A method for suppressing dielectric window breakdown under dual-frequency high-power microwaves

Abstract

This invention discloses a method for suppressing dielectric window breakdown under dual-frequency high-power microwaves, belonging to the field of high-power microwaves. The invention applies a deposition electric field E parallel to the dielectric window and simultaneously perpendicular to its surface on the vacuum side of the dielectric window. dc and high-power microwave electric field E rf The external magnetic field B satisfies the condition that the energy gained by electrons through cyclotron resonance is higher than the second crossover point of the secondary yield curve, thus lowering the upper and lower boundaries of the sensitivity curve. The lower upper boundary leads to the suppression of secondary electron multiplication; where Ω is the cyclotron frequency, and ω1 and ω2 represent the dual-frequency high-power microwave E. rf The angular frequencies of the two microwave components. Under a dual-frequency microwave electric field, when the applied magnetic field is parallel to the dielectric window and perpendicular to both E_dc and E_rf, the present invention can satisfy the upper boundary condition, achieving the effect of suppressing multiplication. Due to the mutual modulation of the applied magnetic field and the microwave electric field, as the field strength of the dual-frequency microwave electric field increases, the upper boundary of the sensitivity curve becomes relatively stable and lower, and multiplication is suppressed.

Description

Technical Field

[0001] This invention belongs to the field of high-power microwaves, specifically relating to a method for suppressing dielectric window breakdown under dual-frequency high-power microwaves. Background Technology

[0002] High-power microwave (HPM) technology has important applications in modern radar, electronic warfare, and directed-energy weapons. As a key component of HPM systems, the dielectric window plays a crucial role in isolating the external environment from the vacuum cavity and transmitting microwave energy. Thanks to the tireless efforts of researchers worldwide, the quality factor of vacuum HPM source devices has increased from 1 GW (GHz) in the 1970s. 2 Upgraded to 104 GW (GHz) in the early 21st century. 2 The output power has reached several GW or even more than 10 GW, and the power flow density is as high as hundreds of MW / cm². 2 However, as the required power specifications for HPM continue to increase, dielectric window vacuum side breakdown is easily induced. Dielectric window breakdown affects the normal operation of HPM devices and is becoming a prominent bottleneck in HPM development. Dielectric window breakdown is the result of multiple physical phenomena, including seed electrons, secondary electron multiplication, particle bombardment, and energy deposition. Suppressing secondary electron multiplication on the dielectric window can effectively suppress dielectric window breakdown.

[0003] Research on dielectric window breakdown can be traced back to the early 1960s, but current research on HPM dielectric window breakdown mainly focuses on single-frequency signals. Domestic researchers, such as Chang Chao, proposed using a sawtooth dielectric window surface and an external magnetic field to suppress dielectric window breakdown, achieving some success. They also found that applying an external resonant magnetic field can effectively suppress secondary electron multiplication, thereby effectively increasing the breakdown threshold of the dielectric window. Compared to single-frequency high-power microwaves, dual-frequency high-power microwaves can more effectively improve the overall efficiency of energy transmission and provide more stable performance, especially in applications such as electronic countermeasures and aerospace communications. The promising application prospects of dual-frequency high-power microwaves make research in this field increasingly important. In dual-frequency signals, the coupling between two different frequency components introduces a more complex mechanism to dielectric window breakdown. Under the nonlinear physical process of dielectric window breakdown, the coupling between the frequency components of dual-frequency HPM can lead to harmonic phenomena such as harmonic overtones, sum frequencies, and difference frequencies, as well as harmonic resonance. These phenomena have a significant impact on the dielectric window breakdown threshold and breakdown mode.

[0004] Current research on dielectric windows in dual-frequency HPM is relatively scarce. Existing single-frequency HPM breakdown suppression schemes cannot be directly applied to dual-frequency HPM breakdown suppression because the parameter selection in suppression schemes commonly used in single-frequency research, such as surface grooving and external magnetic fields, is usually based on the microwave frequency. For example, the choice of the magnitude of the external magnetic field usually depends on the relative relationship between the cyclotron frequency and the microwave frequency. Therefore, referring to the external magnetic field suppression schemes in single-frequency research, this patent proposes to apply a suitable external magnetic field to suppress dielectric window breakdown in dual-frequency high-power microwaves, which has significant theoretical and practical application value. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of the technology for suppressing dielectric window breakdown under dual-frequency high-power microwaves, and to propose a method for suppressing dielectric window breakdown under dual-frequency high-power microwaves.

