An ultrahigh power cerenkov radiation generator and frequency modulation method thereof

Abstract

The application discloses an ultrahigh-power Cherenkov radiation generator, and solves the problems of low output power, low conversion efficiency and narrow frequency modulation range of a current frequency modulation waveform generated by a relativistic backward wave tube, and specifically comprises a ring cathode, 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 in sequence at the back side of the ring cathode; the non-uniform slow wave structure and the uniform slow wave structure are both overmoded structures, compared with a single-mode structure, the device power capacity is improved, and meanwhile, the device can work at a higher working voltage, which is beneficial to generating ultrahigh power.

Description

Technical Field

[0001] This invention relates to Cherenkov radiation generators, and more specifically to an ultra-high power Cherenkov radiation generator and its frequency modulation method. Background Technology

[0002] Laboratory low-power studies have confirmed that by modulating the frequency, amplitude, and pulse width of electromagnetic waves to form agile waveforms, and by using "backdoor" coupling, the electromagnetic interference sensitivity threshold of electronic components and systems has been significantly reduced, which is expected to extend the effective range of high-power microwaves to more than 10 times the current level.

[0003] An existing relativistic backward wave tube for generating frequency-modulated waveforms, as shown in the attached figure. Figure 1 As shown, the relativistic backwave tube includes a ring cathode 01, a dielectric ring 02, a reflector 04, a slow-wave structure 05, an output waveguide 06, and a solenoid 07. During operation, under a high-voltage pulse, the ring cathode 01 emits a ring-shaped relativistic electron beam 03 outward along the axial direction. Guided by the magnetic field generated by the solenoid 07, the beam passes through the reflector 04 and enters the slow-wave structure 05, exciting electromagnetic waves. The electromagnetic waves propagate towards the cathode end, are reflected by the reflector 04, and are 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, thus modulating the frequency of the excited electromagnetic waves.

[0004] In the aforementioned techniques, frequency modulation is achieved by changing the voltage in a relativistic backward wave tube (RWB). This method is only suitable for operation at moderate relativistic voltages, and the RWB's operating point is far from the π point of the dispersion curve, resulting in low coupling impedance. Under these conditions, the RWB's output power and conversion efficiency are relatively low, typically 0.6-0.8 GW, with an efficiency below 30%, and a narrow frequency modulation range of 10 GHz to 9.6 GHz. Summary of the Invention

[0005] To address the technical problems of low output power, low conversion efficiency, and narrow frequency modulation range of existing relativistic backwave tubes used to generate frequency modulation waveforms, this invention provides an ultra-high power Cherenkov radiation generator and its frequency modulation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-power Cherenkov radiation generator is characterized by comprising a ring 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 connected sequentially and coaxially to the rear side of the ring cathode.

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

[0009] Both the non-uniform slow wave structure and the uniform slow wave structure are overmode structures.

[0010] The uniform slow-wave structure is used to cause the ring relativistic electron beam to cluster, thereby exciting electromagnetic waves to propagate towards the ring cathode, so that the subsequent ring relativistic electron beam clusters in advance within the non-uniform slow-wave structure.

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

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

[0013] The coaxial coupling structure is coaxially disposed inside the non-uniform slow wave structure and the uniform slow wave structure. A coupling gap is provided on one end of its side wall near the coaxial reflector to allow electromagnetic waves of different frequencies to enter the coaxial coupling structure and be output from its rear side.

[0014] The magnetic field coil is located around the annular cathode, coaxial reflector, non-uniform slow-wave structure, and uniform slow-wave structure, and is used to provide a guiding magnetic field to the annular relativistic electron beam.

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

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

[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 the end of the inner conductor that is furthest from the non-uniform slow wave structure.

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

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

[0021] Where, r 03 and z03 These represent the maximum ripple amplitude and ripple period of a non-uniform slow-wave structure, respectively, where 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 and 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, and n is the function exponent, with 1≤n≤1.9.

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

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

[0024] Where, r 04 and z 04 These represent the amplitude and period of the ripple in a uniform slow-wave structure, respectively, where λ / 20 ≤ r 04 ≤λ10.

[0025] Furthermore, the number of ripple periodicity N4 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, and its outer conductor and inner conductor are smooth waveguides; the outer conductor of the coaxial coupling structure is connected to the end of the inner conductor of the non-uniform slow wave structure near the coaxial reflector, and the coupling gap is provided between the connection 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 aforementioned ultra-high power Cherenkov radiation generator is characterized by comprising the following steps:

[0029] Step 1: The ring cathode generates a ring relativistic electron beam backward. Under the guidance of the magnetic field generated by the magnetic field coil, the ring relativistic electron beam passes through the coaxial reflector and the non-uniform slow wave structure in sequence and directly reaches the uniform slow wave structure.

[0030] Step 2: The ring relativistic electron beam clusters within the uniform slow-wave structure, exciting electromagnetic waves. These electromagnetic waves propagate toward the ring cathode, causing subsequent ring relativistic electron beams to cluster earlier within the non-uniform slow-wave structure and excite electromagnetic waves of different frequencies at different axial positions.

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

[0032] The beneficial effects of this invention are:

[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 overmode structures. Compared with the single-mode structure, it improves the power capacity of the device and can operate at a higher operating voltage, which is beneficial for generating ultra-high power.

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

[0035] 3. The ultra-high power Cherenkov radiation generator provided by this invention excites electromagnetic waves of different frequencies at different positions of a non-uniform slow-wave structure using a ring relativistic electron beam. At the same time, the ripple amplitude control parameter A of the non-uniform slow-wave structure is set in the range of 0.1 to 0.4, the function exponent n is set in the range of 1 to 1.9, and the number of ripple periods N3 is set in the range of 46 to 50. This enables the ring relativistic electron beam to obtain a wider range of frequency modulation in the non-uniform slow-wave structure. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a relativistic backward wave tube that generates frequency-modulated waveforms.

