A low-magnetic-field high-efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity

Abstract

The invention relates to a microwave source device in the field of high-power microwave technology, in particular to a two-stage modulated low-magnetic field high-efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity, comprising a cathode seat, a cathode, an anode outer cylinder, an inner cylinder, a collimation hole, a primary modulation cavity, a primary second harmonic cavity, a primary drift section, a secondary second harmonic cavity, a secondary drift section, a secondary modulation cavity, a tertiary drift section, an extraction cavity, a collector, a coaxial output waveguide, and a solenoid magnetic field; the entire structure is rotationally symmetric about a central axis; the invention adds two second harmonic cavities between the primary modulation cavity and the secondary modulation cavity, performs quadratic modulation on an electron beam, improves a fundamental wave modulation depth and a second harmonic modulation depth of the electron beam, solves the problem of poor electron beam clustering under a low guiding magnetic field, thereby improving the beam-wave action efficiency of the device under a low magnetic field, increasing the output microwave power of the device, being conducive to miniaturization of the device while increasing an action distance, and broadening the application scenario of the device.

Description

Technical Field

[0001] The invention relates to a microwave source device in the field of high-power microwave technology, in particular to a two-stage modulated low-magnetic-field high-efficiency coaxial relativistic klystron oscillator (RKO) loaded with a second harmonic cavity. Background Art

[0002] High-power microwave (HPM) is usually defined as an electromagnetic wave with a peak power of more than 100MW and a wavelength of 1mm ~ 1m (i.e., a frequency of 400MHz ~ 400GHz). In the 1970s, pulse power technology developed rapidly, and high-current relativistic electron beams with voltages of hundreds of kilovolts and currents of tens of kiloamperes were generated. Applying them to traditional vacuum electronic microwave devices made it possible to generate HPM with a power of more than 100 megawatts. At the same time, through in-depth research on relativistic vacuum electronics and plasma physics, theoretical support was provided for the generation of HPM. In the past fifty years, driven by the application of defense and industrial sectors, HPM technology has made great progress.

[0003] HPM source refers to a device in the HPM system that converts the energy of a high-current relativistic electron beam into microwave field energy, usually an electric vacuum device. According to the different radiation modes of generating microwaves, HPM sources can be divided into Cherenkov radiation devices, transition radiation devices, and Bremsstrahlung radiation devices. RKO and Transit-Time Oscillator (TTO) are both transition radiation devices. This type of device uses a resonant cavity to establish a standing wave field to modulate the velocity and extract energy from the electron beam. It has the characteristics of low magnetic field, high efficiency, high power, and a single working mode, and has attracted extensive attention from researchers.

[0004] Improving conversion efficiency and reducing the guided magnetic field are important development directions for HPM sources. On the one hand, by improving the conversion efficiency of the HPM source, under the condition of equal output power, the power and voltage of the pulse drive source can be reduced, and the volume and insulation requirements of the pulse drive source can be reduced, which is beneficial to improving the stability of the HPM system; on the other hand, reducing the guided magnetic field of the device can reduce the volume and weight of the excitation system, which is beneficial to the miniaturization and compactness of the HPM system and broadening the application scenarios of the HPM system. Therefore, the research on low-magnetic-field and high-efficiency HPM sources has great application value.

[0005] In the research of low magnetic field and high efficiency transition radiation devices, the main related work is as follows:

[0006] In 2020, Deng Xiaobo and others from the National University of Defense Technology studied a new C-band lightweight coaxial transit-time oscillator [Xiao-Bo Deng, Jun-Tao He, Jun-Pu Ling, Bing-Fang Deng, Li-Li Song, Fu-Xiang Yang, Wei-Li Xu. Novel compact and lightweight coaxial C-bandtransit-time oscillator, 2020, Vol.29,No.9, pp. 095205]. (hereinafter referred to as prior art 1, such as Figure 1 As shown). The device consists of a cathode seat, a cathode, an anode outer cylinder, a collimating hole, a cluster cavity, a foil net, a drift section, an extraction cavity, a microwave output port, and a solenoid magnetic field. The cluster cavity and the extraction cavity used in this scheme have only two and a gap respectively. The axial size of the entire device is small, meeting the requirements of lightness and miniaturization. In order to reduce the external guide magnetic field, an open foil net is designed before and after the cluster cavity. Unlike the traditional foil net, the foil net used in this device is open in the middle, which can avoid the electron beam bombarding the foil net to produce plasma. By loading the open foil net, the high-current electron beam of the device is more stable and the saturation time is shorter. In the numerical simulation, when the diode voltage and current are 548 kV and 11.4 kA respectively, and the external guide magnetic field is 0.4T, the device generates 1.88GW of C-band microwaves with a conversion efficiency of about 30%. This scheme improves the stability of the electron beam in a low magnetic field by loading an open foil mesh, thereby achieving efficient beam-wave action. However, the tip of the foil mesh opening can easily cause excessive local field strength and generate plasma, which is not conducive to the long-term stable operation of the device, and the efficiency of the device still needs to be further improved.

