Introducing a low magnetic field, high beam current, C-band high power TTO with a focusing cathode

Abstract

The present invention relates to a microwave source device in the field of high power technology, in particular to a low magnetic field strong beam C-band high power TTO introducing a focusing cathode, belonging to the field of high power microwave technology; comprising a cathode seat, a cathode inner shielding ring, a cathode outer shielding ring, a cathode, an inner conductor, an outer conductor, and an external guide magnetic field structure, the whole structure is rotationally symmetrical about a central axis OO'; the focusing cathode introduced in the present invention reduces the dependence of stable transmission of an electron beam on a magnetic field, and can still work normally in a magnetic field of 0.2 T, has the advantage of working in a low magnetic field, and is beneficial to permanent magnet packaging; when working between 0.2 T and 1.0 T, the power efficiency is further increased from 18% to 39%.

Description

Technical Field

[0001] The invention relates to a microwave source device in the field of high power technology, in particular to a C-band high power transit-time oscillator (TTO) with a low magnetic field and strong beam current and introduced into a focusing cathode, belonging to the field of high power microwave technology. Background Art

[0002] High-power microwaves usually refer to electromagnetic waves with a peak power greater than 100MW and a frequency between 1 and 300GHz. They have been widely used in many defense and industrial fields such as radar satellites, electronic high-energy radio frequency accelerators, remote sensing and radiation measurement.

[0003] High-power microwave source is the core component for generating high-power microwave radiation. It uses the interaction between high-current electron beam and resonant cavity to generate high-power microwave. Transit time oscillator (TTO) uses the energy exchange between high-current electron beam and intrinsic standing wave field in resonant cavity. It has the characteristics of high power, high efficiency and single working mode, and has attracted extensive attention from researchers.

[0004] The C band refers to an electromagnetic wave frequency band with a frequency range of 4.0-8.0 GHz, which is widely used in civil aviation communications, weather warnings, disaster relief, satellite news gathering, etc. Compared with electromagnetic waves in high-frequency bands such as X, Ku, and Ka, the wavelength of electromagnetic waves in the C band is longer, so the electromagnetic waves in this band have the characteristics of strong coverage, especially in remote or sparsely populated areas, where electromagnetic waves have great application prospects. The World Meteorological Organization uses this band to distribute meteorological data worldwide, and information related to maritime and aviation safety is also relayed through earth stations working in this band. In areas with severe rainfall, this band of electromagnetic waves has become the only practically available band for providing high-reliability satellite fixed services because of its weak rain attenuation. The representative C-band coaxial transit-time oscillator is a device designed by Deng Xiaobo of the National University of Defense Technology [Deng Xiaobo. Research on C-band high-efficiency and low-magnetic field transit-time oscillator[D]. National University of Defense Technology, 2020.]. By loading an open foil mesh, under the conditions of a diode voltage of 542.0 kV, a current of 12.0 kA, and a guided magnetic field of 0.4 T, a microwave output of 1.95 GW was simulated with a frequency of 4.28 GHz.

[0005] For high-power microwave source devices in the C band, if you want to exert greater power, you need to output higher microwave power, which requires higher injected electric power, which leads to an increase in the working voltage and working current, so that the device works in a strong beam state. The strong space charge effect of the strong beam will cause the electron beam envelope to increase. On the one hand, in order to confine the strong beam electron beam to a smaller range, a larger guiding magnetic field is often required. A large guiding magnetic field means bulky magnetic field coils and a huge excitation system, which is not conducive to the lightweight and miniaturization of high-power microwave sources. On the other hand, if the working magnetic field is directly reduced or an open foil mesh is used, it will cause significant beam loss and reduce the working efficiency of the device.

[0006] In order to make the C-band high-power microwave source more practical, it is necessary to make the microwave source still have the characteristics of high power and high efficiency under a lower guiding magnetic field. The focusing cathode can reduce the radial electric field dispersion at the diode and reduce the demand for the guiding magnetic field for stable transmission of the electron beam. In addition, when the required guiding magnetic field is low, the permanent magnetic structure can replace the coil magnetic field, which is of great significance for the lightweight and miniaturization of high-power microwave sources.

