A low-Q modulator cavity with high efficiency and low magnetic field relativistic klystron oscillator

Abstract

The invention relates to a microwave source device in the field of high-power microwave technology, in particular to a low-Q value modulation cavity with a weak magnetic field and high-efficiency relativistic klystron oscillator, belonging to the field of high-power microwave technology; the device comprises a cathode seat, a cathode, an anode outer cylinder, a reflection cavity, a modulation cavity, an extraction cavity, a trapezoidal collector, an output waveguide, an inner cylinder, and a solenoid magnetic field, and the entire structure is rotationally symmetric about a central axis OO'; the magnetic field intensity adopted by the invention is 0.37 T, belonging to a weak magnetic field environment, and the low-Q value modulation cavity introduced at the same time cannot store a large amount of energy, resulting in partial microwave energy leakage in the modulation cavity and direct coupling to the extraction cavity, forming a first-level extraction; in a drift tube, an electron beam absorbs part of the leaked microwave energy and re-accelerates it to become a high-energy electron, and is extracted again in the extraction cavity, forming a second-level extraction, and finally, under the conditions of a voltage of 494 kV, a current of 6 kA, and a magnetic field of 0.37 T, a 1.5 GW microwave output is achieved, and a working efficiency of 50.3% is achieved.

Description

Technical Field

[0001] The invention relates to a microwave source device in the technical field of high-power microwaves, in particular to a weak magnetic field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity, belonging to the technical field of high-power microwaves. Background Art

[0002] High-power microwaves usually refer to electromagnetic waves with a peak power greater than 100MW and a frequency between 1GHz and 300GHz. With the development of pulse power technology, plasma physics and electric vacuum technology, high-power microwave technology is a research field that has emerged. It has been widely used in many fields such as radar satellites, electronic high-energy radio frequency accelerators, remote sensing and radiation measurement.

[0003] In recent years, high-power microwave technology has made significant progress in power, repetition rate and life. At present, high-power microwaves are in a critical period of moving towards practical application, and its research direction is gradually focusing on efficiency improvement, lightweight and modular design. Permanent magnet packaged high-power microwave sources have been widely studied due to their advantages such as stable output, small size and light weight. High-power microwave sources are the core components for generating high-power microwave radiation. High-power microwaves are generated based on the interaction between high-current electron beams and resonant cavities. High-quality high-current electron beams are the basis of high-efficiency beam-wave interaction. However, the space charge effect of electron beams under weak magnetic fields is aggravated, which often makes it difficult to improve the working efficiency of microwave source devices. In order to solve this problem, researchers have conducted a lot of research.

[0004] The relativistic klystron oscillator is a device that works in a weak magnetic field. Researchers have carried out a lot of research work. In 2024, Deng Rujin and others from the National University of Defense Technology reported an X-band coaxial relativistic klystron oscillator [Deng Rujin, Li Zhimin, Ge Xingjun, Dang Fangchao, Zhang Peng, Qian Baoliang. Analysis and Suppression of Mode Competition in a Relativistic Klystron Oscillator. IEEE Transactions on Electron Devices. 2024;71(11):7030-7036] (e.g. Figure 1 As shown in Figure 1). The structure consists of a cathode, a first-stage modulation cavity, a second-stage modulation cavity, an extraction cavity, a collector, and an output waveguide. The external quality factor (Q value) of the modulation cavity used is 1034 (higher than 1000), which is a high-Q modulation cavity. The working efficiency reaches 40% at a magnetic field strength of 0.55T, and the output power is 2.80 GW.

[0005] In 2022, Zhang Peng et al. from the National University of Defense Technology reported an X-band low-magnetic field coaxial relativistic klystron oscillator [Zhang Peng, Dang Fangchao, Ge Xingjun et al. An X-band high-power and high-efficiency coaxial relativistic klystron oscillator with four-gap buncher and three-gap extractor [J]. Physics of Plasmas, 2022, Vol. 29(9): 093101] (e.g. Figure 2 As shown in Figure 1). The structure consists of a spiral tube magnetic field, a cathode, a modulation cavity, an extraction cavity, and a collector. The external quality factor (Q value) of the modulation cavity used is 1611 (higher than 1000), which is a high-Q modulation cavity. It achieves a working efficiency of 42% at a magnetic field strength of 0.48 T and an output power of 4.2 GW.

