Elliptical chamfered diameter-variable cathode lead structure and method for suppressing backflow diode and backflow of diode

Abstract

The present application relates to a kind of elliptical chamfer variable-diameter cathode lead structure inhibiting backflow diode and inhibiting diode backflow method, belong to vacuum electron technology field, can effectively reduce the surface field intensity of cathode lead, inhibit field electron emission and delay the ion movement of zero field region to cathode lead.It includes cathode, cathode lead, anode in inhibiting backflow diode.The cathode lead is variable-diameter structure, non-variable-diameter part D is located at both ends, variable-diameter part E is located in the middle, variable-diameter part E is the same throughout radius, chamfer part F adopts elliptical chamfer structure.Non-variable-diameter part D radius is the same with cathode radius, and variable-diameter part E radius is less than cathode radius.The inhibiting diode backflow method includes: reducing the position radius of cathode lead, realizes the optimal cathode lead surface electric field;Both sides of the position radius reduction are smoothly transitioned back to original size, so that the surface electrostatic field of cathode lead position possibly bombarded by anode ion is further reduced.

Description

Technical Field

[0001] This invention belongs to the field of vacuum electronics technology, specifically relating to an elliptical chamfered variable diameter cathode lead structure for suppressing backflow diodes. Background Technology

[0002] Electron reflux in diodes has become a significant factor limiting the application of high-power microwave devices with permanent magnet packaging. Diodes typically exhibit negatively charged particles such as electrons emitted from the reverse-moving cathode side and electrons emitted due to the cathode leads. Simultaneously, during device operation, most of the current emitted from the cathode moves towards the device, while a small portion moves in the reverse direction, including a small number of electrons generated during device operation; these are collectively referred to as reflux electrons. A typical foilless diode structure and its connection to a pulsed power device are shown below. Figure 1 As shown in the diagram, the recirculating electron beam typically travels along three paths, A, B, and C. The recirculating electrons bombard the anode along path A or B, causing plasma to be generated at the anode.

[0003] Because magnetic field lines in permanent magnets always converge rapidly at the N and S poles of the magnet, a zero-field region exists in the magnetic diode where the axial magnetic field is zero. This makes it easy for returning electrons to be accelerated by the anode and bombarded along the magnetic field lines to the surface of the zero-field region, approximating the A-path. The returning electrons damage the zero-field region, and with the generation of plasma or charged dust, ions bombard the cathode lead along the electric field lines, causing the cathode lead to further emit electrons. This phenomenon leads to a significant reduction in diode output efficiency and unstable diode impedance, which is detrimental to the long-term stable operation of the system. Studying and solving the magnetic insulation problem in the zero-field region under the magnetic field configuration of permanent magnets is an important means to improve the long-term stable operation of the system.

[0004] Reducing the radial electric field strength on the cathode and cathode lead surface is the core of suppressing electron backflow. The most conventional method is to increase the radius of the outer region of the cathode lead and design a larger absorption structure on the cathode lead. This structure intersects with the magnetic field lines, or soft iron is used to change the magnetic field lines to suppress electron backflow, which greatly reduces the possibility of backflowing electrons bombarding the anode. However, due to many factors such as volume and weight, this cannot be easily implemented in many application environments, especially when using permanent magnets. The weight of permanent magnets increases rapidly with the increase of radius, and more methods are urgently needed to suppress backflowing electrons. Summary of the Invention

[0005] In order to reduce the surface electric field strength of the cathode lead to suppress field-induced electron emission and delay the movement of ions generated in the zero field region to the cathode lead, this invention proposes an elliptical chamfered variable diameter cathode lead structure to suppress backflow diodes and a method for suppressing diode backflow.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] An elliptical chamfered variable diameter cathode lead structure suppresses backflow diode, comprising a cathode, a cathode lead, and an anode.

[0008] The cathode lead rod and the cathode are located inside the inner cylinder of the anode. The cathode is located at one end of the cathode lead rod and is connected to the cathode lead rod. The cathode is an annular cathode.

