CN108899261B - Optimization design method for PPM structure of high-waveband space traveling wave tube - Google Patents

Abstract

The invention belongs to the technical field of microwave vacuum electronic devices, and relates to a PPM structure optimization design method for a high-waveband space traveling wave tube. According to the invention, the offset of the magnetic ring is preset within the range of 0.2mm, the PPM pole shoe structure of the offset of the magnetic ring is simulated by using magnetic field simulation software, the magnetic field symmetry when the magnetic ring is asymmetric can be reduced by reducing the inner diameter of the pole shoe, the magnetic field asymmetry caused by the asymmetric assembly of the magnetic ring is improved, the electron injection circulation rate is greatly improved, the magnetic field asymmetry is obviously reduced after optimization, and the electron injection fluctuation is reduced. Compared with the prior art, the invention provides a pretreatment thought, the PPM structure is optimized during design to reduce the magnetic field asymmetry caused by the magnetic ring asymmetry caused by assembly, the electron injection circulation rate is improved, the design cost of the traveling wave tube is reduced, and the traveling wave tube is favorable for developing to a high wave band.

Description

Optimization design method for PPM structure of high-waveband space traveling wave tube

Technical Field

The invention belongs to the technical field of microwave vacuum electronic devices, and relates to a PPM structure optimization design method for a high-waveband space traveling wave tube.

Background

The space traveling wave tube is an important core device of national defense equipment such as radar, satellite, electronic countermeasure and the like. With the rapid development of national defense industry, the space traveling wave tube is also developing to a high-waveband, but an electronic optical system is a main technical difficulty of the high-waveband traveling wave tube, after the waveband of the space traveling wave tube rises, the size of a spiral line becomes very small, an electronic beam channel is very thin, and an interaction part needs to have a longer length, which puts a very high requirement on a focusing system. The PPM structure of the high wave band has small size and is difficult to process and assemble, the small asymmetry of the magnetic field of the focusing system can cause the electron beam to swing, the electron beam circulation rate is reduced, the power capacity is reduced, and even the electron breaks the spiral line to damage the traveling wave tube. Therefore, the design of high-circulation-rate and low-pulse PPM becomes a key part in the design of the high-waveband space traveling wave tube. At present, designing a PPM structure by a magnetic conduction method and a magnetic flux method is a common method, obtaining a primary design scheme, then simulating the condition of electron focusing by using electromagnetic calculation software, and optimizing the PPM structure according to the condition of electron focusing.

The circular ring-shaped magnetic rings and the pole shoes in the PPM structure are arranged in a staggered mode, the circular ring-shaped magnetic rings are arranged on the pipe shaft in a split mode in the PPM structure assembly process, however, assembly errors are prone to occurring in the assembly process, and the magnetic rings are asymmetric. The asymmetric magnetic ring assembly may cause the magnetic field of the magnetic system to be asymmetric, which causes electrons to be intercepted in the slow wave structure.

Currently, there are two methods for adjusting the asymmetry of the magnetic field caused by subsequent assembly: one is that the tube is fixed, the magnetic ring is rotated to adjust the magnetic system; the other method is to stick permanent magnetic sheets or soft magnetic sheets on the outer surface of the magnetic system to adjust the asymmetry of the magnetic field, but the magnetic sheets are not stuck too much, and the whole focusing system is too large in volume or even defocusing can occur after a while.

Disclosure of Invention

Aiming at the problems or the defects, the problem of magnetic field asymmetry caused by assembly errors generated by dividing a magnetic ring of a PPM structure of a high-waveband traveling wave tube into two halves in the assembly process is solved. The invention provides a PPM structure optimization design method for a high-waveband space traveling wave tube, which reduces the asymmetry of a magnetic field by adjusting a pole shoe structure during design, so that the electron injection flux rate can be improved.

The specific technical scheme is as follows:

step 1, simulating a PPM structure and a PPM structure with a preset magnetic ring offset by using magnetic field simulation software to obtain the magnetic field distribution of the PPM structure and the PPM structure; the offset of the preset magnetic ring is less than or equal to 0.2 mm.

And 2, reducing the inner diameter of the pole shoe, and recording the magnetic field distribution of the magnetic ring offset PPM structure obtained by reducing the inner diameter of the pole shoe each time.

And 3, bringing the magnetic field distribution obtained in the step 1 and the step 2 into an electron gun to observe the constraint condition of the magnetic field on electron beams, adjusting the inner diameter of the pole shoe according to the fluctuation condition of the electron beams and whether the electrons hit a spiral line or not, continuing adjusting the inner diameter of the pole shoe until the electrons do not hit the spiral line if the requirement of the electron beam circulation rate is not met, and finally recording the magnetic field distribution and the inner diameter of the pole shoe at the moment.