[0007] The Chinese invention patent "Low magnetic field Ka-band coaxial transit time oscillator with introduction of focusing cathode (patent number: ZL2021107815944)" proposes a low magnetic field Ka-band coaxial transit time oscillator with introduction of focusing cathode. This focusing cathode structure can reduce the dependence of electron beam transmission on the magnetic field.

[0008] From the above, we can see that although the coaxial transit time oscillator has the advantages of low guiding magnetic field, high output power and high output efficiency, there are few studies on the C-band under strong beam conditions, especially the low magnetic field and strong beam C-band high-power TTO working under lower guiding magnetic field and introducing a focusing cathode. Summary of the invention

[0009] The present invention proposes a low magnetic field strong beam C-band high power TTO which introduces a focusing cathode, which can realize that the microwave source still has high output power and power efficiency under a low guiding magnetic field, and has the potential of using permanent magnet packaging.

[0010] The technical solution adopted by the present invention is:

[0011] A C-band high-power TTO with a low magnetic field and a strong beam current that introduces a focusing cathode comprises a cathode seat 1, a cathode inner shielding ring 2, a cathode outer shielding ring 3, a cathode 4, an inner conductor 5, an outer conductor 6, and an external guiding magnetic field structure 7, wherein the entire structure is rotationally symmetrical about a central axis OO'; one end of the TTO 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 a coaxial transit time oscillator, and the end connected to the radiation system is defined as the right end of a coaxial transit time oscillator;

[0012] The cathode seat 1 is a cylindrical structure with an axial length of l 1, l 1 Take 15mm-30mm, the radial radius is equal to the radial inner radius r of the cathode 4 10 The left end of the cathode holder 1 is connected to the inner conductor of the pulse power source, and the cathode 4 is connected to the right end of the cathode holder 1, forming concentric circles with the cathode inner shielding ring 2 and the cathode outer shielding ring 3;

[0013] The cathode 4 is used to generate and emit electron beams. It is a thin-walled cylindrical structure with a side wall thickness of t1, a value of t1 of 2 mm, and an inner radius of the cathode 4 of r. 10 , and its radial center radius r2 is between the inner radius r of the outer conductor 6 13 and the outer radius r6 of the inner conductor 5, satisfying r6 <r 10 <r2<r 13 , the axial length of cathode 4 is l 3. l 3. Take 10.0mm~30mm;

[0014] The cathode inner shielding ring 2 is a circular ring structure with a right-angled triangle cross section, and the distance between its right end and the right end of the cathode seat 1 (i.e., the length of a right-angled side) is l 2, l 2 takes a value of 5.0mm~10.0mm. To achieve effective electron beam emission, it is also necessary to meet 0.1mm< l 3- l 2<5mm, the length of another right-angled side of the cathode inner shielding ring 2 located on the right end surface of the cathode seat 1 is t2, and the value of t2 is 3.0mm~20.0mm.

[0015] The cathode outer shielding ring 3 is a composite structure consisting of a circular ring with a right-angled triangle cross section and a circular ring with a quarter circle cross section. The right end of the circular ring with a right-angled triangle cross section is 1 / 80 mm away from the right end of the cathode seat 1 (i.e., the length of a right-angled side). l 4. The radius of the ring with a quarter-circle cross section is R, R=4.0 mm. In order to achieve effective electron beam emission, it is also necessary to meet 0.1mm< l 3- l 4<5mm.

