The Radiation Spectrum of a Classical Electron Moving in a Radiation-Dominated Universe

The motion and radiation of a classical electron in a conformally flat Robertson–Walker space, which corresponds to the quasi-Euclidean model of a radiation-dominated universe, is considered. The spectral-angular distribution of the energy radiated by the electron is found; the dependence of the spectrum on the momentum of the electron is investigated; estimates for the coherence interval are given. The results obtained show that the radiation spectrum of a classical electron coincides with the quasiclassical limit of the spectral distribution of the photons radiated by a Dirac electron moving in a radiation-dominated universe.     

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field

The conductivity of a two-dimensional electron gas in a parallel magnetic field is calculated. We take into account the magnetic-field-induced spin-splitting, which changes the density of states, the Fermi momentum, and the screening behavior of the electron gas. For impurity scattering, we predict a positive magnetoresistance for low electron density and a negative magnetoresistance for high electron density. The theory is in qualitative agreement with recent experimental results found for Si inversion layers and Si quantum wells.     

Observation of enhanced prebreakdown electron beams in a vacuumspark with a hollow-cathode configuration

The generation of prebreakdown electron beams in a low-energy vacuum spark with a hollow-cathode configuration is observed under a range of experimental conditions. The vacuum spark studied is powered by either a 25-kV, 3.3-nF single capacitor discharge or a two-stage, 50-kV, 1.65-nF Marx. The electron beams are detected by observing the X-ray emission from the anode tip produced by electron impact. Results show that an electron beam is formed well before the onset of the electrical breakdown. This prebreakdown electron beam has an initial slow buildup phase followed by an exponential rise, leading to the breakdown of the discharge. This behavior of the electron beam evolution is in good qualitative agreement with the model simulation of the pseudospark phenomenon obtained for a transient hollow-cathode discharge     

Monte carlo analysis of a free electron laser in a storage ring

This paper contains studies of the operation of a one-dimensional storage ring free-electron laser (FEL) using a Monte Carlo technique to generate the electron energy fluctuations produced by the FEL. The energy and phase equations of motion have been numerically integrated to calculate equilibrium values of: a) electron energy spread, b) electron phase spread (e.g. electron bunch length), and c) efficiency of conversion of electron energy into laser radiation. The operation of the storage ring free-electron laser was studied for five different FEL magnet designs. It is found that a “one-dimensional” storage ring free-electron laser can operate on a steady-state basis only with reduced overall efficiency due to the inability of the system to damp effectively the electron energy fluctuations produced by the FEL. Results of operation of a SRFEL in a pulsed mode are also presented. Work supported by U.S. Army BMD-ATC, under contract number DASG 60-77-C-0083.     

Quantum electron self-interaction in a strong laser field

The quantum state of an electron in a strong laser field is altered if the interaction of the electron with its own electromagnetic field is taken into account. Starting from the Schwinger-Dirac equation, we determine the states of an electron in a plane-wave field with inclusion, at leading order, of its electromagnetic self-interaction. On the one hand, the electron states show a pure quantum contribution to the electron quasimomentum, conceptually different from the conventional classical one arising from the quiver motion of the electron. On the other hand, the electron self-interaction induces a distinct dynamics of the electron spin, whose effects are shown to be measurable in principle with available technology.     

Amplification of light during the scattering of a relativistic electron by a nucleus in a moderately strong field of a circularly polarized light wave

The amplification (attenuation) factor of an electromagnetic wave during the scattering of a relativistic electron by a nucleus in a moderately strong field of a circularly polarized electromagnetic wave is studied theoretically. The effect of amplification of an electromagnetic field is discovered in a certain interval of polar angles of the incident electron; this interval of angles essentially depends on the electron energy and the field intensity. It is shown that the amplification of a field attains its maximum for nonrelativistic electrons in the range of medium fields. As the electron energy increases, the amplification decreases and vanishes for ultrarelativistic electrons. An increase in the field intensity for a given electron energy also leads to a slow decrease in the amplification of a field. At high intensities of the wave, the effect of amplification vanishes. It is shown that, in the range of optical frequencies for medium fields (F ～ 10⁶V/cm), the amplification factor of laser light may amount to about μ ～ 10^?1 cm^?1 for sufficiently high-power electron beams.     

