Compact internal injection structure of TE10-TM01-TEM mode

Abstract

The invention relates to an input cavity injection structure of a relativistic klystron amplifier in the technical field of high-power microwaves, in particular to a compact internal injection structure of a TE10-TM01-TEM mode, and belongs to the technical field of high-power microwaves. According to the structure, a single standard rectangular waveguide is introduced to the tail of a relativistic klystron amplifier to serve as an injection waveguide, then injected microwaves are transmitted through a hollow circular waveguide, a mode converter is connected to the left side of the circular waveguide, and finally the injected microwaves are transmitted to an input cavity gap through a coaxial waveguide; when the device works, seed source microwaves are injected through the standard rectangular waveguide, the microwave transmission mode of the seed source microwaves is a TE10 mode, then the seed source microwaves are converted into a TM01 single-mode transmission mode through the hollow circular waveguide, and finally the seed source microwaves are converted into a TEM mode through the mode converter to be transmitted to the front end of the input cavity. According to the invention, the integrity of the magnetic field of the solenoid coil is kept while the high transmission characteristic is ensured, and meanwhile, a non-rotational symmetry mode caused by an overlarge over-mode ratio is avoided.

Description

Technical Field

[0001] The invention relates to an input cavity injection structure of a relativistic klystron amplifier in the technical field of high-power microwaves, in particular to a compact internal injection structure of a TE10-TM01-TEM mode, belonging to the technical field of high-power microwaves. Background Art

[0002] High peak power is a goal that is constantly pursued in the field of high-power microwave technology. At present, high-power microwave source devices based on various beam-wave interaction mechanisms, such as Cherenkov devices, orthogonal field devices, transit time effect devices, and free electron lasers, can achieve high-power microwave output with pulse widths ranging from tens to hundreds of nanoseconds and peak powers of GW or even tens of GW. With the development of high-power microwave source technology, it has been publicly reported that the output power of a single microwave generating device has reached 10GW. However, due to the constraints of physical mechanisms, process structures, and material properties, when further increasing the peak power, these typical high-power microwave generating devices have problems such as RF breakdown, pulse shortening, and power reduction, which restricts the further increase in the peak power of single-tube high-power microwave generating devices. In order to meet the needs of actual applications and further increase the output microwave power, power synthesis of the output microwaves of multiple high-power microwave generating devices has become one of the important directions for the development of high-power microwave technology. Spatially coherent power synthesis can obtain N in the far field. 2 The peak power density can be increased by times (N is the number of high-power microwave generating devices), which can greatly improve the output capacity of existing high-power microwave devices and has received widespread attention in recent years.

[0003] In order to achieve efficient spatial coherent power synthesis, high-power microwave generating devices need to have good frequency-locking and phase-locking characteristics, so that the frequency and phase of the output microwave can be precisely controlled. The output microwave frequency of the relativistic klystron amplifier (RKA) is precisely controlled by the injected microwave, and the phase difference between the output and input microwaves is constant. It is one of the ideal devices for achieving spatial coherent power synthesis. The current coaxial RKA generally adopts an externally fed injection structure, generally using a lateral waveguide dual-port external feeding. The injection physical process is as follows: the injected microwave signal is generated by a high-power RF seed source, and is injected into the RKA input cavity through a rectangular waveguide link, establishing a high-frequency resonant field in the input cavity, and then initially modulating the electron beam. This solution reduces the system complexity of engineering design to a certain extent and improves the experimental reliability, but it also brings the following shortcomings: 1. The externally fed injection structure requires two sections of solenoid coils to control the magnetic field position and intensity, which affects the integrity of the guided magnetic field and makes the guided magnetic field coil more complicated; and the magnetic field uniformity at the connection between the two sections of the solenoid magnetic field deteriorates, resulting in the poor transmission effect of the strong current relativistic electron beam, which directly affects the modulation of the electron beam; 2. The over-mode ratio of the externally fed injection structure is too large, which will more easily excite complex non-rotationally symmetric modes in the experiment, affecting the normal operation of the device and causing pulse shortening; 3. The injection of seed source microwaves adopts dual-port injection. The seed source is transmitted to the input cavity through rectangular waveguides on both sides. The phase and amplitude of the injected microwaves may be different, affecting the angular uniformity of the gap electric field and the modulation of the electron beam.