And 4, taking the inner diameter of the pole shoe recorded finally in the step 3 as the inner diameter of the pole shoe of the final PPM structure of the high-waveband space traveling-wave tube.

According to the invention, the magnetic field simulation software is utilized to simulate the PPM pole shoe structure of the magnetic ring offset by presetting the magnetic ring offset within the range of 0.2 mm; by reducing the inner diameter of the pole shoe, the magnetic field asymmetry when the magnetic ring is asymmetric can be reduced, the magnetic field asymmetry caused by the asymmetric assembly of the magnetic ring is improved, the electron beam circulation rate is greatly improved, the magnetic field asymmetry is obviously reduced after optimization, and the electron beam fluctuation is reduced. The pole shoe has a magnetic conduction effect, so that the thickening of the pole shoe enables magnetic lines of force emitted by the magnetic ring to converge towards the inside of the electron beam channel under the effect of the pole shoe, the pole shoe of the PPM structure has symmetry, the converged magnetic lines of force have better symmetry, and further the symmetry of a magnetic field is improved.

In summary, the invention provides a preprocessing idea compared with the prior art, a PPM structure is optimized during design to reduce magnetic field asymmetry caused by magnetic ring asymmetry due to assembly, improve electron injection circulation rate, reduce design cost of a traveling wave tube, and facilitate the traveling wave tube to develop to a high wave band.

Drawings

FIG. 1 is a diagram of a PPM structure without magnetic ring shift according to an embodiment;

FIG. 2 is a PPM structure diagram of magnetic ring shift of the embodiment;

FIG. 3 shows a third magnetic ring structure according to the embodiment;

FIG. 4 is a fourth magnetic ring structure of the embodiment;

FIG. 5 is an electron beam envelope under magnetic field constraint of the PPM structure when the magnetic ring is not shifted according to the embodiment;

FIG. 6 is an electron trace diagram under the magnetic field constraint of the PPM structure when the magnetic ring is not shifted according to the embodiment;

FIG. 7 is an electron beam envelope under magnetic field constraint of a PPM structure when a magnetic loop of the embodiment is shifted;

FIG. 8 is an electron trace diagram under magnetic field constraint of a PPM structure when a magnetic ring is shifted according to an embodiment;

FIG. 9 is a diagram of electron beam envelopes under magnetic field constraints for a PPM configuration of magnetic ring excursion with decreasing pole piece inner diameter according to an embodiment;

FIG. 10 is a diagram of electron trajectories under magnetic field constraints of a PPM configuration of magnetic ring excursion when reducing pole piece inside diameter of the embodiment;

FIG. 11 is a diagram illustrating the calculation of magnetic field symmetry according to an embodiment.

Detailed Description

The following takes a 10-period PPM structure with a period of 4mm as an example to further describe the technical scheme of the present invention.

(1) Simulating the PPM structure and the offset PPM structure of the magnetic ring by using a Microwave Tube Sleeving Simulator (MTSS) developed by electronics science to obtain the magnetic field distribution;

in the embodiment, the PPM structure is adopted, as shown in figure 1, the circular ring-shaped magnetic rings and the pole shoes are arranged in a staggered way, and the material of the magnetic rings is SmCo₂₈The pole piece material is pure iron _ 1008. The PPM structure with magnetic ring offset is shown in figure 2, wherein the lower half part of the third magnetic ring is offset with 0.2mm in the negative direction of the y axis, as shown in figure 3, the upper half part of the fourth magnetic ring is offset with 0.1mm in the positive direction of the y axis, and the lower half part is offset with 0.1mm in the negative direction of the y axis, as shown in figure 4. The magnetic field distribution of the un-shifted and shifted PPM structures is calculated and derived in MTSS, and the magnetic field is loaded to the magnetic field calculation of the electron gun to obtain the electron trajectory and the electron beam envelope map, as shown in fig. 5, 6, 7 and 8.

(2) Reducing the inner diameter r1 of the pole shoe, and recording the magnetic field distribution obtained by reducing r1 each time;

and (3) performing scanning calculation on the pole shoe inner diameter r1 of the PPM structure with magnetic ring offset by utilizing MTSS software three-dimensional calculation, reducing the pole shoe inner diameter, and when the pole shoe inner diameter r1 is 0.7mm, restraining the electron beam by the magnetic field distribution of the PPM structure so that the electron beam does not strike on a spiral line, and recording the magnetic field distribution at the moment when an electron beam envelope diagram and an electron track are shown in fig. 9 and fig. 10.

