Nonrelativistic Electron Beam Research Articles

Effect of positive ions on the microwave generation in a low-voltage vircator

The effect of vacuum conditions on the characteristics of microwave generation in a nonrelativistic electron beam with a virtual cathode (VC) formed in a retarding field (low-voltage vircator) has been experimentally studied. The ionization of residual gases in the working chamber of a low-voltage vircator leads to displacement of the VC out of the interaction space, which results in breakdown of the microwave generation. The experimental data agree with the results of numerical simulations.

The theoretical simulation of magnetized electron beam effects on radially polarized of an annular cylindrical piezoelectric crystal

By using the equilibrium equations for a hollow cylindrical piezoelectric layer in absence of body forces and taking into the account a magnetized electron beam in hollow region of this system the effects of thermal pressure, electrostatic self field and the strength of external magnetic field of a non-relativistic magnetized electron beam column on radially polarized of an annular cylindrical piezoelectric crystal in the steady state are simulated. The electrostatic potential profile in piezoelectric layer due to the mechanical pressure and electrostatic self field of electron beam are studied. Furthermore the graphs of the difference of potential Δ ϕ between inner and outer surfaces of piezoelectric versus to electron temperature, density of beam and the strength of external magnetic field are presented.

Microwave generation power in a nonrelativistic electron beam with virtual cathode in a retarding electric field

The power of microwave generation in a nonrelativistic electron beam with virtual cathode formed in a static retarding electric field (low-voltage vircator system) has been studied experimentally and by means of numerical simulation within the framework of a one-dimensional theory. The limits of applicability of the one-dimensional theory have been experimentally determined.

Three-dimensional theory and simulation of nonrelativistic elliptic electron and Ion beam generation

Summary form only given. A theory of non-relativistic, laminar, space-charge-limited, ellipse-shaped charged-particle beam formation is presented. In the elliptic diode, electrons or ions are accelerated by a static voltage differential and transversely focused by external electrodes. The electrode surfaces are derived as equipotentials external to the beam using a Laplace transform - Mathieu function formulation of the electrostatic potential. Three-dimensional simulations utilizing the trajectory code OMNITRAK are performed, confirming the analytic predictions of a high-quality, laminar beam. The elliptic diode can aid in the design of high-efficiency sheet-beam microwave sources as well as in heavy ion beam devices. In particular, the theory is applied to the design of a 6:1 elliptic electron beam for a 200 W, 2 GHz amplifier. It is also applied to the design of a 3:2 elliptic heavy ion beam for high-energy density physics research. For these applications, the theoretical treatment of the diode is extended to consider the perturbative effects of anode hole lensing and finiteness and nonuniformities of beam-forming electrodes. Considerations with regard to beam matching into a periodic magnetic focusing lattice are also discussed

Experimental and theoretical investigations of stochastic oscillatory phenomena in a nonrelativistic electron beam with a virtual cathode

Results are presented from experimental investigations of oscillatory phenomena in an electron beam with a virtual cathode in a diode gap with a decelerating field. Experiments have revealed a stochastic broadband generation of the microwave oscillations of a virtual cathode in a decelerating field. Numerical simulations based on a simple one-dimensional model have shown that the onset of the stochastic generation and the broadening of the oscillation spectrum with increasing beam deceleration rate are governed by the processes of regrouping of the electrons in a beam with a virtual cathode.

The Electromagnetic Sector of the Evans Field Theory

The equations of the electromagnetic sector of the Evans field theory are given in terms of differential geometry and are based on the well-known structure relations and Bianchi identities. The equations thus complete Einstein’s basic axiom, that physics is derived from geometry, and extend the axiom to electrodynamics. Precise tests are suggested for the theory using the interaction of circularly polarized electromagnetic radiation with a non-relativistic electron beam. These tests include; the inverse Faraday effect (IFE), radiatively induced fermion resonance (RFR), and the electromagnetic Aharonov-Bohm (EMAB) effect.

Interaction of an Electron Beam with Electromagnetic Waves in a Rectangular Plasma Waveguide

We study the interaction of a rectilinear nonrelativistic electron beam with a solid-state plasma in a rectangular metal waveguide, as well as wave processes in a plasma waveguide of rectangular cross section in the absence of an electron beam. It is shown that in such a system, space-charge waves of an electron beam, which propagate along a semiconductor boundary, become unstable in a wide frequency band.