[0007] In 2023, Zhu Danni and others from the Naval University of Engineering studied a high-efficiency C-band coaxial transit time oscillator with a dual-cavity extractor under low-magnetic field [Dan-Ni Zhu, Yan-Cheng Cui, Jin Meng, Hai-Tao Wang, Bing-Fang Deng, Yu-Zhang Yuan. A high-efficiency C-band coaxial transit time oscillatorwith a dual-cavity extractor under low-magnetic field, 2023, Vol.98, No.6, pp. 065401]. (hereinafter referred to as prior art 2, such as Figure 2As shown). The device consists of a cathode seat, a cathode, an anode outer cylinder, a collimating hole, a three-cavity modulation cavity, a drift section, a dual-cavity extraction cavity, a microwave output port, and a solenoid magnetic field. The left end of the annular cathode is connected to a pulse drive source, and emits a strong relativistic electron beam for axial transmission. The electron beam passes through the three-gap cluster cavity, the drift section, and the dual-cavity extraction cavity in turn, and is finally collected by the collector. The electron beam is velocity modulated by the high-frequency standing wave field in the modulation cavity, and the electron beam gradually changes from velocity modulation to density modulation in the drift section. The dual-cavity extraction cavity is two rectangular cavities. The extraction cavity adopts a dual-cavity structure and has a higher beam-wave conversion efficiency. In the simulation, when the input electron beam voltage and current are 455kV and 9.75kA respectively, and the external magnetic field is 0.8T, microwaves with a power of 1.73GW and a frequency of 6.37GHz are monitored at the end of the coaxial output waveguide, and the conversion efficiency is about 39%. This scheme uses a dual-cavity extraction cavity to improve efficiency, but the magnetic field strength needs to be further reduced, and the efficiency does not exceed 40%.

[0008] In 2022, Ge Xingjun and others from the National University of Defense Technology studied a two-stage modulated coaxial relativistic klystron oscillator [Ge Xingjun, Chi Hang, Deng Rujin, Dang Fangchao, Yang Fuxiang, Zhang Peng, Hu Xiaodong, He Juntao. A two-stage modulated coaxial relativistic klystron oscillator: ZL 202210722494.9[P]] (hereinafter referred to as prior art 3, such as Figure 3 As shown). The device consists of a cathode seat, a cathode, an anode outer cylinder, an inner cylinder, a collimating hole, a primary modulation cavity, a primary drift section, a secondary modulation cavity, a secondary drift section, an extraction cavity, a coaxial output waveguide, a first support rod, a second support rod, a solenoid magnetic field, and a trapezoidal collector. This scheme adopts a two-stage modulation cavity to modulate the electron beam twice, increase the electron beam clustering depth, solve the problem of poor electron beam clustering under low guide magnetic field, and thus improve the beam-wave interaction efficiency of the device under low magnetic field, increase the output microwave power of the device, and facilitate the miniaturization of the device while increasing the action distance. In the particle simulation, under the conditions of diode voltage 500kV, current 12kA, and guide magnetic field 0.46T, the output microwave power is 2.4 GW and the power conversion efficiency is 40%, but the efficiency of the device is difficult to further improve.

[0009] It is not difficult to see that the current transition radiation devices will face the problem of reduced efficiency when developing towards low magnetic fields. It is urgent to study a high-efficiency (>40%) transition radiation device under low magnetic fields (<0.5T). Summary of the invention

[0010] The technical problem to be solved by the present invention is: the present invention provides a low-magnetic field high-efficiency coaxial RKO loaded with a second harmonic cavity, which overcomes the problem of low efficiency under low magnetic field, and through reasonable design of electromagnetic structure, further modulates electrons through the second harmonic cavity under low magnetic field conditions, improves the clustering effect of electrons, and then realizes high-efficiency beam-wave conversion under low guiding magnetic field.