[0009] The cathode lead rod has a variable diameter structure, including a constant diameter section D, a variable diameter section E, and a chamfered section F. The constant diameter section D is located at both ends, the variable diameter section E is located in the middle, the variable diameter section E has the same radius throughout, and the chamfered section F is located between the constant diameter section D and the variable diameter section E. The chamfered section F adopts an elliptical chamfer structure. The radius of the constant diameter section D is the same as the cathode radius, and the radius of the variable diameter section E is smaller than the cathode radius.

[0010] The aforementioned elliptical chamfered variable diameter cathode lead structure suppresses backflow diodes, wherein the radius E of the variable diameter portion is 1 / 2.7 of the radius of the anode inner cylinder.

[0011] The aforementioned elliptical chamfered variable diameter cathode lead structure suppresses backflow diodes, wherein the axial length of the variable diameter portion E is less than 100mm, and the ratio of the major axis to the minor axis of the elliptical chamfered portion F is greater than 3:1.

[0012] The aforementioned elliptical chamfered variable diameter cathode lead structure suppresses backflow diodes. The connection between the chamfered portion F and the variable diameter portion E can be either a smooth transition or a direct right-angle connection.

[0013] The aforementioned elliptical chamfered variable diameter cathode lead structure suppresses backflow diodes, where both the anode and cathode are made of conductive materials.

[0014] The aforementioned elliptical chamfered variable diameter cathode lead structure suppresses backflow diodes, wherein the anode inner cylinder radius is 60mm, the radius of the non-diameter part D is 31mm, the radius of the variable diameter part E is 22mm, the length of the chamfered part F does not exceed 50mm, and the ratio of the major axis to the minor axis of the chamfered part F is 5:1.

[0015] A method for suppressing diode backflow involves reducing the radius of the cathode lead position that may be bombarded by anodic ions, thereby optimizing the surface electric field of the cathode lead in the electric field of the inner conductor on the coaxial line. By utilizing the principle of electrostatic shielding, the radius reduction position is smoothly transitioned back to its original size on both sides, further reducing the surface electrostatic field of the cathode lead position that may be bombarded by anodic ions.

[0016] The aforementioned method for suppressing diode backflow uses an elliptical chamfer structure at the smooth transition point on both sides of the radius reduction position, which significantly reduces the electrostatic field strength at the chamfer and suppresses field emission.

[0017] The beneficial effects of this invention are:

[0018] An elliptical chamfered variable diameter cathode lead structure suppresses backflow diodes, which can effectively reduce the surface field strength of the cathode lead at the position bombarded by anode ions, thereby suppressing field-induced electron emission and delaying the movement of ions generated by the anode bombardment to the cathode lead. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an existing foil-free diode and its connection structure with a pulse power device;

[0020] Figure 2 This is a schematic diagram of an elliptical chamfered variable diameter cathode lead structure for suppressing backflow diodes according to an embodiment of the present invention;

[0021] Figure 3 To simulate the field-induced electron emission when using an elliptical chamfered variable-diameter cathode lead structure to suppress the return diode, the field-induced emission threshold is compared with... Figure 4 same;

[0022] Figure 4 The simulation shows the field-induced electron emission of a diode using a conventional cathode lead.

[0023] Figure 5 To suppress the time it takes for ions to reach the surface of the cathode lead when using an elliptical chamfered variable diameter cathode lead structure in the simulation to suppress the ion movement to the cathode lead surface during the reflux diode;

[0024] Figure 6 The time it takes for ions to travel to the surface of the cathode lead when using a diode with a conventional cathode lead in the simulation;

[0025] Figure 7 Schematic diagram of a diode with chamfered cathode leads of different structures;

[0026] Figure 8 The image shows a comparison of the electrostatic field at the chamfered corner of cathode leads with different structures in the simulation, all with the same input voltage.

