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ABSTRACT: Comparative studies of regularities in plastic deformation and fracture of the Hadfield polycrystalline steel upon quasi-static
tension, impact failure, and shock-wave loading with rear spall are performed. The SINUS-7 accelerator was used as a shock-wave
generator. The electron beam parameters of the accelerator were the following: maximum electron energy was 1.35 MeV, pulse
duration at half-maximum was 45 ns, maximum energy density on a target was 3.4·1010 W/cm2, shock-wave amplitude was ~20 GPa, and strain rate was ~106 s–1. It is established that the failure mechanism changes from ductile transgranular to mixed ductile-brittle intergranular one
when going from quasi-static tensile and Charpy impact tests to shock-wave loading. It is demonstrated that a reason for the
intergranular spallation is the strain localization near the grain boundaries containing a carbide interlayer.
KeywordsHadfield steel–spall fracture–high-current electron beam
Russian Physics Journal 05/2012; 53(10):1046-1052. · 0.41 Impact Factor
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ABSTRACT: The dynamics of breakup of the compressed state of an electron beam with a virtual cathode (VC) transported in a two-section
drift tube of a high-current electron accelerator has been studied. Based on the results of numerical simulations, the method
of partial capture of the injected beam current during the applied voltage pulse is proposed and implemented, which can ensure
the conditions necessary for the breakup of the electron beam compressed state. The VC velocity during the breakup of the
electron beam compressed state amounts to 6–8% of the velocity of light in vacuum. The experimental data qualitatively agree
with the results of analytical estimations and numerical simulations.
Technical Physics Letters 05/2012; 37(2):128-131. · 0.56 Impact Factor
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ABSTRACT: Features of the plastic deformation and dynamic spall fracture of Hadfield steel under conditions of shock wave loading at
a straining rate of ∼106 s−1 have been studied. The shock load (∼30 GPa, ∼0.2 μs) was produced by pulses of a SINUS-7 electron accelerator, which generated
relativistic electron bunches with an electron energy of up to 1.35 MeV, a duration of 45 ns, and a peak power on the target
of 3.4 × 1010 W/cm2. It is established that the spalling proceeds via mixed viscous-brittle intergranular fracture, unlike the cases of quasi-static
tensile and impact loading, where viscous transgranular fracture is typical. It is shown that the intergranular character
of the spall fracture is caused by the localization of plastic deformation at grain boundaries containing precipitated carbide
inclusions.
Technical Physics Letters 04/2012; 36(9):801-803. · 0.56 Impact Factor
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ABSTRACT: A two-section coaxial vircator with radial electron beam injection and electrodynamic feedback was developed. The use of electron beam premodulation in the vircator allows an increase in efficiency and ensures single-mode oscillation. The vircator operates with no external magnetic field, features a comparatively low operating impedance of the vacuum diode (10-15 Ω), and makes feasible wide-band frequency tuning through varying the resonator parameters. The vircator was simulated using the PIC-code KARAT. It is shown that, in a wide range of electron beam power (10-25 GW), the oscillation efficiency is 12%-15% and the frequency tuning bandwidth is 15 %. In the experiments on a compact linear transformer driver at a cathode voltage of 300 kV, diode current of 20 kA, and driving pulse duration of 250 ns, the single H<sub>11</sub> mode oscillation at 2.2 GHz with a 300-MW microwave peak power and 130-ns pulse duration at half the power level was realized.
IEEE Transactions on Plasma Science 11/2010; · 1.17 Impact Factor
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ABSTRACT: The operation of a double-gap S-band vircator has been investigated at submicrosecond duration of a high-current electron beam generated in a planar diode. The experiments were performed at accelerating voltages of les550 kV and diode currents of up to 17 kA using a radio-frequency cavity with a wide coupling window between its two sections. Three types of cathodes have been studied, namely, metal-dielectric, carbon fiber, and velvet cathodes. The main features of the operation of the vircator using each cathode are analyzed. The microwave pulse duration with the metal-dielectric and carbon fiber cathodes reached ~250 ns at the peak power level of ~100 MW; with the velvet cathode, a duration of ~400 ns was achieved. It has been found that, in addition to the common limitations of the microwave pulse duration related to the dynamics of the diode impedance governed by the cathode plasma expansion, there is another factor, namely, the anode-cathode gap, which determines the delay at the beginning of the microwave generation. The latter effect is explained by the role of electrons oscillating between the virtual and real cathodes in the generation process. The issue of radiated microwave frequency behavior is discussed as well.
IEEE Transactions on Plasma Science 08/2009; · 1.17 Impact Factor
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ABSTRACT: In experiment, mechanical pulse-to-pulse frequency tuning was realized in a repetitively pulsed (1 s, 50 Hz) relativistic backward-wave oscillator with a resonant reflector in a 0.36-T magnetic field. The tuning bandwidth was ~ 9% at a level of -3 dB of microwave peak power. The microwave peak power in a batch was 2.5 plusmn 0.6 GW at a frequency of ap3.6 GHz, an efficiency of 20% plusmn 4%, and a microwave pulsewidth of ~ 20 ns.