[0011] The technical solution of the present invention is:

[0012] A low magnetic field high efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity comprises a cathode seat 401, a cathode 402, an anode outer cylinder 403, an inner cylinder 404, a collimation hole 405, a primary modulation cavity 406, a primary second harmonic cavity 407a, a primary drift section 408, a secondary second harmonic cavity 407b, a secondary drift section 409, a secondary modulation cavity 410, a tertiary drift section 411, an extraction cavity 412, a collector 413, a coaxial output waveguide 414, and a solenoid magnetic field 415; the entire structure is rotationally symmetric about the central axis, the left end of the cathode seat 401 is externally connected to the anode of a pulse drive source, the left end of the anode outer cylinder 403 is externally connected to the outer conductor of the pulse drive source, and the right end of the coaxial output waveguide 414 is connected to a mode converter and an antenna;

[0013] Cathode 402 is a thin-walled cylinder with a wall thickness of 2 mm and a radius R 1 The inner tube 404 is a cylindrical conductor with different radii, which together with various cavities on the anode outer tube 403 forms an electron beam modulation cavity and a microwave output structure; the collimation hole 405 is a cylindrical conductor with an outer radius of R 2 , the inner radius is R 3 The circular cavity has a length of L 1 , L 1 The collimation hole 405 is used to cut off the microwave of the working frequency to prevent the leaked microwave from interfering with the normal operation of the diode area; the primary modulation cavity 406 is composed of three pairs of circular ring cavities with rectangular cross sections: the inner radius of the first circular ring cavity on the outer cylinder from left to right is equal to the outer radius R of the collimation hole 405 2 , the outer radius is R 4 , length L 2 , L 2 It is 0.3-0.6 times of the working wavelength λ, and the inner radius of the second circular cavity is R 6 , the outer radius is R 19 , length L 4 , L 4 is 0.3-0.5 times of the working wavelength λ, and the inner radius of the third circular cavity is R 9 , the outer radius is R 11 , length L 5 , L 50.3-0.5 times of the working wavelength λ, satisfying R 4 >R 11 >R 19 >R 9 >R 2 >R 6 ; The interval between each circular cavity is L 3 , L 3 It is 0.1-0.2 times of the working wavelength λ; the inner radius of the first circular cavity on the inner cylinder from left to right is R 5 , the outer radius is R 3 , length L 2 , the inner radius of the second circular cavity is R 8 , the outer radius is R 7 , length L 4 , the inner radius of the third circular cavity is R 12 , the outer radius is R 10 , length L 5 , satisfying R 3 >R 7 >R 10 >R 5 >R 12 >R 8 The first-order second harmonic cavity 407a is composed of a pair of circular ring cavities with rectangular cross sections: the outer radius of the circular ring cavity on the outer cylinder is R 15 , inner radius is R 13 The outer radius of the circular cavity on the inner cylinder is R 16 , inner radius is R 14 , satisfying R 15 >R 13 >R 16 >R 14 The length of the circular cavity of the inner and outer cylinders is L 7 , L 7 is 0.1-0.2 times of the working wavelength λ; the interval between the first-order second harmonic cavity 407a and the first-order modulation cavity 406 is L 6 , L 6 The first drift section 408 is a section with an outer radius of R 13 , the inner radius is R 16 The circular cavity has a length of L 8 , L 8 The second harmonic cavity 407b is composed of a pair of circular cavities with rectangular cross sections. The outer radius of the circular cavity on the outer cylinder is R 17 , inner radius is R 13 The outer radius of the circular cavity on the inner cylinder is R 16 , inner radius is R 18, satisfying R 17 >R 13 >R 16 >R 18 The length of the circular cavity of the inner and outer cylinders is L 9 , L 9 The secondary drift section 409 is a section with an outer radius of R 13 , the inner radius is R 16 The circular cavity has a length of L 10 , L 10 The secondary modulation cavity 410 is composed of a pair of circular ring cavities with rectangular cross sections: the outer radius of the circular ring cavity on the outer cylinder is R 19 , inner radius is R 13 The outer radius of the circular cavity on the inner cylinder is R 16 , inner radius is R 20 , satisfying R 19 >R 13 >R 16 >R 20 The length of the circular cavity of the inner and outer cylinders is L 11 , L 11 is 0.1-0.3 times of the working wavelength λ; the interval between the secondary second harmonic cavity 407b and the secondary modulation cavity 410 is L 10 , L 10 The extraction cavity 412 is composed of two pairs of circular cavities with rectangular cross sections: the inner radius of the first circular cavity on the outer cylinder from left to right is R 23 , the outer radius is R 21 , length L 11 , L 11 is 0.1-0.3 times of the working wavelength λ, and the inner radius of the second circular cavity is R 23 , the outer radius is R 11 , length L 12 , L 12 0.1-0.3 times of the working wavelength λ, satisfying R 21 >R 11 >R 23 ; The distance between the two annular cavities is L 3 ; From left to right, the radius of the first circular cavity on the inner cylinder is R 20 , the outer radius is R 22 , length L 11 , the inner radius of the second circular cavity is R 25 , the outer radius is R 18 , length L 12 , satisfying R 23 >R 22 >R18 >R 20 >R 25 The third drift section 411 is an outer radius of R 23 , the inner radius is R 3 The circular cavity has a length of L 19 , L 19 The collector 413 is composed of a circular ring cavity with a rectangular cross section and a circular ring cavity with a trapezoidal cross section. The outer radius of the circular ring cavity with a rectangular cross section is R 23 , the inner radius is R 24 , length L 15 , L 15 The outer radius and inner radius of the circular cavity with a trapezoidal cross section are R 27 , R 23 The lengths of the upper and lower bases are L 14 , L 13 , satisfying L 13 >L 14 , L 13 1-1.5 times of the working wavelength λ, L 14 0.4-0.7 times of the working wavelength λ;