[0027] Figure labels: 1. Transformer oil, 2. Insulator, 3. Anode, 4. Shielding ring, 5. Cathode lead, 6. Cathode, 7. Transmission waveguide, 8. Magnetic field coil, 9. Electrons actually emitted by the annular cathode and cathode plasma. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] An elliptical chamfered variable-diameter cathode lead structure suppresses backflow in a diode, comprising a cathode, an elliptical chamfered variable-diameter cathode lead, and an anode. The variable-diameter structure means that in a conventional design, the cathode lead and cathode have the same radius, while in this variable-diameter structure, the radius of the cathode lead is locally reduced, with the radius at the reduced point being smaller than the cathode size. The cathode lead of this variable-diameter structure is simply referred to as a variable-diameter cathode lead.

[0031] The elliptical chamfered variable diameter cathode lead is positioned after the cathode to reduce the surface field strength of the cathode lead at the location bombarded by anode ions, thereby suppressing field-induced electron emission and delaying the movement of ions generated by the anode bombardment to the cathode lead.

[0032] The elliptical chamfered reducing cathode lead consists of a constant diameter section D, a reducing diameter section E, and a chamfered section F. The constant diameter section D has the same radius as the cathode, while the reducing diameter section E has a radius 1 / 2.7 of the anode radius. The chamfered section F connects the constant diameter section D and the reducing diameter section E, and F employs an elliptical chamfer structure. The reducing diameter section F is located on the cathode lead that is most susceptible to bombardment by anolyte ions. The axial distance of the reducing diameter section E is less than 100 mm, and the aspect ratio of the elliptical chamfer is greater than 3:1.

[0033] The radius D of the invariant diameter section is the same as that of the cathode, and the cathode size is determined according to the structural design of the high-power microwave device.

[0034] The diameter-changing section E has the same radius throughout.

[0035] The connection between the chamfered part F and the variable diameter part E can be either a smooth transition or a direct right-angle connection.

[0036] Example 2

[0037] The concept of an elliptical chamfered variable-diameter cathode lead structure for suppressing backflow diodes is as follows: The radius of the cathode lead position, which may be bombarded by anode ions, is reduced to 1 / 2.7th of the radius of the anode inner cylinder, achieving optimal electric field on the surface of the inner conductor (cathode lead) within the coaxial inner conductor surface electric field. Subsequently, utilizing the principle of electrostatic shielding, both sides of the radius reduction position smoothly transition back to their original dimensions (generally the same as the cathode), further reducing the electrostatic field on the surface of the cathode lead position that may be bombarded by anode ions. Finally, an elliptical chamfered structure (at the smooth transition point, i.e., the chamfer) is used to significantly reduce the electrostatic field strength at the chamfer, suppressing field emission. Through the above methods, the elliptical chamfered variable-diameter cathode lead structure diode of this invention can effectively reduce the surface electric field strength of the cathode lead at the location bombarded by anode ions, thereby suppressing field emission and simultaneously delaying the movement of ions generated by the anode bombardment to the cathode lead.

[0038] An elliptical chamfered variable diameter cathode lead structure for suppressing backflow diodes, such as... Figure 2As shown, the device includes a cathode, an elliptical chamfered variable-diameter cathode lead, and an anode. Both the anode and cathode are made of conductive materials. The elliptical chamfered variable-diameter cathode lead is located after the cathode and includes a constant-diameter section D, a variable-diameter section E, and a chamfered section F. The constant-diameter section D has the same radius as the cathode, and the radius of the variable-diameter section E is 1 / 2.7 of the anode radius. The chamfered section F is located between the constant-diameter section D and the variable-diameter section E, and the chamfered section F has an elliptical chamfer structure. The variable-diameter section F is a position on the cathode lead that is easily bombarded by anode ions. The axial distance of the variable-diameter section E is less than 100 mm, and the aspect ratio of the elliptical chamfer is greater than 3:1.

[0039] The specific principle is as follows:

[0040] Electrons moving along path B bombard the anode structure, generating plasma. Ions in the plasma move along the electric field lines to the surface of the cathode lead, bombarding the cathode lead surface and causing the cathode lead to emit electrons. Therefore, a new structure is needed, with the ultimate goal of reducing the surface electric field strength of the cathode lead at the bombarded location to suppress field-induced electron emission, while simultaneously delaying the movement of ions generated by the anode bombardment to the cathode lead.