[0004] In summary, most of the current RKAs adopt an externally fed injection structure, which has the advantage of a simple link, but requires two parts of the guiding magnetic field. On the other hand, when the device has a large over-modulus, the externally fed injection structure is more likely to excite a non-rotationally symmetric mode, resulting in a shortened output pulse, especially in higher frequency bands such as Ku. These problems will be more serious. Considering the further development of RKA to higher frequency bands, it is urgent to find a new injection structure. Summary of the invention

[0005] The problem to be solved by the present invention is: in view of the problem that the magnetic field segmentation and excessive over-mode ratio in the current externally fed relativistic klystron amplifier will more easily excite the non-rotationally symmetric mode, a compact internal injection structure of TE10-TM01-TEM mode is proposed. A single standard rectangular waveguide is introduced as an injection waveguide at the tail of the RKA, and then the injected microwave is transmitted through a hollow circular waveguide. The left side of the circular waveguide is connected to a mode converter, and finally the injected microwave is transmitted to the input cavity gap through a coaxial waveguide; when the device is working, the seed source microwave is injected through the standard rectangular waveguide, and its microwave transmission mode is the TE10 mode, and then it is converted to the TM01 mode single-mode transmission through the hollow circular waveguide, and finally converted to the TEM mode through the mode converter and transmitted to the front end of the input cavity. The present invention retains the integrity of the magnetic field of the solenoid coil while ensuring high transmission characteristics, and at the same time avoids the non-rotationally symmetric mode caused by excessive over-mode ratio.

[0006] The technical solution of the present invention is: a compact internal injection structure of TE10-TM01-TEM mode, including a standard rectangular waveguide 01, a hollow circular waveguide 02, a conversion waveguide 03, a transmission waveguide 04, a support rod 05, an inner conductor 06, an outer conductor 07, an input cavity 08, and a drift tube 09. Except for the standard rectangular waveguide 01, the remaining structures are rotationally symmetric about the central axis.

[0007] The standard rectangular waveguide 01 is made of non-magnetic stainless steel. Its axial length is R1, width is L1, and length is 2 times L1. The value of L1 should satisfy the flange size corresponding to the operating frequency and is 0.3 - 0.4 times the microwave wavelength λ to be transmitted. The standard rectangular waveguide 01 is used to inject the microwave of the seed source, and its microwave transmission mode is the TE10 mode. The hollow circular waveguide 02 is a cylindrical cavity with a radius of R2 and a radial length of L3, and is used to transmit the microwave of the TM01 mode in single mode. To ensure that the hollow circular waveguide operates in single mode, the radius of the circular waveguide satisfies: 0.38λ < R2 < 0.6λ, and the value of L3 is 9.5 - 9.8 times the microwave wavelength λ to be transmitted. The distance between the rightmost sides of the standard rectangular waveguide 01 and the hollow circular waveguide 02 is L2, and the value of L2 is 0.8 - 1 times the microwave wavelength λ to be transmitted. The left side of the hollow circular waveguide 02 is connected to the conversion waveguide 03. The conversion waveguide 03 is a coaxial waveguide with a cross-section in the shape of an "L", with a radial width of L5 and a length in the horizontal direction (i.e., the "-" on the "L") of L4 and a length in the vertical direction (i.e., the "|" on the "L") of L6. The value of L4 is 0.8 - 1.2 times the microwave wavelength λ to be transmitted, and the value of L6 is 0.6 - 0.8 times the microwave wavelength λ to be transmitted. The conversion waveguide 03 is used to convert the TM01 mode transmitted by the hollow circular waveguide into the coaxial TEM mode, and the radial width L5 needs to satisfy 0.05λ < L5 < 0.2λ. The conversion waveguide 03 is connected to the transmission waveguide 04. The transmission waveguide 04 is also a coaxial waveguide with a cross-section in the shape of an "L", and its radial width is equal to the radial width L5 of the conversion waveguide 03. The length in the horizontal direction (i.e., the "-" on the "L") is L7, and the length in the vertical direction (i.e., the "|" on the "L") is L8. The value of L7 is 2.0 - 2.5 times the microwave wavelength λ to be transmitted, and the value of L8 is 0.05 - 0.2 times the microwave wavelength λ to be transmitted. The transmission waveguide 04 is used to transmit the TEM mode to the input cavity 08. The support rod 05 is a cubic support block evenly placed angularly, with a width of L9 and a length of 2.5 times L9, and its height is equal to the radial width L5 of the conversion waveguide 03. The value of L9 is 0.1 - 0.25 times the microwave wavelength λ to be transmitted. The support rod 05 is used to connect the inner and outer conductors to ensure the stability of the structure. The inner conductor 06 and the outer conductor 07 are both made of non-magnetic stainless steel. The inner conductor 06 is a solid irregular cylinder, and the outer conductor 07 is a hollow irregular cylindrical tube. The cylinder and the cylindrical tube are coaxially nested: the maximum radius of the inner conductor 06 is R6 and the axial length is L 10 , L 10 The value of is 3.5 - 4 times the microwave wavelength λ to be transmitted. The inner conductor 06 consists of three parts: an irregular chassis with a radius of R6, a cylinder with a radius of R4 and an axial length of L7, and a cylinder with a radius of R3 and an axial length of L4. The irregular chassis is composed of a large disk with a radius R6 and an axial length of L 12 and a small disk with a radius of R8 and an axial length of L 11 . The value of L 12The value of L is 0.2 to 0.3 times of the transmission microwave wavelength λ. 11 The value of is 0.3 to 0.4 times the wavelength of the transmitted microwave. At the radial edge of the large disk, a width L is set. 13 , thickness is L 14 Ring, L 13 The value of L is 0.8 to 1.2 times of the transmission microwave wavelength λ. 14 The value is 0.1 to 0.2 times of the wavelength λ of the transmitted microwave; the maximum radius R5 and the minimum radius R2 are located at the inner wall of the outer conductor 07; the front end of the inner part of the outer conductor 07 is a hollow circular waveguide 02; the rear end of the outer conductor 07 is coaxially nested with the two cylinders of the inner conductor 06 to form a conversion waveguide 03, a transmission waveguide 04 and an input cavity 08;

