Ultrahigh-power Cherenkov radiation generator and frequency modulation method thereof

Abstract

The invention discloses an ultrahigh-power Cherenkov radiation generator which solves the problems that an existing relativistic backward wave tube for generating frequency modulation waveforms is low in output power, low in conversion efficiency and narrow in frequency modulation range. The coaxial reflector, the non-uniform slow wave structure, the uniform slow wave structure, the coaxial coupling structure and the magnetic field coil are sequentially and coaxially connected to the rear side of the annular cathode; the non-uniform slow-wave structure and the uniform slow-wave structure are both over-mode structures, compared with a single-mode structure, the power capacity of the device is improved, meanwhile, the device can work at a high working voltage, and generation of ultra-high power is facilitated.

Description

Technical Field

[0001] The present invention relates to a Cherenkov radiation generator, and in particular to an ultra-high power Cherenkov radiation generator and a frequency modulation method thereof. Background Art

[0002] Laboratory low-power research has confirmed that by modulating the frequency, amplitude and pulse width of electromagnetic waves to form an agile waveform and utilizing "backdoor" coupling, the electromagnetic interference sensitivity threshold of electronic components and systems has been significantly reduced, and it is expected that the effective distance of high-power microwaves will be extended to more than 10 times the current level.

[0003] An existing relativistic backward wave tube that generates a frequency modulated waveform is shown in the attached Figure 1 As shown, the relativistic backward wave tube includes an annular cathode 01, a dielectric ring 02, a reflector 04, a slow wave structure 05, an output waveguide 06 and a solenoid 07. During operation, the annular cathode 01 emits an annular relativistic electron beam 03 axially outward under a high voltage pulse, and under the guidance of the magnetic field generated by the solenoid 07, passes through the reflector 04, enters the slow wave structure 05 to excite electromagnetic waves, and the electromagnetic waves are transmitted to the cathode end, reflected by the reflector 04, and finally output from the output waveguide 06. During operation, the dielectric ring 02 breaks down, generating plasma, causing the high voltage pulse voltage to decrease over time and the current to increase, so that the excited electromagnetic waves generate frequency modulation.

[0004] In the above technology, frequency modulation is obtained by changing the voltage in the relativistic backward wave tube, which is only suitable for working at medium relativistic voltage, and the working point of the relativistic backward wave tube is far away from the π point of the dispersion curve, and the coupling impedance is low. In this case, the output power and conversion efficiency of the relativistic backward wave tube are relatively low, the output power is usually 0.6-0.8GW, the efficiency is less than 30%, and the frequency modulation range is also narrow, from 10GHz to 9.6GHz. Summary of the invention

[0005] In order to solve the technical problems of low output power, low conversion efficiency and narrow frequency modulation range of the existing relativistic backward wave tube that generates frequency modulation waveform, the present invention provides an ultra-high power Cherenkov radiation generator and a frequency modulation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] An ultra-high power Cherenkov radiation generator, which is special in that it includes an annular cathode and a coaxial reflector, a non-uniform slow-wave structure, a uniform slow-wave structure, a coaxial coupling structure and a magnetic field coil, which are coaxially connected to the rear side of the annular cathode in sequence;

[0008] The annular cathode is used to generate an annular relativistic electron beam backward under the action of a high-voltage pulse, so that the annular relativistic electron beam passes through a coaxial reflector and a non-uniform slow-wave structure and then reaches a uniform slow-wave structure;

[0009] The non-uniform slow-wave structure and the uniform slow-wave structure are both over-moded structures;

[0010] The uniform slow-wave structure is used to cluster the annular relativistic electron beam, thereby stimulating the electromagnetic wave to propagate toward the annular cathode, so that the subsequent annular relativistic electron beam clusters in advance in the non-uniform slow-wave structure;

[0011] The ripple amplitude of the non-uniform slow-wave structure increases backward along its axial direction, so as to excite different frequencies of electromagnetic waves during propagation;

[0012] The coaxial reflector is used to reflect electromagnetic waves of different frequencies, so that the electromagnetic waves of different frequencies are sequentially coupled into the coaxial coupling structure;

[0013] The coaxial coupling structure is coaxially arranged inside the non-uniform slow-wave structure and the uniform slow-wave structure, and a coupling gap is provided on one end of the side wall close to the coaxial reflector, so as to allow electromagnetic waves of different frequencies to enter the coaxial coupling structure and be output from the rear side thereof;

[0014] The magnetic field coil is arranged at the periphery of the annular cathode, the coaxial reflector, the non-uniform slow-wave structure and the uniform slow-wave structure, and is used for providing a guiding magnetic field to the annular relativistic electron beam.