[0041] 1. According to the formula for the electric field E on the surface of a conductor inside a coaxial line. r (As shown in the formula at the end of this section) it can be seen that, under the same voltage, to minimize the electrostatic field strength on the surface of the cathode lead, the optimal ratio of the inner diameter of the permanent magnet anode inner cylinder to the radius of the cathode lead is 2.7, and the inner radius of the permanent magnet anode inner cylinder is r. a The outer radius of the cathode lead is r. c V0 represents the voltage between the inner and outer conductors. When the ratio of the inner diameter of the permanent magnet anode inner cylinder to the radius of the cathode lead is 2.7, the electrostatic field strength on the surface of the cathode lead reaches its optimal value under the existing structure. Therefore, considering reducing the local radius of the cathode lead so that the ratio of the magnet sleeve inner diameter to that region is 2.7, thereby reducing the field strength in that region, calculations show that the minimum radius should be r. c / 2.7. Furthermore, if the cathode lead only undergoes a diameter change near the cathode, i.e., the radius remains 22mm from the root of the cathode lead to the cathode tip, it is impossible to achieve the lowest electrostatic field value on the surface of the cathode lead. Considering the shielding effect of the large-radius structure on both sides on the internal structure, a local diameter change is made in the region of the cathode lead directly facing the zero-field region, reducing the radius of the region of the cathode lead directly facing the zero-field region to r. c / 2.7, it can be observed that the maximum electrostatic field in the region directly opposite the zero field region on the cathode lead rod is reduced by about 2.5% compared to the optimal value obtained by the formula.

[0042]

[0043] PIC simulation results are as follows Figure 3 and Figure 4As shown, the emission area on the cathode lead rod is significantly reduced after adopting the variable diameter structure.

[0044] 2. The strongest electrostatic field on the surface of the variable-diameter cathode lead is at the chamfer (the inflection point where the large radius of the variable-diameter cathode lead decreases to a smaller radius). The field strength at the chamfer of a conventional rounded (perfectly round) variable-diameter cathode lead is about 30% higher than at other locations with larger radii. This makes the chamfer a highly likely new point of strong backflow electron emission, resulting in more yellow marks in the experiment. To reduce the electrostatic field strength at this chamfer, an optimization design was carried out for the chamfer structure. Through literature review, elliptical, parabolic, and double-tangent curve chamfer structures were mainly studied. The simulated structure is shown below. Figure 7 As shown. Since the parabolic structure cannot perfectly connect to the cylindrical structure, an interpolated curve is used for a smooth transition in the final part. Additionally, as the axial length of the chamfer increases, the maximum surface electric field decreases. Figure 8 A comparison of electrostatic field strengths for chamfering is presented. Elliptical, parabolic, and double tangent curve chamfering structures can all significantly reduce the maximum electrostatic field strength. The elliptical chamfer has the lowest maximum electrostatic field strength and is simple in structure, easy to process and design. Therefore, the elliptical chamfer is finally adopted to prepare a new type of variable diameter cathode lead rod.

[0045] 3. Increase the distance the ions travel to the cathode lead rod, thus delaying the time it takes for the ions to reach the cathode lead rod.

[0046] Simulation results are as follows Figure 5 , 6 As shown, under the premise that the anode gas layer density and other structural parameters remain unchanged, it can be observed that the time for ions generated by the anode to move to the cathode lead is delayed by 2ns (when there is no structure, the ions move to the cathode lead in 36ns), thereby achieving the effect of suppressing the backflow of emission on the cathode side.

[0047] This invention cannot be simply replaced by increasing the anode radius, as this would exponentially increase the weight of the permanent magnet and make manufacturing and fabrication more difficult, thus reducing its application value. Therefore, this invention lays a solid foundation for the miniaturization and lightweighting of high-power microwave devices packaged with permanent magnets.