[0008] The input cavity 08 is a circular cavity with an inverted "L"-shaped cross section and a cavity thickness of L. 15 , the length in the horizontal direction (i.e. the length of the “-” on “L”) is L 13 , the length of the vertical direction (i.e. the length of the “|” on “L”) is L 16 , L 15 The value of L is 0.3 to 0.5 times of the transmission microwave wavelength λ. 16 The value of is 1.0 to 1.3 times of the wavelength λ of the transmitted microwave. The microwave is injected into the input cavity 08 to establish a standing wave field and pre-modulate the electron beam. The thickness of the drift tube 09 is L 17 , L 17 The value of is 0.3 to 0.5 times the wavelength λ of the transmitted microwave, which is used to convert the speed modulation of the electron beam into density modulation and to cut off the device working mode to prevent microwave leakage into other cavities.

[0009] The working principle of the compact internal injection structure of the TE10-TM01-TEM mode is as follows: the seed source microwave is injected through the standard rectangular waveguide 01, and its microwave transmission mode is the TE10 mode. After the microwave enters the hollow circular waveguide 02, it is converted into the TM01 mode and transmitted to the conversion waveguide 03. The microwave mode is converted into the coaxial TEM mode and transmitted to the input cavity 08 via the transmission waveguide 04. The TM01 mode is established in the input cavity 08 to pre-modulate the electron beam.

[0010] Compared with the existing externally fed injection structure, the present invention can achieve the following technical effects:

[0011] 1. A compact internal injection structure for TE10-TM01-TEM mode is designed. The electric field distribution of the injection structure during operation is as follows: Figure 3As shown, microwaves are injected into the cavity in TE10 mode by a standard rectangular waveguide, and then converted to TM01 mode single-mode transmission through a hollow circular waveguide, and then converted to coaxial TEM mode and transmitted to the input cavity. Through parameter design, it is possible to ensure that the structure has a high transmission coefficient, and at the same time, a single injection waveguide is used to avoid phase inconsistency of the injected microwaves. Compared with the externally fed injection structure, the internal injection structure can reduce the device over-mode ratio and avoid exciting non-rotationally symmetric modes. The operating frequency of the embodiment is 14.25 GHz, as shown in FIG. Figure 4 The transmission coefficient of the S21 parameter of the internally fed injection structure is shown to be above 99% in the range of 14.1 GHz-14.4 GHz, indicating that the structure meets the design requirements of high transmission coefficient.

[0012] 2. The seed source microwave injection port is located at the rear end of RKA. Microwaves are transmitted from the inside of the conductor to the input cavity. The external guiding magnetic field only requires one solenoid coil, which not only achieves compactness and lightness, but also retains the integrity of the external guiding magnetic field, simplifies the structure of the solenoid coil, makes the guiding magnetic field more uniform, ensures good transmission quality of the electron beam, and is conducive to improving the efficiency of the beam action. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the AA cross-sectional structure of a compact internal injection structure in TE10-TM01-TEM mode provided by the present invention;

[0014] Figure 2 A schematic diagram of the support rod region of a compact internal injection structure in a TE10-TM01-TEM mode provided by the present invention;

[0015] Figure 3 A schematic diagram of the electric field when a compact internal injection structure in a TE10-TM01-TEM mode provided by the present invention is working;