[0014] The coaxial output waveguide 414 is composed of a circular ring cavity with a rectangular cross section and a circular ring cavity with a trapezoidal cross section. The outer radius of the circular ring cavity with a rectangular cross section is R 5 , the inner radius is R 25 , length L 15 +L 18 , L 15 +L 18 The inner radius and outer radius of the circular cavity with a trapezoidal cross section are R 5 , R 28 The lengths of the upper and lower bases are L 16 , L 17 , satisfying L 17 >L 16 , L 16 1-1.5 times of the working wavelength λ, L 17 It is 1.5-2 times of the working wavelength; the solenoid magnetic field 415 is sleeved on the outer wall of the anode outer cylinder 403.

[0015] The working process of the present invention is as follows: the high voltage generated by the pulse driving source acts on the cathode 402 through the cathode seat 401, and the right end face of the cathode 402 generates a strong relativistic electron beam based on the explosive emission, which is transmitted along the axial direction of the microwave source under the guidance of the solenoid magnetic field 415, and passes through the collimating hole 405, the first-level modulation cavity 406, the first-level second harmonic cavity 407a, the first-level drift section 408, the second-level second harmonic cavity 407b, the second-level drift section 409, the second-level modulation cavity 410, the third-level drift section 411, the extraction cavity 412, and finally enters the collecting electrode 413. In the primary modulation cavity 406, the electron beam excites the radio frequency field and is velocity modulated by the radio frequency field; then the electron beam enters the primary second harmonic cavity 407a and the secondary second harmonic cavity 407b, and excites the standing wave field of the second harmonic signal therein, and at the same time, the excited radio frequency field further velocity modulates the electron beam; the modulated electron beam enters the secondary modulation cavity 410 again, and the electron beam clustering is further deepened; then, the clustered electron beam enters the extraction cavity 412, and strong transition radiation occurs in the extraction cavity 412, generating HPM and radiating outward through the coaxial output waveguide 414; finally, the electron beam with a large amount of energy extracted enters the collector 413 and is collected, thereby avoiding the electron beam directly bombarding the surface of the electromagnetic structure to generate plasma, thereby affecting the normal operation of the device.

[0016] Compared with the prior art, the present invention can achieve the following technical effects:

[0017] 1. The coaxial RKO loaded with a second harmonic cavity provided by the present invention adds two second harmonic cavities between the primary modulation cavity and the secondary modulation cavity, modulates the electron beam four times, improves the fundamental modulation depth and the second harmonic modulation depth of the electron beam, solves the problem of poor electron beam clustering under a low guiding magnetic field, and further improves the beam-wave action efficiency of the device under a low magnetic field, increases the output microwave power of the device, is conducive to miniaturization of the device while increasing the action distance, and broadens the application scenarios of the device.

[0018] 2. The coaxial RKO loaded with the second harmonic cavity provided by the present invention adopts a first-level drift section connecting the first-level second harmonic cavity and the second-level second harmonic cavity, and a second-level drift section connecting the second-level second harmonic cavity and the second-level modulation cavity, so as to regulate the clustering phase of the electron beam reaching the second-level second harmonic cavity and the second-level modulation cavity, thereby improving the fundamental modulation depth and the second harmonic modulation depth of the electron beam. Reasonable design of the first-level drift section is conducive to achieving the optimal clustering effect of the electron beam.

[0019] 3. The coaxial RKO loaded with the second harmonic cavity provided by the present invention adopts a three-level drift section to connect the secondary modulation cavity and the extraction cavity. The three-level drift section affects the beam-wave interaction efficiency in the extraction cavity. Reasonable design of the three-level drift section is conducive to achieving the highest efficiency beam-wave interaction.