[0006] It is not difficult to see from the above research that in current research, the magnetic field strength is usually higher than 0.4 T, the conversion efficiency is difficult to exceed 50%, and the modulation cavity often works under high Q value (>1000). Therefore, it is urgent to study a high-power microwave device with high conversion efficiency (≥50%) that can work under low Q value (<500) and weak magnetic field (<0.4 T) conditions. Summary of the invention

[0007] The technical problem to be solved by the present invention is: the present invention proposes a weak magnetic field high-efficiency relativistic klystron oscillator with a low Q value modulation cavity, which overcomes the difficulty that the working efficiency of high-power microwave devices in a weak magnetic field is difficult to exceed 50%, and has the advantages of fast start-up time and high conversion efficiency.

[0008] The technical solution of the present invention is:

[0009] A low-magnetic-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity comprises a cathode seat 1, a cathode 2, an anode outer cylinder 3, a reflection cavity 4, a modulation cavity 5, an extraction cavity 6, a trapezoidal collector 7, an output waveguide 8, an inner cylinder 9, and a solenoid magnetic field 10. The entire structure is rotationally symmetric about the central axis OO'. One end of the relativistic klystron oscillator is connected to a pulse power source, and the other end is connected to a radiation system. The end connected to the pulse power source is defined as the left end of the relativistic klystron oscillator, and the end connected to the radiation system is defined as the right end of the relativistic klystron oscillator;

[0010] Cathode 2 is a thin-walled cylinder with a wall thickness of 2 mm, which is nested and installed on cathode holder 1 with an outer radius of R. 15 , the inner radius is R1, R15 >R1, the anode outer tube 3 is composed of two cylindrical tubes with different radii, and the inner radius of the cylindrical tube on the left end close to the cathode side is R2. 16 , the inner radius is R3, and the width is L1. The value of L1 is 0.2-0.3 times of the working wavelength λ. The reflection cavity 4 is a circular cavity with an outer radius of R 17 , a circular cavity with an inner radius of R4, R 17 >R 16 >R3>R4, width L2, L2 is 0.5-0.7 times of the working wavelength λ, all parameters of the reflection cavity 4 need to be optimized as a whole in the electromagnetic field simulation software (such as CHIPIC) according to the working wavelength λ. There is a cavity with an outer radius of R between the reflection cavity 4 and the modulation cavity 5. 16 The modulation cavity 5 is composed of four circular ring cavities with rectangular cross sections. The outer radius of the four circular ring cavities is R 18 , the inner radius is R5, R 18 >R5; the first circular cavity width is L4, the second circular cavity width is L6, the third circular cavity width is L8, the fourth circular cavity width is L 10 , L4, L6, L8 and L 10 The value is 0.2-0.5 times of the working wavelength λ; the intervals between the four annular cavities on the outer cylinder are L5, L7 and L9 from left to right, and the radius is R 19 , R 20 and R 21 , R 21 >R 19 =R 20 , L5, L7 and L9 are 0.1-0.3 times of the working wavelength λ; the intervals between the four annular cavities on the inner cylinder 9 are consistent with the outer cylinder, and the radius from left to right is R6, R7 and R8, R8>R6>R7. There is a cavity with an outer radius of R between the modulation cavity 5 and the extraction cavity 6. 22 , inner radius is R9, width L 11 The annular cavity, L 11 The value is 0.4-0.6 times the working wavelength λ; the value of R9 will affect the Q value of the modulation cavity 5. By adjusting the size of R9, a modulation cavity design with a low Q value (<500) can be achieved. The extraction cavity 6 consists of three circular cavities with rectangular cross sections. The inner radius of the first, second and third circular cavities from left to right is the same, which is R 10 , the outer radius of the first circular cavity is R 23 The outer radius of the second and third circular cavities is the same, both R 25 , R 23>R 25 >R 10 The first and second circular cavities are both wide L 12 , the width of the third circular cavity is L 15 , L 12 With L 15 The value is 0.1-0.3 times of the working wavelength λ; the intervals of the three annular cavities on the outer cylinder are L 13 With L 14 , the radius from left to right is R 24 and R 26 , R 26 >R 24 , L 13 With L 14 The value is 0.1-0.2 times of the working wavelength λ; the spacing of the three annular cavities on the inner cylinder is consistent with that of the outer cylinder, and the radius is R 11 The trapezoidal collector 7 is a circular cavity with a right-angle trapezoidal cross section, and the radius of the upper bottom surface is R 28 , length L 16 , the radius of the lower base is R 27 , the projection length of the hypotenuse on the center line OO' is L 17 , L 16 and L 17 The output waveguide 8 is designed in an electromagnetic field simulation software (such as CHIPIC) according to the electron beam bombardment position and magnetic field configuration. The output waveguide 8 consists of two sections: one section is a circular ring cavity with a right-angled trapezoidal cross section, and the other section is a circular ring cavity with a rectangular cross section. The projection length of the hypotenuse of the circular ring cavity with a right-angled trapezoidal cross section on the center line OO' is L 18 , L 18 The value is 0.1-0.3 times of the working wavelength λ, and the outer radius of the circular cavity with a rectangular cross section is R 12 , the inner radius is R 13 , R 12 >R 13 The inner cylinder 9 is composed of two cylinders with different radii. The side close to the cathode on the left end is a cylinder with a maximum radius of R9, on which various grooves are processed. The right end is a cylinder with a radius of R 13 The cylindrical body has a smooth surface and forms an output waveguide together with the anode outer cylinder 3 for outputting high-power microwaves; the output waveguide 8 has a distance L from the left end. 19 There is a circular protrusion with a rectangular cross section at the position of 12 , inner radius R 14 , width L 21 , L 21 The value is 0.1-0.2 times of the working wavelength λ; the magnetic field system adopts a solenoid magnetic field 10, which can generate an axial guide magnetic field intensity of 0.37 T, which belongs to a weak electromagnetic environment.