[0016] Figure 4 A schematic diagram of S21 parameters of a compact internal injection structure in TE10-TM01-TEM mode provided by the present invention; DETAILED DESCRIPTION

[0017] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1The AA cross-sectional structure schematic diagram of a preferred embodiment of a compact internal injection structure for a TE10-TM01-TEM mode provided by the present invention; the present invention is a compact internal injection structure for a TE10-TM01-TEM mode, which includes a standard rectangular waveguide 01, a hollow circular waveguide 02, a conversion waveguide 03, a transmission waveguide 04, a support rod 05, an inner conductor 06, an outer conductor 07, an input cavity 08, and a drift tube 09. Except for the standard rectangular waveguide 01, the remaining structures are rotationally symmetric about the central axis.

[0019] This embodiment realizes an internal injection structure of a coaxial relativistic klystron amplifier for Ku band (center frequency is 14.25 GHz, corresponding to the transmission microwave wavelength λ=21.0 mm) (the corresponding dimensions are designed as follows: R1=60 mm, R2=12 mm, R3=7 mm, R4=28 mm, R5=32 mm, R6=44 mm, R7=57 mm, R8=35 mm, R9=57 mm, ... 10 =53mm, L1=7.9mm, L2=18mm, L3=200mm, L4=22mm, L5=3mm, L6=13mm, L7=44mm, L8=2.5mm, L9=3mm, L 10 = mm, L 11 =6.5mm, L 12 =4.5mm, L 13 =21mm, L 14 =3mm, L 15 =6mm, L 16 =23mm, L 17 =7mm).

[0020] Figure 2 This is a schematic diagram of support rods of a compact internal injection structure of a TE10-TM01-TEM mode provided by the present invention. As can be seen from the figure, the support structure uses 10 rectangular support rods that are evenly placed in the angular direction.

[0021] Figure 3 A schematic diagram of the electric field when a compact internal injection structure in TE10-TM01-TEM mode provided by the present invention is working (in order to avoid electric field breakdown, chamfering was performed during simulation); it can be seen from the figure that the injected microwave is injected through a standard rectangular waveguide, and its working mode is TE10 mode, and then it is transmitted in single mode in the hollow circular waveguide in TM01 mode, and finally the conversion waveguide is converted to TEM mode. This shows that the structural design meets the requirements, and each transmission component works in the expected working mode; Figure 4A schematic diagram of the S21 parameters of a compact internal injection structure in the TE10-TM01-TEM mode provided by the present invention illustrates that the transmission characteristics of the compact internal injection structure at the operating frequency are good, and the S21 parameter reaches more than 99%, meeting the device design requirements.

[0022] It can be seen from the above results that the compact internal injection structure of the TE10-TM01-TEM mode provided by the present invention solves the two major problems of the existing externally fed injection structure, namely, the split guide magnetic field and the easy excitation of non-rotationally symmetric modes under large over-mode ratio, while ensuring high transmission characteristics. It has important reference significance for the design of injection structures required for similar relativistic klystron amplifiers.