Coherent inelastic electron reflection from a random medium with a sharp boundary

The weak localization of electrons inelastically scattered in a random medium with a sharp boundary is considered. An inelastic electron collision is accompanied by the excitation of a single bulk plasmon. The coherence of electron scattering results from the interference of electron waves related to two possible realizations of the process in which an electron excites a bulk plasmon and undergoes high-angle elastic scattering by chaotically arranged force centers. The sharpness of the boundary means that the statistically averaged length scale and depth of the surface mocroroughnesses are much smaller than the decay length of the wave field of fast electrons in the medium. The same condition is also imposed on the tail size of the electron density of the medium in vacuum. The theory developed makes it possible to determine the bulk-plasmon generation intensity by measuring the ratio of the electron fluxes inelastically and elastically reflected from the surface of a random medium. For this purpose, one should find the dependence of the ratio of these fluxes on three angles, namely, the polar angle of incidence of electrons, the polar angle of electron exit from the medium, and the azimuth angle between the projections of the velocities of the incident (v) and escaping (v′) electrons on the surface plane. Optimum conditions for the detection of this specific azimuth dependence are theoretically grounded for the case where both electron collisions occur in the near-surface region.     

Generating a low-energy high-current electron beam in a gun having a plasma anode

Research has been done on major physical processes governing the scope for generating magnetized low-energy high-current electron beams in a plasma-filled system. Conditions are considered for efficient excitation of the explosive electron emission at a large-area cathode at low accelerating voltages, together with the trends in beam formation in the nonstationary double layer formed between the cathode and anode plasmas, as well as the beam transport to the collector in the inhomogeneous guiding plasma. It is found that a gun having a plasma anode enables one to generate wide-aperture electron beams of microsecond duration having a mean electron energy of 10–20 keV and an energy density of up to 20 J/cm² or more, which goes with homogeneity sufficient for technological purposes.High-Current Electronics Institute, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh, Fizika, No. 3, pp. 100–114, March, 1994.     

Structural instabilities of a two-dimensional Wigner crystal in a lateral superlattice

We consider the instability of a two-dimensional Wigner crystal in a short-period lateral superlattice. To find instabilities, we calculate the phonon spectrum of the electron lattice deformed by a periodic potential. We show that one of the transverse modes of the deformed electron crystal becomes soft when the electron density exceeds a critical value. This can result in a phase transition with the formation of a charge-density wave.     

Emission of a photon by an electron in a radiation-dominant universe

The process by which a photon is emitted by an electron in a radiation-dominant universe is considered, under the assumption that an arbitrary number of pairs are produced from a vaccum. In a flat space this process is forbidden by the laws of conservation. The dependence of the probability and the mean number of created particles on the energy of the initial electron is investigated. In the limiting cases (initial electron with high or low energies), approximate expressions are found for the probability that a photon is emitted by an electron as well as for the total probability of the process, including production of photons and pairs from a vacuum. Approximate expressions are obtained for the mean number of particles that are produced in the course of inelastic scattering of an electron in the early Universe. Biy State Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 98–102, September, 1996.     

Excitation of a wake field by a relativistic electron bunch in a semi-infinite dielectric waveguide

A wake field excited by a relativistic electron bunch in a semi-infinite metal waveguide filled with a dielectric consists of the Vavilov-Cherenkov radiation, the “quenching”-wave field, and transient radiation, which interfere with each other. An exact analytic expression for the transient component of the field of a thin relativistic annular bunch is derived for the first time. The evolution of the space distribution of a field excited by a finite-size electron bunch is numerically calculated. The excitation of the wake field by a periodic train of electron bunches in a finite-length waveguide is studied.     

Completely bound motion of a positive-energy electron in the coulomb field of a motionless nucleus and a uniform magnetic field

We show that the completely bound classical motion of a positive-energy electron is realized in the Coulomb field of a motionless nucleus and a uniform magnetic field. Such a motion exists due to conservation of the so-called invariant tori in the phase space of the system for not only the negative, but also for the positive energy of an electron. The completely bound trajectories occupy a much larger interval of the velocity directions compared with free trajectories for the same energy in a range of distances from the nucleus in which the typical time of the electron transit near the nucleus is larger than the cyclotron-gyration period, while the negative energy of Coulomb interaction is larger (in absolute value) than the total electron energy. The indicated range of distances is realized in the case of a low electron energy or a strong magnetic field when the Larmor radius of the electron is smaller than the characteristic impact parameter of the close Coulomb collisions in the absence of a magnetic field. The required conditions are realized in the photospheres of isolated magnetic white dwarfs and in the experiments on creation of antihydrogen.     