[0011] The cathode 2 is made of graphite material with good emission performance.

[0012] The external quality factor (Q value) of the modulation cavity 5 is inversely proportional to the value of R9. When the inner radius of the annular cavity between the modulation cavity 5 and the extraction cavity 6 is close to the center distance of the cavity, the external quality factor (Q value) of the modulation cavity 5 decreases. At the same time, the influence of the electron beam envelope must be considered to prevent the electron beam envelope from scratching the inner cylinder 9 of the device in a weak electromagnetic environment.

[0013] In order to reduce the surface electric field, chamfering is performed on all protrusion corners.

[0014] The working process of the present invention is as follows: the pulse voltage generated by the pulse power driving source acts on the cathode 2 through the cathode seat 1, and the right end face of the cathode 2 generates a strong current relativistic electron beam based on the explosive emission, which is transmitted to the right end under the guidance of the magnetic field of 0.37 T. The electron beam transmitted to the right end passes through the reflection cavity 4, the modulation cavity 5, and the extraction cavity 6 respectively, and finally bombards the trapezoidal collector 7. In the modulation cavity 5, the electron beam is subjected to the electric field in the cavity to produce oscillations to obtain speed modulation. Due to the use of a low Q value modulation cavity, a large amount of energy cannot be stored in the modulation cavity 5, and part of the energy leakage will occur. This part of the leaked energy will be directly coupled to the extraction cavity 6 to be extracted to generate microwaves; at the same time, the electrons in the drift tube (the annular cavity formed between the anode outer cylinder 3 and the inner cylinder 9) will also absorb part of the leaked energy to obtain modulation again and finally hand over the energy to the radio frequency field in the extraction cavity 6, thereby oscillating to generate microwaves. The generated microwaves are radiated outward through the output waveguide 8.

[0015] Compared with the prior art, the present invention can achieve the following technical effects:

[0016] The magnetic field strength used in the present invention is 0.37 T, which belongs to a weak magnetic field environment. At the same time, the low Q value modulation cavity introduced cannot store a large amount of energy, resulting in the leakage of part of the microwave energy in the modulation cavity and direct coupling to the extraction cavity, forming the first-level extraction. In the drift tube, the electron beam absorbs part of the leaked microwave energy and re-accelerates it into high-energy electrons, which are extracted again in the extraction cavity, forming the second-level extraction. Finally, under the conditions of voltage 494 kV, current 6 kA, and magnetic field 0.37 T, 1.5 GW microwave output was achieved, with a working efficiency of 50.3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an X-band relativistic backward wave tube oscillator disclosed in the prior art in the background introduction;

[0018] Figure 2 It is a structural schematic diagram of an X-band low magnetic field relativistic klystron oscillator disclosed in the prior art in the background introduction;

[0019] Figure 3 It is a structural schematic diagram of a low-magnetic-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention;

[0020] Figure 4 It is a relationship diagram between the external quality factor of the modulation cavity and the frequency of a preferred embodiment of a low-magnetic-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention;

[0021] Figure 5 It is a schematic diagram of the spatial distribution and phase velocity of the electron beam of a preferred embodiment of a low-magnetic-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention;

[0022] Figure 6 It is a schematic diagram of fundamental current and output power flow of a preferred embodiment of a weak magnetic field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention;