[0048] Example 3

[0049] The selected permanent magnet has an anode inner cylinder radius of 60 mm and a cathode lead outer radius of 31 mm. The ratio of the anode inner cylinder inner diameter to the cathode lead radius is 1.94. Under the existing structure, the electrostatic field strength on the cathode lead surface is 10% higher than the optimal value. Therefore, it is considered to reduce the radius of the cathode lead locally, making the ratio of the magnet sleeve inner diameter to this region 2.7, thereby reducing the field strength in this region. Calculations show that the minimum radius should be 22 mm. In the calculation results, the electrostatic field in the variable diameter region decreases from 415 kV / cm to 385 kV / cm (diode voltage 850 kV). Considering that the region on the cathode lead directly facing the zero field area is the core region for suppressing backflow, and utilizing the shielding effect of the large-radius structures on both sides of the internal structure, a local diameter change is made in the region on the cathode lead directly facing the zero field area. Reducing the radius of this region on the cathode lead to 22 mm, it can be observed that the maximum electrostatic field in this region on the cathode lead directly facing the zero field area decreases to 375 kV / cm, a decrease of approximately 10%. However, due to the limited distance between the cathode and the zero-field region, and considering the magnetic field configuration of the permanent magnet, the total axial length of the chamfered variable-diameter cathode lead designed in this embodiment does not exceed 50mm. Therefore, an elliptical chamfer with a major-to-minor axis ratio of 1:5 was ultimately chosen to prepare the novel variable-diameter cathode lead.

Claims

1. A backflow suppression diode with an elliptical chamfered variable diameter cathode lead structure, characterized in that, Includes cathode (6), cathode lead rod (5), and anode (3); The cathode lead rod (5) and cathode (6) are located inside the inner cylinder of the anode (3). The cathode (6) is located at one end of the cathode lead rod (5) and is connected to the cathode lead rod (5). The cathode (6) is an annular cathode. The cathode lead rod (5) is a variable diameter structure, including a constant diameter part D, a variable diameter part E and a chamfered part F; the constant diameter part D is located at both ends, the variable diameter part E is located in the middle, the variable diameter part E has the same radius throughout, and the chamfered part F is between the constant diameter part D and the variable diameter part E, and the chamfered part F adopts an elliptical chamfer structure. The radius of the constant diameter section D is the same as the cathode radius, while the radius of the variable diameter section E is smaller than the cathode radius.

2. The elliptical chamfered variable diameter cathode lead structure for suppressing backflow diode according to claim 1, characterized in that, The radius of the variable diameter section E is 1 / 2.7 of the radius of the inner cylinder of the anode (3).

3. The elliptical chamfered variable diameter cathode lead structure for suppressing backflow diode according to claim 1, characterized in that, The axial length of the variable diameter section E is less than 100mm, and the ratio of the major axis to the minor axis of the elliptical chamfered structure of the chamfered section F is greater than 3:

1.

4. The elliptical chamfered variable diameter cathode lead structure for suppressing backflow diode according to claim 1, characterized in that, The chamfered portion F and the variable diameter portion E are either smoothly transitioned or directly connected at a right angle.

5. The elliptical chamfered variable diameter cathode lead structure for suppressing backflow diode according to claim 1, characterized in that, Both the anode (3) and the cathode (6) are conductive materials.

6. The elliptical chamfered variable diameter cathode lead structure for suppressing backflow diode according to claim 1, characterized in that, The inner cylinder of the anode (3) has a radius of 60 mm, the radius of the constant diameter part D is 31 mm, the radius of the variable diameter part E is 22 mm, the length of the chamfered part F does not exceed 50 mm, and the ratio of the major axis to the minor axis of the chamfered part F is 5:

1.

7. A method for suppressing diode backflow, characterized in that, The radius of the cathode lead, which may be bombarded by anodic ions, is reduced to achieve the optimal electric field on the surface of the cathode lead within the electric field of the conductor on the coaxial line. Utilizing the principle of electrostatic shielding, the radius is smoothly transitioned back to its original size on both sides of the reduced position, further reducing the electrostatic field on the surface of the cathode lead that may be bombarded by anodic ions.

8. The method for suppressing diode backflow according to claim 7, characterized in that, An elliptical chamfer structure is used at the smooth transition on both sides of the radius reduction position to significantly reduce the electrostatic field strength at the chamfer and suppress field emission.

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