[0020] Please refer to the following description of various embodiments of the coaxial RKO loaded second harmonic cavity according to the present invention, which will make the above and other aspects of the present invention apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a novel lightweight and miniaturized coaxial transit time oscillator in the C-band disclosed in the prior art 1 in the background introduction;

[0022] Figure 2 It is a schematic diagram of the structure of a high-efficiency C-band coaxial transit time oscillator with a dual-cavity extraction cavity under a low magnetic field disclosed in the prior art 2 in the background introduction;

[0023] Figure 3 A schematic diagram of the structure of a two-stage modulated coaxial relativistic klystron oscillator disclosed in prior art 3 in the background introduction;

[0024] Figure 4 The AA cross-sectional view of a preferred embodiment of a coaxial relativistic klystron oscillator loaded with a second harmonic cavity provided by the present invention;

[0025] Figure 5 The AA cutaway perspective diagram of a preferred embodiment of a coaxial relativistic klystron oscillator loaded with a second harmonic cavity provided by the present invention;

[0026] Figure 6 A comparison diagram of the electron power flow when the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is provided with or without the second harmonic cavity;

[0027] Figure 7 A comparison diagram of the axial fundamental current when the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention has a second harmonic cavity and does not have a second harmonic cavity;

[0028] Figure 8 A comparison diagram of axial second harmonic current when the preferred embodiment of the coaxial relativistic klystron oscillator loaded with a second harmonic cavity provided by the present invention has a second harmonic cavity and does not have a second harmonic cavity;

[0029] Fig. 9 A comparison diagram of the variation trend of the output microwave power over time when the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is provided with or without the second harmonic cavity;

[0030] Fig.10 The output microwave spectrum diagram of the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention;

[0031] Fig.11 The length L of the first drift section of the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is8 Schematic diagram of the impact on the maximum value of fundamental current;

[0032] Fig.12 The length L of the first drift section of the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is 8 Schematic diagram of the effect on the maximum value of the second harmonic current;

[0033] Fig.13 The length L of the secondary drift section of the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is 10 Schematic diagram of the impact on the maximum value of fundamental current;

[0034] Fig.14 The length L of the secondary drift section of the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is 10 Schematic diagram of the effect on the maximum value of the second harmonic current;

[0035] Fig.15 The length L of the third drift section of the preferred embodiment of the coaxial relativistic klystron oscillator loaded with the second harmonic cavity provided by the present invention is 19 Schematic diagram of the effect on beam-wave interaction efficiency. DETAILED DESCRIPTION

[0036] 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.

[0037] Figure 4 This is a schematic diagram of the structure of the coaxial RKO loaded with the second harmonic cavity of the present invention.

[0038] The present invention comprises: cathode seat 401, cathode 402, anode outer cylinder 403, inner cylinder 404, collimation hole 405, primary modulation cavity 406, primary second harmonic cavity 407a, primary drift section 408, secondary second harmonic cavity 407b, secondary drift section 409, secondary modulation cavity 410, tertiary drift section 411, extraction cavity 412, collector 413, coaxial output waveguide 414, solenoid magnetic field 415. The whole structure is rotationally symmetric about the central axis.

[0039] The cathode seat 401, cathode 402, anode outer cylinder 403, and inner cylinder 404 are usually made of non-magnetic stainless steel. In order to improve the power capacity of the device, the surface of the extraction cavity 412 can be plated with titanium alloy material and polished. The cathode 402 can be made of high-hardness graphite or heat-resistant glass cloth-epoxy resin copper foil (FR-5) material, and the solenoid magnetic field 415 is wound with enameled copper wire or glass fiber copper wire. The left end of the cathode seat 401 is connected to the inner conductor of the pulse power driving source, and the left end of the anode outer cylinder 403 is connected to the outer conductor of the pulse power driving source. The right end of the coaxial output waveguide is connected to the mode converter and the radiating antenna.

[0040] When the present invention is in operation, the pulse power driving source loads a high voltage onto the cathode 402, and the cathode 402 emits a strong relativistic electron beam, which successively excites and acts on the radio frequency field in the primary modulation cavity, the second harmonic cavity, the secondary modulation cavity, and the extraction cavity, and is successively modulated by the standing wave field in the primary modulation cavity, the second harmonic cavity, and the secondary modulation cavity, and then the energy is extracted by the standing wave field in the extraction cavity to generate HPM. The HPM is externally coupled to the mode converter and the radiating antenna by the coaxial output waveguide.

