The possibility of using modern energy-intensive storage devices based on supercapacitors in relation to the tasks of powering magnetic systems of high-power microwave generators based on a relativistic backward wave tube (BWT) is described. Magnetic systems of such generators consist of a two-section solenoid. During the operation of the generator, a current of up to 700 A flows through the windings of a solenoid for few seconds. The magnetic system is powered from a capacitive storage device based on supercapacitor modules through step-down current regulators. Current stabilization is carried out by increasing the duration of the open state of the switches as the storage device is discharged. The control system contains a microprocessor that controls the power switches of current regulators as well as the management of the drive charging processes and interaction with peripheral devices. The work presents all the necessary formulas for calculating the parameters of the current regulator and estimating the storage capacity and its energy characteristics. Also, two variations for the implementation of similar power supplies are presented: the maximum output power of the first one is 280 kW with an output current duration of up to 1.5 s, and the maximum output power of the second one is 90 kW with an output current duration of up to 2.5 s.

Introduction. The magnetic systems of high power microwave generators, such as relati­vistic reverse wave lamps and klystrons, are powered with a direct current of up to 1 000 A from supercapacitor storage for several seconds. When designing power supplies for these magnetic systems, there is always necessary to determine the energy characteristics of the storage device. The analytical calculation of the characteristics is difficult, because of dynamic changes in some parameters of the magnetic system and storage device during current flow.Aim of the Study. The aim of the article is to create and experimentally test a mathematical model describing the process of powering a multi-section magnetic system with direct current from a supercapacitor storage device.Materials and Methods. The simulation takes into account the dynamic changes in the magnetic system parameters when current flows. The supercapacitor storage device is represented as a simple RC-circuit, the parameters of which are the nameplate data of its capacitance and internal resistance. The description of a storage device discharge process is based on the energy balance data. This model is implemented in the National Instruments LabView 2012 software package and has a user-friendly graphical interface. The simulation results were tested on equipment consisting of a power supply based on a supercapacitor storage device and two-section magnetic system.Results. The simulation results showed a good agreement with the experimental ones. According to the experiment results, the waveform of the current and voltage of the sto­rage device, and the maximum duration of current stabilization were close to the simulation results. At the same time, the nameplate data of the capacity and internal resistance of the storage device characterize well its real parameters, taking into account the peculiarities of working together with the current regulator and the pulsed nature of energy consumption.Discussion and Conclusion. The slight difference in the results is explained by the deviation of the actual parameters of the storage device from its passport data and by the diffe­rence in the temperature of the windings used in the experiment and simulation. The calculation of the energy characteristics of the storage device is performed on the basis of the energy balance, which allows scaling the load through adding any number of energy consumers with independent current stabilization in each.

The paper considers such modifications of an ordinary pulse-forming line (PFL) as double-width and triple-width forming lines (DWFL, TWFL) built around the PFL by nesting one and two additional uncharged lines, respectively, into its free volume inside the inner conductor of the PFL. The theoretical analysis is supported by simulation and experimental data, showing that the TWFL provides a 3-fold increase in the voltage pulse width and that it can be further increased by an arbitrary integer factor k. The results of the numerical simulations also show the electric field behavior and other features, including the edge effect in the TWFL. The proposed method opens up new opportunities for designing compact high-power microwace (HPM) sources.

This letter describes a recent activity in the development of a high-power microwave source based on a modified relativistic backward wave oscillator that is driven by an advanced version of a SINUS-family accelerator using a double-width pulse-forming line insulated with a modern synthetic oil. The relatively compact source of microwave pulses (0.6 GW, 20 ns, 9.4 GHz) can operate at a 100 pps repetition rate in a batch mode with batches of duration up to 15 s. The long-term stability of the oscillator performances during $10^{{6}}$ pulses was achieved due to the improved conditions for explosive emission of the graphite cathode and the use of a titanium slow wave structure. Both factors prevented the shortening of the microwave pulses. With a proper choice of the magnetic field strength and longitudinal distribution and of the position of the resonant reflector, the pulse-to-pulse deviation of the microwave power was reduced with sacrifice in efficiency, which decreased from a simulated maximum efficiency of 44% to 40% in the simulation and to 35 ± 4% in the experiment. At an accelerating voltage of 418 kV and a magnetic induction of 0.64 T at the cathode, the standard deviation of the microwave pulsed power could be close to the voltage deviation.