(3) And comparing the magnetic field symmetry and result analysis after the magnetic ring has no offset and the inner diameter of the pole shoe is reduced.

Referring to fig. 11, the magnetic field symmetry is obtained by comparing the magnetic field mode values of A, B, C, D symmetric points on the x-axis and the y-axis in the same radius and taking the maximum relative error between two magnetic field mode values at the four symmetric points. Based on the derived magnetic field distribution, the magnetic field symmetry at each radius of 0.02mm within the radius of 0.1mm of the electron beam passage at the magnetic ring offset center position in the above three cases is compared, and the comparison results are shown in tables 1 and 2.

TABLE 1

Table 1 is a comparison graph of the magnetic field symmetry at the position where z is 4.75mm of the shift magnetic ring with three PPM structures described in the embodiment;

TABLE 2

Table 2 is a comparison graph of the magnetic field symmetry at the position where z is 6.75mm of the shift magnetic ring of the three PPM structures described in the examples.

From the comparison, it can be seen that the magnetic field asymmetry at the offset can be effectively reduced by reducing the radius of the pole shoe when the magnetic ring is offset, wherein the magnetic field asymmetry at the center position of the magnetic ring where the third magnetic ring is offset is reduced by 0.36% at least and can reach 1.58% at most. And the asymmetry of the magnetic field at the central position of the magnetic ring with the offset fourth block is reduced by 0.28 percent at least and reaches 0.82 percent at most. On the other hand, the constraint condition and the electron track of the electron beam emitted by the same electron gun by the magnetic field can be seen, when the PPM structure magnetic ring is not shifted, the magnetic field generated by the PPM structure magnetic ring can constrain the electron beam, the electron beam circulation condition is better, and no electron strikes a spiral line. And after the magnetic ring is deflected, the magnetic field symmetry of the PPM structure deflected by the magnetic ring is influenced, the electron beam can not be constrained by the magnetic field at the moment as seen from the envelope of the electron beam, and the electron beam fluctuation is enlarged as seen from the electron trajectory graph 8, and part of electrons hit a spiral line to cause the fracture of an electron trajectory. However, when PPM of magnetic ring offset of the inner diameter of the pole shoe is reduced, electron beam fluctuation is small, electron beam circulation rate is improved, and electrons do not hit the spiral line.

In summary, the present invention provides an optimized design method of a PPM structure, i.e. adjusting a pole shoe structure, taking a 10-cycle PPM structure of a traveling wave tube as an example. Embodiments reduce pole piece inner diameter r1 from 0.8mm to 0.7 mm. The design of low-pulse PPM in a traveling wave tube with a high wave band has an important influence on the electron beam circulation rate, the small magnetic field asymmetry can cause the electron beam to have great fluctuation, and even the electron breaks a spiral line. The PPM structure optimization design method provided by the scheme can effectively reduce the magnetic field asymmetry when the magnetic ring is deviated in the assembling process, and has certain practical value on the expansion of the traveling wave tube to a high wave band. Meanwhile, as can be seen from the examples, the pole shoe structure can be adjusted according to the actual situation for different PPM structures.

Claims (1)

1. A PPM structure optimization design method for a high-waveband space traveling wave tube comprises the following specific steps:

step 1, simulating a PPM structure and a PPM structure with a preset magnetic ring offset by using magnetic field simulation software to obtain the magnetic field distribution of the PPM structure and the PPM structure with the preset magnetic ring offset less than or equal to 0.2 mm;

step 2, reducing the inner diameter of the pole shoe, and recording the magnetic field distribution of the magnetic ring offset PPM structure obtained by reducing the inner diameter of the pole shoe each time;

step 3, bringing the magnetic field distribution obtained in the step 1 and the step 2 into an electron gun to observe the constraint condition of the magnetic field on electron beams, adjusting the inner diameter of a pole shoe according to the fluctuation condition of the electron beams and whether the electrons hit a spiral line or not, if the requirement of the electron beam circulation rate is not met, continuously adjusting the inner diameter of the pole shoe until the electrons do not hit the spiral line, and finally recording the magnetic field distribution and the inner diameter of the pole shoe at the moment;

and 4, taking the inner diameter of the pole shoe recorded finally in the step 3 as the inner diameter of the pole shoe of the final PPM structure of the high-waveband space traveling-wave tube.

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