[0023] Figure 7 It is a schematic diagram of electron beam power flow of a preferred embodiment of a weak magnetic field high-efficiency relativistic klystron oscillator with a low Q value modulation cavity provided by the present invention;

[0024] Figure 8 This is a spectrum diagram of a preferred embodiment of a weak magnetic field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention;

[0025] Fig. 9 It is an output microwave power diagram of a preferred embodiment of a weak magnetic field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention;

[0026] Fig.10 The graph is a relationship curve between the external quality factor (Q value) of the modulation cavity 5 and R9 of a preferred embodiment of a low-magnetic-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity provided by the present invention. DETAILED DESCRIPTION

[0027] 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.

[0028] The present invention comprises a cathode seat 1, a cathode 2, an anode outer cylinder 3, a reflection cavity 4, a modulation cavity 5, an extraction cavity 6, a trapezoidal collector 7, an output waveguide 8, an inner cylinder 9, and a spiral tube magnetic field 10, and the entire structure is rotationally symmetrical about the central axis OO'. One end of the relativistic klystron oscillator is connected to a pulse power source, and the other end is connected to a radiation system. It is defined that the end connected to the pulse power source is the left end of the relativistic klystron oscillator, and the end connected to the radiation system is the right end of the relativistic klystron oscillator.

[0029] The parameter determination process of an embodiment of the present invention is as follows: the above-mentioned radial radius parameters are determined according to the empirical formula f =15 / Δ r ,in f Indicates the design target frequency in GHz, Δ r is the difference between the inner and outer radii of the blades at the above positions, in cm. Based on this formula, the design target frequency can be calculated. f Calculate Δ r The value of the inner and outer radius of the blade is obtained by combining the radial dimension of the pulse power source to be connected at the left end.

[0030] When the present invention is in operation, the pulse power driving source loads the pulse voltage onto the cathode seat 1, the cathode 2 emits a strong relativistic electron beam and blocks and absorbs the returning electrons, the electron beam is first subjected to velocity modulation at the modulation cavity 5, and clustering occurs due to the different fields felt by the electrons at various positions. The clustered electron beam is subjected to density modulation at the extraction cavity 6, and a strong beam-wave interaction occurs, generating transition radiation, handing over energy to microwaves, and thus generating high-power microwaves.

[0031] This embodiment realizes an X-band relativistic klystron oscillator with an operating frequency of 10.22 GHz (corresponding to a microwave wavelength λ=2.99 cm), and the corresponding dimensions are designed as follows: R1=34 mm, R2=63 mm, R3=30 mm, R4=22 mm, R5=27 mm, R6=29.5 mm, R7=29 mm, R8=31 mm, R9=31 mm, R 10 =25.5 mm, R 11 =29 mm, R 12 =28.5 mm, R 13 =22.5 mm, R 14 =26.5 mm, R 15 =36 mm, R 16 =40 mm, R 17 =44 mm, R 18 =45 mm, R 19 =39 mm, R 20 =39 mm, R 21 =40 mm, R 22 =41 mm, R 23 =47.5 mm, R 24 =39.5 mm, R 25 =46.5 mm, R 26 =41 mm, R 27 =31 mm, R 28=39 mm, L1=8mm, L2=20 mm, L3=15 mm, L4=10.5 mm, L5=6 mm, L6=6 mm, L7=7 mm, L8=6.5 mm, L9=5.5 mm, L 10 =9 mm, L 11 =15.5 mm, L 12 =6 mm, L 13 =5 mm, L 14 =5.5 mm, L 15 =5.5 mm, L 16 =29.5 mm, L 17 =20 mm, L 18 =8 mm, L 19 =17 mm, L 20 =34 mm, L 21 =3.5 mm.

[0032] In the particle simulation, under the guidance of the helical magnetic field of 494 kV diode voltage, 6 kA current and 0.37 T, the high-power microwave with an output frequency of 10.22 GHz, an output microwave power of 1.5 GW and a conversion efficiency of 50.3% were output. It can be seen from the above results that the present invention has the ability to overcome the difficulty of power efficiency being less than 50% under weak magnetic field conditions.

[0033] See also Figure 4 It can be seen that at the operating frequency of the device, the Q value of the modulation cavity is lower than 175, which belongs to a low Q value modulation cavity.

[0034] See also Figure 5 and Figure 6 It can be seen that the electron beam is preliminarily modulated in the reflection cavity and fully modulated in the modulation cavity, and finally transfers energy to microwaves in the extraction cavity; the maximum value of the fundamental current is 7.04 kA, and the modulation depth is 117%.