IEEE Transactions on Plasma Science 11/2008; · 1.17 Impact Factor
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ABSTRACT: We present the results of investigations of a resonance S-band relativistic backward wave oscillator (RBWO) that employs a
submicrosecond pulsed high-voltage source based on a Marx generator scheme with a water-filled pulse-forming line. It is shown
that the spontaneous limitation of the microwave pulse duration in the RBWO is caused by the emission of charged particles
from plasma generated at the surface of a slow-wave system under the action of intense high-frequency fields. An increase
in the electric strength of the electrodynamic system of the resonance RBWO, which was achieved by processing the surface
with a high-current low-energy electron beam, allowed the pulse energy to be increased to 250 J at a peak output radiation
power of about 3 GW.
Technical Physics Letters 06/2008; 34(7):581-583. · 0.56 Impact Factor
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ABSTRACT: An electron beam with a virtual cathode (VC) transported in a two-section drift tube of a SINUS-7 high-current electron accelerator
has been studied. The dependence of the VC velocity on the injected current has been experimentally determined for the first
time. It is established that the VC motion in the drift tube is accompanied by microwave oscillations, which are caused by
transient processes involved in the formation of a compressed electron beam.
Technical Physics Letters 06/2008; 34(7):546-548. · 0.56 Impact Factor
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ABSTRACT: Effective generation regime with a high output pulse power has been experimentally realized in a relativistic backward wave
oscillator (RBWO) with a resonant reflector and a slow-wave system having a diameter 1.6 times the radiation wavelength. At
a guiding magnetic field of 4.5 T, the maximum peak power amounted to 4.3 GW at a frequency of 9.4 GHz, an efficiency of 31%,
and a microwave pulse duration of 22 ns.
PACS numbers07.57.Hm
Technical Physics Letters 03/2008; 34(3):235-237. · 0.56 Impact Factor
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ABSTRACT: We have studied a periodic pulse train regime (1 s, 50 Hz) of a relativistic backward wave oscillator with a resonant reflector,
which can be mechanically tuned from pulse to pulse within a frequency band of 9% on a level of −3 dB of the maximum in the
entire microwave peak power range in a magnetic field of 0.36 T. The maximum peak power in a pulse train amounted to 2.5 GW
at a frequency of 3.6 GHz, an efficiency of 20%, and a microwave pulse duration of 20 ns.
Technical Physics Letters 11/2007; 33(12):1057-1060. · 0.56 Impact Factor
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ABSTRACT: The electron beam transported in a two-section drift tube of a SINUS-7 setup has been studied. A high-density electron beam
in the “squeezed” state has been obtained with a relativistic factor γb below that corresponding to the limiting current (γ > Γ1/3).
Technical Physics Letters 10/2005; 31(11):982-985. · 0.56 Impact Factor
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ABSTRACT: High-power microwave radiation has been generated using a relativistic backward wave oscillator (BWO) powered by a high voltage
source comprising an inductive energy storage and an electric-explosion current switch. The high voltage source and the BWO
magnetic system are energy pumped by explosive magnetocumulative generators. In experiments, the proposed setup generated
30-ns single-mode radiation pulses with a carrier frequency of 3.6 GHz at an output power of 0.75 GW.
Technical Physics Letters 08/2005; 31(9):775-778. · 0.56 Impact Factor
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ABSTRACT: The output current I
out of a magnetized annular electron beam transported in a homogeneous drift tube of a SINUS-7 setup has been studied as a function
of the injected beam current I
inj. The electron beam was injected via an anode inset of smaller radius and had a current above the Fedosov limit for the given
drift tube (I
inj ≥ I
F). It is established that, to within the experimental uncertainty, a virtual cathode (VC) is formed when the injected beam
current exceeds the corresponding limiting I
lim. In this state, the current transmitted behind VC is approximately equal to the limiting value (I
out ≈ I
lim).
Technical Physics Letters 12/2004; 31(1):55-57. · 0.56 Impact Factor
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ABSTRACT: The advent of pulsed power technology in the 1960s has enabled the development of very high peak power sources of electromagnetic radiation in the microwave and millimeter wave bands of the electromagnetic spectrum. Such sources have applications in plasma physics, particle acceleration techniques, fusion energy research, high-power radars, and communications, to name just a few. This article describes recent ongoing activity in this field in both Russia and the United States. The overview of research in Russia focuses on high-power microwave (HPM) sources that are powered using SINUS accelerators, which were developed at the Institute of High Current Electronics. The overview of research in the United States focuses more broadly on recent accomplishments of a multidisciplinary university research initiative on HPM sources, which also involved close interactions with Department of Defense laboratories and industry. HPM sources described in this article have generated peak powers exceeding several gigawatts in pulse durations typically on the order of 100 ns in frequencies ranging from about 1 GHz to many tens of gigahertz.