We propose and study a scheme of a microwave pulse generator operating in the frequency ranges near 37 and 73 GHz, in which the electron interaction with both the (−1)st harmonic of the counterpropagating TM02 mode and the synchronous slowed-down TM01 mode is combined in a sectionalized slow-wave system with an average diameter of 2.5λ. An efficient current modulation at the input of the slow-wave system is ensured in the region of the cathode–anode gap and the matching section, which reduces the diffraction loss of the energy flow directed towards the cathode. Numerical modeling shows that the efficiency of converting the electron-beam power to microwave radiation is up to 50%. Experiments demonstrate a stable regime of generation of subgigawatt pulses at an efficiency of more than 40% in the upper part of the millimeterwavelength range, which have a reproducible spatial wave structure corresponding predominantly to the TM01 mode at the input of the emitting horn.

A wide-aperture (16 cm × 27 cm) source of e-beams for sterilization of plastic packages based on a“SINUS- 320” high-current accelerator with 450 keV energy, 9 kA current, 12 ns pulse duration, and repetition rate up to 100 Hz is described. A metal-dielectric cathode forms e-beam by explosive emission during a few nanoseconds of the voltage pulse. A high degree of e-beam uniformity can be achieved because of a large number of triple points (~800) and of electron scattering in a foil and in a 3 cm air layer for characteristic electron free paths in air up to half a meter.

In the experiment with an electron energy of ≈500 keV, the long-pulse (~300T, where T is the oscillation period) the generation regime of a relativistic Cherenkov microwave oscillator without a guiding magnetic field at a carrier frequency of 3.8 GHz has been obtained. A high-power microwave radiation pulse length of ~75 ns, a peak generation power of 210 ± 30 MW, and a power conversion efficiency of 9 ± 2% were attained.

Генерация импульсов СВЧ излучения с несущей частотой 3.8 GHz и длительностью 75 ns релятивистским черенковским СВЧ генератором без ведущего магнитного поля

This paper presents the results of numerical and experimental study of a Ka-band relativistic Cherenkov oscillator with average diameter of the slow-wave structure D approximate to 2.6 lambda. (lambda is a wavelength). The combined mode selection including the diffraction loss in the electron diode was applied. The high-current accelerator SINUS-200 provided the thin-walled annular electron beam in the range of voltages 350-420 kV and currents of 2.9-3.8 kA at pulse width of 10 ns. The generation of 2.5-3-ns pulses at the central frequency 36.4-36.8-GHz and 400-600-MW output microwave peak power was realized. The corresponding efficiency of 42% +/- 5% in power conversion has been obtained.

The design and research results for a high-power source of ultra-wideband radiation with a nineelement array excited by a bipolar high-voltage pulse with 2-ns duration are presented. The radiation pulses with an effective potential of 1 MV at a pulse repetition rate of 100 Hz were obtained.

This paper presents the results of an experimental study of a relativistic traveling wave oscillator with a tubular electron beam of enlarged cross section. Repetitively pulsed (30 Hz) generation of 10.1-GHz, 80-ns microwave pulses in 1-s batches is realized. The microwave pulse power a level of quasi-steady-state oscillation was 220 +/- 44 MW. The driving electron beam (370-keV, 2.4-kA, 107-ns pulsewidth) was transported along the interaction space by a quasi-constant (few seconds in duration) external magnetic field with an induction of 0.6 T. The power efficiency of the generator is 25% +/- 5%. The energy in a single microwave pulse is about 15 J as measured with an aperture calorimeter.