[0016] The inner conductor 5 is coaxially nested in the outer conductor 6, and the distance between the left end and the right end of the cathode 4 is l6, the right end is connected to the radiation system. The inner conductor 5 consists of two sections of cylindrical structures: the radial radius of the first section of the cylinder is r6, and 6 inner rectangular grooves are engraved on its outer side wall from left to right, namely the first inner rectangular groove 5-1, the second inner rectangular groove 5-2, the third inner rectangular groove 5-3, the fourth inner rectangular groove 5-4, the fifth inner rectangular groove 5-5 and the sixth inner rectangular groove 5-6. The distance from the left end of the inner conductor 5 to the left side of the first inner rectangular groove 5-1 is l 7, and the width is l 8, l 7, l 8 are all in the range of 5mm to 35mm. The radial radius at the bottom of the first inner rectangular groove 5-1 is r5, and r5 < r6; the distance to the right side of the first inner rectangular groove 5-1 is l 9, and there are 3 inner rectangular grooves with exactly the same dimensions: the second inner rectangular groove 5-2, the third inner rectangular groove 5-3, and the fourth inner rectangular groove 5-4. The width of each inner rectangular groove is l 10 , and the spacing between two inner rectangular grooves is l 11 , and on the premise of satisfying l 10 > l 11 , l 10 , l 11 are all in the range of 5mm to 35mm. The radial radius at the bottom of each inner rectangular groove is r7, and r7 < r6. The distance to the right side of the fourth inner rectangular groove 5-4 is l 12 , and there are 2 inner rectangular grooves with exactly the same dimensions: the fifth inner rectangular groove 5-5 and the sixth inner rectangular groove 5-6. The width of each inner rectangular groove is l 13 , l 13 is in the range of 5mm to 35mm; the spacing between two inner rectangular grooves is l 14 , l 14 is in the range of 1mm to 20mm. The radius at the bottom of each inner rectangular groove is r8, and r8 < r6; the radial radius of the second section of the cylinder is r 17 , and r6 < r 17 , and the axial length is l 18 , l 18The value ranges from 40 mm to 100 mm. On the left side of the second cylindrical body, a circular ring-shaped cavity with a right trapezoidal cross-section is dug out. This cavity forms an electron beam collector for collecting electron beams. The inner radius r9 of the circular ring-shaped cavity satisfies r6 < r9, and the outer radius is r 16 , satisfying r9 < r 16 <r 17 . The upper base length of the trapezoid is l 15 , l 15 The value ranges from 5 mm to 35 mm, and the lower base length is l 16 , satisfying l 16 l 15 , l 16 The value ranges from 5 mm to 35 mm.

[0017] The outer conductor 6 is composed of a smooth inner wall cylindrical tube with a relatively large inner radius and a cylindrical tube with a relatively small inner radius. The outer radii of the two cylindrical tubes are both r 11 , r 11 is equal to the outer radius of the outer conductor of the pulse power source. The radial inner radius of the smooth inner wall cylindrical tube with a relatively large inner radius is r4, and the axial length is l 5, satisfying l 5 = l 1 + l 3 + l 6; The inner radius of the cylindrical tube with a relatively large inner radius is r 13 , satisfying r 11 > r4 > r 13 . On the inner side wall of the cylindrical tube with a relatively small inner radius, 5 outer rectangular grooves are engraved in sequence from left to right, namely the first outer rectangular groove 6-1, the second outer rectangular groove 6-2, the third outer rectangular groove 6-3, the fourth outer rectangular groove 6-4, and the fifth outer rectangular groove 6-5; The positions and axial dimensions of the 5 outer rectangular grooves correspond one by one to the first 5 inner rectangular grooves on the inner conductor 5; Among them, the radial radius at the bottom of the first outer rectangular groove 6-1 is r 12 , r 12 satisfying r4 > r 12 > r 13 ; The radial radii at the bottoms of the second outer rectangular groove 6-2, the third outer rectangular groove 6-3, and the fourth outer rectangular groove 6-4 are all r 14 , satisfying r4 > r 14 > r 13 ; The radial radius at the bottom of the fifth outer rectangular groove 6-5 is r 15 , r4 > r 15 > r 13. On the right side of the cylinder with smaller inner radius and the fifth outer rectangular groove 6-5 spacing l 14 At the point where the inner radius is r 18 The inner wall is smooth and cylindrical. l 14 The value is between 1mm and 20mm, r 18 Satisfy 18 =r 15 , the axial length of the cylinder with smooth inner wall is l 17 ,satisfy l 17 = l 18 + l 13 The annular cavity formed between the cylinder with smooth inner wall and the second cylindrical section of the inner conductor is the microwave output port.

