Relativistic Backward Wave Tube Research Articles

SPECTROSCOPY AND DYNAMICS OF NONLINEAR PROCESSES IN RELATIVISTIC BACKWARD-WAVE TUBE WITH ACCOUNTING FOR EFFECTS OF SPACE CHARGE, DISSIPATION AND WAVE REFLECTIONS

An effective universal, approach to solving the problems of quantitative modelling and analysis of the fundamental characteristics of spectroscopy and dynamics of the nonlinear processes in relativistic microwave electronics devices, in particular, a relativistic backward wave tube (RBWT) has been developed and implemented. It has been performed modelling, analysis, and prediction of chaotic dynamics of RBWT with simultaneous consideration of not only relativistic effects, but also the effects of dissipation, presence of space charge, wave reflections at the ends of the decelerating system, etc in a wide range of changes at different values of control parameters, which are characteristic for the distributed relativistic electron-wave self-oscillating systems. From physical viewpoint the transition to chaos in the dynamics of the studied RBWT occurs according to the scenario everywhere in the sequence of period-doubling bifurcations, but with the growth of relativism, the dynamics become fundamentally complicated with the alternation of quasi-harmonic and chaotic regimes (including the appearance of the "beak" effect on the bifurcation diagram) and the transition everywhere intermittency to the high-D attractor.

ADVANCED COMPUTING TOPOLOGICAL AND DYNAMICAL INVARIANTS OF RELATIVISTIC BACKWARD-WAVE TUBE TIME SERIES IN CHAOTIC AND HYPERCHAOTIC REGIMES

The advanced results of computing the dynamical and topological invariants (correlation dimensions values, embedding, Kaplan-York dimensions, Lyapunov’s exponents, Kolmogorov entropy etc) of the dynamics time series of the relativistic backward-wave tube with accounting for dissipation and space charge field and other effects are presented for chaotic and hyperchaotic regimes. It is solved a system of equations for unidimensional relativistic electron phase and field unidimensional complex amplitude. The data obtained make more exact earlier presented preliminary data for dynamical and topological invariants of the relativistic backward-wave tube dynamics in chaotic regimes and allow to describe a scenario of transition to chaos in temporal dynamics.

Comparison of Efficiencies of External Signal Supply Circuits in a Relativistic Backward-Wave Tube with Resonant Reflector

Input signal connection circuits for a backward-wave tube with resonant reflector have been compared. It has been shown that the supply of radiation from an external source through an input cavity is more efficient than the supply from the collector side of the device. This advantage is reflected in higher linear gain of the input signal and lower power required for synchronization of the backward-wave tube self-oscillator by the external source.

ХАОТИЧНА ДИНАМІКА РЕЛЯТИВІСТСЬКОЇ ЛАМПИ ЗВЕРНЕНОЇ ХВИЛІ З УРАХУВАННЯМ ВПЛИВУ ПОЛЯ ПРОСТОРОВОГО ЗАРЯДУ ТА ДИСИПАЦІЇ: НОВІ ЕФЕКТИ

We have performed an advanced modelling nonlinear dynamics elements for relativistic backward-wave tube (RBWT) with accounting for dissipation and space charge field effects etc. The temporal dependences of the normalized field amplitude (power) in a wide range of variation of the controlling parameters (electric length of an interaction space N, bifurcation parameter L and relativistic factor g0) are computed. The dynamic and topological invariants of the RBWT dynamics in auto-modulation and chaotic regimes such as correlation dimensions values, embedding, Kaplan-York dimensions, Lyapunov’s exponents, Kolmogorov entropy etc are calculated. It has been discovered the "beak" effect on the plane of parameters: bifurcation Piers-like parameter L – relativistic factor g0.

NONLINEAR DYNAMICS OF RELATIVISTIC BACKWARD-WAVE TUBE IN AUTOMODULATION AND CHAOTIC REGIME WITH ACCOUNTING THE EFFECTS WAVES REFLECTION, SPACE CHARGE FIELD AND DISSIPATION

It has been performed quantitative modelling, analysis of dynamics relativistic backward-wave tube (RBWT) with accounting relativistic effects, dissipation, a presence of space charge etc. There are computed the temporal dependences of the normalized field amplitudes in a wide range of variation of the controlling parameters which are characteristic for distributed relativistic electron-waved selfvibrational systems: electric length of an interaction space N, bifurcation parameter L and relativistic factor γ0. The computed temporal dependence of the field amplitude is in a good agreement with theoretical data by Ryskin-Titov regarding the RBWT dynamics with accounting the reflection effect, but without accounting dissipation effect and space charge field influence etc. The analysis techniques including multi-fractal approach, methods of correlation integral, false nearest neighbour, Lyapunov exponent’s, surrogate data, is applied analysis of numerical parameters of chaotic dynamics of RBWT. There are computed the dynamic and topological invariants of the RBWT dynamics in automodulation, chaotic regimes, correlation dimensions values), embedding, Kaplan-York dimensions, LE(+,+) Kolmogorov entropy.