On Possible Mechanism of Spontaneous Radiation from Non-Relativistic Free Electron Beam in the Motz Undulator

On Possible Mechanism of Spontaneous Radiation from Non-Relativistic Free Electron Beam in the Motz Undulator

Pulsed Orotron—A new microwave source for submillimeter pulse high-field electron paramagnetic resonance spectroscopy

A vacuum-tube device for the generation of pulsed microwave radiation in the submillimeter range (up to 380 GHz) is presented, designed for use as a source in a 360 GHz high-field/high-frequency electron paramagnetic resonance (EPR) spectrometer—the pulsed Orotron. Analogous to the known continuous wave (cw) version, in the pulsed Orotron microwave radiation is generated by the interaction of a nonrelativistic electron beam with a diffraction grating (stimulated Smith–Purcell radiation) in feedback with an open Fabry–Pérot resonator construction. The presented design extends the cw Orotron by a gate electrode and a high-voltage pulsing unit to control the electron beam current. The generated pulses at 360 GHz have pulse lengths from 100 ns–10 μs and a pulse power of (22±5) mW. The output in a broader frequency band between 320 and 380 GHz ranges from 20 up to 60 mW. Within a 10 μs time slot, incoherent pulse trains of arbitrary duration can be generated. The pulsed Orotron has been incorporated in the quasioptical microwave bridge of a heterodyne induction mode EPR spectrometer. The first free induction decay measurements at a microwave frequency of 360 GHz and a magnetic field of 12.8 T on a polycrystalline perylenyl–ion sample are presented and future applications and extensions of Orotron-EPR spectroscopy are discussed.

Nonlinear theory of the collective Cherenkov interaction of a dense relativistic electron beam with a dense plasma in a waveguide

A nonlinear theory of the instability of a straight relativistic dense electron beam in a plasma waveguide is derived for conditions of the stimulated collective Cherenkov effect. A study is made of a waveguide with a dense plasma such that the plasma wave excited by the beam during the instability can be escribed, with a good degree of accuracy, as a potential wave. General relativistic nonlinear equations are btained that describe the temporal dynamics of beam-plasma instabilities with allowance for plasma nonlinearity and the generation of harmonics of the initial perturbation. Under the assumption that the resonant interaction between the beam waves and the plasma waves is weak, the general equations are reduced to relativistic equations with cubic nonlinearities by using the method of expansion in small perturbations of the trajectories and momenta of the beam and plasma electrons. The reduced equations are solved analytically, the time scales on which the instability saturates are determined, and the nonlinear saturation amplitudes are obtained. A comparison between analytical solutions to the reduced equations and numerical solutions to the general nonlinear equations shows them to be in good agreement. Nonlinear processes caused by the relativistic nature of the beam are found to prevent stochastization of the system in the nonlinear stage of the well-developed instability. In contrast, a nonrelativistic electron beam is found to be subject to significant anomalous nonlinear stochastization.

Nonlinear oscillations of a semiconductor plasma with a nonrelativistic electron beam

Nonlinear oscillations of a semiconductor plasma with a low-density electron beam in the absence of an external magnetic field are studied in the hydrodynamic approximation. The beam is assumed to be nonrelativistic and monoenergetic. Cases are studied in which the Langmuir frequency of the electron oscillations in a semiconductor is much higher or much lower than the electron momentum relaxation rate. The self-similar solution obtained for the first case describes the damping of the nonlinear oscillations of the wave potential. Numerical analysis of the second case shows that the electric field distribution in the beam may correspond to that in a shock wave.

Interaction of a long pulsed high-density electron beam with a jet of solid-target destruction products

Results are presented from experimental studies of the destruction of a solid target by a high-density nonrelativistic electron beam at a deposited power density of 20 MW/cm2 in millisecond pulses. Results of studying beam transportation under these conditions are presented as well.

Cherenkov Excitation of Spatial Waves by a Straight Nonrelativistic Electron Beam in a Plasma Waveguide

The problem of the excitation of plasma waves by a thin-walled annular electron beam in a waveguide filled entirely with a plasma is analyzed in the quasistatic approximation. The instability growth rates are derived and are studied as functions of the waveguide parameters. The evolution of different seed perturbations in the nonlinear stage of the instability is investigated.