[0018] The external guided magnetic field structure 7 can be formed by a solenoid coil wound by enameled wire, and the size of the generated magnetic field can be controlled by controlling the current in the enameled wire.

[0019] The cathode 4 may be made of graphite, dielectric copper, stainless steel, etc. The inner conductor 5, outer conductor 6 and cathode seat 1 are all made of stainless steel. The cathode inner shielding ring 2 and cathode outer shielding ring 3 are made of materials with a higher emission threshold, such as titanium.

[0020] The present invention is based on the following principle: by adding an inner shielding ring 2 and an outer shielding ring 3 on both sides of the annular emission cathode 4 of the C-band TTO, a new focusing cathode is formed. The focusing cathode can improve the electric field distribution in the diode area, increase the axial electric field in the electron beam emission area and reduce the radial electric field, so that the electron beam emitted by the cathode has a smaller beam envelope, thereby reducing the device's demand for the guiding magnetic field, and finally achieving high output power and power efficiency under a low guiding magnetic field (0.4 T), and has the potential to use permanent magnet packaging.

[0021] Based on the advantages and disadvantages of the focusing cathode in the prior art, the present invention optimizes and designs a new focusing cathode structure, and the specific differences are as follows:

[0022] 1. Lightweight and miniaturized structure: The cross-sectional views of the inner and outer shielding rings of the original focusing cathode are both large rectangular structures, covering the entire cathode seat 1 and cathode 4; while the cross-sectional view of the inner shielding ring of the newly designed focusing cathode is a right-angled triangle structure, and the cross-sectional view of the outer shielding ring is a structure in which a right-angled triangle is smoothly connected to a quarter circle. This new focusing cathode is small in size and only covers a portion of the area around the cathode 4, which can reduce the weight increase caused by the introduction of the focusing cathode.

[0023] 2. Reduce negative impact: Since the original focusing cathode covers the entire cathode holder 1, it is equivalent to increasing the axial and longitudinal dimensions of the cathode holder 1, which is equivalent to reducing the longitudinal distance between the cathode holder 1 and the outer conductor 6, and reducing the axial distance between the cathode holder 1 and the inner conductor 5. In actual simulation, the change of these two distances will greatly change the device impedance and affect its working state. The newly designed focusing cathode only covers part of the area near the cathode 4, and will not face the problem of excessive device impedance change, and has better practical application effect.

[0024] Compared with the prior art, the present invention can achieve the following technical effects:

[0025] (1) In the high-power microwave particle simulation, the present invention can normally output high-power microwaves with a frequency of 4.24 GHz in the magnetic field range of 0.2 T~1.0 T under the voltage condition of 850 kV. In the range of 0.3-0.4 T, the output microwave power is greater than 5.0 GW, which is in line with the trend of high-power microwaves expanding to higher power and lower magnetic field.

[0026] (2) The focusing cathode introduced in the present invention reduces the dependence of the stable transmission of the electron beam on the magnetic field. The device can still work normally in a magnetic field of 0.2 T, which has the advantage of working in a low magnetic field and is beneficial to permanent magnet packaging. When working between 0.2 T and 1.0 T, the power efficiency is further increased from 18% to 39%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A three-dimensional schematic diagram of the C-band high-power transit time oscillation of a low-magnetic field strong beam introduced into a focusing cathode in the present invention;

[0028] Figure 2 It is a schematic structural diagram of the low magnetic field strong beam C-band high power transit time oscillation introduced into the focusing cathode of the present invention;

[0029] Figure 3 is an injected electrical power diagram of an embodiment of the present invention;

[0030] Figure 4 is a diagram of average microwave power output under different magnetic field conditions according to an embodiment of the present invention;

[0031] Figure 5 is a diagram of microwave power efficiency output under different magnetic field conditions according to an embodiment of the present invention;