Claims

1. A compact internal injection structure for TE10-TM01-TEM mode, characterized by: It comprises a standard rectangular waveguide (01), a hollow circular waveguide (02), a conversion waveguide (03), a transmission waveguide (04), a support rod (05), an inner conductor (06), an outer conductor (07), an input cavity (08), and a drift tube (09). Except for the standard rectangular waveguide (01), the remaining structures are rotationally symmetrical about the central axis. The standard rectangular waveguide (01) has an axial length R1, a width L1, and a length of 2L1. The value of L1 should satisfy the flange size corresponding to the operating frequency and is 0.3 - 0.4 times the microwave wavelength λ to be transmitted. The standard rectangular waveguide (01) is used to inject the seed source microwave, and its microwave transmission mode is the TE10 mode; the hollow circular waveguide (02) is a cylindrical cavity with a radius of R2 and a radial length of L3, which is used to transmit the microwave in the TM01 mode in single mode. To ensure that the hollow circular waveguide operates in single mode, the radius of the circular waveguide satisfies: 0.38λ < R2 < 0.6λ, and the value of L3 is 9.5 - 9.8 times the microwave wavelength λ to be transmitted; the distance between the rightmost sides of the standard rectangular waveguide (01) and the hollow circular waveguide (02) is L2, and the value of L2 is 0.8 - 1 times the microwave wavelength λ; the left side of the hollow circular waveguide (02) is connected to the conversion waveguide (03). The conversion waveguide (03) is a coaxial waveguide with an "L"-shaped cross-section, a radial width of L5, a horizontal length of L4, and a vertical length of L6. The value of L4 is 0.8 - 1.2 times the microwave wavelength λ, the value of L6 is 0.6 - 0.8 times the microwave wavelength λ, and the conversion waveguide (03) is used to convert the TM01 mode transmitted by the hollow circular waveguide into the coaxial TEM mode. The radial width L5 needs to satisfy 0.05λ < L5 < 0.2λ; the conversion waveguide (03) is connected to the transmission waveguide (04). The transmission waveguide (04) is also a coaxial waveguide with an "L"-shaped cross-section, and its radial width is equal to the radial width L5 of the conversion waveguide (03). The horizontal length is L7, and the vertical length is L8. The value of L7 is 2.0 - 2.5 times the microwave wavelength λ, and the value of L8 is 0.05 - 0.2 times the microwave wavelength λ. The transmission waveguide (04) is used to transmit the TEM mode to the input cavity 08; the support rod (05) is a cubic support block evenly placed angularly, with a width of L9, a length of 2.5L9, and a height equal to the radial width L5 of the conversion waveguide (03). The value of L9 is 0.1 - 0.25 times the microwave wavelength λ, and the support rod (05) is used to connect the inner and outer conductors to ensure the stability of the structure; the inner conductor (06) is a solid irregular cylinder, and the outer conductor (07) is a hollow irregular cylindrical tube. The cylinder and the cylindrical tube are coaxially nested: the maximum radius of the inner conductor (06) is R6, and the axial length is L 10 , L 10 has a value of 3.5 - 4 times the microwave wavelength λ to be transmitted. The inner conductor (06) consists of three parts: an irregular chassis with a radius of R6, a cylinder with a radius of R4 and an axial length of L7, and a cylinder with a radius of R3 and an axial length of L4. The irregular chassis consists of a large disk with a radius of R6 and an axial length of L 12 and a small disk with a radius of R8 and an axial length of L 11 . L 12 has a value of 0.2 - 0.3 times the microwave wavelength λ, L 11 The value of is 0.3 to 0.4 times the wavelength of the transmitted microwave. 13 , thickness is L 14 Ring, L 13 The value of L is 0.8 to 1.2 times of the transmission microwave wavelength λ. 14 The value is 0.1 to 0.2 times the wavelength λ of the transmitted microwave; the inner wall of the outer conductor (07) has a maximum radius R5 and a minimum radius R2; the front end of the inner part of the outer conductor (07) is a hollow circular waveguide (02); the rear end of the outer conductor (07) is coaxially nested with two cylinders of the inner conductor (06) to form a conversion waveguide (03), a transmission waveguide (04) and an input cavity (08); The input cavity (08) is a circular cavity with an inverted "L"-shaped cross section and a cavity thickness of L. 15 , the length in the horizontal direction is L 13 , the vertical length is L 16 , L 15 The value of L is 0.3 to 0.5 times of the transmission microwave wavelength λ. 16 The value of is 1.0 to 1.3 times the wavelength λ of the transmitted microwave. The injected microwave establishes a standing wave field in the input cavity (08) to pre-modulate the electron beam. The thickness of the drift tube (09) is L 17 , L 17 The value of is 0.3 to 0.5 times the wavelength λ of the transmitted microwave, which is used to convert the speed modulation of the electron beam into density modulation and to cut off the device working mode to prevent microwave leakage into other cavities.

2. The compact internal injection structure of TE10-TM01-TEM mode according to claim 1, characterized in that: The standard rectangular waveguide (01) is made of non-magnetic stainless steel material.

3. The compact internal injection structure of TE10-TM01-TEM mode according to claim 1, characterized in that: The inner conductor (06) is made of non-magnetic stainless steel material.

4. The compact internal injection structure of TE10-TM01-TEM mode according to claim 1, characterized in that: The outer conductor (07) is made of non-magnetic stainless steel material.

5. The compact internal injection structure of TE10-TM01-TEM mode according to any one of claims 1 to 4, characterized in that: An internal injection structure for a Ku-band coaxial relativistic klystron amplifier, wherein the corresponding dimensions are designed as follows: R1 = 60 mm, R2 = 12 mm, R3 = 7 mm, R4 = 28 mm, R5 = 32 mm, R6 = 44 mm, R7 = 57 mm, R8 = 35 mm, R9 = 57 mm, R 10 =53mm, L1=7.9mm, L2=18mm, L3=200mm, L4=22mm, L5=3mm, L6=13mm, L7=44mm, L8=2.5mm, L9=3mm, L 10 = mm, L 11 =6.5mm, L 12 =4.5mm, L 13 =21mm, L 14 =3mm, L 15 =6mm, L 16 =23mm, L 17 =7mm.

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