[0041] This embodiment realizes a coaxial relativistic klystron oscillator with a second harmonic cavity loaded with a center frequency of 4.31 GHz (corresponding to a microwave wavelength of 6.96 cm) (the corresponding dimensions are designed as follows: R 1 =50 mm, R 2 =57 mm, R 3 =44 mm, R 4 =71mm, R 5 =32 mm, R 6 =55 mm, R 7 =40 mm, R 8 =30 mm, R 9 =62 mm, R 10 =38 mm, R 11 =70 mm, R 12 =31 mm, R 13 =56mm, R 14 =35.5 mm, R 15 =61 mm, R 16 =41 mm, R 17 =63 mm, R 18 =35 mm, R 19 =69 mm, R 20 =29 mm, R 21 =72mm, R 22 =43 mm, R 23 =54 mm, R 24 =46 mm, R 25=27 mm, R 26 =80 mm, R 27 =60 mm, R 28 =38 mm, L 1 =20 mm, L 2 =32 mm, L 3 =4.5 mm, L 4 =21 mm, L 5 =38 mm, L 6 =16.5 mm, L 7 =5.5 mm, L 8 =58.5 mm, L 9 =5 mm, L 10 =16 mm, L 11 =11 mm, L 12 =8.5 mm, L 13 =76 mm, L 14 =41 mm, L 15 =99 mm, L 16 =95 mm, L 17 =110 mm, L 18 =25 mm, L 19 =15.5 mm). In the particle simulation, under the conditions of diode voltage 600 kV, current 15 kA, and guide magnetic field 0.48 T, the microwave power output was 4.07 GW, and the power conversion efficiency was 45.2%. From the above results, it can be seen that the present invention overcomes the problem of low efficiency of beam-wave interaction under low magnetic field. By modulating the electron beam four times, the electron beam clustering effect is better, thereby achieving a more efficient beam-wave interaction, which has important reference significance for designing low magnetic field and high efficiency devices in other bands.

[0042] See also Figure 6 It can be seen that compared with the case without a second harmonic cavity, the electron beam is weakly modulated twice between the primary modulation cavity and the secondary modulation cavity when there is a second harmonic cavity, and a stronger radio frequency field is excited in the secondary modulation cavity.

[0043] See also Figure 7 It can be seen that compared with the case without the second harmonic cavity, the extracted fundamental current in the cavity is higher when there is a second harmonic cavity, which means that the electron beam grouping is further deepened and the beam-wave interaction efficiency is further improved.

[0044] See also Figure 8 It can be seen that compared with the case without a second harmonic cavity, the second harmonic current extracted from the cavity with a second harmonic cavity is higher, which means that the electron beam clustering is further deepened and the beam-wave interaction efficiency is further improved.

[0045] See also Fig. 9It can be seen that compared with the case without the second harmonic cavity, when there is a second harmonic cavity, strong transition radiation occurs in the extraction cavity, the microwave starts to oscillate in 6ns, saturates in 22ns, and the microwave power after saturation is 4.07GW.

[0046] See also Fig.10 It can be seen that the output microwave frequency is 4.31 GHz, the spectrum is pure, without noise, and the double frequency component is small.

[0047] See also Fig.11 , we can know that the length of the first-stage drift section is L 8 It has an impact on the maximum value of the fundamental current. 8 The maximum value of the fundamental current increases first and then decreases. 8 =58.5 mm, the maximum value of the fundamental current reaches its maximum.

[0048] See also Fig.12 , we can know that the length of the first-stage drift section is L 8 It has an impact on the maximum value of the second harmonic current. 8 The maximum value of the second harmonic current increases first and then decreases. 8 =58.5 mm, the maximum value of the second harmonic current reaches its maximum.

[0049] See also Fig.13 , we can know that the length of the secondary drift section is L 10 It has an impact on the maximum value of the fundamental current. 10 The maximum value of the fundamental current increases first and then decreases. 10 =16 mm, the maximum value of the fundamental current reaches its maximum.

[0050] See also Fig.14 , we can know that the length of the secondary drift section is L 10 It has an impact on the maximum value of the second harmonic current. 10 The maximum value of the second harmonic current increases first and then decreases. 10 =16 mm, the maximum value of the second harmonic current reaches its maximum.

[0051] See also Fig.15 , we can know that the length of the third-level drift section is L 19 The output microwave beam-wave efficiency is affected. 19 As the beam-wave effect increases, the efficiency increases first and then decreases. 19 =15.5 mm, the beam-wave interaction efficiency reaches its maximum.

[0052] Of course, in this preferred embodiment, other connection methods can also be used between the components, and the device structure can also be processed with other materials. The above is only a preferred implementation method of the present invention. The protection scope of the present invention is not limited to the above embodiment. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

[0053] It will be clear to those skilled in the art that the scope of the present invention is not limited to the examples discussed above, and that several changes and modifications may be made thereto without departing from the scope of the present invention as defined in the appended claims. Although the present invention has been illustrated and described in detail in the drawings and the specification, such illustration and description are merely illustrative or schematic and not restrictive. The present invention is not limited to the disclosed embodiments.