[0037] Numbering on the map:

[0038] 01-Ring cathode, 02-Dielectric ring, 03-Electron beam, 04-Reflector, 05-Slow wave structure, 06-Output waveguide, 07-Solenoid;

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

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

[0041] Figure 4 This is a graph showing the output power of the ultra-high power Cherenkov radiation generator in this embodiment of the invention as a function of time.

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

[0043] Icon labels:

[0044] 1-Ring cathode, 2-Coaxial reflector, 3-Non-uniform slow-wave structure, 4-Uniform slow-wave structure, 5-Coaxial coupling structure, 6-Ring relativistic electron beam, 7-Magnetic field coil. Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] An embodiment of the present invention provides an ultra-high power Cherenkov radiation generator, such as... Figure 2 As shown, the ultra-high power Cherenkov radiation generator includes a ring 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 sequentially coaxially connected to the rear side of the ring cathode 1.

[0047] The annular cathode 1 is located at the front end of the structure and emits the 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 behind the annular cathode 1 in sequence; the coaxial coupling structure 5 is located inside 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 ring cathode 1 generates a ring-shaped relativistic electron beam 6. Guided by the magnetic field generated by the magnetic field coil 7, the beam sequentially passes through the coaxial reflector 2, the non-uniform slow-wave structure 3, and the uniform slow-wave structure 4. The ring-shaped relativistic electron beam 6 first clusters within the uniform slow-wave structure 4, exciting electromagnetic waves. These electromagnetic waves propagate towards the ring cathode 1, causing subsequent ring-shaped relativistic electron beams 6 to cluster ahead of the non-uniform slow-wave structure 3. This results in electromagnetic waves of different frequencies being excited at different axial positions within the non-uniform slow-wave structure 3. Specifically, the ripple amplitude of the non-uniform slow-wave structure 3 increases axially. Lower-frequency electromagnetic waves are excited where the ripple amplitude is larger, while higher-frequency electromagnetic waves are excited where the ripple amplitude is smaller. Lower-frequency electromagnetic waves lead higher-frequency electromagnetic waves. Electromagnetic waves of different frequencies are sequentially reflected by the coaxial reflector 2 and coupled into the coaxial coupling structure 5, ultimately outputting from the right end of the structure. Therefore, the frequency of the output microwave gradually increases over time.

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

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

[0054] In the formula, r 03 and z 03 These represent the maximum ripple amplitude and ripple period of the non-uniform slow-wave structure 3, respectively, where λ20≤r 03 ≤λ10,z 03 <λ2, A is the ripple amplitude control parameter, 0.1≤A≤0.4, r 04 and z 04 The amplitude and period of the ripples are given by the uniform slow-wave structure, 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 exponent, and 1≤n≤1.9.

[0055] The ultra-high power Cherenkov radiation generator described in this embodiment operates in the X-band, and its 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. Its dispersion curves for different slow-wave structures are as follows: Figure 3 As shown, the frequency range of the intersection point between the electron beamline and the slow-wave structure dispersion curve is greater than 2 GHz. In particle simulation, with a diode voltage of 760 kV, a rise time of 4.1 ns, a flat-top time of 5.0 ns, a fall time of 4.1 ns, a current of 78 kA, and a guiding magnetic field of 3.4 T, as follows... 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 The corresponding power conversion efficiency is 59%. Compared with existing technologies, this embodiment achieves higher output power, conversion efficiency, and a wider frequency modulation range.

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

Claims

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

2. The ultra-high power Cherenkov radiation generator according to claim 1, characterized in that: Both the non-uniform slow wave structure (3) and the uniform slow wave structure (4) are coaxial slow wave structures, and their outer conductors are corrugated waveguides and their inner conductors are smooth waveguides. The average radius r0 of the outer conductor satisfies: 2r0 / λ>1.76, where λ is the microwave wavelength; 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 the 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) 3w for: r 3w (z)=r0+r 03 [A+(1-A) / ]cos[2π(z-z3) / z 03 ] Where, r 03 and z 03 The maximum ripple amplitude and ripple period of the non-uniform slow wave structure (3) are respectively, λ / 20≤r 03 ≤λ / 10,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 non-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 exponent, 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) 4w for: r 4w (z)=r0+r 04 cos[2π(z-z4) / z 04 ] Where, r 04 and z 04 The ripple amplitude and ripple period of the uniform slow wave structure (4) are respectively, λ / 20≤r 04 ≤λ / 10.

5. The ultra-high power Cherenkov radiation generator according to claim 4, characterized in that: The number of ripple period N4 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 the inner conductor of the non-uniform slow wave structure (3) near 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). 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 the ultra-high power Cherenkov radiation generator according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: The ring cathode (1) generates a ring relativistic electron beam (6) backward. Under the guidance of the magnetic field generated by the magnetic field coil (7), the ring relativistic electron beam (6) passes through the coaxial reflector (2) and the non-uniform slow wave structure (3) in sequence and directly reaches the uniform slow wave structure (4). Step 2: The ring relativistic electron beam (6) clusters in the uniform slow wave structure (4), exciting electromagnetic waves. The electromagnetic waves propagate towards the ring cathode (1), causing the subsequent ring relativistic electron beam (6) to cluster in the non-uniform slow wave structure (3) in advance, and exciting electromagnetic waves of different frequencies at different axial positions. Step 3: Electromagnetic waves of different frequencies are sequentially coupled into the coaxial coupling structure (5) by the coaxial reflector (2) and finally output from the rear side.

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