[0032] Figure 6 is an electron beam transmission diagram under a 0.4 T magnetic field condition of an embodiment of the present invention;

[0033] Figure 7 This is a diagram of the average microwave power output under a 0.4 T magnetic field condition according to an embodiment of the present invention;

[0034] Figure 8 This is a microwave spectrum diagram output under a 0.4 T magnetic field condition of an embodiment of the present invention;

[0035] Fig. 9 This is an electric field distribution diagram of the diode region under a 0.4 T magnetic field condition before and after the introduction of the focusing cathode in one embodiment of the present invention;

[0036] Fig.10 This is an electron beam distribution diagram of electron beam transmission under 0.4 T magnetic field conditions before and after the introduction of the focusing cathode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] Figure 1 The three-dimensional schematic diagram of the C-band high-power transit time oscillation of the low magnetic field strong beam introduced into the focusing cathode of the present invention; Figure 1 As shown, the present invention comprises a cathode seat 1, a cathode inner shielding ring 2, a cathode outer shielding ring 3, a cathode 4, an inner conductor 5, and an outer conductor 6, and the entire structure is rotationally symmetrical about the central axis OO'. One end of the coaxial transit time 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 coaxial transit time oscillator, and the end connected to the radiation system is defined as the right end of the coaxial transit time oscillator.

[0038] The parameter determination process of Example 1 is as follows: the above radial radius parameters are determined according to the empirical formula , where f represents the design target frequency in GHz, is the difference between the inner and outer radii of the rectangular grooves at the above positions, in cm; from this formula, it can be calculated according to the design target frequency f The value of the inner and outer radius of the groove is obtained by combining the radial size of the pulse power source to be connected at the left end. According to design experience, in order to make better use of the electron beam, the radius r2 at the radial center of the cathode 4 (i.e., the center radius of the electron beam) is usually made to satisfy r2=(r6+r 13 ) / 2, to ensure that the center line of the side wall of the cathode 4 is in the same straight line with the central axis O1O1' of the reflection cavity, cluster cavity and extraction cavity of the microwave high-frequency structure. From this, the inner and outer radii of the groove can be obtained. The thickness t1 of the cathode 4 of the microwave high-frequency structure is usually 2mm.

[0039] The axial length of the rectangular groove (i.e., the groove width) usually satisfies the following relationship with the wavelength λ of the microwave field in free space: l <λ / 2, where λ satisfies the relationship with the design target frequency , (c is the speed of light in vacuum, f is the design target frequency) from which the axial length of each groove can be determined. The interval between the grooves ranges from 5mm to 35mm. For the collecting cavity (the second section radius of the inner conductor 5 is r17 On the left side of the cylinder, a circular cavity with a trapezoidal cross section is dug out. This cavity forms an electron beam collector for collecting electron beams). l 15 , l 16 satisfy l 16 ≥ l 15 Under the premise of, the two are usually taken in the range of 5mm~35mm; for the microwave output port, l 17 , l 18 satisfy l 17 - l 18 = l 13 Under the premise of , the values ​​of the two are relatively flexible. Since this part is connected to the microwave radiation system, it has little effect on the performance parameters of the device and can be flexibly selected according to the position space reserved in the actual application environment. Then, electromagnetic simulation was performed using CHIPIC software to obtain the output C-band microwave under the conditions of voltage 850 kV and magnetic field strength 0.2T~1.0T. The structural parameters of Example 1 are as follows:

[0040] l 1=20mm, l 2=8.8mm, l 3=10mm, l 4=8.8mm, l 5=66mm, l 6=36mm, l 7=27mm, l 8=25.5mm, l 9=23mm, l 10 =21mm, l 11 =10.8mm, l 12 =30mm, l 13 =17.2mm, l 14 =6mm, l 15 =27mm, l 16 =47mm, l 17 =93.6mm, l 18 =76.4mm;

[0041] r1=75mm,r2=70mm,r3=69mm,r4=112mm,r5=51.5mm,r6=58mm,r7=49.8mm,r8=47.6mm,r9=61mm,r 10 =69mm,r 11 =120mm,r 12 =92.3mm,r 13 =82mm,r 14 =90.8mm,r 15 =93.7mm,r 16 =80.1mm,r 17 =86.5mm,r 18 =93.7mm;

[0042] t1=2mm, t2=9mm, t3=8mm, R=4mm.