[0054] By studying the drawings, the description and the claims, those skilled in the art can understand and implement variations of the disclosed embodiments when practicing the invention. In the claims, the term "comprising" does not exclude other steps or elements. The fact that certain measures are cited in mutually different dependent claims does not mean that a combination of these measures cannot be used to advantage. Any reference signs in the claims do not constitute a limitation of the scope of the invention.

Claims

1. A low magnetic field high efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity, characterized by: The invention comprises a cathode seat (401), a cathode (402), an anode outer cylinder (403), an inner cylinder (404), a collimating hole (405), a primary modulation cavity (406), a primary second harmonic cavity (407a), a primary drift section (408), a secondary second harmonic cavity (407b), a secondary drift section (409), a secondary modulation cavity (410), a tertiary drift section (411), an extraction cavity (412), a collector (413), a coaxial output waveguide (414), and a solenoid magnetic field (415); the entire structure is rotationally symmetrical about the central axis, the left end of the cathode seat (401) is externally connected to the anode of a pulse driving source, the left end of the anode outer cylinder (403) is externally connected to the outer conductor of the pulse driving source, and the right end of the coaxial output waveguide (414) is connected to a mode converter and an antenna; The cathode (402) is a thin-walled cylinder, whose radius R1 is equal to the electron beam radius, and is sleeved on the right end of the cathode seat (401); the inner cylinder (404) is a cylindrical conductor with different radii, and together with various cavities on the anode outer cylinder (403) forms an electron beam modulation cavity and a microwave output structure; the collimating hole (405) is a circular ring cavity with an outer radius of R2, an inner radius of R3, and a length of L1, L1 is 0.3-0.8 times the working wavelength λ, and the collimating hole (405) is used to cut off microwaves of the working frequency to prevent leaked microwaves from interfering with the normal operation of the diode area; the primary modulation cavity (406) is composed of three pairs of circular ring cavities with rectangular cross sections: from left to right, the inner radius of the first circular ring cavity on the outer cylinder is equal to the outer radius R2 of the collimating hole (405), the outer radius is R4, and the length is L2, L2 is 0.3-0.6 times the working wavelength λ; the inner radius of the second circular ring cavity is R6, and the outer radius is R 19 , the length is L4, L4 is 0.3-0.5 times of the working wavelength λ, the inner radius of the third circular cavity is R9, and the outer radius is R 11 , the length is L5, L5 is 0.3-0.5 times of the working wavelength λ, satisfying R4>R 11 >R 19 >R9>R2>R6; the interval between each circular cavity is L3, L3 is 0.1-0.2 times of the working wavelength λ; from left to right, the inner radius of the first circular cavity on the inner cylinder is R5, the outer radius is R3, and the length is L2; ​​the inner radius of the second circular cavity is R8, the outer radius is R7, and the length is L4; the inner radius of the third circular cavity is R 12 , the outer radius is R 10 , the length is L5, satisfying R3>R7>R 10 >R5>R 12 >R8; The first-order second harmonic cavity (407a) is composed of a pair of circular ring cavities with rectangular cross sections: the outer radius of the circular ring cavity on the outer cylinder is R 15 , inner radius is R 13 The outer radius of the circular cavity on the inner cylinder is R 16 , inner radius is R 14 , satisfying R 15 >R 13 >R 16 >R 14 The lengths of the inner and outer cylindrical annular cavities are both L7, L7 being 0.1-0.2 times of the working wavelength λ; the interval between the first-order second harmonic cavity (407a) and the first-order modulation cavity (406) is L6, L6 being 0.2-0.3 times of the working wavelength λ; the first-order drift section (408) is a section with an outer radius of R 13 , the inner radius is R 16 The length of the annular cavity is L8, and L8 is 0.8-1.1 times of the working wavelength λ; the secondary second harmonic cavity (407b) is composed of a pair of annular cavities with rectangular cross sections, and the outer radius of the annular cavity on the outer cylinder is R 17 , inner radius is R 13 The outer radius of the circular cavity on the inner cylinder is R 16 , inner radius is R 18 , satisfying R 17 >R 13 >R 16 >R 18 The lengths of the inner and outer cylindrical annular cavities are both L9, and L9 is 0.1-0.3 times the working wavelength λ; the secondary drift section (409) is an outer radius R 13 , the inner radius is R 16 The circular cavity has a length of L 10 , L 10 The secondary modulation cavity (410) is composed of a pair of circular ring cavities with rectangular cross sections: the outer radius of the circular ring cavity on the outer cylinder is R 19 , inner radius is R 13 The outer radius of the circular cavity on the inner cylinder is R 16 , inner radius is R 20 , satisfying R 19 >R 13 >R 16 >R 20 The length of the circular cavity of the inner and outer cylinders is L 11 , L 11 is 0.1-0.3 times of the working wavelength λ; the interval between the secondary second harmonic cavity (407b) and the secondary modulation cavity (410) is L 10 , L 10 The extraction cavity (412) is composed of two pairs of circular ring cavities with rectangular cross sections: the inner radius of the first circular ring cavity on the outer cylinder from left to right is R 23 , the outer radius is R 21 , length L 11 , L 11 is 0.1-0.3 times of the working wavelength λ, and the inner radius of the second circular cavity is R 23 , the outer radius is R 11 , length L 12 , L 12 0.1-0.3 times of the working wavelength λ, satisfying R 21 >R 11 >R 23 ; The distance between the two annular cavities is L3; The inner radius of the first annular cavity on the inner cylinder from left to right is R 20 , the outer radius is R 22 , length L 11 , the inner radius of the second circular cavity is R 25 , the outer radius is R 18 , length L 12 , satisfying R 23 >R 22 >R 18 >R 20 >R 25 The third drift section (411) is a section with an outer radius of R 23 , a circular cavity with an inner radius of R3 and a length of L 19 , L 19 The collector (413) is composed of a circular ring cavity with a rectangular cross section and a circular ring cavity with a trapezoidal cross section. The outer radius of the circular ring cavity with a rectangular cross section is R 23 , the inner radius is R 24 , length L 15 , L 15 The outer radius and inner radius of the circular cavity with a trapezoidal cross section are R 27 , R 23 The lengths of the upper and lower bases are L 14 , L 13 , satisfying L 13 >L 14 , L 13 1-1.5 times of the working wavelength λ, L 14 0.4-0.7 times of the working wavelength λ; The coaxial output waveguide (414) is composed of a circular ring cavity with a rectangular cross section and a circular ring cavity with a trapezoidal cross section. The circular ring cavity with a rectangular cross section has an outer radius of R5 and an inner radius of R 25 , length L 15 +L 18 , L 15 +L 18 The inner radius and outer radius of the circular cavity with a trapezoidal cross section are R5 and R 28 The lengths of the upper and lower bases are L 16 , L 17 , satisfying L 17 >L 16 , L 16 1-1.5 times of the working wavelength λ, L 17 The wavelength is 1.5-2 times of the working wavelength; the solenoid magnetic field (415) is sleeved on the outer wall of the anode outer cylinder (403).