[0015] Furthermore, the non-uniform slow-wave structure and the uniform slow-wave structure are both coaxial slow-wave structures, their outer conductors are both corrugated waveguides, and their inner conductors are both smooth waveguides;

[0016] The average radius r0 of the outer conductor satisfies: 2r0 / λ>1.76, where λ is the wavelength of the microwave;

[0017] The radius r1 of the inner conductor satisfies r0-r1<λ / 2;

[0018] The outer conductor of the uniform slow-wave structure is connected to an end of the inner conductor away from the non-uniform slow-wave structure.

[0019] Furthermore, the outer radius r of the corrugated waveguide of the non-uniform slow-wave structure is 3w for:

[0020] r3w(z)=r0+r 03 [A+(1-A)(z-z3)n / (z4-z3)n]cos[2π(z-z3) / z 03 ]

[0021] Among them, r 03 and z03 are the maximum ripple amplitude and ripple period of the non-uniform slow wave structure, λ / 20≤r 03 ≤λ10,z 03 <λ / 2, A is the ripple amplitude control parameter, 0.1≤A≤0.4, z3 and z4 are the uniform slow wave structure and the starting position of the uniform slow wave structure, and z4-z3=N3z 03 , N3 is the number of ripple periods of the non-uniform slow wave structure, satisfying 46≤N3≤50, n is the function index, and 1≤n≤1.9.

[0022] Furthermore, the outer radius r of the corrugated waveguide of the uniform slow-wave structure is 4w for:

[0023] r4w(z)=r0+r 04 cos[2π(z-z4) / z 04 ]

[0024] Among them, r 04 and z 04 are the ripple amplitude and ripple period of the uniform slow wave structure, λ / 20≤r 04 ≤λ10.

[0025] Furthermore, the number N4 of corrugation periods of the uniform slow-wave structure satisfies: 5≤N4≤15.

[0026] Furthermore, A = 0.15, r0 = 73 mm, r 03 =2.25mm, z 03 =12mm, r 04 =2.25mm, z 04 =12.5mm, N3=50, N4=11, n=1.5.

[0027] Furthermore, the coaxial coupling structure is a coaxial waveguide, whose outer conductor and inner conductor are smooth waveguides; the outer conductor of the coaxial coupling structure is connected to one end of the inner conductor of the non-uniform slow-wave structure close to the coaxial reflector, and the coupling gap is provided between the connecting end face and the inner conductor of the coaxial reflector; the inner conductor of the coaxial coupling structure is connected to the inner conductor of the coaxial reflector; a matching cavity is provided on the inner conductor of the coaxial coupling structure, and the matching cavity corresponds to the coupling gap.

[0028] A frequency modulation method for the ultra-high power Cherenkov radiation generator is characterized in that it comprises the following steps:

[0029] Step 1, the annular cathode generates an annular relativistic electron beam backwards, and the annular relativistic electron beam is guided by the magnetic field generated by the magnetic field coil and passes through the coaxial reflector and the non-uniform slow-wave structure in sequence to directly reach the uniform slow-wave structure;

[0030] Step 2: The annular relativistic electron beam is clustered in the uniform slow-wave structure, exciting electromagnetic waves, which propagate toward the annular cathode, so that the subsequent annular relativistic electron beam is clustered in the non-uniform slow-wave structure in advance, and electromagnetic waves of different frequencies are excited at different axial positions thereof;

[0031] Step 3: Electromagnetic waves of different frequencies are sequentially coupled by the coaxial reflector into the coaxial coupling structure and finally output from the rear side thereof.

[0032] Beneficial effects of the present invention:

[0033] 1. The ultra-high power Cherenkov radiation generator provided by the present invention adopts a non-uniform slow-wave structure and a uniform slow-wave structure, both of which are over-mode structures. Compared with the single-mode structure, the power capacity of the device is improved, and at the same time, it can work at a higher operating voltage, which is conducive to generating ultra-high power.