NONLINEAR DYNAMICS OF RELATIVISTIC BACKWARD-WAVE TUBE IN SELF-MODULATION AND CHAOTIC REGIME

It has been performed quantitative modelling, analysis, forecasting dynamics relativistic backward-wave tube (RBWT) with accounting relativistic effects (γ0 = 1.5-6.0), dissipation (factor D), a presence of space charge etc. There are computed the temporal dependences of the normalized field amplitudes (power) in a wide range of variation of the controlling parameters which are characteristic for distributed relativistic electronwaved self-vibrational systems: electric length of an interaction space N, bifurcation parameter proportional to (~current I) Pirse one J and relativistic factor γ0 . The computed temporal dependence of the field amplitude (power) Fmax in a good agreement with theoretical estimates and experimental data by Ginzburg etal (IAP, Nizhny Novgorod) with using the pulsed accelerator "Saturn". The analysis techniques including multi-fractal approach, methods of correlation integral, false nearest neighbour, Lyapunov exponent’s, surrogate data, is applied analysis of numerical parameters of chaotic dynamics of RBWT. There are computed the dynamic and topological invariants of the RBWT dynamics in auto-modulation(AUM)/chaotic regimes, correlation dimensions values (3.1; 6.4), embedding, Kaplan-York dimensions, Lyapunov’s exponents (+,+) Kolmogorov entropy. There are constructed the bifurcation diagrams with definition of the dynamics self-modulation/ chaotic areas in planes, namely, "J-γ0 ", "D-J".

Frequency-tunable relativistic coaxial backward-wave oscillator with a modulating reflector

The theoretical and numerical analyses of a relativistic backward-wave tube with a coaxial slow-wave structure and modulating reflector are carried out. The incident working TEM mode reflects because of a coaxial TM01 mode excited in the reflector at a near-cutoff frequency. It is shown that the longitudinal component of the electric field present near the reflector provides the energy premodulation of an electron beam and conditions for oscillation frequency tuning. The mechanical tuning of the oscillation frequency of a relativistic coaxial backward-wave oscillator with a modulating reflector within 10% is demonstrated in numerical simulation and experiment. Tuning is accomplished by varying the drift length between the reflector and the entrance to the slow-wave structure of the oscillator.

Relativistic backward-wave tube with a smooth control over output radiation pulse duration

The effect of failure of oscillations in a low-impedance backward-wave tube is described and the possibility of using this effect for controlling the duration of output radiation pulses is considered.

Relativistic backward-wave tube with mechanically tunable generation frequency over a 14% range

A tunable-frequency low-magnetic-field relativistic microwave oscillator is realized experimentally based on a relativistic backward-wave tube with a modulating resonance reflector. The generated frequency is tuned mechanically by moving the oscillator slow-wave structure relative to the reflector. At fixed parameters of the corrugations and of the electron bunch, a frequency tuning range of about 14% measured between −3-dB (relative to the maximum peak generated microwave power) points is realized. The maximum pulse power of 3.4 ± 0.7 GW was obtained at a carrier frequency of 3.65 GHz in a magnetic field of 0.44 T.

Operation of a relativistic backward wave tube affected by the noise of electron flows formed by explosive emission cathodes

One of the mechanisms of appearance of the high-frequency noise of intense electron flows formed by explosive emission cathodes is theoretically analyzed. It is shown that the main source of noise radiation in devices using explosive emission electron injectors can be the Shot effect related with the partial character of particle emission. The main energy characteristics of electron flow noise radiation are estimated and the influence of noise on the operation of a relativistic backward wave tube (BWT) is studied. The rate of formation of steady-state oscillations in BWT self-oscillators, the minimal level of the input signal necessary for stable BWT amplifier operation, and the spectral density of the input electromagnetic signal excitation-equivalent to the electron flow noise radiation are estimated.

A high-power periodic nanosecond pulse source of coherent 8-cm electromagnetic radiation

The generation of short electromagnetic pulses excited in an extended slow-wave system (SWS) of a relativistic backward wave tube (BWT) operating in the so-called superradiance regime with a carrier frequency of 3.7 GHz has been simulated and experimentally studied. At a decreased magnetic field (about 0.2 T) in the SWS, the BWT generated 2.5-ns microwave pulses with a power of up to 800 MW. At a pulse repetition rate of 100 Hz, the working life of the system was limited by the lifetime of an explosive emission cathode (106 pulses). The possibility of phase synchronization of the high-frequency field of the relativistic microwave oscillator with respect to the voltage pulse front is demonstrated for the first time.