2. The low magnetic field high efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity according to claim 1, characterized in that: The cathode (402) wall thickness is 2 mm.

3. The low magnetic field high efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity according to claim 1, characterized in that: The cathode seat (401), cathode (402), anode outer cylinder (403), and inner cylinder (404) are made of non-magnetic stainless steel material, the surface of the extraction chamber (412) is plated with titanium alloy material, the cathode (402) is made of high-hardness graphite or heat-resistant glass cloth-epoxy resin copper foil plate material, and the solenoid magnetic field (415) is wound with enameled copper wire or glass fiber coated copper wire.

4. The low magnetic field high efficiency coaxial relativistic klystron oscillator loaded with a second harmonic cavity according to any one of claims 1 to 3, characterized in that: The coaxial relativistic klystron oscillator loaded with a second harmonic cavity with a center frequency of 4.31 GHz has the following dimensions: R1=50 mm, R2=57 mm, R3=44 mm, R4=71 mm, R5=32 mm, R6=55 mm, R7=40 mm, R8=30 mm, R9=62 mm, R 10 =38 mm, R 11 =70 mm, R 12 =31 mm, R 13 =56 mm, R 14 =35.5 mm, R 15 =61 mm, R 16 =41 mm, R 17 =63 mm, R 18 =35 mm, R 19 =69 mm, R 20 =29 mm, R 21 =72 mm, R 22 =43 mm, R 23 =54 mm, R 24 =46 mm, R 25 =27 mm, R 26 =80 mm, R 27 =60 mm, R 28 =38 mm, L1=20 mm, L2=32 mm, L3=4.5 mm, L4=21mm, L5=38 mm, L6=16.5 mm, L7=5.5 mm, L8=58.5 mm, L9=5 mm, L 10 =16 mm, L 11 =11 mm, L 12 =8.5mm, L 13 =76 mm, L 14 =41 mm, L 15 =99 mm, L 16 =95 mm, L 17 =110 mm, L 18 =25 mm, L 19 =15.5 mm.

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