waveguide tube 5 and the cooling ring 4 are connected to the second protective shell 6, as shown in FIG. Figure 3 As shown, in order to make the overall structure more reliable, the present invention provides a protrusion structure at the corresponding position of the component at each connection, and the welds at the connection parts are all full penetration welds, ensuring that the overall structure is more reliable.

[0030] The material of the window piece 9 of the present invention is diamond, and the materials of the cooling diagnosis ring 1, the cooling ring 4, the first circular waveguide tube 3 and the second circular waveguide tube 5 are copper-chromium-zirconium alloy; the first copper ring 7, the second copper ring 8 and the window piece 9 are connected by brazing, and the other parts such as the first circular waveguide tube 3 and the first copper ring 7, the second circular waveguide tube 5 and the second copper ring 8 are connected by electron beam welding.

[0031] For the convenience of observation, the present invention is provided with a cooling channel and four diagnostic holes on the cooling diagnostic ring 1, through which the pressure and other data inside the component are observed; a cooling channel is provided on the cooling ring 4, and for the convenience of operation, the cooling channels on the same side of the cooling diagnostic ring 1 and the cooling ring 4 are connected by a three-way pipe to form a pipe for passing cooling water.

[0032] In order to improve the heat dissipation performance of the component, the present invention provides a plurality of ribs on the first copper ring 7 and the second copper ring 8 .

[0033] Embodiment: In this embodiment, the diameters of the first circular waveguide tube 3 and the second circular waveguide tube 5 are both 50 mm, the output microwave frequency is 170 GHz, the output mode is Gaussian mode, and the power is 1 MW.

[0034] Figure 1 Figure 2 They are the schematic diagram and front view of the microwave window assembly. Figure 3It is a front view cross-sectional view. As shown in the figure, the window piece 9 is brazed between the first copper ring 7 and the second copper ring 8. The first circular waveguide tube 3, the second circular waveguide tube 5 and the flange connection are provided with a protrusion structure, the first circular waveguide tube 3 and the first protective shell 2 are connected, the second circular waveguide tube 5 and the second protective shell 6 are connected, the cooling diagnosis ring 1 and the first protective shell 2 are connected, the cooling ring 4 and the second copper ring 8 are connected, etc. are also provided with a protrusion structure. The welds at the connecting parts are all full penetration welds, and the overall structure is more reliable.

[0035] When the assembly of the present invention is working, microwaves pass through the first circular waveguide 3 on the left side through the window 9 to the second circular waveguide 5 on the other side. To allow microwaves to pass through the window 9 without reflection, the thickness of the window needs to meet certain requirements. In order to obtain the required window thickness, the derivation process of the present invention is as follows:

[0036] The phase difference δ generated by the electromagnetic wave propagating once in the window 9 is:

[0037] δ=βd

[0038] Where β is the propagation constant and d is the window thickness.

[0039] Assuming that the amplitude of the electromagnetic wave incident on the output window is 1, the amplitude of the reflected wave is:

[0040]

[0041] r 12 is the reflection coefficient of microwaves entering the window from vacuum, t 12 is the transmission coefficient of microwaves from vacuum into the window, r 21 is the reflection coefficient of microwaves from the window into the vacuum, t 21 is the transmission coefficient of microwaves from the window into vacuum, e is a natural constant, j is an imaginary unit, and n is the number of microwave reflections in the window;

[0042] To make the total amplitude of the reflected wave 0, we only need 1-e -j2δ =0, according to Euler's formula:

[0043] e -j2δ =cos(-2δ)+jsin(-2δ)=1

[0044] but:

[0045] δ=Nπ(N=1,2,3,...)

[0046] Combined with the following formula:

[0047]

[0048] Where π is the circumference of a circle, λ is the g is the waveguide wavelength, λc is the cut-off wavelength, ε r is the dielectric constant, c is the speed of light, f is the frequency of the electromagnetic wave, μ mn is the nth zero point of the derivative of the m-th order Bessel function, and R is half of the inner diameter of the waveguide.

[0049] The thickness d of the non-reflective microwave window is:

[0050]

[0051] When f = 170 GHz, the output mode is TE11, diamond ε r =5.67,μ mn =1.841184Calculation yields:

[0052] d=0.3755N(N=1,2,3,...)

[0053] Take N=3, and the thickness of the window piece d=1.13 mm.