[0043] Figure 3 The injected average electric power diagram of Example 1 obtained by simulation under the condition of 850 kV is shown in the figure, where the vertical axis is power in GW and the horizontal axis is time in ns. Figure 3 It can be seen that Example 1 obtained an injected average electromotive force of about 15 GW.

[0044] Figure 4 850 kV, magnetic field in the range of 0.2 T to 1.0 T, the average power diagram of the C-band microwave output of Example 1 obtained by simulation, the ordinate is power, the unit is GW, the abscissa is magnetic field intensity, the unit is T. Figure 4 It can be seen that under the conditions of 0.2 T ~ 1.0 T, Example 1 can work normally and output microwaves.

[0045] Figure 5 850 kV, magnetic field in the range of 0.2 T to 1.0 T, the power efficiency of the C-band microwave output of Example 1 is simulated, the ordinate is efficiency, the abscissa is magnetic field intensity, the unit is T. Figure 5 It can be seen that under the conditions of 0.2 T ~ 1.0 T, Example 1 can work normally and output microwaves. As the magnetic field intensity increases, the power efficiency is further improved.

[0046] Figure 6 This is the electron beam transmission diagram of Example 1 obtained by simulation under the conditions of 850 kV and 0.4 T. Figure 6 It can be seen that in Example 1, under the condition of a magnetic field strength of 0.4 T, the electron beam can be effectively emitted and stably transmitted.

[0047] Figure 7This is the average power diagram of the C-band microwave output of Example 1 obtained by simulation under the conditions of 850 kV and 0.4 T. The ordinate is power in GW and the abscissa is time in ns. Figure 7 It can be seen that, under the condition of a magnetic field strength of 0.4 T, the average microwave output power of Example 1 is 5.9 GW.

[0048] Figure 8 This is the spectrum diagram of the C-band microwave output of Example 1 obtained by simulation under the conditions of 850 kV and 0.4 T. Figure 8 It can be seen that the frequency of microwave output in Example 1 is 4.24 GHz.

[0049] Fig. 9 This is the electric field distribution diagram of the diode area before and after the introduction of the focusing cathode obtained by simulation under the conditions of 850 kV and 0.4 T. It can be seen from the dotted circle on the left that when there is no focusing cathode, the electric field at this position is mainly composed of radial components, and the axial component is smaller. It can be seen from the dotted circle on the right that after the introduction of the focusing cathode, the direction of the electric field at this position has changed, the radial component has decreased, and the axial component has increased, indicating that the introduction of the focusing cathode can increase the axial component of the electric field at the electron beam emission position, which is beneficial to improving the electron beam quality.

[0050] Fig.10 This is the electron beam distribution diagram of the electron beam transmission before and after the introduction of the focusing cathode obtained by simulation under the conditions of 850 kV and 0.4 T. It can be seen from the figure that the introduction of the focusing cathode can improve the electron beam quality and reduce the envelope thickness of the electron beam.