[0034] 2. The ultra-high power Cherenkov radiation generator provided by the present invention has a structure that enables its operating point to be located near the π point of the dispersion curve, and has a high coupling impedance, which is beneficial to improving the beam conversion efficiency.

[0035] 3. In the ultra-high power Cherenkov radiation generator provided by the present invention, the annular relativistic electron beam excites electromagnetic waves of different frequencies at different positions of the non-uniform slow-wave structure. At the same time, the range of the ripple amplitude control parameter A of the non-uniform slow-wave structure is set at 0.1-0.4, the function index n is set at 1-1.9, and the number of ripple periods N3 is set at 46-50. In this way, the annular relativistic electron beam can obtain a wider range of frequency modulation in the non-uniform slow-wave structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of an existing relativistic backward wave tube for generating a frequency modulated waveform;

[0037] Numbers in the figure:

[0038] 01- annular cathode, 02- dielectric ring, 03- electron beam, 04- reflector, 05- slow wave structure, 06- output waveguide, 07- solenoid;

[0039] Figure 2 It is a structural schematic diagram of an embodiment of an ultra-high power Cherenkov radiation generator of the present invention;

[0040] Figure 3 is a dispersion curve diagram of a slow-wave structure in an embodiment of the present invention;

[0041] Figure 4 is a curve diagram of output power variation over time of an ultra-high power Cherenkov radiation generator in an embodiment of the present invention;

[0042] Figure 5 1 is an output electric field waveform and a corresponding time-frequency curve diagram of the ultra-high power Cherenkov radiation generator in an embodiment of the present invention.

[0043] Figure Number:

[0044] 1- annular cathode, 2- coaxial reflector, 3- non-uniform slow-wave structure, 4- uniform slow-wave structure, 5- coaxial coupling structure, 6- annular relativistic electron beam, 7- magnetic field coil. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] An ultra-high power Cherenkov radiation generator provided by an embodiment of the present invention is Figure 2 As shown, the ultra-high power Cherenkov radiation generator includes an annular cathode 1 and a coaxial reflector 2, a non-uniform slow-wave structure 3, a uniform slow-wave structure 4, a coaxial coupling structure 5 and a magnetic field coil 7 which are coaxially connected to the rear side of the annular cathode 1 in sequence.

[0047] The annular cathode 1 is located at the front end of the structure, and emits an annular relativistic electron beam 6 backward under the action of a high-voltage pulse; the coaxial reflector 2, the non-uniform slow-wave structure 3, and the uniform slow-wave structure 4 are placed in sequence on the rear side of the annular cathode 1; the coaxial coupling structure 5 is located on the inner side of the non-uniform slow-wave structure 3 and the uniform slow-wave structure 4; the magnetic field coil 7 is installed on the periphery of the entire structure to provide a guiding magnetic field for the annular relativistic electron beam 6.

[0048] During operation, the annular cathode 1 generates an annular relativistic electron beam 6, which is guided by the magnetic field generated by the magnetic field coil 7 and passes through the coaxial reflector 2, the non-uniform slow-wave structure 3 and the uniform slow-wave structure 4 in sequence. The annular relativistic electron beam 6 first generates clusters in the uniform slow-wave structure 4, excites electromagnetic waves, and the electromagnetic waves propagate in the direction of the annular cathode 1, so that the subsequent annular relativistic electron beam 6 clusters in advance at the non-uniform slow-wave structure 3, thereby exciting electromagnetic waves of different frequencies at different axial positions of the non-uniform slow-wave structure 3. Specifically, the ripple amplitude of the non-uniform slow-wave structure 3 increases along the axial direction, and electromagnetic waves with lower frequencies are excited at the places where the ripple amplitude of the slow-wave structure is larger, and electromagnetic waves with higher frequencies are excited at the places where the ripple amplitude of the slow-wave structure is smaller. Electromagnetic waves with lower frequencies lead electromagnetic waves with higher frequencies. Electromagnetic waves of different frequencies are reflected by the coaxial reflector 2 in sequence, coupled into the coaxial coupling structure 5 in sequence, and finally output from the right end of the structure. Therefore, the frequency of the output microwave gradually increases with time.