Nonlinear theory of resonant beam-plasma interaction: Nonrelativistic case

Analytic and numerical methods are used to study the nonlinear dynamics of the resonant interaction between a dense nonrelativistic electron beam and a plasma in a spatially bounded system. Regimes such as collective (Raman) and single-particle (Thomson) Cherenkov effects are considered. It is shown that in the first case, the motion of both the beam and plasma electrons exhibits significant nonlinearities. However, because of the weak coupling between the beam and the plasma, the nonlinear dynamics of the instability can be studied analytically and it can be strictly shown that saturation of instability is caused by a nonlinear shift of the radiation frequency and loss of resonance. In the second case, the nonlinear instability dynamics can only be studied numerically. In this regime, at low beam densities significant nonlinearity is only observed in the motion of the beam electrons while the plasma remains linear and saturation of the instability is caused by trapping of beam electrons in the field of the beam-excited plasma wave.

Panoramic measurements of electron beam densities by Thomson scattering of laser radiation

The possibility of using a panoramic detector with a television signal-recording system in an apparatus to observe Thomson scattering of laser radiation by a nonrelativistic electron beam is discussed. Panoramas of Thomson and Rayleigh scattering and of the electron beam luminescence are presented. Estimates are given of the sensitivity and spatial resolution of the apparatus. Results of panoramic and single-point methods of investigation are compared. Possibilities for extending the range of the Thomson scattering method to measure the density distribution in nonrelativstic electron beams are discussed.

Comparison between the Landau and Cyclotron Resonances in the Electron Beam-Plasma Interactions

It is well-known that a cool field-aligned electron beam streaming in a plasma can destabilize electrostatic waves, in the frequency ranges of 0<ω< m i n (Ω e ,ω p ) and m a x (Ω e ,ω p )<ω<ω uh , where ω p , Ω e , and ω uh are the plasma, the electron cyclotron, and the upper-hybrid frequencies, respectively. Although both the Landau and cyclotron resonances lead to the generation of the waves, not much attention has been paid to the wave generation via the cyclotron resonance. In this paper we compare the two types of interactions for both non-relativistic and relativistic electron beams by considering a simple plasma model which consists of main and beam electrons and background ions. The plasma is charge neutral and current carrying. The linear theory based on this model predicts that, when the electron beams are non-relativistic, the waves are generated predominantly via the Landau interaction for a wide range of plasma parameters, except for a limited parameter regime with cool main electrons, Ω e /...

Vacuum insulation and discharge phenomena in high-power devices with magnetic confinement of electron flow

Results of the experimental investigation of processes determining vacuum insulation maintenance and discharge phenomena in high-power crossed-field and electron-beam devices are presented. Data from crossed-field devices on accumulation and steady-state parameters of the space charge between cold cathode and anode, spatial, temporal and energy characteristics of electron flows onto surrounding electrodes are given. Techniques of gun breakdown prevention and formation of a dense nonrelativistic long-pulsed electron beams with energy density /spl les/100 kJ/cm/sup 2/ are described, as well as the effect of RF discharge development on the beam transport in this system. Models of observed phenomena considering the effect of nonuniform electromagnetic fields, oscillatory processes and generation of secondary particles accompanying electron bombardment of electrodes are also proposed.

Ion sound wave excitation in a plasma under a Langmuir turbulence regime

Ion sound wave excitation in a warm non-relativistic ( W b ≤ 400 eV) electron beam unmagnetized plasma system is studied experimentally. The spectrum of these waves shows two peaks at frequencies of 70 and 230 kHz respectively. The origin of these waves is connected with modulational instability and cavity collapse. We show that the energy of bulk accelerated electrons can explain the measured value of kr De for high-frequency sound waves. The energy of ion sound waves is not high enough to have an influence on the Langmuir turbulence dynamics.

Polarization Effects in Current Deposition During Excitation of Cherenkov Radiation by a Nonrelativistic Electron Beam in an Isotropic Dielectric

Polarization Effects in Current Deposition During Excitation of Cherenkov Radiation by a Nonrelativistic Electron Beam in an Isotropic Dielectric

Polarization effects of electron current settling when the cerenkov radiation is excited by a nonrelativistic electron beam in an open dielectric resonator

We study the effect of electron current settling of a strip nonrelativistic electron beam (EB) on the Cerenkov radiation (CR) in a metal-dielectric channel formed by the metal surface and the surface of a rectangular open dielectric resonator having isotropic properties and operated at millimeter wavelengths (3.6–5.8 mm). The choice of this channel was substantiated by theoretical studies of the CR energy density. We experimentally examined several effects, including the neutralization of the dielectric surface dipole charge by electrons, the accumulation of electron charge at the dielectric surface, and the influence of the electron charge on the EB and CR. Conclusions are drawn on the prospects of using short pulses of EB and special metal-dielectric diffraction gratings for the excitation of CR.