The stability of the microwave radiation phase of A relativistic coaxial backward-wave oscillator with a modulating reflector relative to a fixed voltage at a rising edge of the feeding high-voltage pulse is shown. At a carrying frequency of 1.3 Ghz, the standard phase deviation in a series of 50 consecutive pulses was not more than 20 ps for the microwave pulse duration of 80 ns.

The paper deals with the application features of capacitive probes for subnanosecond voltage pulse measurements. The relation for the amplitude of distortions determined by the finite electrical length of a capacitive divider was obtained. This relation could serve for quantitative estimation of capacitive divider suitability. Probes of various designs were used for recording the high voltage pulses with subnanosecond voltage changes. The pulse shapes with voltage change durations of 0.2 - 20 ns from different voltage probes were compared. It was shown that the use of capacitive divider with high- and low-voltage arms filled with the same material is more appropriate. This divider provides the same voltage ratio for voltage changes of durations from tens to fractions of nanoseconds.

The effective 1-s batch of 100-Hz pulse repetition rate mode of an X-band relativistic backward-wave oscillator with a resonance reflector (RBWO-RR) was realized using the “SINUS” pulse-periodic nanosecond accelerator allowing mechanically installed high voltage pulse length of 13 and 42 ns. Magnetic held about of 2 T was produced by two-section solenoid to transport the electron beam along RBWO-RR electrodynamic system. T M 01 to T E 11 mode converter connected to the oscillator output allowed Gaussian radiation pattern. The microwave oscillator allowed producing the microwave pulse length of 4.7 and 29 ns. The energy of the microwave pulse measured by the X-band aperture calorimeter was 1.4 or 6.3 J corresponding to the mentioned above microwave pulse length of 4.7 or 29 ns, respectively. That allowed estimations of the microwave peak power as high as 280 ± 30 MW and 210 ± 20 MW related to the pulse lengths. The efficiency of the oscillator was 23-25%. A possibility of the microwave pulse length fine tuning within 25 to 34 ns range in the “long pulse mode” by changing the solenoid magnetic held conhguration was shown.

We study the generation of electromagnetic pulses with a carrier frequency of 3.7 GHz in a relativistic backward-wave oscillator with a long slow-wave system in the superradiance regime of super-radiation for a magnetic induction of 0.2 T (below the cyclotron resonance). To decrease transverse velocities of the electrons, we use decompression of a hollow electron beam. Decompression in combination with a sharp leading edge of the high-voltage pulse (460 kV) applied to the explosive-emission cathode are used for increasing the cathode lifetime and improving the azimuthal uniformity of the beam. As a result, the achieved peak power of the microwave radiation amounts to 800 MW for a pulse duration of 2.5 ns and a repetition rate of 100 Hz. The uninterrupted operation in such a regime determined by the lifetime of the explosive-emission cathode is increased up to 10 5 –10 6 pulses. The efficiency of conversion of the electron-beam power into the electromagnetic-wave power is increased up to 50%, The possibility of locking the electromagnetic oscillations phase by a sharp edge of the high-voltage pulse at the cathode was observed for the first time in such a relativistic generator.

An excimer laser system having an output aperture diameter of 40 cm and consisting of five lasers, three of which are excited by an electric discharge and the remaining two by an electron beam, is built. The first laser produces a 308-nm radiation with a duration of 200—250 ns, a spectral linewidth of 0.9 cm-1 and the beam divergence close to the diffraction limit. This pulse is amplified in the active media of the other lasers. As a result, radiation with an energy of 5 J, spectral linewidth 0.9 cm-1 and beam divergence 37 μrad is produced at the output of the third laser. The output energy of the entire system amounts to 330 J and the pulse duration is 200—250 ns.

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 (10(6) 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.

Sources of high-power ultrawideband electromagnetic pulses are described. They consist of a generator of single-polarity pulses, a bipolar pulse former, and a radiating system, for which either a single antenna or a 16-element antenna array is used. The values of the effective potential E p R = 440 kV for the single antenna and 1.7 MV for an array excited by a bipolar pulse with a duration of 2 ns and a repetition rate of 100 Hz are obtained.