[0049] The non-uniform slow-wave structure 3 and the uniform slow-wave structure 4 are both coaxial slow-wave structures, and their outer conductors are both corrugated waveguides. The average radius r0 of their outer conductors satisfies: 2r0 / λ>1.76, λ is the microwave wavelength, and their inner conductors are both smooth waveguides. The inner conductor radius r1 of the two satisfies r0-r1<λ2. The outer conductor of the uniform slow-wave structure 4 is connected to the end of the inner conductor away from the non-uniform slow-wave structure 3.

[0050] The outer radius r of the corrugated waveguide of the non-uniform slow-wave structure 3 3w It is expressed as:

[0051] r 3w (z) = r0 + r 03 [A+(1-A)(z-z3) n / (z4-z3) n ]cos[2π(z-z3) / z 03 ]

[0052] The outer radius r of the corrugated waveguide of the uniform slow-wave structure 4 4w It is expressed as:

[0053] r4w(z)=r0+r 04 cos[2π(z-z4) / z 04 ]

[0054] In the formula, r 03 and z 03 are the maximum ripple amplitude and ripple period of the non-uniform slow wave structure 3, λ20≤r 03 ≤λ10,z 03 <λ2, A is the ripple amplitude control parameter, 0.1≤A≤0.4, r 04 and z 04 are the ripple amplitude and ripple period of the uniform slow wave structure 4, λ20≤r 04 ≤λ10,z 04 <λ2, z3 and z4 are the starting positions of uniform slow-wave structure 3 and uniform slow-wave structure 4, satisfying z4-z3=N3z 03 , N3 is the number of ripple periods of the non-uniform slow-wave structure 3, satisfying 46≤N3≤50, the number of ripple periods N4 of the uniform slow-wave structure 4 satisfies 5≤N4≤15, n is the function index, and 1≤n≤1.9.

[0055] The ultra-high power Cherenkov radiation generator described in this embodiment works in the X-band, and the main structural parameters are as follows: A = 0.15, r0 = 73 mm, r 03 =2.25mm, z 03 =12mm, r 04 =2.25mm, z04 =12.5mm, N3=50, N4=11, n=1.5. The dispersion curves of different slow-wave structures are as follows: Figure 3 As shown in Figure 2, the frequency range of the intersection of the electron beam line and the slow-wave structure dispersion curve is greater than 2 GHz. In the particle simulation, when the diode voltage is 760 kV, the rising edge is 4.1 ns, the flat top is 5.0 ns, the falling edge is 4.1 ns, the current is 78 kA, and the guide magnetic field is 3.4 T, as shown in Figure 2. Figure 4 As shown, the electromagnetic wave output power is 35GW, the pulse width is 3ns, and the frequency modulation range within the main pulse is 8.9GHz-11GHz ( Figure 5 ), and the corresponding power conversion efficiency is 59%. Compared with the prior art, this embodiment achieves higher output power, conversion efficiency and wider frequency modulation range.

[0056] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An ultra-high power Cherenkov radiation generator, characterized in that: It comprises an annular cathode (1), a coaxial reflector (2), a non-uniform slow-wave structure (3), a uniform slow-wave structure (4), a coaxial coupling structure (5) and a magnetic field coil (7) which are coaxially connected in sequence to the rear side of the annular cathode (1); The annular cathode (1) is used to generate an annular relativistic electron beam (6) backward under the action of a high-voltage pulse, so that the annular relativistic electron beam (6) passes through a coaxial reflector (2) and a non-uniform slow-wave structure (3) and then reaches a uniform slow-wave structure (4); The non-uniform slow-wave structure (3) and the uniform slow-wave structure (4) are both over-moded structures; The uniform slow-wave structure (4) is used to cluster the annular relativistic electron beam (6), thereby stimulating electromagnetic waves to propagate in the direction of the annular cathode (1), so that the subsequent annular relativistic electron beam (6) is clustered in advance in the non-uniform slow-wave structure (3); The ripple amplitude of the non-uniform slow-wave structure (3) increases backward along its axial direction, so as to excite electromagnetic waves of different frequencies during propagation; The coaxial reflector (2) is used to reflect electromagnetic waves of different frequencies, so that the electromagnetic waves of different frequencies are sequentially coupled into the coaxial coupling structure (5); The coaxial coupling structure (5) is coaxially arranged inside the non-uniform slow-wave structure (3) and the uniform slow-wave structure (4), and a coupling gap is provided on the side wall thereof at one end close to the coaxial reflector (2), so as to allow electromagnetic waves of different frequencies to enter the coaxial coupling structure (5) and be output from the rear side thereof; The magnetic field coil (7) is arranged at the periphery of the annular cathode (1), the coaxial reflector (2), the non-uniform slow-wave structure (3) and the uniform slow-wave structure (4), and is used to provide a guiding magnetic field for the annular relativistic electron beam (6).