Claims

1. Introducing a low magnetic field, strong beam, C-band high power TTO with a focused cathode, characterized by: It comprises a cathode seat (1), a cathode inner shielding ring (2), a cathode outer shielding ring (3), a cathode (4), an inner conductor (5), an outer conductor (6), and an external guide magnetic field structure (7), wherein the entire structure is rotationally symmetrical about a central axis OO'; one end of the TTO is connected to a pulse power source, and the other end is connected to a radiation system; The cathode seat (1) is a cylindrical structure with an axial length of l 1, l 1 Take 15mm-30mm, the radial radius is equal to the radial inner radius r of the cathode (4) 10 The left end of the cathode seat (1) is connected to the inner conductor of the pulse power source, and the cathode (4) is connected to the right end of the cathode seat (1) to form a concentric circle with the cathode inner shielding ring (2) and the cathode outer shielding ring (3); The cathode (4) is used to generate and emit electron beams and is a thin-walled cylindrical structure with a side wall thickness of t1 and an inner radius of r. 10 , and its radial center radius r2 is between the inner radius r of the outer conductor (6) 13 and the outer radius r6 of the inner conductor (5), satisfying r6 <r 10 <r2<r 13 , the axial length of the cathode (4) is l 3. l 3. Take 10.0mm~30mm; The cathode inner shielding ring (2) is a circular ring structure with a right triangle cross section, and the distance between its right end and the right end of the cathode seat (1) is l 2, l 2 The value is 5.0mm~10.0mm, satisfying 0.1mm< l 3- l 2<5mm, the length of another right-angled side of the cathode inner shielding ring (2) located on the right end surface of the cathode seat (1) is t2, and the value of t2 is 3.0mm~20.0mm; The cathode outer shielding ring (3) is a composite structure consisting of a circular ring with a right-angled triangle cross section and a circular ring with a quarter circle cross section. The right end of the circular ring with a right-angled triangle cross section is 1 / 4 of the distance from the right end of the cathode seat (1). l 4. The radius of the ring with a quarter-circle cross section is R, R=4.0 mm; 0.1mm< l 3- l 4<5mm; The inner conductor (5) is coaxially nested inside the outer conductor (6), and the distance between the left end and the right end of the cathode (4) is l 6, and the right end is connected to the radiation system; the inner conductor (5) is composed of two cylindrical structures: the radial radius of the first cylindrical section is r6, and 6 inner rectangular grooves are successively engraved on its outer side wall from left to right, namely the first inner rectangular groove (5-1), the second inner rectangular groove (5-2), the third inner rectangular groove (5-3), the fourth inner rectangular groove (5-4), the fifth inner rectangular groove (5-5) and the sixth inner rectangular groove (5-6). The distance from the left side of the first inner rectangular groove (5-1) to the left end of the inner conductor (5) is l 7, and the width is l 8, l 7, l 8 are all within the range of 5mm to 35mm. The radial radius at the bottom of the first inner rectangular groove (5-1) is r5, and r5 < r6; the distance from the right side of the first inner rectangular groove (5-1) l 9 is 3 inner rectangular grooves with exactly the same dimensions: the second inner rectangular groove (5-2), the third inner rectangular groove (5-3), the fourth inner rectangular groove (5-4). The width of each inner rectangular groove is l 10 , and the distance between two inner rectangular grooves is l 11 . On the premise of satisfying l 10 > l 11 , l 10 , l 11 are all within the range of 5mm to 35mm. The radial radius at the bottom of each inner rectangular groove is r7, and r7 < r6; the distance from the right side of the fourth inner rectangular groove (5-4) l 12 is 2 inner rectangular grooves with exactly the same dimensions: the fifth inner rectangular groove (5-5), the sixth inner rectangular groove (5-6). The width of each inner rectangular groove is l 13 , l 13 is within the range of 5mm to 35mm; the distance between two inner rectangular grooves is l 14 , l 14 is within the range of 1mm to 20mm; the radius at the bottom of each inner rectangular groove is r8, and r8 < r6; the radial radius of the second cylindrical section is r 17 , and r6 < r 17 , and the axial length is l 18 , l 18 The value ranges from 40 mm to 100 mm. On the left side of the second cylindrical body, a circular ring-shaped cavity with a right trapezoidal cross-section is dug out. The cavity forms an electron beam collector for collecting electron beams. The inner radius r9 of the circular ring-shaped cavity satisfies r6 < r9, and the outer radius is r 16 and satisfies r9 < r 16 < r 17 The upper base length of the trapezoid is l 15 l 15 The value ranges from 5 mm to 35 mm, and the lower base length is l 16 and satisfies l 16 l 15 l 16 The value ranges from 5 mm to 35 mm;​​ The outer conductor (6) is composed of a section of a smooth inner cylinder with a larger inner radius and a section of a cylinder with a smaller inner radius. The outer radii of the two sections of the cylinder are both r 11 , r 11 The outer radius of the outer conductor of the pulse power source is equal to the outer radius; the inner radius of the smooth inner wall cylinder with a larger inner radius is r4, and the axial length is l 5. Satisfaction l 5= l 1+ l 3+ l 6; The inner radius of the cylinder with the larger inner radius is r 13 , satisfying r 11 > r4>r 13 ; Five outer rectangular grooves are engraved from left to right on the inner side wall of the cylinder with a smaller inner radius, namely a first outer rectangular groove (6-1), a second outer rectangular groove (6-2), a third outer rectangular groove (6-3), a fourth outer rectangular groove (6-4), and a fifth outer rectangular groove (6-5); the positions and axial dimensions of the five outer rectangular grooves correspond one by one to the first five inner rectangular grooves on the inner conductor (5); wherein the radial radius at the bottom of the first outer rectangular groove (6-1) is r 12 , r 12 Satisfy r4>r 12 >r 13 The radial radius at the bottom of the second outer rectangular groove (6-2), the third outer rectangular groove (6-3), and the fourth outer rectangular groove (6-4) is r 14 , satisfying r4>r 14 >r 13 The radial radius of the fifth outer rectangular groove (6-5) at the bottom of the groove is r 15 , r4>r 15 >r 13 ; The distance between the right side of the cylinder with smaller inner radius and the fifth outer rectangular groove (6-5) l 14 At the point where the inner radius is r 18 The inner wall is smooth and cylindrical. l 14 The value is between 1mm and 20mm, r 18 Satisfy 18 =r 15 , the axial length of the cylinder with smooth inner wall is l 17 ,satisfy l 17 = l 18 + l 13 The annular cavity formed between the smooth inner wall cylinder and the second cylindrical section of the inner conductor is the microwave output port; The external guided magnetic field structure (7) is formed by a solenoid coil wound by enameled wire, and the size of the generated magnetic field is controlled by controlling the size of the current in the enameled wire.

