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(a) Output signal versus driving frequency for A inj = 2.0. (b) Output signal versus driving amplitude for two different frequencies. Other parameters are the same as in Fig. 3(b).
Source publication
For a relativistic backward-wave oscillator (RBWO), various nonstationary phenomena, such as irregular transients, mode competition, self-modulation, and chaos, are typical. Phase locking by injection of the external signal helps to minimize transient times and to stabilize a single-frequency regime of operation. In this paper, phase locking of an...
Contexts in source publication
Context 1
... Fig. 4(a), the output signal amplitude is plotted as function of the injection frequency. The peaks at the frequen- cies close to the cold eigenfrequencies (15) clearly illustrate resonances with different axial modes. Outside the synchro- nization tongues, i.e., in the domain of multifrequency beating oscillation, the averaged values of the ...
Context 2
... to the cold eigenfrequencies (15) clearly illustrate resonances with different axial modes. Outside the synchro- nization tongues, i.e., in the domain of multifrequency beating oscillation, the averaged values of the output amplitude are plotted by dashed lines. The output amplitude grows with the increase of the injection amplitude, as shown in Fig. 4(b). It is important to estimate the power required for the injec- tion locking. Assume that the driver is perfectly matched with the cold RF structure at the resonance frequency. In addition, assume that the driver is coupled to the RF structure through a circulator and is not affected by the reflected signal. In such a case, the ...
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Citations
... In the case of strong reflections, the spectral lines of radiation in the regime of periodic self-modulation are close to eigen-frequencies of the overall electrodynamic system consisting an intrinsic electrodynamic system and external reflector. This is a rather universal feature of microwave oscillators that is also typical, in particular, of BWOs with an external reflector [15][16][17]. ...
Oscillatory regimes with simultaneous excitation of several longitudinal modes of the overall electrodynamic system have been experimentally realized by introducing external reflections in a gyroresonance backward wave oscillator (gyro-BWO) based on a helical corrugated waveguide. Radiation in the 24-GHz band was obtained with an average power within 0.9–1.2 kW and a typical distance between spectral components 96- to 120-, 232- to 280-, and 464- to 640-MHz corresponding to the excitation of longitudinal modes with various indices.
... Note that in contrast with the cold-cavity fixed field profile simulation, the self-consistent theory allows simulation of excitation and interaction of different axial modes. The possibility of locking of different axial modes may be used for fast mode switching operation (see [5]), which is required for some applications. ...
Injection locking of the 0.4-THz second-harmonic gyrotron by an external signal is studied by self-consistent numerical simulation. The locking of the fundamental mode (FM) as well as of the higher-order axial mode (HOAM) is investigated. The possibility of locking of different axial modes may be used for fast mode-switching operation.
... В случае сильных отражений спектральные линии излучения в режиме периодической автомодуляции близки к резонансным частотам совокупной электродинамической системы, образованной электродинамической системой и внешним отражателем. Это достаточно универсальное свойство СВЧ-генераторов характерно, в частности, и для генераторов на основе ЛОВ с внешним отражателем [15][16][17]. ...
When external reflections are added to the helical gyro-BWO, the simultaneous excitation of several longitudinal modes are experimentally implemented. Radiation of 24 GHz band with average power of 0.9-1.2 kW with typical distance between spectral components 96-120 MHz, 232-280 MHz and 464-640 MHz corresponding to excitation of longitudinal modes with different indexes was obtained.
... Let us apply the well-known formalism of the 1D nonlinear time-domain (nonstationary) theory of Cherenkov electron beam interaction with a traveling electromagnetic wave. [19][20][21] Consider the axial component of the RF field of the slow wave as Eðz; tÞ ¼ Re½Eðz; tÞexp ðihÞ, where E is the slowly varying complex envelope, h ¼ x 0 ðt À z=v 0 Þ, and x 0 is the angular frequency of synchronism at which the wave phase velocity v / ðx 0 Þ is equal to the electron drift velocity v 0 . The equation of electron motion in the field of the synchronous wave reads ...
... The excitation equation of the slow electromagnetic wave by the electron beam current reads [19][20][21] @F @s þ @F @n ¼ ÀI; ...
This paper reports the results of studies of super-radiance pulse amplification in the case of Cherenkov interaction of a relativistic electron beam with a traveling electromagnetic wave. 1D Nonstationary (time-domain) nonlinear models of a Cherenkov traveling-wave-tube amplifier are considered in two approximations, namely, in the cases of small variation of electron velocity and small variation of electron energy. For both cases, self-similar solutions, which describe the pulse amplification and compression, are derived and limiting transition between them is discussed. The results of numerical simulation of amplification of a seed pulse are presented showing that the main characteristics of the pulse (peak amplitude, pulse width, etc.) behave in time and space in good agreement with the self-similar solutions.
... In general, due to the dispersion characteristics of its slow-wave structure with dvp/dω>0 (where vp is the phase velocity), the oscillation frequency increases with the increase of the electron beam voltage. When a stable frequency is required, an external reference can be used to achieve phase lock 49,50 . ...