[0035] See also Figure 7 It can be seen that in the third and fourth cavities of the modulation cavity, the electron beam transfers part of its energy to the microwave, forming the first-level extraction. Subsequently, in the drift tube, the electron beam absorbs part of the leaked microwave energy and re-accelerates it into high-energy electrons, which are extracted again in the extraction cavity, forming the second-level extraction, achieving high-efficiency and high-power microwave output.

[0036] See also Figure 8 , it can be seen that the output microwave frequency of the device is 10.22 GHz and the spectrum is pure.

[0037] See also Fig. 9 , it can be seen that the output microwave power of the device is 1.5 GW and the conversion efficiency is 50.3%.

[0038] See also Fig.10 It can be seen that the external quality factor (Q value) of the device modulation cavity 5 is inversely proportional to R9, and the design of a low Q value modulation cavity can be achieved by adjusting the value of R9; in one embodiment of the present invention, when the value of R9 is greater than 30 mm, the external quality factor (Q value) of the modulation cavity 5 is less than 500, which belongs to a low Q value modulation cavity; since the center distance of the electron beam in the embodiment is 35 mm, in order to avoid the electron beam envelope from scratching the device inner cylinder 9 in a weak magnetic field environment, the value of R9 is 31 mm after comprehensive consideration.

Claims

1. A low-field high-efficiency relativistic klystron oscillator with a low-Q modulation cavity, characterized in that: It comprises a cathode seat (1), a cathode (2), an anode outer cylinder (3), a reflection cavity (4), a modulation cavity (5), an extraction cavity (6), a trapezoidal collector (7), an output waveguide (8), an inner cylinder (9), and a solenoid magnetic field (10), and the entire structure is rotationally symmetrical about a central axis OO'; one end of the relativistic klystron oscillator is connected to a pulse power source, and the other end is connected to a radiation system; The cathode (2) is a thin-walled cylinder, which is nested and installed on the cathode seat (1) with an outer radius of R 15 , the inner radius is R1, R 15 >R1, the anode outer tube (3) is composed of two cylindrical tubes with different radii, wherein the inner radius of the cylindrical tube at the left end close to the cathode side is R2; the left end of the reflection cavity (4) is connected to a cylindrical tube with an outer radius of R 16 , the inner radius is R3, the width is L1, and the value of L1 is 0.2-0.3 times of the working wavelength λ; the reflection cavity (4) is a cavity with an outer radius of R 17 , a circular cavity with an inner radius of R4, R 17 >R 16 >R3>R4, width L2, L2 is 0.5-0.7 times of the working wavelength λ, all parameters of the reflection cavity (4) need to be optimized as a whole in the electromagnetic field simulation software according to the working wavelength λ; between the reflection cavity (4) and the modulation cavity (5) is a cavity with an outer radius of R 16 , a circular ring cavity with an inner radius of R3 and a width of L3, where L3 is 0.4-0.6 times the working wavelength λ; the modulation cavity (5) is composed of four circular ring cavities with rectangular cross sections, and the outer radii of the four circular ring cavities are R 18 , the inner radius is R5, R 18 >R5; the first circular cavity width is L4, the second circular cavity width is L6, the third circular cavity width is L8, the fourth circular cavity width is L 10 , L4, L6, L8 and L 10 The value is 0.2-0.5 times of the working wavelength λ; the intervals between the four annular cavities on the outer cylinder are L5, L7 and L9 from left to right, and the radius is R 19 , R 20 and R 21 , R 21 >R 19 =R 20 , L5, L7 and L9 are 0.1-0.3 times of the working wavelength λ; the intervals between the four annular cavities on the inner cylinder (9) are consistent with those of the outer cylinder, and the radii are R6, R7 and R8 from left to right, R8>R6>R7; between the modulation cavity (5) and the extraction cavity (6) is a cavity with an outer radius of R 22 , inner radius is R9, width L 11 The annular cavity, L 11 The value is 0.4-0.6 times of the working wavelength λ; the value of R9 affects the Q value of the modulation cavity (5), and the modulation cavity design with a low Q value is achieved by adjusting the size of R9; the extraction cavity (6) is composed of three circular ring cavities with rectangular cross sections, and the inner radius of the first, second and third circular ring cavities from left to right is the same, which is R 10 , the outer radius of the first circular cavity is R 23 The outer radius of the second and third circular cavities is the same, both R 25 , R 23 >R 25 >R 10 The first and second circular cavities are both wide L 12 , the width of the third circular cavity is L 15 , L 12 With L 15 The value is 0.1-0.3 times of the working wavelength λ; the intervals of the three annular cavities on the outer cylinder are L 13 With L 14 , the radius from left to right is R 24 and R 26 , R 26 >R 24 , L 13 With L 14 The value is 0.1-0.2 times of the working wavelength λ; the spacing of the three annular cavities on the inner cylinder is consistent with that of the outer cylinder, and the radius is R 11 The trapezoidal collector (7) is a circular cavity with a right-angle trapezoidal cross section, and the radius of the upper bottom surface is R 28 , length L 16 , the radius of the lower base is R 27 , the projection length of the hypotenuse on the center line OO' is L 17 , L 16 and L 17 The output waveguide (8) is designed comprehensively in electromagnetic field simulation software according to the electron beam bombardment position and magnetic field configuration; the output waveguide (8) consists of two sections: one section is a circular ring cavity with a right-angled trapezoidal cross section, and the other section is a circular ring cavity with a rectangular cross section. The projection length of the hypotenuse of the circular ring cavity with a right-angled trapezoidal cross section on the center line OO' is L 18 , L 18 The value is 0.1-0.3 times the working wavelength λ, and the outer radius of the circular cavity with a rectangular cross section is R 12 , the inner radius is R 13 , R 12 >R 13 The inner cylinder (9) consists of two cylinders with different radii, one of which is close to the cathode on the left end and has a maximum radius of R9, on which various grooves are machined, and the other is on the right end and has a radius of R 13 The cylindrical body (8) has a smooth surface and together with the anode outer cylinder (3) forms an output waveguide for outputting high-power microwaves; the output waveguide (8) has a distance L from the left end. 19 There is a circular protrusion with a rectangular cross section at the position of 12 , inner radius R 14 , width L 21 , L 21 The value is 0.1-0.2 times of the working wavelength λ; the magnetic field system adopts a solenoid magnetic field (10), which can generate an axial guide magnetic field intensity of 0.37 T, belonging to a weak electromagnetic environment.