2. The C-band high-power TTO with a low magnetic field and strong beam current introduced into a focusing cathode according to claim 1, characterized in that: The cathode (4) side wall thickness t1 is 2 mm.

3. The C-band high-power TTO with low magnetic field and strong beam current introduced into the focusing cathode according to claim 1, characterized in that: The cathode (4) is made of graphite, dielectric copper and stainless steel, the inner conductor (5), the outer conductor (6) and the cathode seat (1) are all made of stainless steel, and the cathode inner shielding ring (2) and the cathode outer shielding ring (3) are made of materials with a relatively high emission threshold.

4. The C-band high-power TTO with low magnetic field and strong beam current introduced into the focusing cathode according to claim 3, characterized in that: The material of the cathode inner shielding ring (2) and the cathode outer shielding ring (3) is titanium.

5. The C-band high-power TTO with a low magnetic field and a strong beam current introduced into a focusing cathode according to any one of claims 1 to 4, characterized in that: Under the conditions of voltage 850 kV and magnetic field strength 0.2 T~1.0 T, the structural parameters of the C-band microwave high-power TTO are simulated as follows: l 1=20mm, l 2=8.8mm, l 3=10mm, l 4=8.8mm, l 5=66mm, l 6=36mm, l 7=27mm, l 8=25.5mm, l 9=23mm, l 10 =21mm, l 11 =10.8mm, l 12 =30mm, l 13 =17.2mm, l 14 =6mm, l 15 =27mm, l 16 =47mm, l 17 =93.6mm, l 18 =76.4mm; r1=75mm,r2=70mm,r3=69mm,r4=112mm,r5=51.5mm,r6=58mm,r7=49.8mm,r8=47.6mm,r9=61mm,r 10 =69mm,r 11 =120mm,r 12 =92.3mm,r 13 =82mm,r 14 =90.8mm,r 15 =93.7mm,r 16 =80.1mm,r 17 =86.5mm,r 18 =93.7mm; t1=2mm, t2=9mm, t3=8mm, R=4mm.

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