Since the first vacuum tube (X-ray tube) was invented by Wilhelm Röntgen in Germany, after more than one hundred years of development, the average power density of the vacuum tube microwave source has reached the order of 108 [MW][GHz]2. The maximum power density record was created by the Free Electron Lasers. In the high-power microwave field, the vacuum devices are still the mainstream microwave sources for applications such as scientific instruments, communications, radars, magnetic confinement fusion heating, microwave weapons, etc. The principles of microwave generation by vacuum tube microwave sources include Cherenkov or Smith-Purcell radiation, transition radiation, and Bremsstrahlung. In this paper, the vacuum tube microwave sources were reviewed in order according to the three radiation principles. Among them, the Vircators can produce 22 GW output power in P-band (0.23-1GHz). Vacuum tubes that can achieve continuous-wave operation include Traveling Wave Tubes, Klystrons, Free Electron Lasers, and Magnetrons, with output power up to 1MW. Vacuum tubes that can generate frequencies of the order of 100 GHz and above include Klystrons, Traveling Wave Tubes, Gyrotrons, Backward Wave Oscillators, Magnetrons, Surface Wave Oscillators, Free Electron Lasers, Orotrons, etc. Gyrotrons are very attractive in the millimeter wave and THz fields. The Gyrotrons can output power at the MW level with 3000s pulse width at millimeter wavelengths.
... The physical pattern of phase locking in RBWOs with external power injection was analyzed by Ryskin et al., who found that the external driving signal allowed rapid frequency tuning due to the axial mode switching effect. 30 Wu et al. studied the phase induction regime of RBWOs: the external power was injected into an independent input cavity upstream of the slowwave structures (SWSs) of RBWOs to generate an RF field that premodulated the electron beam. 31 The phase and frequency locking of an X-band RBWO was accomplished experimentally with an input power of 90 kW, an output power of 1.5 GW, a pulse width of 50 ns, and a phase fluctuation of less than 20 . ...
Even after 50 years of development, narrowband high-power microwave (HPM) source technologies remain the focus of much research due to intense interest in innovative applications of HPMs in fields such as directed energy, space propulsion, and high-power radar. A few decades ago, the main aim of investigations in this field was to enhance the output power of a single HPM source to tens or hundreds of gigawatts, but this goal has proven difficult due to physical limitations. Therefore, recent research into HPM sources has focused on five main targets: phase locking and power combination, high power efficiency, compact sources with a low or no external magnetic field, high pulse energy, and high-power millimeter-wave generation. Progress made in these aspects of narrowband HPM sources over the last decade is analyzed and summarized in this paper. There is no single type of HPM source capable of excellent performance in all five aspects. Specifically, high pulse energy cannot be achieved together with high power efficiency. The physical difficulties of high power generation in the millimeter wave band are discussed. Semiconductor-based HPM sources and metamaterial (MTM) vacuum electron devices (VEDs) are also commented on here. Semiconductor devices have the advantage of smart frequency agility, but they have low power density and high cost. MTM VEDs have the potential to be high power efficiency HPM sources in the low frequency band. Moreover, problems relating to narrowband HPM source lifetime and stability, which are the important determinants of the real-world applicability of these sources, are also discussed.
... 10,11 Coherent summation of radiation from several HPM generators driven by relativistic electron beams requires phasing of such sources. This task can be solved using electrodynamic coupling between the channels, 12 by a seed electromagnetic signal arising at the sharp edge of a current pulse, 13 by the HPM excitation using an external rf signal, [14][15][16][17] or by the method of electron beam pre-modulation. [18][19][20] In this letter, the channel power sum- mation from two relativistic backward wave oscillators (RBWOs) by the method of electron beam pre-modulation will be demonstrated theoretically and experimentally. ...
We demonstrate both theoretically and experimentally the possibility of the generation of powerful microwave pulses by channel power summation of two X-band phase-locked relativistic backward wave oscillators (RBWOs). A modulated electron beam induced by an external signal can lead the microwave field with an arbitrary initial phase to the same equilibrium phase, which is determined by the initial phase of the external signal. A high-current dual-beam accelerator was built to drive the two RBWOs. An external signal was divided into two channels with an adjusted relative phase and injected into the two RBWOs through two TE10-TEM mode converters. The generated microwaves were combined with a power combiner consisting of two TM01-TE11 serpentine mode converters with a common output. In the experiments, as the input power for each channel was 150 kW, the two RBWOs output 3.1 GW and 3.7 GW, respectively, the jitter of the relative phase of two output microwaves was about 20°, and the summation power from the power combiner is 6.2 GW, corresponding to a combination efficiency of 91%.
The article is devoted to overview of different types of vacuum electronic devices with two or more charged particle beams. There are travelling wave and backward wave tubes, free electron lasers and masers, volume free electron lasers. Two different cases take place in such situation: multiple-beam instability in such devices and multiple-stream instability. In the first case some charged particle beams moves in the system with different velocities. In the second one there are beams with almost equal velocities (streams). Two systems of equations for volume free electron laser with two electron beams are proposed. Some numerical results of VFEL numerical simulation are given and discussed.