2. The low-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity according to claim 1, characterized in that: The wall thickness of the cathode (2) is 2 mm.

3. The low-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity according to claim 2, characterized in that: The cathode (2) is made of graphite material.

4. The low-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity according to claim 1, characterized in that: The external quality factor of the modulation cavity (5) is inversely proportional to the value of R9. When the inner radius of the annular cavity between the modulation cavity (5) and the extraction cavity (6) approaches the cavity center distance, the external quality factor of the modulation cavity (5) decreases. At the same time, the influence of the electron beam envelope must be considered to prevent the electron beam envelope from scratching the device inner cylinder (9) in a weak electromagnetic environment.

5. The low-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity according to claim 1, characterized in that: In order to reduce the surface electric field, chamfering is performed on all protrusion corners.

6. The low-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity according to claim 1, characterized in that: The electromagnetic field simulation software is CHIPIC.

7. The low-field high-efficiency relativistic klystron oscillator with a low-Q value modulation cavity according to any one of claims 1 to 6, characterized in that: The operating frequency is 10.22 GHz, corresponding to the microwave wavelength λ=2.99 cm. The corresponding dimensions are designed as follows: R1=34 mm, R2=63 mm, R3=30 mm, R4=22 mm, R5=27 mm, R6=29.5 mm, R7=29 mm, R8=31 mm, R9=31 mm, R 10 =25.5 mm, R 11 =29 mm, R 12 =28.5 mm, R 13 =22.5 mm, R 14 =26.5 mm, R 15 =36 mm, R 16 =40 mm, R 17 =44 mm, R 18 =45 mm, R 19 =39 mm, R 20 =39 mm, R 21 =40 mm, R 22 =41 mm, R 23 =47.5 mm, R 24 =39.5 mm, R 25 =46.5 mm, R 26 =41 mm, R 27 =31 mm, R 28 =39 mm, L1=8 mm, L2=20 mm, L3=15 mm, L4=10.5 mm, L5=6 mm, L6=6 mm, L7=7 mm, L8=6.5 mm, L9=5.5 mm, L 10 =9 mm, L 11 =15.5mm, L 12 =6 mm, L 13 =5 mm, L 14 =5.5 mm, L 15 =5.5 mm, L 16 =29.5 mm, L 17 =20 mm, L 18 =8 mm, L 19 =17mm, L 20 =34 mm, L 21 =3.5 mm.

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