Simulation of pulse shortening phenomena in high power microwave tube using PIC method

Pulse shortening is an universal phenomenon in highpower microwave tubes, which hinders the improvement of microwave output energy. So far, it is also an unres olved problem in the field of high-power microwave devices. In this paper, the relativistic backward wave tube (RBWO) is treated as an example to study the pul se shortening phenomena. The influences of explosive emission in the inner surface of RBWO and fluctuation of the relativistic electron beam on the pulse width and output power are investigated by means of the particle in cell(PIC) method .Through the simulation results, some useful conclusions have been drawn. The explosive emission in the surface of the slow wave structure due to intense elec tric field is one of the most important factors causing pulse shortening in high-power microwave tube. The fluctuation of the electron beam can also lead to pulse shortening. Some methods to overcome pulse shortening are given in this paper.

Pulsed 5-GW resonance relativistic BWT for a decimeter wavelength range

The results of numerical modeling and experimental investigation of a high-power, resonance relativistic backward wave tube are presented. By using the working TM01 mode reflections from the ends of the electrodynamic system, optimum conditions for the electron beam interaction with both the (−1)st harmonic of the backward electromagnetic wave and the main harmonic of the concurrent wave are achieved. A single mode generation with 5 GW output power and a 30% efficiency was obtained in experiments at a frequency of 3.6 GHz. The working frequency can be controlled within 15% (at the half maximum power level) by changing the slow-wave structure period at the constant electron beam parameters.

On the synthesis of radiation spectrum in a sectioned relativistic backward wave tube

We have studied the possibility of controlling the radiation spectrum of a high-power relativistic backward wave tube (BWT) by varying the period of its delay system. For a BWT comprising several sections with different corrugation periods, two-and three-mode generation regimes with commensurate amplitudes of spectral components have been found, the separation of which can be controlled by changing the corrugation period. It is shown that, for a sufficiently large detuning, such a configuration of the interaction space makes possible the generation of noiselike chaotic signals with separated or overlapping spectra. In the latter case, the width of the radiation spectrum is almost twice that of a regular BWT of the same length.

High-efficiency subnanosecond microwave pulse generation in a relativistic backward wave tube

The regime of nonstationary oscillations with a short-time power burst, which is typical of the initial stage of a transient process developed when a beam current significantly exceeds the starting level, is studied in a relativistic backward wave tube (BWT) operating in the millimeter wavelength range. The results of numerical calculations allowed conditions to be established that provide for a nearly 90% efficiency of the power transfer from an electron beam with the parameters 300 keV, 2 kA, 1 ns to the microwave pulse with a duration of 8–10 periods of the microwave field oscillations. The experiments showed the possibility of generating such pulses with a width of 200–250 ps and a power of up to ∼400 MW at a central frequency of about 38 GHz.

Relativistic Gigawatt BWT microwave pulse duration increased upon treating the slow-wave structure surface with a low-energy high-current electron beam

A new method of insulator surface treatment, which allows the electric strength of the material to be increased, is proposed and verified. Using this method for treating the slow-wave structure of a relativistic backward wave tube (BWT), the microwave pulse duration was increased from ∼6 to ∼30 ns at an output BWT radiation power of 3 GW.

Experimental study of the transient process in a pulsed relativistic backward-wave tube for the millimeter range

The influence of the rise time of the current pulse of a nanosecond high-current electron beam on the self-oscillation regime that is established in a relativistic backward-wave tube for the 38 GHz range is investigated experimentally. It is shown that a peak power of more than 50 MW is attained in a time of ∼300 ps.

38-GHz relativistic backward-wave tube based on a modulator with an inductive energy accumulator and a semiconductor current interrupter

The results of an investigation of a 38-GHz relativistic backward-wave tube with an output power up to 40 MW are presented. An electron-beam injector based on a 5-ns high-current pulsed periodic modulator with an inductive energy accumulator and a semiconductor current interrupter is used for the first time in experiments.

Nonlinear dynamics of a backward-wave tube under the condition of competition of two modes

We study the nonlinear dynamics of backward-wave tubes in the regime of interaction of an electron flux with two transverse modes. In the region where the threshold values of parameters are slightly exceeded, one can observe a stationary single-mode oscillation when the other mode is suppressed, which is in good agreement with experimental observations of the competition of two modes in the relativistic backward-wave tube. It is shown that nonlinear competition can lead to the establishment of a single-mode stochastic regime of oscillation in the wide range of parameters in which the conditions of stochastic self-modulation are fulfilled for each mode individually.

A possible method of reducing the magnetic field in a relativistic backward-wave tube

A new configuration is proposed and implemented for a relativistic backward-wave tube using the symmetric TM01 mode which can appreciably enhance, by a factor of 2–3, the generation efficiency of high-power 3 cm radiation pulses using low magnetic fields.