[0006] The technical solution of this invention is: a method for suppressing dielectric window breakdown under dual-frequency high-power microwaves, wherein the method comprises: applying a deposition electric field E parallel to the dielectric window and simultaneously perpendicular to the surface of the dielectric window on the vacuum side of the dielectric window. dc and high-power microwave electric field E rf The external magnetic field B satisfies This causes the energy gained by electrons through cyclotron resonance to be higher than the second crossover point of the secondary yield curve, lowering the upper and lower boundaries of the sensitivity curve. The lower upper boundary leads to the suppression of secondary electron multiplication; where Ω is the cyclotron frequency, and ω1 and ω2 represent the dual-frequency high-power microwave E rf The angular frequencies of the two microwave components.

[0007] Furthermore, the external magnetic field B = Ωm / e, where m is the electron mass and e is the charge.

[0008] Furthermore, the external magnetic field B = 0.1T.

[0009] Furthermore, ω1 and ω2 satisfy:

[0010] E rf =E[sin(ω1t+θ1)+sin(ω2t+θ2)]

[0011] Where E is the magnitude of the electric field strength, and θ1 and θ2 represent the electric field strength of the dual-frequency high-power microwave. rf The phase angle of the two microwave components. In this invention, under a dual-frequency microwave electric field, the external magnetic field is parallel to the dielectric window and simultaneously perpendicular to E. dc and E rf When the conditions are higher than the upper boundary, the multiplication effect can be suppressed. Due to the mutual modulation of the external magnetic field and the microwave electric field, as the field strength of the dual-frequency microwave electric field increases, the upper boundary of the sensitivity curve becomes relatively stable and lower, and the multiplication is suppressed. Description of the Drawings

[0012] Figure 1 It is a classic curve of the secondary electron yield varying with the electron collision energy.

[0013] Figure 2 In (1)-(4), diagrams of the non-application of magnetic field and three ways of applying external magnetic fields are shown.

[0014] Figure 3 Diagrams showing the secondary electron multiplication sensitivity curves when no external magnetic field is applied and when three external magnetic fields with different directions are respectively applied. Detailed Implementation Manner

[0015] The average number of secondary electrons generated by each primary electron is called the secondary electron yield δ, which is a function of the impact energy E i of the primary electron and the angle ξ at which the primary electron impacts the surface of the dielectric window. As Figure 1 shown, the secondary electron yield curve has two crossover points E1 and E2, which are called the first and second crossover points. When the impact energy falls between the two crossover points, δ > 1, and secondary electron multiplication occurs; when E i < E1 and E i > E2, δ < 1, and secondary electron multiplication is suppressed. The relationship between the secondary electron yield, the impact energy, and the impact angle is described by the Vaughan empirical formula:

[0016] δ = δ(E i ) = δ max (we 1-w ) k ,

[0017]

[0018] E i and ξ are expressed as:

[0019]

[0020] δ max is the maximum value of the yield, E max is the electron impact energy at which the yield is maximum. When w < 1, k = 0 .62, and when k > 0.25, w > 1. E max0 and δ max0 are the corresponding parameters when the impact angle is 0, and k sThe surface smoothness coefficient is set to 1. The first and second intersection points in the secondary electron yield curve correspond to the lower and upper boundaries of the multiplication sensitivity curve, respectively. When the electron yield is below the upper boundary but above the lower boundary, δ>1, and secondary electron multiplication occurs; when the electron yield is below the lower boundary but above the upper boundary, δ<1, and secondary electron multiplication is suppressed. By applying an external magnetic field that meets the conditions, electron cyclotron resonance is induced, leading to an increase in electron impact energy and a decrease in the upper and lower boundaries of the sensitivity curve. Even under a relatively low microwave electric field environment, the electron yield can still be suppressed above the upper boundary.