[0054] The 1 / 4 window loss distribution obtained by 3D electromagnetic simulation software is as follows Figure 4 As shown, using the field calculator, the volume loss density is integrated over the entire volume to obtain a 1 / 4 window power loss of 198.4W, then the power loss of the entire window is 793.6W, and the heat transfer area is derived by the following calculation:

[0055] Cooling water qualitative temperature = 50℃

[0056] According to fluid dynamics and heat transfer, the convective heat transfer coefficient of the heat transfer surface can be calculated by the following criteria:

[0057]

[0058] Where: Nu = Nusselt number; λ = thermal conductivity of the coolant (water); d = equivalent diameter of the water channel.

[0059] The state of the fluid can be determined based on the Reynolds number:

[0060]

[0061] where u is the flow velocity and ν is the kinematic viscosity.

[0062] The coolant is in a turbulent state. Nu in the turbulent state can be determined by the following criteria:

[0063]

[0064] Where f is the Darcy friction coefficient.

[0065] f=(0.79ln(Re)-1.64) -2

[0066] Bring in:

[0067] h=1152.3W / (m 2 ·K)

[0068] Total heat transfer area:

[0069]

[0070] The heat transfer load Q = 793.6W, the average heat transfer temperature difference Δt m =50℃.

[0071] Consider area margin:

[0072] A′=A×(1+15%)=0.01320016m 2

[0073] The heat exchange area of ​​the cooling channel is 0.01320016m 2 .

[0074] The first copper ring 7 and the second copper ring 8 are provided with fins, which greatly enhances the heat exchange capacity of the structure.

[0075] A gap of 0.08 mm is set between the first circular waveguide tube 3, the second circular waveguide tube 5 and the window plate 9. This waveguide structure can suppress parasitic oscillations in the cavity and avoid parasitic high-order modes, thereby ensuring transmission efficiency.

[0076] The novel high-power microwave window assembly obtained by the present invention has improved heat dissipation performance, improved transmission power, a more compact structure, a simplified manufacturing process, smaller residual stress after welding, and a safer and more reliable overall assembly.

Claims

1. A high-power microwave window assembly, comprising a first protective shell (2), a second protective shell (6), a cooling diagnosis ring (1), a cooling ring (4), a first circular waveguide (3), a second circular waveguide (5), a first copper ring (7), a second copper ring (8) and a window sheet (9), Features The first copper ring (7) and the second copper ring (8) are arranged on both sides of the window sheet (9); the first circular waveguide tube (3) and the first copper ring (7) are connected respectively, and the second circular waveguide tube (5) and the second copper ring (8) are connected respectively, and a gap is left between the first circular waveguide tube (3), the second circular waveguide tube (5) and the window sheet (9); the cooling diagnosis ring (1), the first copper ring (7), the second copper ring (8) and the cooling ring (4) constitute a cooling system of the microwave window assembly; The material of the window sheet (9) is diamond, and the materials of the cooling diagnosis ring (1), the cooling ring (4), the first circular waveguide tube (3) and the second circular waveguide tube (5) are copper-chromium-zirconium alloy; the first copper ring (7), the second copper ring (8) and the window sheet (9) are connected by brazing, and the other parts of the first circular waveguide tube (3) and the first copper ring (7), and the second circular waveguide tube (5) and the second copper ring (8) are connected by electron beam welding.

2. A high-power microwave window assembly according to claim 1, Features The gap between the first circular waveguide tube (3), the second circular waveguide tube (5) and the window plate (9) is 50-100 μm.

3. A high-power microwave window assembly according to claim 1 or 2, Features The cooling diagnosis ring (1) is provided with a cooling channel and four diagnosis holes, and the cooling ring (4) is provided with a cooling channel.

4. A high-power microwave window assembly according to claim 3, Features The cooling channels on the same side of the cooling diagnosis ring (1) and the cooling ring (4) are connected via a three-way pipe for passing cooling water.

5. A high-power microwave window assembly according to claim 1 or 2, Features A plurality of ribs are provided on the first copper ring (7) and the second copper ring (8).

6. A high-power microwave window assembly according to claim 1 or 2, Features When microwaves pass through the window sheet (9) without reflection, the thickness d of the window sheet (9) is calculated as follows: Where π is the circumference of a circle, ε is the r is the dielectric constant of the window, c is the speed of light, f is the frequency of the electromagnetic wave, μ mn is the nth zero point of the derivative of the m-th order Bessel function, and R is half of the inner diameter of the waveguide.

7. A high-power microwave window assembly according to claim 1, Features The parts corresponding to the electron beam welding connection are all provided with protrusions.

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