2. The ultra-high power Cherenkov radiation generator according to claim 1, characterized in that: The non-uniform slow-wave structure (3) and the uniform slow-wave structure (4) are both coaxial slow-wave structures, their outer conductors are both corrugated waveguides, and their inner conductors are both smooth waveguides; The average radius r0 of the outer conductor satisfies: 2r0 / λ>1.76, where λ is the wavelength of the microwave; The radius r1 of the inner conductor satisfies r0-r1<λ / 2; The outer conductor of the uniform slow-wave structure (4) is connected to an end of the inner conductor that is away from the non-uniform slow-wave structure (3).

3. The ultra-high power Cherenkov radiation generator according to claim 2, characterized in that: The outer radius r of the corrugated waveguide of the non-uniform slow-wave structure (3) is 3w for: r3w(z)=r0+r03[A+(1-A)(z-z3)n / (z4-z3)n]cos[2π(z-z3) / z03] Among them, r 03 and z 03 are the maximum ripple amplitude and ripple period of the non-uniform slow wave structure (3), λ / 20≤r 03 ≤λ10,z 03 <λ / 2, A is the ripple amplitude control parameter, 0.1≤A≤0.4, z3 and z4 are the starting positions of the uniform slow wave structure (3) and the uniform slow wave structure (4), and z4-z3=N3z 03 , N3 is the number of ripple periods of the non-uniform slow wave structure (3), satisfying 46≤N3≤50, n is the function index, and 1≤n≤1.

9.

4. The ultra-high power Cherenkov radiation generator according to claim 3, characterized in that: The outer radius r of the corrugated waveguide of the uniform slow-wave structure (4) is 4w for: r4w(z)=r0+r04cos[2π(z-z4) / z04] Among them, r 04 and z 04 are the ripple amplitude and ripple period of the uniform slow wave structure (4), λ / 20≤r 04 ≤λ / 10.

5. The ultra-high power Cherenkov radiation generator according to claim 4, characterized in that: The number N4 of corrugation periods of the uniform slow-wave structure (4) satisfies: 5≤N4≤15.

6. The ultra-high power Cherenkov radiation generator according to claim 5, characterized in that: A=0.15,r0=73mm,r 03 =2.25mm,z 03 =12mm,r 04 =2.25mm,z 04 =12.5mm,N3=50,N4=11,n=1.5。 7. The ultra-high power Cherenkov radiation generator according to claim 6, characterized in that: The coaxial coupling structure (5) is a coaxial waveguide, and its outer conductor and inner conductor are smooth waveguides; the outer conductor of the coaxial coupling structure (5) is connected to an end of the inner conductor of the non-uniform slow-wave structure (3) close to the coaxial reflector (2), and the coupling gap is provided between the connection end face and the inner conductor of the coaxial reflector (2); the inner conductor of the coaxial coupling structure (5) is connected to the inner conductor of the coaxial reflector (2); and a matching cavity is provided on the inner conductor of the coaxial coupling structure (5), and the matching cavity corresponds to the coupling gap.

8. A frequency modulation method for an ultra-high power Cherenkov radiation generator according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, the annular cathode (1) generates an annular relativistic electron beam (6) backwards, and the annular relativistic electron beam (6) is guided by the magnetic field generated by the magnetic field coil (7), passes through the coaxial reflector (2), the non-uniform slow-wave structure (3) in sequence, and directly reaches the uniform slow-wave structure (4); Step 2: The annular relativistic electron beam (6) is clustered in the uniform slow-wave structure (4), exciting electromagnetic waves, which propagate toward the annular cathode (1), so that the subsequent annular relativistic electron beam (6) is clustered in the non-uniform slow-wave structure (3) in advance, and electromagnetic waves of different frequencies are excited at different axial positions thereof; Step 3: Electromagnetic waves of different frequencies are sequentially coupled by the coaxial reflector (2) into the coaxial coupling structure (5), and finally output from the rear side thereof.

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