[0021] E rf =E[sin(ω1t+θ1)+sin(ω2t+θ2)]

[0022] u x u y u z These are the velocity components of the electron along the x, y, and z directions, respectively; m is the electron mass; and E is the electron mass. dc E represents the deposition electric field on the surface of the dielectric window. rf For a high-power microwave electric field, B is the external magnetic field, Ω is the cyclotron frequency, and T is the electron flight time. rf When / B≈eE / mΩc, B is negligible when eE / mΩ<<c. rf The following are the electron dynamics equations for three different external magnetic fields in different directions and for when no external magnetic field is applied:

[0023] (1) No additional magnetic field is applied;

[0024]

[0025] u z (t)=u z (0)

[0026]

[0027] (2) The external magnetic field is parallel to E dc ;

[0028]

[0029] (3) The external magnetic field is parallel to E rf and the surface of the medium window;

[0030]

[0031] (4) The external magnetic field is parallel to the dielectric window and perpendicular to E. dc and E rf Please explain all the symbols below in Chinese.

[0032]

[0033] Analysis based on dynamic theory shows that the external magnetic field is parallel to E. dc At that time, electronic time of flight is determined by E dc The change in [the field] determines that, compared to the first case without a magnetic field, where energy can be obtained from a dual-frequency microwave field through electron cyclotron, obtaining higher energy requires a sufficiently long flight. Therefore, compared to the case without a magnetic field, an external field parallel to E [is needed]. dc The sensitivity curve is altered under magnetic field conditions, requiring a sufficiently small E. dc The external magnetic field is parallel to E. rf When the electrons are at the surface of the dielectric window, their cyclotron motion cannot gain energy from the dual-frequency microwave field, and the sensitivity curve remains unchanged compared to when no magnetic field is applied. Only in the fourth case, the electron motion time is modulated by the external magnetic field and the dual-frequency microwave electric field, and the electrons gain higher energy through cyclotron resonance acceleration when Ω = ω1~ω2, resulting in a decrease in both the upper and lower boundaries. The external magnetic field can be chosen to satisfy... Numerical calculations were performed to determine the changes in the sensitivity curve, and the doubling sensitivity curves for all cases were plotted as follows: Figure 3 As shown. By Figure 3 As can be seen, the numerical results are consistent with the theoretical results, and the applied magnetic field is parallel to the dielectric window and perpendicular to E. dc and E rf When this occurs, the upper boundary of the sensitivity curve decreases significantly, even lower than the lower boundary in other cases. Therefore, under a dual-frequency microwave electric field, the applied magnetic field is parallel to the dielectric window and simultaneously perpendicular to E. dc and E rf When the conditions are higher than the upper boundary, the multiplication effect can be suppressed. Due to the mutual modulation of the external magnetic field and the microwave electric field, as the field strength of the dual-frequency microwave electric field increases, the upper boundary of the sensitivity curve becomes relatively stable and lower, and the multiplication is suppressed.

Claims

1. A method for suppressing dielectric window breakdown under dual-frequency high-power microwaves, the method comprising: applying a deposition electric field E parallel to the dielectric window and simultaneously perpendicular to the surface of the dielectric window on the vacuum side of the dielectric window. dc and high-power microwave electric field E rf The external magnetic field B satisfies This causes the energy gained by electrons through cyclotron resonance to be higher than the second crossover point of the secondary yield curve, lowering the upper and lower boundaries of the sensitivity curve. The lower upper boundary leads to the suppression of secondary electron multiplication; among which, The cyclotron frequency, , These represent dual-frequency high-power microwave E rf The angular frequencies of the two microwave components; The quadratic output curve has two intersection points. and These are called the first and second intersection points, which correspond to the lower and upper boundaries of the sensitivity curve, respectively.

2. The method for suppressing dielectric window breakdown under dual-frequency high-power microwave as described in claim 1, characterized in that, The external magnetic field B = Ωm / e, where m is the electron mass and e is the charge.

3. The method for suppressing dielectric window breakdown under dual-frequency high-power microwave as described in claim 1, characterized in that, External magnetic field B 0.1T.

4. The method for suppressing dielectric window breakdown under dual-frequency high-power microwave as described in claim 1, characterized in that, in , satisfy: ； in, The magnitude of the electric field strength, , These represent dual-frequency high-power microwave E rf The phase angle of the two microwave components.

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