Diagnostics of a hollow relativistic electron beam from the transfer function of a converting target

Methods for measuring angular, geometrical, and energy characteristics of a hollow relativistic electron beam using the transfer function of a converting target are developed. A relationship between the anisotropy parameters of bremsstrahlung behind the target, angular characteristics of electrons, and geometrical parameters of the electron beam in the target plane is established. The energy balance equation that describes the interaction between the electron beam and converting target is studied. The transfer function of the target and its behavior versus electron energy are found. The time and integral characteristics of the electron beam are examined.     

Magnetoplasma oscillations of a two-dimensional electron layer in a bounded system

The spectrum of magnetoplasma oscillations of a two-dimensional electron layer in a transversal magnetic field is studied under the condition that the electron system is unbounded along the layer plane and screened in the perpendicular direction. It is shown that under certain conditions oscillation frequencies much lower than the electron cyclotron frequency exist. Also the electromagnetic wave-guided oscillations in the system are described. It is shown that a strong magnetic field causes a frequency shift and splitting, depending inversely on the external magnetic field and the transversal specific dimension.     

Rapid formation of an electron beam in a magnetron gun with a secondary-emission metallic cathode

The initial stage of forming the electron sheath and electron beam generation in magnetron guns for the case when the secondary emission process is triggered by nanosecond pulses is considered. In the guns with small transverse sizes, tubular electron beams with an outer diameter of 4–6 mm and a current of 1–2 A are produced at a cathode voltage of 5–10 kV. It is shown that the formation of the electron cloud and beam current pulse front for a time of ≥2 ns is a possibility.     

Bound states of an electron and a macroscopic cluster at a liquid helium surface

In a strong electric field, there are bound states of an electron at the surface of liquid helium, interacting with a large cluster of atoms in the bulk of liquid. This phenomenon is related to long-range interaction between the electron and the dipole moment of the cluster. The electron, holding the cluster under the liquid surface, is localized at this surface. One electron is capable of binding a cluster of up to 10⁶ atoms. The value of the binding energy may reach up to several kelvins.     

Ground State of a Polaron in a Symmetric Triangular Quantum Well

We study the effects of electron-phonon interaction on the electron ground state in a symmetric triangular quantum well, and calculate the ground state energy of an electron in the GaAs/Al0.96Ga0.04As triangular quantum well including the effects of the interaction between electrons and confined LO phonons by using a modified Lee-Low-Pines variational method. The electron wavefunction in the triangular well is chosen as the Airy function. The numerical results are given and discussed.     

Photodetachment microscopy of a hydrogen negative ion in an electric field near a metal surface

According to the semi-classical theory, we study the photodetachment microscopy of H- in the electric field near a metal surface. During the photodetachment, the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector. The electron flux distribution is measured as a function of position. Two classical paths lead the ion to any point in the classically allowed region on the detector, and waves traveling along these paths produce an interference pattern. If the metal surface perpendicular to the electric field is added, we find that the interference pattern is related not only to the electron energy and the electric-field strength, but also to the ion-surface distance. In addition, the laser polarization also has a great influence on the electron flux distribution. We present calculations predicting the interference pattern that may be seen in experiment. We hope that our study can provide a new understanding of the electron flux distribution of negative ions in an external field and surface, and can guide future experimental research on negative ion photo-detachment microscopy.     

Studying the possibility of building a single-electron transistor based on a molecule with a monatomic charge center

The single-particle electron energy spectrum and total electron energy spectra of a hydrogenically passivated central fragment of a coordination compound of rhodium with an aurophile terpyridine derivative (CCRATD) in different charge states ranging from–3e to +3e are obtained. The electron transport characteristics for a single-electron molecular transistor based on a CCRATD molecule are calculated and analyzed.     

Oblique Electron Thermal Waves in a Magnetized Plasma

Propagations of an oblique electron thermal mode under the electron plasma frequency without boundary effects are investigated experimentally and theoretically in a magnetized plasma. The phase, ray, and group velocity surfaces of the electron thermal mode are obtained in a polar coordinate. The experimental observation of the electron mode radiated from a point source is found to be in fair accord with the theoretical wave fronts which are obtained from the ray velocity surface. Wave fronts and ray trajectories of an oblique electron thermal mode radiated from a point source are numerically obtained in an inhomogeneous magnetized plasma with a use of an electrostatic kinetic theory. The spatial numerical results are indicated mainly below the electron plasma and cyclotron frequencies. Reflections of the mode in the plasma density lower than the electron plasma frequency are made clear numerically.