Proceedings of the IEEE 07/2004; 92(7):1082 - 1095. · 6.81 Impact Factor
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ABSTRACT: 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.
Technical Physics Letters 02/2003; 29(3):259-261. · 0.56 Impact Factor
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ABSTRACT: In this paper, we present the results of numerical and experimental studies of a resonant relativistic backward-wave oscillator. Using reflections of the operating TM01 mode from the ends of an electrodynamic system, optimal conditions for the interaction of an electron beam with both the backward (-1)st-order spatial harmonic and the forward fundamental harmonic are reached. Single-mode oscillations at 3.6GHz with a peak pulse power of 5GW and an efficiency of 30% were obtained in the experiment. We show the possibility of a 15% oscillation-frequency change corresponding to the FWHM power level by varying the period of a slow-wave structure at constant electron-beam parameters.
Radiophysics and Quantum Electronics 01/2003; 46(10):797-801. · 0.71 Impact Factor
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ABSTRACT: This paper describes an S-band vircator system with electron beam premodulation, built on the base of the MARINA compact high-voltage pulser with inductive energy storage. The peak microwave output was ∼1 GW with ∼5% power efficiency and 50-ns full-width at half-maximum. The microwave frequency was constant during the pulse as determined by the resonator. Substantial spontaneous shortening of the microwave pulse was observed. Possible mechanisms for this phenomenon are discussed and supported by three-dimensional KARAT simulations.
IEEE Transactions on Plasma Science 07/2002; · 1.17 Impact Factor
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ABSTRACT: Theoretical, numerical, and experimental studies of a vircator with the premodulation of a dm-wave electron beam are performed.
Possible oscillation mechanisms in virtual-cathode systems (modulation of passing current, effect of reflex klystron, and
inertial bunching of particles reflected) are analyzed. The microwave efficiency of the vircator using a two-gap electrodynamic
system is shown to be significantly higher than that of the vircator with a one-gap system. Based on the results of the numerical
experiment, a prototype of a two-stage vircator in the absence of an external magnetic field is designed. In experiments using
a high-current pulsed-periodic accelerator, single-mode oscillations with a power of up to 1 GW, a duration of ≈25 ns, and
an efficiency of ≈5% are generated in the dm-wave range. The oscillation frequency is demonstrated to be stable during a pulse
and from pulse to pulse, which suggests the decisive effect of the electrodynamic system. It is shown that the oscillation
frequency can continuously be tuned in a half-power bandwidth of ≈15% by varying the parameters of the resonator.
Technical Physics 04/2002; 47(5):595-603. · 0.50 Impact Factor
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ABSTRACT: The paper describes theoretical, numerical, and experimental
studies of a decimeter wavelength vircator with electron beam
premodulation. Possible mechanisms for the excitation of electromagnetic
oscillations in virtual cathode systems are analyzed (modulation of
current, reflex klystron effect, and inertial bunching of reflected
particles). It is demonstrated that the microwave efficiency in a
double-gap virtual-cathode system may be substantially higher than that
in a single-gap one. Based on one- and three-dimensional numerical
simulations, an experimental mockup of double-gap vircator without
external magnetic field has been developed. In experiments employing the
SINUS-7 high-current repetitively-pulsed electron accelerator,
single-mode microwave generation in the S-band was obtained with ~1 GW
peak power and ~25 ns pulse width at about 5% efficiency. The generator
showed frequency stability from pulse to pulse and throughout each
pulse, which proves the dominant role of the electrodynamic system used
in the vircator construction. Varying the cavity parameters allowed
continuous frequency tuning within about 15% at half power. Sample batch
operation of the system at 20 and 50 p.p.s. was demonstrated
IEEE Transactions on Plasma Science 03/2002; · 1.17 Impact Factor
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A. M. Efremov,
A. A. Zherlitsyn,
S. A. Kitsanov,
A. I. Klimov,
S. D. Korovin,
B. M. Koval’chuk,
I. K. Kurkan,
O. P. Kutenkov,
S. V. Loginov,
I. V. Pegel’, S. D. Polevin
[show abstract]
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ABSTRACT: An experimental S-band vircator with premodulated electron beam based on a compact generator with inductive energy storage
is described. The vircator radiation power was 300 MW at a power efficiency of about 5% and a pulse duration of 50 ns. The
oscillation frequency, determined by the electrodynamic system parameters, remained unchanged during the pulse.
Technical Physics Letters 03/2001; 27(4):289-291. · 0.56 Impact Factor
